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Alternative physiological strategies can increase protein concentration in soybean: (i) more‐than‐proportional increases in seed protein content (mg seed−1) relative to increases in carbohydrate and oil content in large‐seeded genotypes or (ii) more‐than‐proportional reductions in carbohydrate and/or oil content relative to protein content reductions in small‐seeded genotypes. Because these strategies differentially affect crop growth and development, we hypothesized that populations developed from high‐protein (HP) parents with contrasting seed sizes will present differences in how seed yield and protein concentration correlate. To test this, three breeding strategies were developed by mating high‐yielding cultivars and HP ones that differ in seed sizes, reflecting the alternative strategies mentioned above. Neither tested crossing strategies showed differences in their correlation values between seed yield and protein concentration, as initially expected. Nevertheless, populations developed from crossing a HP‐small‐seeded parent to a HP‐large‐seeded one showed the highest number of transgressive segregants for protein yield. Our results showed that parent selection based on seed size has no beneficial effects on the development of high‐yielding, HP soybean populations, but it might affect the number of transgressive segregants for protein yield. [ABSTRACT FROM AUTHOR]

A series of DNA markers for various agronomic traits may accelerate the success of marker‐assisted selection in practical plant breeding programmes. Here, we developed DNA markers for the blast resistance gene Pi‐cd. In this study, we examined the effects of the Pi‐cd locus on not only blast resistance but also agronomic traits in agriculture. We developed three pyramiding lines (PLs) coupling Pi‐cd with three blast resistance genes, pi21, Pi35 and Pi39. The effect of Pi‐cd on blast resistance was dependent on the coupled resistance genes. Then, we evaluated the effects of Pi‐cd on 13 agronomic traits. Amylose content and 1,000‐grain weight showed significant differences between the PLs and current commercial varieties, which had no negative effects on agronomic trait values. Furthermore, we investigated the distribution of genotype for the Pi‐cd locus among varieties of upland rice. The KT genotype specific to rice blast resistance may be predominant in the varieties. The results suggested that Pi‐cd has the potential to be useful for improving blast resistance in rice breeding programmes. [ABSTRACT FROM AUTHOR]

Seed yield is a major breeding target in tetraploid red clover. We investigated if marker‐assisted parentage analysis can identify progeny plants with two high seed‐yielding parents in tetraploid red clover and if this technique is more advantageous than traditional half‐sib selection. Parentage analysis was successfully performed on the progeny from the 10% highest seed‐yielding genotypes from a second‐cycle family selection trial: 16.0% of progeny were identified with a high seed‐yielding father. However, progeny plants with two high seed‐yielding parents did not produce more seeds than traditionally selected progeny (27.3 g vs. 30.7 g/plant, respectively). The 10% highest seed‐yielding genotypes displayed on average 2% self‐fertilization. Four genotypes were self‐fertile with individual selfing rates up to 20%. Our results discourage the use of marker‐assisted parentage analysis to improve seed yield in tetraploid red clover when the material has been preselected for seed yield. Breeders should be aware that intensive selection for seed yield in tetraploid red clover may inadvertently lead to selection for increased self‐fertility, which may increase inbreeding in the long term. [ABSTRACT FROM AUTHOR]

Possibility of using interspecific hybridization to increase genetic diversity of drought tolerance in safflower (Carthamus tinctorius L.) and effectiveness of different selection methods is poorly understood. The main objectives of this study were to evaluate the effectiveness of (a) interspecific hybridization to expand genetic diversity in safflower for agronomic traits and drought tolerance in advance generations and (b) different selection methods (direct vs. indirect) for improving seed yield. Interspecific hybridizations were performed between species of C. tinctorius × C. palaestinus (TP), C. palaestinus × C. oxyacantha (PO) and C. tinctorius × C. oxyacantha (TO). Based on the field screening of genotypes in F3 generation, four groups of selected genotypes (derived from combination of direct and indirect selection under both drought and normal environments along with selection based on drought tolerance index (STI)) were evaluated in F4 and F5 generations. Indirect selection for seed yield was significantly more efficient than direct selection. Selection in stress environment resulted to more efficiency than selection in normal environment. No significant difference was observed between direct selection and selection based on STI. The result showed that TP was the best population to combine high seed yield and drought tolerance in safflower. [ABSTRACT FROM AUTHOR]

Natto, a traditional soyfood fermented by Bacillus subtilis (natto), is prepared by steaming/cooking of soaked soybean seeds followed by inoculation with the bacteria and incubation. Natto soybean has increased in popularity due to its nutritional value and health benefits. Thus, the natto soybean market provides additional opportunities for farmers. The development of soybean cultivars with improved natto quality characteristics is crucial for maintaining and increasing the natto soybean market. Good‐quality characteristics of natto are determined by soybean cultivar, processing conditions and bacteria strain. Natto quality evaluation generally determined by sensory panels is time consuming. Therefore, indirect selection for natto quality based on seed traits is preferred. Seed morphological and physiological characteristics and seed compositions play an important role in producing natto of good quality. In this review, we have summarized natto processing conditions, natto quality characteristics, seed traits involved in natto quality and their genetic variation, as well as the genetic diversity in food‐grade soybean germplasms and B. subtilis strains. Information presented will be helpful for natto soybean cultivar development and natto manufacture. [ABSTRACT FROM AUTHOR]

Weed competition can severely reduce soybean ( Glycine max (L.) Merr.) yields, particularly in organic systems. An efficient screening and breeding approach is needed to increase breeding progress for weed tolerance. This study sought to (i) establish a system for direct selection of competitive genotypes, (ii) evaluate genotypic differences in weed tolerance among six early-maturing genotypes and (iii) assess the contribution of selected morphological traits to weed tolerance. A direct selection system providing two different levels of weed competition through all development stages of a soybean crop was developed, using mixtures of selected crop species as sown competitors. Two resulting mixtures induced intermediate (<30%) and strong (>50%) yield reduction, respectively. This selection system can be applied in screening and breeding programmes to facilitate breeding for weed tolerance. No significant difference in weed tolerance was detected between six soybean genotypes of maturity groups 000 to 00. Morphological traits that might influence competitive ability, for example light absorption, leaf area and lateral shoots, were assessed, and their potential for indirect selection for weed tolerance is discussed. [ABSTRACT FROM AUTHOR]

Interspecific hybrids between Trifolium uniflorum and cultivated white clover ( Trifolium repens) have highly useful characteristics for temperate pastoral systems derived from both parent species. However, the early hybrids (F1 and BC1) also have unacceptably poor seed production for commerce. This study analysed the basis for the poor seed production and investigated breeding strategies for overcoming the problem. The BC1F1 generation produced lower-than-expected numbers of heads per plant and seeds per floret. Backcrossing of selected hybrids to white clover corrected these deficiencies and created new variation. Seed numbers were also returned to near target levels by recurrent selection within the BC1 generation. Thus, it was possible to retain a theoretical average of 25% of T. uniflorum genome and still achieve high seed production per plant. The BC1F2 and BC2F1 generations produced high seed numbers per plant, along with reasonable variation. Both of these second-generation hybrid forms have high reproductive potential and should be the focus for the selection of the desired combinations of agronomic and seed production traits. [ABSTRACT FROM AUTHOR]

Selection for heavy seed was implemented to overcome establishment problems in Panicum coloratum var. makarikariense. A collection covering the genetic diversity of the species available in Argentina was used as a base population ( BP), and two cycles of recurrent phenotypic selection to increase seed weight were performed. Seedlings, obtained from seeds from each cycle and the BP, were further evaluated in the greenhouse. An increase of 17% in mean seed weight was obtained after two cycles of recurrent selection. No differences in germination or emergence were detected among the selected materials and the BP. However, seedlings from selected materials were taller and showed higher leaf elongation rate, adventitious roots elongation rate and total growth rate than that from BP. This research also revealed that in P. coloratum var. makarikariense, more vigorous seedlings can be selected from genotypes that produce heavier seeds. [ABSTRACT FROM AUTHOR]

Selection within families can be conducted as family deviation (FDS) or strict within-family selection (WFS). Our objectives were to (i) investigate two breeding schemes combining selection among families with FDS or WFS and (ii) compare the optimum allocation of test resources for these breeding schemes. We focused on selection among S1 families and doubled haploid (DH) lines within S1 families and used Monte Carlo simulations to determine the selection gain (ΔĜ), its standard deviation (SDΔĜ), and the average coefficient of coancestry among the selected DH lines ( ). For breeding schemes focusing only on within-family selection, as employed in animal breeding, the maximum ΔĜ, its SDΔĜ, and were larger for FDS than for WFS. However, for breeding schemes combining among- and within-family selection, as employed commonly in plant breeding programmes, the maximum ΔĜ, SDΔĜ, and were almost equal for FDS and WFS. Furthermore, the optimum allocation of test resources was similar for FDS and WFS. We conclude that FDS and WFS are equally suited for short- and long-term success in breeding schemes where among-family selection is followed by within-family selection. [ABSTRACT FROM AUTHOR]

The effect of peat moss on fusarium wilt of melon ( Cucumis melo L.) was studied in order to improve the selection process of resistant melons during breeding programmes. Disease symptoms were evident earlier and disease progress was faster in seedlings that were transplanted to peat following inoculation than in those transplanted to sand. The resistant breeding line used as a control did not show any wilt symptoms in either medium. Mixing the peat with sand or perlite reduced the disease development rate and the final disease incidence. The effects of peat and sand on disease progress were evaluated with two segregating melon populations in which the expected susceptible : resistant ratio was 25 : 75. In both populations, disease incidence was higher in the peat, which enables breeders to identify resistant plants and to lower the risk of using escapees as resistant plants. The mechanism of disease enhancement may include both biotic and abiotic components. There is an indication that peat induces plant susceptibility before inoculation. Melon seedlings germinated in peat and transplanted into sand exhibited significantly greater wilt incidence than those that germinated in sand and were transplanted into sand following the inoculation. Disease progress in sterile peat was significantly slower than that in non-sterile peat, which suggests the possible involvement of microbial activity. [ABSTRACT FROM AUTHOR]

Recurrent selection programmes use one or just a few selection criteria, however other indirect traits may be unpredictably changed in a population. This study was conducted to determine the indirect effects of 10 cycles of bi-directional recurrent selection for cotyledon size in the model system of rapid-cycling Brassica rapa. Eight sub-populations (four large- and four small-cotyledon sizes) were phenotypically and cytologically evaluated. Each sub-population was measured by five phenotypic traits. Ploidy and pollen viability were studied and compared with the initial population. Total weight was significantly different in broad and bottleneck-1 sub-populations. Total cell number exhibited statistically significant differences in broad and bottleneck-1 sub-populations, while cell number per unit area exhibited statistically significant differences in broad, bottleneck-2 and bottleneck-3 sub-populations. Decreases in pollen viability in comparison with the base population were observed in three sub-populations. Among the eight sub-populations studied, the most significant phenotypic differences were observed within broad sub-populations. Based on the above, it is possible that bi-directional recurrent selection for cotyledon size may have been a result of indirect selection for two processes, endoreduplication and cell division. [ABSTRACT FROM AUTHOR]

Six simple methods for extracting DNA from rice seedlings were evaluated for marker-assisted selection (MAS). The assessment of each method was based on PCR amplification of SSR markers, DNA yield and purity, time and cost. Based on these criteria, two methods were selected as being superior to other methods. The best two methods included the standard method developed at the International Rice Research Institute (IRRI), which utilizes a sodium dodecyl sulfate extraction buffer followed by chloroform/isoamyl alcohol extraction and a previously published method using sodium hydroxide and Tris. These two methods produced nearly identical PCR amplification results. The sodium hydroxide method is considerably simpler, quicker and cheaper than the standard IRRI method, and may be particularly useful for many applications of MAS or high-resolution mapping. This method was also adapted into an effective high throughput method utilizing 96-well plates emphasizing its versatility. [ABSTRACT FROM AUTHOR]

‘Minghui 63’ is a restorer line widely used in hybrid rice production in China for the last two decades. This line and its derived hybrids, including ‘Shanyou 63’, are susceptible to bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae ( Xoo). To improve the bacterial blight resistance of hybrid rice, two resistance genes Xa21 and Xa7, have been introgressed into ‘Minghui 63’ by marker-assisted selection and conventional backcrossing, respectively. The single resistance gene-introgressed lines, Minghui 63 ( Xa21) and Minghui 63 ( Xa7) had higher levels of resistance to bacterial blight than their derived hybrids, Shanyou 63 ( Xa21) or Shanyou 63 ( Xa7). Both Xa21 and Xa7 showed incomplete dominance in the heterozygous background of rice hybrids by infection with GX325 and KS-1-21. The improved restorer lines, with the homozygous genotypes, Xa21Xa21 or Xa7Xa7, were more resistant than their hybrids with the heterozygous genotypes Xa21xa21 or Xa7xa7. To further enhance the bacterial blight resistance of ‘Minghui 63’ and its hybrids, Xa21 and Xa7 were pyramided into the same background using molecular marker-aided selection. The restorer lines developed with the resistance genes Xa21 and Xa7, and their derived hybrids were evaluated for resistance after inoculation with 10 isolates of pathogens from China, Japan and the Philippines, and showed a higher level of resistance to BB than the restorer lines and derived hybrids having only one of the resistance genes. The pyramided double resistance lines and their derived hybrids have the same high level of resistance to BB. These results clearly indicate that pyramiding of dominant genes is a useful approach for improving BB resistance in hybrid rice. [ABSTRACT FROM AUTHOR]

High frequencies of regeneration are desirable characteristics of in vitro culture from elite wheat cultivars. The effect of the source spike, the scutellum size and the induction temperature on embryogenesis, regeneration and number of plants per explant were optimized in three varieties of wheat and later determined in fifteen varieties of both bread and durum wheat. The highest frequencies of embryogenesis, regeneration and plants per explant were obtained when the first spike was used as source of scutella and decreased using the scutella from the second and third spikes. Scutella from the third spike yielded half the number of plants per explant than those from the first spike. Significant differences were also found for embryogenesis, regeneration and plants per explant as affected by scutellum size. The number of plants per explant drastically decreased in commercial varieties when scutella larger than 2.0 mm were used. The optimum induction temperature was 21 and 25°C for commercial and model genotypes, respectively. However, no differences were found for the number of plants per explant as affected by the induction temperature. The in vitro culture response of twelve and four cultivars of, respectively, bread and durum wheat were then determined. In all wheat varieties tested embryogenesis, regeneration and plants per explant varied over a wide range of values. In elite wheat varieties the selection of the source spike and the scutellum size can yield high frequencies of embryogenesis and regeneration and high numbers of plants per explant. [ABSTRACT FROM AUTHOR]

Dry matter (DM) content and quality parameters of maize grain are important traits in breeding of maize hybrids. New developments in near-infrared spectroscopy (NIRS) allow to determine DM content and product quality parameters directly on plot combine harvesters. The main objective of our study was to examine the potential of NIRS on combine harvester (NOCH) for determination of DM, crude protein (CP) and starch (ST) contents in maize grain. Plot combine harvesters equipped with spectrometers were used. Eleven locations were harvested in Europe during 2003 and 2004. The NOCH calibration models were developed with standard error of prediction (SEP) and coefficient of determination for validation ( R ) of 1.2% and 0.95 for DM, 0.3% and 0.88 for CP, and 1.0% and 0.79 for ST, respectively. NOCH is a promising technology for determination of DM, CP and ST contents of maize grain for breeding purposes, because it automates the assessment of each harvested plot, and the information for making selection decision is rapidly available to plan the next generation. [ABSTRACT FROM AUTHOR]

Abstract Upgrading levels of disease resistance are a primary objective of maize breeding programmes. Efficacy of S1 recurrent selection in improving levels of resistance to downy mildew (DM) infection was assessed in Nigeria from 1997 to 2000 in six maize populations. Improvement procedures consisted of evaluating S1 progenies under artificial infection with DM spores and in disease-free environments and using a selection index to combine selection for reduced DM infection with appropriate agronomic characters from more than one environment. Three to four cycles of selection were completed in each of the populations. Products from the different cycles of selection were evaluated and data collected on DM infection parameters and agronomic traits. Result obtained showed 3–4 cycles of selection were adequate to reduce DM infection levels significantly and increase grain yield. Downy mildew infection decreased by between 58 and 100% while grain yield increases ranged from 10 to 98% for the 2–4 cycles of selection relative to the C0 (original). Selection increased grain yield with acceptable changes in plant height while maintaining maturity in disease-free environments. [ABSTRACT FROM AUTHOR]

Abstract Five cycles of phenotypic recurrent selection for increased essential oil content were carried out in East Indian lemongrass, Cymbopogon flexuosus . In each cycle, the top 5% of plants for essential oil content were selected and their ramets were planted in isolated polycross blocks to produce the seed of the next cycle. Response to selection for essential oil content and its effect on three unselected traits, leaf yield, dry matter content in leaves and citral content in the essential oil, were determined by evaluating C0 –C5 populations in a replicated trial. Genetic variation, heritability estimates and intertrait correlations for essential oil content, leaf yield, leaf width, tiller number and citral content in the essential oil in C4 were determined, by evaluating 40 clones and their half-sib progenies produced from 40 randomly selected C4 plants, in a replicated experiment. These were compared with those determined in C0 earlier. The mean essential oil content increased from 0.66% in C0 to 1.67% in C5 (i.e. by about 31% per cycle over C0 ). Selection for essential oil content did not affect leaf yield and its effect on dry matter content in leaves was marginal. The first three cycles of selection for essential oil content did not affect citral content in the oil but two further cycles significantly decreased citral content. Heritabilities and intertrait correlations between all traits studied, except citral content and essential oil content, were similar to those found in C0 . [ABSTRACT FROM AUTHOR]

Anther culturability of rice is a quantitative trait controlled by nuclear-encoded genes. The identification of quantitative trait loci (QTL) and associated marker selection for anther culturability is important for increasing the efficiency of green plant regeneration from microspores. QTL associated with the capacity for green plant regeneration in anther culture of rice were mapped on chromosomes 3 and 10 using 164 recombinant inbred (RI) lines from a cross between `Milyang 23' and `Gihobyeo'. The quantitative trait locus located on chromosome 10 was detected repeatedly when three anther culture methods were applied and was tightly linked to the markers, RG323, RG241 and RZ400. Associations between these markers and the efficacy of green plant regeneration in 43 rice cultivars and two F2 populations, `MG RI036'/`Milyang 23', and `MG RI036'/`IR 36' were analysed. One of these markers, RZ400, was able to identify effectively genotypes with good (> 10.0%) and poor (< 3.0%) regenerability, based on the marker genotypes in the cultivars and two F2 populations. This marker enables the screening of rice germplasm for anther culturability and introgression into elite lines in breeding programmes. [ABSTRACT FROM AUTHOR]

Farmers in western Rajasthan (north-west India) produce and maintain their landrace populations of pearl millet through their own distinct seed management practices. The objective of this study was to characterize morphological and agronomic variability of different traits between and within three farmers' populations using quantitative–genetic parameters. Populations examined were a typical landrace and two modified landraces, which were generated through farmer introgression of modern varieties with different levels of subsequent selection. From these three populations, 100 random full-sib progenies were evaluated in field trials at two locations in western Rajasthan over two years. Significant genetic variation existed within the three populations. Estimates of heritability were moderate to high for all observed traits. Predicted selection response for grain yield across environments was 1.6% for the typical landrace and 2.2% for both the modified landraces. Results suggest that the introgression of modern varieties into landraces had increased the genetic diversity. Therefore, farmers' current breeding activities could open up new resources for plant breeding programmes aiming at plant improvement for the semiarid zones of India. [ABSTRACT FROM AUTHOR]

The objective of this paper is to review the possibilities for using allelopathy to improve overall crop competitive ability against weeds, using rice, Oryza sativa , as an example. Laboratory, greenhouse and field screenings for allelopathy and overall weed suppression in rice have been made and allelopathic rice germplasm has been identified in laboratory and greenhouse screening. Field experiments revealed that allelopathy accounted for 34% of overall competitive ability in rice. For strongly allelopathic cultivars, allelopathy was the dominant factor determining competitive ability. Based on the results of the screenings, recombinant inbred line populations were developed for identification of quantitative trait loci (QTL) controlling allelopathy. Populations of recombinant inbred lines (RILs) were derived through single-seed descent from crosses between varieties with contrasting behaviour and QTL controlling allelopathy were identified. For rice and most probably also for other cereal crops, the findings presented can explain the limited success in previous breeding programmes for weed competition, as allelopathy has never before been acknowledged as an important factor. The findings in allelopathy indicate that it is possible to improve allelopathy in rice using marker-assisted selection. Optimizing allelopathy in combination with breeding for competitive plant types could result in crop cultivars with superior weed-suppressive ability. [ABSTRACT FROM AUTHOR]

Genetic variation for forage yield of orchardgrass is abundant, but there are few reports of progress from selection for increased forage yield. The objective of this study was to estimate direct effects of selection from one cycle of half-sib family selection for forage yield in orchardgrass. Eleven selected populations were compared with their parent populations within three maturity groups. Populations were evaluated under hay management at three locations and management-intensive rotational grazing at two locations. Nine of the 11 selected populations differed, by an average of 7.4%, from their parent population in forage yield. Nine of the selected populations also showed changes in Drechslera leafspot reaction, all indicating a negative genetic correlation with forage yield. Selection for high forage yield tended to result in greater ground cover and later relative maturity. However, changes in net herbage accumulation (NHA) under rotational grazing were generally not significant and were uncorrelated with changes in forage yield, indicating that forage yield of hay plots is not correlated with the NHA of grazed plots. Although genetic gains in forage yield measured under hay management were very favourable relative to other reports from the literature, the lack of correlated progress under grazing management indicates that directed selection for NHA of orchardgrass should be conducted under grazing management. [ABSTRACT FROM AUTHOR]

The possibility of using random amplified polymorphic DNA (RAPD) markers previously mapped in the common bean PC50/XAN159 population to select for resistance to common bacterial blight (CBB) in different populations was examined. Two out of 13 selected RAPD markers were polymorphic in HR67 and W1744d, the parental lines used in this experiment. Cosegregation analysis of the two polymorphic markers and disease reaction in a recombinant inbred (RI) population derived from HR67/W1744d confirmed that one of the two RAPD markers, BC420900, was significantly associated with a major quantitative trait locus-conditioning resistance to CBB in HR67. This locus accounted for approximately 62% of the phenotypic variation. The RAPD marker was transformed into a sequence characterized amplified region (SCAR) marker and used for selection in a different population derived from ‘Envoy’/HR67. Prediction for resistance to CBB with the BC420.900 SCAR marker was 94.2% accurate in this population. A comparison between marker-assisted selection (MAS) and conventional greenhouse screening showed that the cost of MAS is about one-third less than that of the greenhouse test. [ABSTRACT FROM AUTHOR]

AbstractMost traits of interest in hazelnut are quantitative, yet there is little information available on heritability, variance components, or correlations. In this study, 13 morphological and four phenological traits were observed for 3 years on 41 parental genotypes, and for 2 years on seedlings representing 35 progenies. Narrow-sense heritability estimates obtained by regression of offspring means on midparent values were all high, ranging from 0.56 for amount of kernel fibre to 0.89 for nut depth. Data on the parent genotypes was used to analyse variance components and showed that genotypic variance accounted for most of the phenotypic variance for all traits, and there was very little variation among trees within genotypes. Genotype–year interaction accounted for only a very small part of the phenotypic variance for most traits, and changes in genotype rank were few and minor. Thus, selection based on genotype means is appropriate. The largest genotype–year interaction components were observed for time of nut maturity, time of stigma exsertion, time of catkin elongation, number of nuts per cluster and amount of kernel fibre. For these five traits, evaluation over a period of years is advised. Correlation coefficients were large and positive for four nut size traits, indicating some redundancy in these measurements. Three of the phenological traits (time of stigma exsertion, time of catkin elongation, and time of leaf budbreak) were also highly and positively correlated. A large genetic correlation (0.44 < r < 0.73) was noted between good blanching and early phenology (catkin elongation, stigma exsertion and leaf budbreak), although plots of individual seedling values showed a large degree of scattering. Genetic correlations also indicated that seedlings with small nuts also tend to have compressed nuts, short husks and catkins that elongate later, but plots of individual seedling values showed large scattering. Correlations among the six traits directly related to the objectives of the Oregon State University hazelnut breeding programme (kernel weight, per cent kernel, nut shape index, blanching ability, relative husk length and nut maturity) were very low, indicating that they can be handled as independent traits. [ABSTRACT FROM AUTHOR]

AbstractThe proportion of pod walls is considered as a potential selection criterion for seed yield in white lupin. It has a negative and highly significant phenotypic relationship with the seed yield and the genetic correlation between both traits is negative and high. The present study over 2 years (1996 and 1998) evaluated the genetic variation of proportion of pod walls in a set of 325 spring-sown white lupin accessions originating from 17 different countries. Wide ranges of variation for this trait and other pod components were observed. This variation has a geographical distribution. Egyptian ecotypes had the lowest proportions of pod walls while the Greek and Italian ecotypes had the highest. The between-country range of variation for the proportion of pod walls, was lower than the within-country range (0.25–0.31 and 0.21–0.36, respectively) and the within-country variance accounted for 51% of the total genetic variation. The broad-sense heritabilities of pod wall proportion and proportion of pod walls for one full locule were moderate (0.44 and 0.57, respectively), which indicates that the proportion of pod walls can be used in breeding. [ABSTRACT FROM AUTHOR]

The effects of self, wind and open pollination on yield components were investigated in five strawberry genotypes, the cultivars 'Dukat', 'Paula', 'Redgauntlet', 'Senga Sengana' and the breeding clone B-302. Investigations were also conducted to look for additional plant characteristics associated with strawberry yield components after various modes of pollination. Such characteristics would facilitate the indirect selection of highly self-compatible strawberry genotypes. The greatest effect of self pollination was observed in B-302 and 'Redgauntlet', while the least effect of autogamy was shown in 'Paula'. Conversely, the last cultivar revealed the greatest effect of entomophily, whereas the greatest effect of wind pollination was observed in 'Dukat'. Relationships between yield components and some flower and pollen characteristics after various pollinations indicated that the degree of self compatibility in straw- berry can be predicted from the pollen grain length and the pollen size index. Genotypes producing long pollen grains with large size indices exhibited the greatest effect of autogamy. Anther size, especially length, which correlated more strongly with yield components than width, could also be used as an index of autogamy in the strawberry. Pollen yield per flower and pollen viability were less important for estimating self compatibility. [ABSTRACT FROM AUTHOR]

An efficient procedure is described for cultivar identification in lily, based on polymorphism in bulb scale proteins analysed by isoelectric focusing (IEF). Seventy (84%) out of 83 cultivars from which in vivo bulbs were analysed showed a unique banding pattern. Analysis of in vitro bulblets from 62 commercial cultivars resulted in 47 (76%) unique banding patterns. Cultivars with identical protein patterns always belonged to the same cultivar classification group (i.e., Asiatic hybrids, Oriental hybrids or Lilium Iongiflorum). Protein bands characteristic for the cultivar groups have been found. The protein patterns appeared to be very consistent and were not affected by the soil-type on which the bulbs were grown, long-term bulb storage, different protein sample storage methods, in vitro growing conditions, or in vitro bulblet storage. However, in six out of 10 cultivars from which in vito bulbs and in vitro bulblets were analysed, protein patterns from in vito bulbs consisted of a greater number of, and/or more intensely stained bands than those from in vitro bulblets of the same cultivar. The protein patterns appeared to be unsuitable markers for selection of reference cultivars for distinctness, uniformity and stability (DUS) testing as no relation was found between morphological characters and protein patterns. Cultivars with identical or very similar protein patterns were generally clearly distinct on the basis of morphological characters. [ABSTRACT FROM AUTHOR]

A field experiment was designed to compare control with tissue culture-derived plants of rice, and to study the effects of natural selection pressure applied to the first generation (R0) of in vitro plants on the performance of their progeny. Control- and R0 in vitro plants of four rice varieties from middle altitude in Burundi, i.e. 'Facagro 57', 'Facagro 76', 'Kirundo 3' and 'Kirundo 9', were cultivated at four different altitudes (800, 1380, 1650 and 1900 m). Several parameters concerning tillering capacity, plant height development and seed production were measured. The means for most measured parameters were higher in control plants than in the in vitro plants, while the higher variation coefficients and most extreme values were usually found in the in vitro plants. For each variety, the 20 control plants and 20 in vitro plants having the highest production were selected at each altitude of 1380 and 1650 m, and their progenies were cultivated on the same site at 1580 m Among the plants arising from 1650 m, most maximum values, higher variation coefficients and, in some cases, higher means were found in the in vitro plants. In contrast, among the plants arising from 1380 m, higher means most usually corresponded to control plants, while the tendency for maximum values and variation coefficients were unclear. These results indicate the positive effect of natural selection pressure applied in the first generation to plants rising from tissue culture. They also demonstrate that considerable variation may be generated in vitro. The interest for plant breeding purposes is discussed. [ABSTRACT FROM AUTHOR]

In the Mediterranean environment, root systems are very important for water utilization. For this reason, the effects of selection for increased root dimensions upon root and shoot characteristics of a natural population of Lolium rigidum Gaud. were analysed. Two cycles of phenotypic recurrent selection were carried out on a population collected in Nurra (north-western Sardinia, Italy). Plants derived after two cycles of selection, together with unselected plants, were grown hydroponically in a greenhouse. Data on root volume, longest root length, number of stems and leaves, leaf length, shoot and root dry weight were collected from the selected material and also from unselected material for use as a control. An analysis of variance was performed and correlation coefficients were calculated. The increased size of the root system did not have a negative effect on the above-ground biomass and there was genetic variation for root traits in the 'Nurra' population. The improved population will be utilized for further breeding work to obtain L. rigidum varieties capable of withstanding dry periods during the vegetative phase. [ABSTRACT FROM AUTHOR]

Two populations of common bean, Phaseolus vulgaris L., were used to make three independent location-specific selections at Palmira, Quilichao, and Popayán, Colombia. Also, three across-location selections were made by alternating generations between Palmira and Popayán, between Quilichao and Popayán, and among Palinira, Quilichao, and Popayán. The seven highest yielding lines selected from each environment and population along with 14 parents and two checks were evaluated for seed yield, seed weight, maturity, and reaction to anthracnose, angular leaf spot, and common bacterial blight. Mean squares due to evaluation and selection environments, selected lines, and their interactions were significant for all traits. Mean yields of selected lines were higher than the mean of parents in both populations. Among location-specific selections, lines yielded higher at their respective selection site. Moreover, selections made at Popayán were higher yielding than those made at Quilichao or Palmira when tested across locations and years. Use of Popayán, a relatively wetter and cooler site, either alone or in combination with other locations resulted in higher yield, higher seed weight, and higher resist- ance to anthracnose. On the average, location-specific selections were lower yielding than the across-location selections. Among across-location selections, those selected between Palmira and Popayán were the highest yielding in both populations. Selections at Palmira and across all three locations resulted in greater stability. [ABSTRACT FROM AUTHOR]

Black shank, a fungal disease caused by Phytophthora parasitica var. nicotianae, is a major hazard in the production of burley tobacco (Nicotiana tabacum L.). Moderate levels of resistance have been bred into cultivars, but little success has been achieved in utilizing high levels of resistance found in the cigar line, Beinhart 1000-1. Beinhart 1000-1 and seven burley cultivars were combined into a synthetic population and three cycles of selection for increased black shank resistance were conducted. The objectives of this study were (i) to estimate genetic variability for agronomic traits in the original base population (C[sub0]) and the three selection cycles and (ii) to characterize the effects of selection for black shank resistance on the agronomic traits. Fifty selfed lines from the base population and each of three selection cycles were evaluated in replicated field trials at Lexington and Princeton, KY. Differences among cycle means for six agronomic traits were not statistically significant. Genetic variation for the six traits among lines within cycles was highly significant and did not change during selection. The results indicated that previously assumed association between black shank resistance in Beinhart 1000-1 and undesirable agronomic traits were due to chromosomal linkages which were apparently broken by inter-crossing. The C[sub3] population would be a useful base population for selection to improve agronomic performance in black shank resistant genotypes. [ABSTRACT FROM AUTHOR]

Three or four-way recurrent selection is proposed for the development of three or four-way crosses. In term of genetic effects, it could be justified if there are interactions between more than three genes, whether alleles or not, if autopolyploids are also considered. For autotetraploids, in particular with tetragenic interaction, four-way recurrent selection could be more effective than reciprocal recurrent selection (two-way selection). According to the types of progenies used to develop the tests, different selection procedures are considered, the two ex- tremes being called method 1 and method 3. With method 1 (selection for three or four-way general combining ability) a plant from a population is used to produce three-way or four-way progenies with the other populations used as testers. With method 3 (selection for three or four-way specific combining ability) three-way or four-way crosses are developed with one plant from each population. To study the genetic advance, the theory is developed to consider either diploidy or autotetraploidy. It is shown that method 3 will allow a greater genetic advance than method 1 for low heritability and low selection intensity. The way towards hybrid development with three and four-way pedigree selection is discussed: again selection can be for general or specific three or four-way combining ability. It is em- phasized that an advantage of recurrent selection for three or four-way specific combining ability is that it allows direct varietal development with pedigree selection on three or four-way specific combining ability. Some other practical aspects are also considered. [ABSTRACT FROM AUTHOR]

Selection for yield in early generations is difficult, mainly due to a shortage of seed. In the breeding company Fr. Strube the breeder uses three-way crosses and first selects for yield between F2'-derived lines in the F4'. The generations are called F2', F2', etc., because the first generation is already segregating. The efficiency of this selection was checked in the F5' and F2. For this purpose F3'-derived progenies, corresponding to poor and good yielding bulks in F4', were selected. In later generations the average yield of the group of strains with good yield in the F4' was 4 % (F5') and 3% (F6') higher, respectively, than the mean of the strains with low yield in the F4'. Strains with very low yielding potential can easily be discarded in the F4'. The risk of discarding lines with a very high yield is minimal. Selection for yield in the F4' was as effective as in the F5' The importance of testing F2'-derived bulks in the F2' is not only based on the assessment of yield but also on the possibility of reliable intensive selection through recording visual characters (height, resistance against diseases) in a second environment in parallel to the single plant progenies. [ABSTRACT FROM AUTHOR]

The quantity of N2 fixed in common bean (Phaseolus vulgaris L.) is a quantitatively inherited trait that shows sufficient genetic variability for improvement through breeding, but there is little information on gain from selection for N15-determined N2 fixation ability. The objective was to determine whether intrapopulation recombination and selection could be used to improve N2 fixation. Four agronomically acceptable lines were selected, based on their acetylene reduction-determined N2 fixation ability, from an inbred backcross (IB) line population created from a cross between the high N2-fixing donor parent 'Puebla 152' and a commercial, low N2-fixing recurrent parent 'Sanilac'. These four TB lines were intercrossed, advanced to the F3, and the six resulting F3 populations with 25 F3 families per population were evaluated for N2 fixation in a low-N field using N15-depleted (NH4)N2SO4. The six F3 population means differed significantly and were superior to 'Sanilac' for N2 fixation ability and yield, indicating significant improvement over 'Sanilac'. Four F3 population means were similar to 'Puebla 152', indicating selection advance towards high N2 fixation while retaining favorable agronomic characteristics. Fifty percent of the F3 families were superior to 'Sanilac' for N2 fixation and one family exceeded 'Puebla 152', indicating that intrapopulation recombination produced improvement of N15-determined N2 fixation. [ABSTRACT FROM AUTHOR]

Investigations were carried out to study the effect of different plot sizes and plot types on the performance of peas and to determine plot size and plot type combinations suitable for the reliable evaluation of varietal yield performance realized in commercial stands of pea crops. Four pea varieties were tested in 1981 and 1982 in combinations of plot sizes ranging from 0.25 m2 to 19.50 m2 with plot types either unbordered, bordered with faba beans, surrounded with perforated plastic foil or only central sections of plots harvested (net plots). With decreasing plot size the performance mean as well as the error variance of grain yield and thousand grain weight increased disproportionately. Thus, changes in grain yield were much higher than those for thousand grain weight. The four varieties tested reacted differently to changing plot sizes and as a result, highly significant variety × plot size interactions were found. Although overestimation of grain yield in small plots could be strongly reduced by bordering the plots with faba beans or surrounding them with plastic foil, their suitibility for yield testing was limited by highly significant variety × plot type interactions. Compared to the largest net plot (15 m²) reliable results were still obtained with plot sizes larger than 6.5 m², no matter whether edge effects were eliminated or not. If only a small quantity of seed is available, plots may be reduced even to 1.00 m², if surrounded by plastic foil. The results presented in peas were compared to those in other crops and discussed concerning their relevance for variety testing as well as for selection of grain yield in early generations. [ABSTRACT FROM AUTHOR]

Genetic variation for NaCl tolerance at the vegetative stage was assessed in nutrient solution culture in maize (Zea mays L.). Shoot growth, and plant fresh and dry weight of the two cultivars, Akbar and Sadaf were severely reduced alter three weeks growth in 120, 150, and 180 mol m³ NaCl, There was however considerable variability between seedlings. Ten-thousands seeds of cv. Akbar were therefore screened for shoot growth at 180 mol m ³ NaCl after four weeks growth in sand culture. A selection intensity of 0.42 % was achieved, Eighteen selected plants were polycrossed for estimation of narrow-sense heritability based on female parent-progeny regression. A narrow-sense heritability estimate of 0.54 was obtained. The progeny of the salt-tolerant selection line and selfed progeny plants of the unselected control lines of cvs Akbar and Sadaf were grown for six weeks in 0, 30, 60, 90, 120, 150, and 180 mol m³ NaCI in sand culture. The tolerant line produced significantly greater fresh and dry biomass and had greater shoot length than the unselected cv. Akbar, but the selection line derived from cv. Akbar was equal to the salt tolerant cv. Sadaf in all the growth parameters measured. These data suggest that in maize, improvement in salt tolerance could be obtained through further cycles of selection and breeding. [ABSTRACT FROM AUTHOR]

For maximizing genetic gains, with given resources, plant breeders generally conduct large hut un- or inadequately-replicated field trials especially during early generation evaluations and population improvement programmes. Checks are often used to improve the precision of test plot comparisons. Adjustments by moving or weighted means etc. are, however, empirical or based on assumptions too difficult to verify. An alternative stochastically best linear tin biased optimal locally weighted method of spatial prediction of in micro-environmental heterogeneity indices of treatment plots was examined. Two checks used in an unreplicated evaluation of 1560 test lines of winter wheat expressed the micro-environmental variation in similar ways. About 46, 38 and 16 percent of the total variation in yield was a simple row and column effects, spatially dependent, and random errors, respectively. Optimal weights derived to simulate the micro-environmental heterogeneity indices were sensitive to the position of the test plot and thus provided a better local control. The model was validated, and prediction standard deviations of simulations computed. [ABSTRACT FROM AUTHOR]

Modified mass and family selection for selection yield production of berseem clover (Trifolium alexandrinum L. ) c. v. 'Fahl' were applied for two generations. Two hundred plants (5% intensity of selection) were selected for seed yield in the first season, 1985/86. In the second season, 1986/87, selection between and within half-sib families was practiced. In addition, equal parts of seeds from each of the 200 selected plants were bulked to form the C1 modified mass selection; alter establishing, the same procedure was adopted to form the C2 generation. The cycles 1 and 2 of half-sib families and modified mass selection along with the base population family were evaluated for forage and seed yields. The realized gains from modified mass selection were 6.03 and 9.51 % for fresh forage yield, 5.57 and 10.86 % for protein yield and 13.23 and 16.19 % for seed yield in cycles 1 and 2, respectively, over the base population. The realized gain from family selection in cycle 2 as a percentage of the base population mean amounted to 11.32, 13.35, 17.47 and 3.15 % for forage, protein, and seed yield and seed index, respectively. The broad sense heritability, as estimated from the variance components was 89.63, 63.03, and 76.67 to for dry forage, seed yield and seed index, respectively. Although, all these live traits (fresh, dry, protein, and seed yield and seed index) had positive correlation with each other, weak correlations were found between seed yield and forage yields. Furthermore, close associations were found among forage yield traits. [ABSTRACT FROM AUTHOR]

The objectives of the study were to estimate the genetic components of variance, predict the response to selection and to evaluate observed response to selection using two populations namely, PSB 7 and NB 3, of pearl millet (Pennisetum americanum, [L,] Leeks). The observed response was studied using four methods of selection based on single and multitrait criteria in three types of families, namely S1 half-sib (HS) and full-sib (FS) families. One hundred S1, HS and FS families each were developed in PSB 7 and PSB 3. Plants within a population were pollinated with bulk pollen of other population to develop HS families. Crosses were made between a pair of plants using one plant from each of the two populations to develop PS families. Data were corded on days to flower, plant height, tiller number, spike length. spike girth, seed, yield per plant and spike weight. Additive genetic variance estimates were significant for all traits. The estimates of dominance and additive × location and dominance × location interaction components were not significant, except additive × location component in PSB 7 for seed yield and spike weight. The genotypic component of variance among S1 families and S1 × location interactions were significant except S1 × location interactions in PSB 7 for days to flower, spike length and spike girth. Twenty-four strains were developed by intermating superior families identified on the basis of four selection methods in each of the six types of families. The selection methods were high seed yield (YS) per se; index selection (IS) for high tiller number and long and thick spike; truncation selection (TS) for high yield among the families having days to flower and plant height lower than the population mean: and visual selection (VS) after completion of flowering for good vigour, uniformity in plant height and good inflorescence attributes. [ABSTRACT FROM AUTHOR]

Experiments were conducted with early segregating generations of a selected narrow leaf lupin cross to determine the effectiveness of selection for yield based on alternative criteria. F[SUB2] plants were selected on the basis of seed yield and several other yield-related characters to generate separate F[SUB3] populations. Randomly selected plants from each population were grown over the summer (off-season) in a glasshouse to generate F[SUB4] populations. Analyses of relationships between F[SUB2] plant measurements and F[SUB3] progeny mean yields revealed significant correlations only for those characters with the highest heritabilities --- flowering time. 100 seed weight and harvest index. However, selection for the earliest flowering F[SUB2] plants followed by selection within this group of plants with the highest number of pod bearing branches would result in the greatest increase in F[SUB3] mean yield. The F[SUB2]-derived F[SUB2] populations with the highest seed yields were those obtained by selection for total plant dry weight, number of pod bearing branches and number of pods per plant. Improvement in commercial crop yield should therefore be obtained through selection in early generations for those characters contributing to the greatest number of pods per unit area. A scheme involving selection for early flowering and high number of pod bearing branches in the F[SUB2] combined with replicated yield tests in the F[SUB4] is proposed. [ABSTRACT FROM AUTHOR]

The breeding materials used in this study were the F[sub3], F[sub4] and F[sub5]-generations of the cross between Giza 158 × Sonora 64 (Triticum aestivum l.). The objective of this study was to compare the relative merits of Smith-Hazel, desired gain selection indices, independent culling levels and single trait selection in improving grain yield, heading date and several agronomic traits. Highly significant differences among F[sub3] families and a satisfactory genotypic coefficient of variability were obtained for all the traits studied. The genotypic correlations were high between yield and each of spike weight, kernels/spike and spikes/plant, intermediate with 1000 kernel weight and very low with heading date, plant height and spike length. After two cycles of selection, the results of the gains realized indicated that the most effective method for improving yield was the Smith-hazel index (SH[sub7]) of seven traits followed by the desired gain index of seven traits (DG[sub7]), SH[sub5], independent culling levels, DG[sub5] and direct selection for grain yield/plant. Direct selection for heading date, plant height and spike length was the best method for improving these traits, but undesirable correlated responses in the other traits were obtained. [ABSTRACT FROM AUTHOR]

Selection of superior host genotypes in symbiosis with native Bradyrhizobium has been suggested as a means of increasing nitrogen fixation in peanut (Arachis hypogaea L.). In this study progeny from a cross of cultivars 'Florigiant' and 'Florunner' intermated twice and selected for yield formed the base population. The 44 selected S[subz,1] families, 'Florigiant' and Florunner' were evaluated at two sampling dates at each of two locations for traits indicative of nitrogen fixation. Five families were selected in each of four selection groups - high hand low acetylene reduction and high and low plant weight. Selected families were retested in a second year and intermated. S[subz,1] progeny within each selection group were bulked and evaluated for nitrogen-fixing characteristics at two sampling dates at two locations. After intermating, the mean of the high acetylene reduction group, 62.9 μmoles C[sub2]H[sub4]/plant/hr, was significantly greater than the mean of the low acetylene reduction group, 52.5 μmoles [sub2]H[sub4]/plant/hr, and of the mid-parent, 55.8 μmoles [sub2]H[sub4]/plant/hr. The associated estimate of realized heritability was 055 ± .08 indicating the response to selection was approximately half the selection differential and that the distinction between families selected for high and low acetylene reduction was maintained after intermating. However, the realized heritability estimate obtained from the means of the base population and the selected families inbred one generation was .14 ± .06 indicating a failure to maintain distinct groups after one generation selection for enhanced N[sub2] fixation is, therefore, doubtful in this population. Selection based on plant weight was not effective. A significant difference in the plant weight means of the high hand low plant weight groups was not detected when selections were retested or after intermating. [ABSTRACT FROM AUTHOR]

Handcrosses were made in a factorial manner with 24 Vicia faba inbred lines in three sets, each between four male and four female parents. The resulting 48 hybrids, their parental inbreds and three commercial varieties were grown in performance trials during the years 1985-87 with three replications at one location. Yield and yield components were recorded on single plant basis. The average superiority of the hybrids above the control varieties was 26 % in plant yield. The best crosses outyielded the controls by more than 50 %. However, a few inbred lines also reached the yield level of the controls. The average heterosis was significant for all characters except for maturity date. In plant yield the average heterosis was 75 %, ranging between 34 % and 148 % in the various cross combinations. The highest average heterosis of 110 % was observed in yield at the lateral stems. In all characters the best inbreds were superior to the lower hybrids and in some characters even equal to the average of the hybrids. A strong positive relationship was found for all characters between hybrid performance and midparent value and between the per se performance of the inbreds and their general combining ability. Genotypic differences between the hybrids as well as between the inbreds were highly significant. Most of the variability between the hybrids in all characters were attributed to general combining ability with only little evidence for specific combining ability. In the discussion the results are evaluated according to the choice of the breeding category of the partial allogamous faba bean species. [ABSTRACT FROM AUTHOR]

High performing V. faba genotypes have been successfully selected using an approach that combines the univariate and multivariate biometrical analyses of F[SUB1]s from two complete 7 × 7 and 9 × 9 diallel cross experiments. The method used in the analyses included canonical analysis and cluster analysis of the phenotypic and genetic variance-covariance matrices. All analyses have been applied to the yield and yield components. Results of analyses provided information on the unit of selection, the selection criteria, and the selection procedure. The choice of an array of F[SUB1]s seems to be more efficient than the choice of a single F[SUB1]. Among the yield components studied, 100-seed weight is the most important selection, criterion which can improve yield most efficiently. The detected importance of the nonadditive genetic effects is that selection after intercrossing random plants from the mixed F[SUB1] progenies of the same array is expected to be more effective than selection after selling. [ABSTRACT FROM AUTHOR]

Field and controlled environment studies revealed significant genetic variation in nitrogen uptake and utilization within an F2 population of spring rape. However, narrow-sense heritabilities of measures of these characters were consistently low, and were less than that of seed yield in the field. Flowering time in the field had a much higher heritability than seed yield and the expected yield response to selection for this character was 34 % greater than the response to direct yield selection. An even greater yield response was expected from selection based on an index combining measurements of flowering time, nitrogen uptake and nitrogen utilization. The expected yield response to selection for an index incorporating these characters and seed yield was 81 % greater than that for direct yield selection. [ABSTRACT FROM AUTHOR]

Two landrace accessions of amaranth, UCC 192 (Amaranthu cruentus) and UCH213 (A. hypochondriacus), were used in a mass selection experiment; five per cent of the tallest and highest yielding plants in both popuIations were selected for three cycles. Selection gain was largest in the first cycle for both traits. Realized heritability estimates for plant height were 0.22 in the UCC 192 population and 0.49 in UCH 213, and 0.09 in both populations for yield. The results supported earlier findings for the existence of genetic variability within amaranth landrace populations. [ABSTRACT FROM AUTHOR]

Inter-generation correlations between F2-F3, F––F4 and F3–F4 in six crosses of chickpea were calculated by using individual plant/progeny means. In general, correlation values in case of plant height, seeds per pod and 100-seed weight were higher between F3 and F4 than those between F2 and F3 and F2 and F4. However, inter-generation correlations were mostly nonsignificant in case of pods per plant and grain yield. These results clearly show that selection in F3 can be fruitful for seeds per pod and 100-seed weight. However, selection for pods per plant and grain yield in early generations may not show any relationship with later generation performance for these traits. [ABSTRACT FROM AUTHOR]

Phenotypic selection under spaced planting is frequently used in forage species. This study aimed to compare the predicted efficiency of direct selection for lucerne seed or forage yield under dense planting with indirect selection based on the same traits or seed yield components evaluated under spaced planting. Sixteen genotypes randomly chosen from a representative sample of locally adapted germplasm were grown for two years as individual clones spaced at 75 cm (density =1.78 plants/m2) and in dense plots formed by one row of four clones spaced at 10 cm (density = 50 plants/m2) using a randomized complete block design with three replications. Indirect selection based on seed yield under spaced planting was just 19% less efficient than direct selection, owing to moderate genetic correlation between plant densities ( rg = 0.66) and somewhat higher broad-sense heritability under spaced planting than under dense planting. The relative efficiency of indirect selection for seed yield in density based on individual seed yield components under spaced planting ranged from modest to very low and was always below 45%. The efficiency of indirect selection for dry matter yield based on yield response under spaced planting was moderate for total yield (64%) and very low for second-year yield (32%) relative to direct selection. [ABSTRACT FROM AUTHOR]

Selection and random genetic drift are the main forces affecting selection response in recurrent selection (RS) programmes. The correct assessment of both forces allows a better comparison of the efficiency of different RS schemes. The objective of this study was to extend the population diallel analysis proposed by Hammond and Gardner in 1974 and the model proposed by Smith in 1979 with full consideration of inbreeding depression due to random genetic drift. The effect of random genetic drift is expected to be large, particularly in studies with many selection cycles and/or high rates of inbreeding. Therefore, the extension of the population diallel allows a better assessment of the selection response in RS programmes. [ABSTRACT FROM AUTHOR]

Abstract Reciprocal crosses may have significantly distinct performances regarding tuber characteristics in potato, suggesting the importance of cytoplasmic effects in this crop. The selection of parents for true potato seed breeding therefore needs to consider this potential effect when determining the direction of a cross. The aim of this research was to determine whether a broad-based true potato seed breeding population, developed at the Centro Internacional de la Papa, could be affected by cytoplasmic effects in the short-day length environments of the tropics. Two random sets of reciprocal biparental crosses were included in the first set of experiments, which were grown in two contrasting Peruvian locations. Only one out of 14 reciprocal crosses showed significantly distinct performance for tuber yield and tuber set. In the second set, only one of each of the 12 reciprocal crosses had distinct performance for vine earliness, days to flowering and flowering intensity, but four of the reciprocal crosses in the second set showed distinct pollen production. The results suggest that cytoplasmic effects in this breeding population are more important for reproductive characteristics such as pollen production than for tuber yield. This finding is not surprising because male sterility in potato results from the interaction between sensitive cytoplasm and dominant nuclear genes. [ABSTRACT FROM AUTHOR]

Cocoa breeding seeks to increase the yield by area unit. In this context, one must consider the resistance to Phytophthora disease, the most serious one in cocoa culture. Thus, herein two traits were used: yield, i.e. number of healthy pods obtained in 7 years and Phytophthora resistance, estimated by pod rot rate. A combined individual-family selection is proposed on the basis of the total genetic value in order to spread clonal material. This selection method was applied in a 6 × 6 diallel scheme in Cameroon. The heritability of Phytophthora resistance (near 0.2) was higher than for yield (0.13). A selection index was constructed to obtain good genetic gains on each of the two traits (yield and Phytophthora resistance). To improve prediction of genetic values, a third trait, potential yield, was used. With the chosen weight, the expected genetic gain was about 35% for resistance at 1% level of selection. This selection was applied and a confirmation trial is being established with the selected trees. [ABSTRACT FROM AUTHOR]