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The adoption of reduced height (Rht) genes has dramatically enhanced yield potential of cereal crops. The semi-dwarfing gene uzu in barley is widely used in East Asia. Its value as an Rht gene in the warm and dry environments in Australia was evaluated in this study. In addition to plant height, this gene showed significant effects on a wide range of characteristics. It reduced the overall plant height by an average of 33.7 % with the most significant reduction occurred on the internode below the peduncle. The gene reduces spike length by 31.6 % and grain weight by 18.8 %. It increases grain number per spike by 5.6 % and grain density by 51.8 %. Seedling assays suggested that the effects of this gene became more significant with increased temperature. It reduced coleoptile and seedling length by 19.4 % and 15.1 %, respectively at 7 °C. The reduction increased to 61 % and 46.7 %, respectively, at 25 °C. These results indicated that the uzu gene could have limited values in some high temperature and drought prone environments.

Maize (Zea mays L.) is severely affected by drought and this challenge is expected to worsen with climate change. One of the most promising solutions is breeding for drought tolerance that requires the identification of sources of drought tolerance. Eighteen maize populations from the Algerian Sahara were evaluated along with three European and two American checks in two Algerian locations under drought and control conditions. Under drought conditions, Algerian populations had large variability for most traits and the populations BTM and LOM out yielded most checks. The ratio yield under drought/yield under control conditions was 65.90, 65.33, and 53.23% for BTM, TAO and LOM, respectively. These populations maintained also yield components such as grain weight, ear length, number of kernel rows, ears per plant, and leaf area under stress conditions; furthermore, they have reduced leaf rolling. TAO and BTM presented the highest relative water content, and LOM had the highest proline content. Algerian populations can be considered as a novel source of favorable alleles for drought tolerance and show a wide variety of mechanisms of response to drought.

Made available in DSpace on 2018-12-11T17:33:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Grain yield (GY) is a direct function of its components and these traits to being less complex and highly correlated with yield. The objectives of this study were to map Quantitative Trait Loci (QTL) for GY and its components in maize lines and GY in their testcrosses, to verify its congruence and the possibility to select testcrosses from the predict means of the lines by using markers information. Two hundred and fifty-six S1 lines derived from the cross L-08-05F × L-14-04B of tropical germplasm and the testcrosses of these lines with two testers were evaluated in six environments. The traits analysed in the lines were GY, prolificacy, ear height and diameter, number of rows per ear and kernels per row, kernel depth, grain weight, and GY in the testcrosses. QTL were mapped in the lines and in testcrosses and the predicted means of the lines were computed based on QTL effects and in all markers of the genome. Few QTL detected for GY and its components in the lines were coincident with the QTL for yield in testcrosses. The correlations between the predicted means of the lines and the phenotypic means of the testcrosses were not significant or low for most of the components. The coincidence of the selected lines and testcrosses was very low for all traits and the results were similar for both testcrosses and intensity. It is not possible to select testcrosses by using GY or its components information from the lines, even with the aid of molecular markers. Department of Plant Production School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp) Embrapa Beef Cattle Plant Production Group Department of Genetics University of São Paulo, P.O. Box 83 Department of Plant Production School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp) CNPq: 140964/2006-1

Dissection of qTGW1.2, a minor quantitative trait locus (QTL) for 1,000-grain weight located on the long arm of rice chromosome 1, was reported here. Six sets of near isogenic lines (NILs) were developed from six BC2F9 plants of the indica rice cross Zhenshan 973/Milyang 46, respectively, segregated in a sequential order covering the region for qTGW1.2. They were tested for 1,000-grain weight, grain length, grain width and heading date. The SAS procedure GLM was used to analyze the phenotype differences among three genotypic groups in each NIL set. The qTGW1.2 was separated into three QTLs, including qTGW1.2a located in the 933.6 kb interval RM11730–RM11762, qTGW1.2b in the 418.8 kb interval RM11781–RM11800, and qTGW1.2c in the 2.1 Mb interval RM11800–RM11885. While qTGW1.2a and qTGW1.2c displayed the genetic action mode of negatively partial dominance, qTGW1.2b appeared to have a positively dominance effect as large as its additive effect. In addition, the effects of the three QTLs were consistently detected in different NIL sets. It was also shown that the effects of qTGW1.2a and qTGW1.2b on grain weight were related more to grain length than grain width, and qTGW1.2c related more to grain width than grain length. Our results indicate that the effects of minor QTLs could be steadily detected in a highly isogenic background and suggest that dominance effects of minor QTLs might play an important role in the genetic control of heterosis in rice.

Common wheat is unique in providing a large number of diverse end-products, including chapati, biscuits, bread and noodles. Grain weight and other grain traits contribute to grain yield and milling quality. Many earlier QTL studies reported at least 332 QTLs for grain traits including grain weight. We conducted a QTL analysis (composite interval mapping) of grain traits using a set of 92 recombinant inbred lines (RILs) derived from a cross between Rye Selection 111 (superior grain traits) and Chinese Spring (inferior grain traits). Forty-five QTLs for six grain traits, on 19 of the 21 chromosomes (except 2D and 3D) were identified. Nineteen of these QTLs, each for 2–3 traits were located on six chromosomes (2A, 3B, 6B, 6D, 7A and 7D). The pleiotropic nature or tight linkage of QTLs controlling different correlated traits (except the one on 6DS) was confirmed by joint MCIM. Meta-QTL (M-QTL) analysis of grain traits (including grain weight) was conducted using earlier reported QTL results (including QTLs reported in the present study). From this analysis, 23 M-QTLs were identified on eight chromosomes. These results were compared with those of our current QTL analysis and previous studies; three M-QTLs were identified as relatively more important for molecular breeding and will facilitate further work on genetic architecture and cloning of QTLs for grain traits including grain weight.

Grain size is one of the three productivity related traits in rice and hence a major target for genetic improvement. Since understanding genetic variation in grain size between Basmati and indica genotypes is important for rice improvement, a recombinant inbred population was developed from a traditional aromatic cultivar ‘Basmati 370’ and a non-aromatic indica genotype ‘IRBB60’. This population was phenotyped in two locations for grain length (GL), grain breadth (GB), GL/GB ratio (LBR) and grain weight (GW). Though the RIL population reported in the current study exhibited segregation distortion (SD) for 54 % of the markers, they were utilized in analysis using an appropriate statistical package, PROC QTL in the SAS environment. Interval mapping revealed a total of 15 QTLs for GL, seven for GB, 15 for LBR and two for GW. Among them 13 were not reported earlier and thus novel. For a known major QTL identified in the study, GW8 for GB, a PCR based functional marker was designed and validated. This is the first report wherein a very high proportion of markers (>50 %) exhibiting SD have been successfully used for QTL mapping.

The objective of this investigation was to check if epistasis is present in Andean × Mesoamerican beans crosses using triple test cross (TTC) method. The parents of the segregating population were Carioca–MG (Mesoamerican) and BRS Radiante (Andean). In July 2005, F2 progenies (backcrossed with the parents and F1 generation) were evaluated at two locations for three characters: number of pods plant−1, number of grains plant−1 and grain weight plant−1. The presence of epistasis was detected for all yield components. In the partitioning of epistasis in additive x additive (i) and dominant x dominant (j) and dominant × additive (l) it was observed that, for the traits number of pods/plant and number of grains/plant, only epistasis of the type (j) + (l) were significant. For the trait grain mass/plant, all types of epistasis were significant.

The relationship between Hagberg falling number and grain size was investigated in field-grown winter wheat varieties. Data was obtained for all varieties included in the UK Recommended List from 1997 to 2007. Overall, a negative association was found between thousand grain weight and Hagberg falling number. The negative association was detected between varieties in all years and within varieties in the majority of cases. Detailed Recommended List data from 2001 was used to examine variation in the relationship across 19 trial sites. Again, a negative association overall with both within and between variety associations was detected. However, there were also many cases where the association was not found. The association appears to be driven by both genetic and environmental factors; however, the association is not consistent enough to indicate a direct mechanistic link across all varieties.

Twelve field experiments comparing 24 durum wheat varieties from three periods—old (

Eight malting cultivars of barley released from 1944 to 1998 in Argentina were sown in two growing seasons to evaluate the effect of breeding on malting quality. An adequate grain weight and screening percentage as in the older varieties were maintained in the recent releases. The grain protein concentration decreased in the modern cultivars together with a decreased in C-and an increased in B-hordein. These results were achieved without a clear trend through the time. Malt extract was increased by 0.054% per year in the period analysed and the most important contribution in the quality improvement was the introduction of Beka (known as a high quality cultivar released in Europe) in1966. There was not a clear trend in the breeding process to obtain more stability between years in the quality attributes, at least, in the characteristics analysed in the present study. Conversely, malt extract was less variable and this tendency was observed through the years of release of the cultivars.

Although individual grain weight is an important source of variation forgrain yield, there is still poor understanding of the causes determining finalgrain weight. Almost all studies conducted for understanding thedeterminants of grain weight have been focused on the post-anthesis period.However, there is important evidence that pre-anthesis conditions couldalso modify final grain weight. Three experiments including different sowingdates, genotypes and temperature regimes between booting and anthesis,were carried out in Argentina and Mexico to analyse the effect oftemperature and associated traits during the pre- and post-anthesis periodson grain weight under field conditions. In these experiments final grainweight could not be explained by average or maximum temperature duringthe post-anthesis period. However, average temperature between bootingand anthesis was closely related to the observed grain weight differences,probably as a consequence of the effects of this factor on carpel growth.Differences in grain weight between genotypes and grain position weresuccessfully explained by differences in carpel weight at anthesis. Theseresults suggest that our knowledge to determine grain weight could improveif the immediately pre-anthesis period conditions were taken into account.

High rough rice yields are important for the profitable production of rice (Oryza sativa L.). The value of rough rice is determined primarily by head rice (whole milled grains) and broken rice, together referred to as total milled rice. The objective of this study was to optimize selection for rough rice yield, head rice, and total milled rice using path-coefficient analysis and selection indices. Thirty-seven long grain pure lines were grown in an experiment at three Arkansas locations during 1993 and 1994. In another test, twenty-eight F1 hybrids obtained from an eight-parent half diallel of long-grain rices were grown at two locations in Arkansas during 1991. For the pure lines, path analysis revealed that rough rice yield was approximately twice as important in determining total milled rice/ha than head rice. Path analysis for the hybrids revealed that rough rice yield was an even greater component in determining total milled rice/ha. Based on yield components for hybrid rice, panicle density had the largest direct effect determining total milled rice/ha. Filled grain/panicle, grain weight, and head rice, in that order, were secondary, but positive, factors determining total milled rice/ha. A selection index for pure lines based only on selection for head rice was 19.2 percent as effective as selection for total milled rice/ha directly. When selection for total milled rice/ha was based solely on rough rice yield, selection was 82.7 percent as effective as selecting for total milled rice/ha directly. Selection to improve total milled rice/ha should concentrate on increasing both rough rice yield and head rice. Rough rice yield should receive greater priority than head rice in selection strategies.

Grain size in wheat is the most stable yield component and has a favorable effect on flour yield. To identify the chromosomes associated with the large grains of line G603-86, (grain weight over 60 mg and grain length of about 9 mm), F3 lines, extracted from F2 populations obtained from F1 monosomics of crosses between G603-86 (P1) and the monosomic set of Favorit (P2) were tested in the field. ANOVA showed significant differences among parents for grain weight and grain length, but not for grain width or the factor expressing the difference in grain form and density. Homoeologous groups had significant effects on grain weight and on all components of grain weight, while genomes were not significantly different for any of these characters. Grain weight was significantly increased by chromosomes 6D and 4A of G603-86. Grain length was significantly increased by chromosomes 4A, 4B, 2B, 3A and 1B, grain width by chromosomes 1A and 1B, and the factor form-density by chromosomes 6D and 6A. The high grain size in G603-86 results from the effects of genes located on many chromosomes which affect grain dimensions, form and density.

Two kinds of wheat hybrids with the same nuclear genotype but different cytoplasms (one with T.timopheevi cytoplasm, i.e., A/R, and the other with T.aestivum cytoplasm, i.e., B/R) were produced by two 3 × 5 incomplete diallel crosses of 3 A-lines, 3 corresponding B-lines and 5 R-lines, respectively. Experimental results did not show significant differences between the hybrids of A/R and B/R in grain filling characteristics and grain weight. The beterosis of grain weight seems mainly determined by the nuclear genotype. Although the seeds set on most A-lines were shrivelled, such a phenomenon was not found in grains set on F1. The duration of the lag period (D1) and the average grain filling rates during the linear period and the mature period (i.e., FR2 and FR3) were significantly and positively related to 1000-grain weight. It was in these factors that most hybrids displayed clear mid-parent (MP) heterosis. The amount of grain weight heterosis was not significantly related to MP value. This indicates that the grain weight heterosis of wheat hybrids will not decrease with an increase of the MP value.

Temperature is one of the most important factors affecting grain quality in the majority of cereal growing areas. It has been shown that brief periods of high temperature during grain filling can reduce grain weight and quality. However, it is not known whether breeding for increased yields has altered the sensitivity to high temperatures after flowering. Four malting barley cultivars, chosen from previous studies to represent a series of successful breeding releases in Argentina, were sown under field conditions. The high temperature treatments consisted of increasing the spike temperature by about 5 ∘C for 6 h/day (from 10 am to 4 pm) for 20 days starting nine days after flowering (DAF), or for two periods of 10 days each, between 9 to 19 DAF or from 20 to 29 DAF. In all cultivars, grain weight and screening percentages decreased significantly with the treatments. In general, the two more modern cultivars (Q. Pampa and Q. Ayelen) were more sensitive to heat stress than the older ones (Heda and Union). A similar pattern was found for malt extract. Thus it appears that breeding for higher yields has concomitantly increased sensitivity of grain weight (and yield) and quality to the episodes of high temperatures during the grain-filling period in barley.

The reactions of 233 Triticum dicoccoides acessions, collected at 10 sites in Israel and elsewhere, to infection with cultures of Erysiphe graminis tritici, were determined. The reactions indicated that the number of sources of resistance to E. graminis tritici which can be obtained from T. dicoccoides plants growing wild in Israel and elsewhere is almost unlimited. One hundred and fourteen or 49% of the accessions were resistant, and 137 or 59% of the accessions were resistant or moderately resistant to infection with four cultures of E. graminis tritici which possess the virulence genes corresponding to most of the identified resistance genes in wheat. Accessions collected at sites with marginal habitats where T. dicoccoides grows poorly and has lower grain weight, were more susceptible than were accessions collected at sites with an optimal habitat for growth of T. dicoccoides. The results agreed with those in a previous study with Hordeum spontaneum, and indicate that to obtain H. spontaneum or T. dicoccoides accessions with the highest level of resistance to the powdery mildew pathogens, plants should be collected at sites in ecological and geographic regions where those two species occupy optimum habitats and are exposed to the powdery mildew pathogens.

The triple test cross analysis in rice brought out that significant epistasis is present for most of the characters in the three crosses except for 100 grain weight in two crosses (Co 39 × Co 41) and (Co 39 × Co 40) and plant height in one cross (Co 39 × IR 20). Epistasis of ‘i’ (homozygote × heterozygote) and ‘l’ (heterozygote × heterozygote) interactions are also detected in all the three crosses. The D component was significant for all the traits in the three crosses and H was significant in cross Co 39 × Co 41 for all characters. For tiller number in cross Co 39 × IR 20 and for tiller number and 100 grain weight in cross Co 39 × Co 40, the H component was not significant. In all the crosses D component was higher than H.

The 21 intervarietal chromosome substitution lines of the cultivar Hope in Chinese Spring were used to analyse the genetic differences between the two cultivars Hope and Chinese Spring in grain protein content and grain weight.

Yield components and yield were studied in F1 barley hybrids produced by hand pollination or male sterility. Grain number exhibited only partial dominance but grain weight showed dominance or overdominance and contributed to the heterotic situation particularly in 2×6-row crosses. For the commercial exploitation of heterosis it is essential that hybrids should be found which show greater dominance for high grain number.

The effect of selection for two-seeded pods in diploid and tetraploid populations and the effect of chromosome doubling on two-seededness were studied. The material obtained was examined to find out how important two-seeded pods are for seed set, grain weight and seed yield.