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St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a popular southern turfgrass with poor cold tolerance. The objective of this study was to evaluate the inheritance of cold tolerance in St. Augustinegrass. Eight diploid genotypes were chosen as parents for a complete diallel mating with reciprocals. Three replications of each single cross and the parents were planted in a field trial at Mississippi State, MS, and winter survival was evaluated from 1994 to 1996. Differential thermal analysis was used to predict lethal low temperatures for parents and single cross progenies. Lethal temperatures of parental genotypes ranged from -3.65 to -5.25°C. Combining ability analysis revealed that general combining ability was the largest source of variation for lethal temperature and winter survival. Specific combining ability was significant only for winter survival in 1996. Redprocal effects were significant for winter survival each year. Estimated narrow sense heritability was 0.58 for lethal temperature and ranged from 0.70 to 0.98 for winter survival. Lethal temperatures were significantly correlated to winter survival of each year.

The recent conversion of primitive cotton (Gossypium hirsutum L.) stocks to the day-neutral flowering habit has effectively made these accessions readily available for direct use in plant breeding programs. Genetic analysis of these accessions would be useful in ascertaining parental material for improvement of specific traits. The objective of this study was to estimate genetic variances for 13 yield, fiber, and other agronomic traits in 79 accessions and 11 cultivars. A minimum norm quadratic unbiased estimation (MINQUE) method was used for estimating genetic variance components and an adjusted unbiased prediction method for predicting genetic effects. Additive x environment interaction variances were significant for lint yield and node of first fruiting branch. The additive variance components made relatively high contributions to the phenotypic variances for lint percentage and boll size. Additive variances were relatively low for other traits. Narrow-sense heritabilities ranged from 8 to 50% for the traits studied. The proportion of accessions displaying significant, positive effects ranged from 12.7% for 50% span length to 30.4% for lint percentage and 2.5 span length. Positive additive effects for yield, lint percentage, and fiber traits except micronaire and negative effects for N1FB, NOMS, and plant height could be considered favorable effects. Although 16 of the primitive accessions showed significant positive additive effects for lint yield, only MDN-74 and MDN-101could be predicted to produce stronger fiber, as well as higher lint yield and lint percentage. Results indicate that many primitive accessions may be used in crosses with commercial cultivars without serious loss of agronomic potential in the progeny.

Pearl millet [Pennisetum glaucum (L.) R. Br.] production in semi-arid areas is primarily limited by poor seedling emergence and poor stands, which result in low yields. The objectives of this study were to measure selection response for seedling root length and coleoptile length, and to compare the effectiveness of greenhouse and laboratory screening procedures for these traits. Divergent phenotypic recurrent selection for seedling root length and coleoptile length was practiced within each of two populations, Tift #2 S1 (TIFT2) and Nebraska Early Dwarf Synthetic (NPM2). The parental and respective selected populations were evaluated in sand in the greenhouse and in paper germination towels in the laboratory. Significant genetic variation was found for seedling root length in the genetically diverse TIFT2 population, but not in the NPM2 population. The TIFT2 subpopulation selected for long seedling root length in sand had significantly longer seedling root length than the subpopulation selected for short seedling root length. Genetic variation for coleoptile length was high in both populations. There were significant responses to selection in the TIFT2 population for seedling root length evaluated in sand and coleoptile length evaluated in germination towels. Selection response for long seedling root length in the TIFT2 population was greater when root length was evaluated in sand than when evaluated in germination towels. Realized heritabilities of TIFT2 subpopulations selected for long and short seedling root length in sand were 0.23 and 0.29, respectively. Realized heritabilities of TIFT2 populations selected for long and short seedling root length in paper germination towels were 0.0 and 0.33, respectively. Sand was a better selection medium than germination towels. Realized heritabilities for long and short coleoptile length were 0.21 and 0.55, respectively, for the TIFT2 population. For the NPM2 population, realized heritabilities for long and short seedling root length were 0.60 and 0.0, respectively, in sand and 0.0 and 0.26, respectively, in germination towels. Realized heritabilities for long and short coleoptile length were 0.0 and 0.90, respectively, for the NPM2 population. Pearl millet coleoptile and seedling root lengths were heritable and further selection gains should be possible.

Although pest-resistant cotton (Gossypuim hirsutum L.) germplasm is available, it is generally not equal to adapted cultivars and other elite germplasm in yield. Cotton F 2 hybrids could provide a means to combine beneficial traits of high-yielding adapted cultivar (elite) germplasm with those of pest-resistant germplasms. In the F 2 heterosis and combining ability were studied for lint yield and the primary yield component boll number as well as for the secondary yield components of lint percentage and boll weight (.)

Estimates of combining ability and heterosis for fiber properties among pest-resistant cotton (Gossypium hirsutum L.) gene pools and cultivars are necessary for efficient F 2 hybrid development. Four cultivars were crossed as female with 16 pest-resistant germplasm lines in a North Carolina Design II to evaluate combining ability and potential heterosis of F 2 hybrids for six fiber characteristics. The 20 parents and 64 F 2 hybrids were evaluated in four environments at Mississippi State, MS (.)

Anthesis date is the major factor controlling distribution of forage yield and quality of annual ryegrass (Lolium multiflorum Lam.) in the spring. This study was initiated to evaluate variation and selection response for anthesis date and to measure correlated responses in annual ryegrass. Four annual ryegrass cultivars were evaluated for heading date, anthesis date, spikelets per spike, and florets per spikelet over 3 yr in the field at Mississippi State, MS. Only spikelets per spike and florets per spikelet, showed significant cultivar × year interactions (.)

Date of anthesis is the major factor controlling the seasonal distribution of forage yield and quality in tall fescue (Festuca arundinacea Schreb.). The objective of this experiment was to evaluate the response to divergent selection for anthesis date in three cultivars of tall fescue that differ for date of anthesis. Three cultivars, Fawn, Alta, and Kentucky 31, were evaluated for date of anthesis in the field from 1981 to 1983. There was a strong juvenile requirement for some genotypes within each cultivar; however, this tended to be more of a problem with the earlier-maturing cultivars, Fawn and Alta. Correlations of establishment year data (1981) with mature plant data (1982 and 1983) were low; consequently, establishement year data were not utilized in selecting for anthesis date

(...) We present COTMAP, a technique in which the primary fruiting sites (first and second sympodial positions) are individually mapped and fruit on remaining sites are considered collectively. Yield variables calculated by COTMAP include total bolls, boll distribution, and boll retention in prime fruiting sites. Plant structure variables include node of first fruiting branch, number of monopodia, number of sympodia, number of effective sympodia, number of sympodia with at least two flowering positions, total number of main axis nodes, plant height, and average internode length. (...)

The southern root-knot nematode (RKN), Meloidogyne incognita (Kofoid and White) Chitwood, is a serious pest of cotton (Gossypium hirsutum L.). This study determined the combining abilities of eight cotton lines for RKN resistance. The 28 possible single crosses among the susceptible M8, the adapted resistant M-315 RNR, and the day-neutral converted primitive resistant lines M19-RNR, M25-RNR, M75-RNR, M78-RNR, M188-RNR and M487-RNR were evaluated for resistance in two greenhouse environments. Number of eggs per plant was determined on the basis of a five-pot row 40 d after planting one seed per 250-cm −3 pot 7 d after each pot was inoculated with 10000 Race 3 RKN eggs. Since the relative plant resistance to RKN is inversely proportional to RKN reproduction, negative combining ability effects indicated resistance. The general combining ability (CGA) effects were highest for M-315 RNR. Specific combining ability (SCA) effects of six hybrids were significant in both environments. The SCA effects for M8 crossed with M-315 RNR or M75-RNR were negative, while the SCA effect of M-315 RNR with M75-RNR was positive. Although M-315 RNR and M75-RNR had the highest GCA, the two lines combined poorly together suggesting that they may have the same resistance genes. The SCA effects for M8 crossed with M78-RNR and M188-RNR were positive, while the SCA effect of M78-RNR with M188-RNR was negative. This suggests that M78-RNR and M188-RNR may have different resistance genes that combined to produce progeny more resistant than predicted from the GCA effects

Fifteen single-crosses of a six-parent diallel of tall fescue (Festuca arundinacae, Schreb.) were evaluated for perloline concentration, N content, and in vitro digestibility. The crosses were planted at Corvallis, Oregon, and Columbia, Missouri, and harvested on 8 Apr. and 22 Sept. 1975 at Corvallis and on 16 Oct. 1975 at Columbia. The data were analyzed as two experiments. Experiment I consisted of the two harvests at Corvallis and experiment II consisted of the harvests of 22 September at Corvallis and 16 October at Columbia. Both experiments were analyzed for perloline concentration and N content, but only experiment II was analyzed for in vitro digestibility. General (GCA) and specific combining ability (SCA) were significant sources of variation for perloline concentration. SCA indicated some nonadditive gene action for perloline concentration. There were differences between environments as well as genotype ✕ environment interactions in both experiments. GCA was a significant source of variation for nitrogen content in each experiment. However, environmental differences were larger than genetic differences. No differences were found among the crosses for in vitro digestibility, but there was a rather large difference between the two locations. It appeared that digestibility could be improved more by management than by selection in this population.