General Combining Ability For Yield Research Articles

Use of molecular marker diversity to increase forage yield in timothy (Phleum pratense L.)

AbstractMolecular marker technologies may provide a tool to overcome the forage yield plateau in timothy (Phleum pratense L.). Therefore, a study was designed to investigate the relationship between marker‐based genetic distance (GD) estimates and yield. Genetic distances were estimated using Dice coefficients framed by 28 simple sequence repeat markers. In Experiment 1, parents with high general combining ability (GCA) from two contrasting first‐generation synthetic strains (exhibiting high and low yields) were compared. Average GDs of each strain were 0.74 (high) and 0.68 (low). These differences indicated that GD may be partially the basis for contrasting yields. In Experiment 2, GDs among 40 parents of a polycross were used for calculating general genetic distance (GGD), which is indicative of their allelic complementation. Analyses revealed a significant (P < 0.01) moderate correlation (r) between GGD and GCA for yield (r = 0.45) and a significant (P < 0.01) residual mean square for the regression of yield on GGD, suggesting that considerable non‐additive effects were associated with GCA. The results are indicative of the potential use of GD estimation for yield improvement in timothy.

Use of GGE biplot methodology for genetic analysis of yield and related traits in melon (Cucumis melo L.)

Dehghani, H., Feyzian, E., Jalali, M., Rezai, A. and Dane, F. 2012. Use of GGE biplot methodology for genetic analysis of yield and related traits in melon (Cucumis melo L.). Can. J. Plant Sci. 92 :7 7� 85. A complete diallel cross experiment of six local Iranian melon populations (Eyvanaki, Abasali, Tashkandi, Hose-sorkh, Mashhadi and Mirpanji) and one cultivar (Ananasi) was conducted. Fruit number, average weight per fruit, yield and acceptable yield were re-evaluated using GGE biplot methodology. The two principal components of biplot explained 70, 58, 86 and 88% of total observed variation for yield, acceptable yield, average weight per fruit and fruit number per plant, respectively. Mirpanji had the highest GCA for yield, acceptable yield and average weight per fruit, but the highest negative GCA for fruit number per plant. Abasali showed the highest positive GCA for fruit number. Biplot analysis allowed a rapid and effective overview of general combining ability (GCA) and specific combining ability (SCA) effects of the populations, their performance in crosses, as well as grouping patterns of similar genotypes.

Use of single cross hybrids to measure heterosis for yield in diverse lucerne genotypes growing in a subtropical environment

Yield stagnation is a worldwide issue for lucerne breeding, and reasons for the yield plateau include emphasis on disease and pest resistance and not yield per se, and the broad-based synthetic approach to lucerne breeding which is generally used. In this study, an incomplete diallel was made between 50 lucerne clones with representatives from the 3 hypothetical heterotic groups, Medicago sativa subsp. falcata, dormant subsp. sativa, and non-dormant subsp. sativa. Male sterile clones were also included among the dormant group. The single crosses were compared in a subtropical environment at Gatton, Queensland, for yield and other relevant agronomic traits against the adapted synthetics Sequel (dormancy group 9), UQL-1 (group 7), and a highly non-dormant experimental synthetic (line B) derived by introgression of highly non-dormant Arabian germplasm into Sequel. The trial was conducted in a known low-disease-pressure site for Phytophthora root rot, and anthracnose was managed by regular application of prophylactic treatments. The best single cross outyielded Sequel and line B by 13% and 8%, respectively. In this environment, yield was very much influenced by the dormancy group of the test material, with group 9 material significantly outyielding more dormant material. General combining ability (GCA) effects were more important determinants of cumulative yields than specific combining ability (SCA) effects, with these effects being significantly greater than zero for only 4 of the 236 crosses tested over the 15-month period. Similarly, GCA effects were more important for determining autumn height and persistence. The research did identify a small number of clones with good GCA for yield per se, and it would appear that future work should focus on developing more narrow-based synthetics with 4–8 parents which have been selected on the basis of their GCA for yield per se. DNA markers would appear to have a role in selecting clones carrying multiple resistances, and in establishing marker pedigrees for high-yielding parental clones such as we have identified, which can be traced through subsequent generations of recurrent selection in cultivar improvement.

Genetic Parameter Estimates for Five Traits in Male Hop Accessions: A Preliminary Study

Much information on hop (Humulus lupulus) production and maintenance exists but little is known about the genetics of specific traits. The objective of this study was to determine general combining ability (GCA) and genetic correlations (rg) for five traits in six male hop accessions crossed to 14 different female accessions. Data for the study were extracted from USDA hop breeding records covering the past 25 years. The analysis was performed with females nested within males across four replicates (years). We observed significant (P ≤ 0.05) GCA for all traits, with male 21361M exhibiting the highest GCA for yield (paternal half-sib avg. = 1,934 kg/ha); 21268M exhibiting the highest GCA for α-acid levels (paternal half-sib avg. = 7.20%), 19046M exhibiting the highest GCA for β-acid levels (paternal half-sib avg. = 6.54%), 64035M exhibiting the most desirable cohumulone (COH) levels relative to total α-acids (paternal half-sib avg. = 24.1%), and 64037M exhibiting the most desirable value for hop storage index (HSI) (paternal half-sib avg. = 0.246). Significant positive genetic correlations were observed between COH and yield (0.492) and between COH and HSI (0.763). Significant negative genetic correlations were observed between α-acid and β-acid levels (–0.743) and β-acid levels and HSI (–0.788). The results of this study, while preliminary, provide valuable information for hop breeders on choice of males for specific traits and a selection protocol guide for multiple trait selection.

Heterosis and combining ability effects on cotton. I. Combining ability

Combining ability for a number of yield and quality attributes of cultivated cotton (Gossypium) was studied in two diallel experiments under high-yielding conditions in northern Australia. The first diallel comprised nine G. hirsutum parents of North American and African origin, the second diallel of thirteen parents besides American and African cultivars also included an Indian line, some Australian lines and an American G. barbadense cultivar. Each set of hybrids was grown as a half-diallel (plus the parents), first as a plant crop and then as a ratoon crop in the following season. Generally variation due to general combining ability (GCA) was significant and substantial for all traits, although specific combining ability (SCA) was also significant. GCA was shown to be closely associated with parental performance per se which may, therefore, be used with good reliability in choosing parents for use in a breeding program. The plant and ratoon performances were very similar in most instances. The African cultivars together with some medium-quality American ones showed high combining ability for yield, but the best GCA for quality characters was found in the high- quality parents. The G. barbadense cultivar was exceptional in this regard, hut it had a low GCA for yield, and there are other technical problems associated in establishing good inbred lines from hybrids between the two cultivated tetraploid species. Genotypic correlations between a pair of traits were usually similar for the plant and its respective ratoon crop, but often quite different for the two diallel combinations. In both populations selection for increased lint yield would tend to be accompanied by adverse changes in some other important characteristics.