General Combining Ability (general + combining_ability)

Distribution by Scientific Domains


Selected Abstracts


Genetic analysis of tocopherol content and composition in winter rapeseed

PLANT BREEDING, Issue 2 2001
F. D. Goffman
Abstract The improvement of the nutritional value and the stability properties of rapeseed oil is partly hindered by the lack of information on the genetic control of tocopherols. The objectives of this investigation were to characterize the inheritance of tocopherols by using two factorial mating designs (North Carolina Design II, NCII). The first (NCII -A) was produced with two sets of nine parents each, one selected for high and the other for low total tocopherol contents. In the second (NCII -B), each set consisted of six parents, which were either high or low for the ,/,-tocopherol ratio. Parents and F1 hybrids from both experiments were tested under field conditions in 1998 and 1999 using a completely randomized design with two replications. Only small differences were detected between mean values of parents and F1 hybrids. General combining ability (GCA) variation in both experiments was highly significant (P < 0.01) for all tocopherol traits. Significant specific combining ability (SCA) effects were only detected for a-tocopherol in NCIIA and therefore for the ,-/,-tocopherol ratio. These results indicate that tocopherol contents and composition are controlled mainly by genes with additive effects. Interactions of F1 hybrids and GCA effects with the environment were significant for only tocopherol contents and not for tocopherol composition. [source]


Genetic Analysis of the Latent Period of Stripe Rust in Wheat Seedlings

JOURNAL OF PHYTOPATHOLOGY, Issue 6 2004
H. Dehghani
Abstract Genetics of slow-rusting resistance to yellow rust (Puccinia striiformis f.sp. tritici) was studied by a half-diallel design using six wheat varieties, Tiritea (susceptible), Tancred, Kotare, Otane, Karamu, and Briscard. The parents and 15 F1 progenies were evaluated in the greenhouse by three pathotypes 7E18A,, 38E0A+, and 134E134A+. The latent period was measured as the number of days from inoculation to the appearance of the first pustule. For each pathotype a randomized complete block design was used and data were analysed by methods of Griffing and Hayman. The range of average degree of dominance was from complete dominance to over-dominance. Positive and negative degrees of dominance were observed for each pathotype that showed the reversal of dominance. Analysis of variance showed the importance of both additive and dominance effects in controlling the latent period. Broad-sense heritabilities were 0.99 and narrow-sense heritabilities ranged from 0.85 to 0.94. Briscard and Karamu for the pathotypes 38E0A+ and 134E134A+, Kotare for the pathotype 7E18A, and Tancred for the pathotype 38E0A+ had significant and positive general combining ability (GCA) (more resistance) for latent period. The crosses of Kotare with Tancred, Briscard and Karamu indicated the highest and positive specific combining ability (SCA) for the pathotype 7E18A,. Significant additive genetic component and moderate narrow-sense heritability indicate the possibility of improving for longer latent period of stripe rust in breeding programmes. [source]


Top-cross vs. poly-cross as alternative to test-cross for estimating the general combining ability in potato

PLANT BREEDING, Issue 5 2008
J. Gopal
Abstract Test-crosses for estimating combining ability in potato although useful are difficult to make being labour intensive and time consuming, and due to the problem of sterility. The objective of the present study was to test methods for estimating general combining ability (GCA) of parents based on fewer matings. The GCA of 12 females estimated based on matings with specific single testers (top-cross) and three types of bulk pollen (poly-cross) were compared with those estimated by 72 (12 × 6) test-crosses, using common testers in three types of matings. The study was conducted for 2 years at each of the two locations representing short-days subtropical conditions in plains and long-days temperate conditions in hills of India. Analysis of variance of test-crosses showed that both general and specific combining ability effects were important for tuber yield, late blight resistance as well as general impression, the characters studied. Correlation coefficients among three types of matings showed that bulk pollen matings had poor effectiveness in predicting the GCA of the females, whereas matings with selected individual testers resulted in GCA estimates similar to those based on six testers. Thus use of top-cross involving selected tester could substantially reduce the number of matings required for estimating the GCA. Among the six testers used, the tester CFK69.1 could estimate the GCA of the females with reasonably high accuracy both for tuber yield and general impression, and ,Tobique' for reaction to late blight. [source]


Trends in genetic variance components during 30 years of hybrid maize breeding at the University of Hohenheim

PLANT BREEDING, Issue 5 2008
S. Fischer
Abstract The ratio of variance due to specific vs. general combining ability (GCA) (,2SCA:,2GCA) is of central importance for predicting hybrid performance from GCA effects. The objectives of our study were to (1) analyse the changes in estimates of ,2GCA, ,2SCA and their ratio during 30 years of hybrid maize breeding and (2) compare the observed trends in genetic variances with those expected under a simple genetic model. We analysed multilocation yield trials based on the North Carolina Design II conducted in the maize breeding programme of the University of Hohenheim from 1975 to 2004 for grain yield (GY) and dry matter content (DMC). GY showed a significant (P < 0.05) annual increase of 0.17 Mg/ha, but no linear trend was found for DMC. Since the beginning of hybrid breeding at the University of Hohenheim, the sum of estimates of ,2GCA of the flint and dent heterotic groups were higher than the estimates of their ,2SCA. This predominance did not change with ongoing inter-population improvement. Consequently, superior hybrids can be identified and selected mainly based on their prediction from GCA effects. [source]