Diallel analysis of the time to heading in spring barley

SASHAYDIALL: A SAS Program for Hayman's Diallel Analysis

Different methods of diallel crossing are commonly used in plant breeding. The diallel cross analysis method proposed by Hayman is particularly useful because it provides information, among others, on additive and dominance effects of genes, average degree of dominance, proportion of dominance, direction of dominance, distribution of genes, maternal and reciprocal effects, number of groups of genes that control a trait and exhibit dominance, ratio of dominant to recessive alleles in all the parents, and broad-sense and narrow-sense heritability. In this paper, we fully describe a SAS-based software SASHAYDIALL for performing a complete diallel cross analysis based on Hayman's model with or without reciprocals. We demonstrate the use of SASHAYDIALL with two data sets; one is a published diallel cross data set with reciprocals in cabbage (Brassica oleracea L.), and the second is a data set from a multilocation diallel cross trial in maize (Zea mays L.) without reciprocals. With SASHAYDIALL, diallel experiments conducted in single sites can be analyzed to estimate various genetic parameters, and this analysis is extended over locations or environments to assess genetic effect × environment interaction. SASHAYDIALL is user-friendly software that provides detailed genetic information from diallel crosses involving any number of parents and locations.

Genetic analysis of photosynthesis and productivity in corn

The genetic relationships among different inbred stocks of corn with respect to different indices of photosynthetic efficiency and plant productivity was assessed by means of diallel graphs. The salient feature of the current study was "apparent overdominance" for some important indices of photosynthetic efficiency, viz. photosynthetic rate/unit leaf area (at the silking stage), total chlorophyll content and chlorophyll a content, as well as for total dry matter production and economic yield. The results could be explained in terms of complementary gene action and the multiplicative effects of the sub-components that comprise these traits. However, complete dominance was recorded for photosynthetic rate (at the grain filling period), leaf area/plant, number of leaves/plant, number of leaves above the ear, ratio of chlorophyll a/b and harvest index. In the majority of cases graphic analysis was possible only when a number of epistatic parents were omitted from the analysis. Although the position of the array points for different indices of photosynthetic efficiency was consistent across the years, the ontogenetic and seasonal differences in the genetic behaviour of parents, meaning thereby, different loci being active at different stages and seasons, was apparent. The same was true for the epistatic parents. Non-allelic interaction of the genes rather than the non-random distribution of the genes among the parents seemed to be the most common cause of disturbance in the Wr/Vr relationship.Inbred stock MG 115 was identified to be the most promising because it embodied an efficient photosynthetic machinery by virtue of increasing the number of alleles for a majority of the indices of photosynthetic efficiency, thereby enabling it to register the highest biological productivity and economic yield. Further, inbred stocks MG 138, MG 121, and MG 125 were also promising for different photosynthetic parameters.

Cross prediction studies on spring barley : 1. Estimation of genetical and environmental control of morphological and maturity characters

The genetical and environmental control of three height characters, two maturity characters and neck length in five barley pair crosses was studied using both F2 triple test cross and model fitting analysis.Significant additive and dominance effects were found for all six characters with some evidence of epistasis for each character. Generally, dominance was incomplete for the height characters but was significantly directional for increased height in those crosses where dwarfing genes were segregating. Variable dominance effects were found for both the maturity characters. Complete dominance was found in three cases, otherwise incomplete dominance was found. Significant directional dominance for earliness was found for both maturity characters in one cross but this was attributed to the presence of a daylength insensitivity factor in one of the parents. Most of the genetic variation for neck length was additive, though some evidence of dominance was found.Broad sense and narrow sense heritability estimates generally were found to be high for the height and maturity characters but low for neck length. It was concluded that early generation selection for height at ear emergence, for final height and for awn emergence was worthwhile. Early generation selection for neck length was not recommended from the results of this study.

The genetic control of morphological and yield characters in Vicia faba L

Complete diallel crosses were made within each of three populations of Vicia faba to examine the genetic control of morphological and yield characters. The Afghanistan and USSR populations consisted of five and the European of four genotypes. The phenotypic range of the genotypes in each population was similar for the characters studied.In each character additive gene effects were partly responsible for genetic variation but non-additive effects varied greatly in importance depending on the population examined. Differences were found in: a) the presence or absence of dominance; b) the partitioning of the dominant effects; c) the degree and direction of dominance; d) the presence or absence of epistasis; and e) the size of narrow-sense heritability estimates.It appears that in V. faba there exists much greater genetic variability than is evident by the examination of plant phenotypes. As different breeding techniques can be used to exploit different components of genetic variability, it is recommended that the possibility of differences in genetic architecture between geographical populations be taken into account in the planning of plant breeding programs. Advantage could then be taken of interactions between breeding methods and populations that are phenotypically but not genetically similar.

The inheritance of diastatic power and alpha-amylase contents in spring barley

In a diallel cross of 13 spring barley varieties, non-allelic interactions interfered with the analysis of diastatic power. Regression of W r on V r was less than unity both in the full experiment and in the sub-set of two-row varieties. The simple additive-dominance model was adequate for the analysis of alpha-amylase. Regression of W r on V r indicated directional dominance, increasing alphaamylase. For both characters non-additive variance was detected and the effects of directional dominance, asymmetry of gene distribution and SCA were evident. Significant GCA effects were also present. No serious obstacles to the improvement of either character in adapted two-row varieties were apparent.

A 9 × 9 diallel analysis in peanuts (A. hypogaea L.): Flowering time, tops' weight, pod yield per plant and pod weight

Four quantitative traits were studied by analysing F2 data derived from a 9 × 9 diallel cross utilizing widely divergent, inbred, erect cultivars of peanuts, A. hypogaea. Bidirectional dominance was found in the traits total pod yield per plant and number of days from planting to first flower; in pod size, the alleles giving small pods were consistently dominant and for high tops' weight, dominance and overdominance were found. The high heritability of pod yield/plant (0.79) indicates that breeding for higher yield/plant can succeed if large F2 populations are grown and rigorous visual selection combined with progeny testing are employed. The genetic correlations of pod yield/plant with other traits were low. Breeding for plants with large (jumbo) pods can be aided by the fact that they are homozygous recessive, or nearly so. Simultaneous breeding for high yields and large pods is possible: there was a positive (but low) genetic correlation between the two (0.16). A modification by which less biased estimates of the number of effective factors can be obtained and a possible relationship between bidirectional dominance and genic interaction were proposed.

A study of the inheritance and inter-relationships of some agronomically important characters in spring barley

The results of genetical analyses of data for the characters ear number, grain number per ear, 1000 corn weight and straw length are presented. These data were obtained from the F1 and F2 generations of a half diallel cross between 13 barley varieties, 4 of which were six-row types. Separate analyses were also conducted on the sub-set comprising two-row genotypes only.Analyses of variance detected a high level of dominance in F1 for all the characters and in general the dominance effects were directional and positive. Apparent overdominance resulting from interaction was detected in the F1 of crosses between two-row and six-row parents for 1000 corn weight.Evidence suggested that selection had resulted in the accumulation of dominant genes having an increasing effect on the morphological components of yield. A high proportion of dominant genes acting to increase straw length was also detected and it was concluded that considerable further shortening of the straw might be possible by selection in a segregating population though possibly at the expense of yield.Genotypic correlation coefficients were computed and provided evidence that further genetic improvement for yield should be possible within the two-row genotypes.