Combining ability analysis in bitter gourd (Momordica charantia L.) for potential quality improvement

Combining ability analysis provides useful information for the selection of parents, also information regarding the nature and magnitude of involved gene actions. Crops improvement involves strategies for enhancing yield potentiality and quality components. Targeting the improvement of respective characters in bitter gourd, combining ability and genetic parameters for 19 characters were estimated from a 6×6 full diallel analysis technique. The results revealed that the variances due to general combining ability (GCA) and specific combining ability (SCA) were highly significant for most of the important characters. It indicated the importance of both additive and non-additive gene actions. GCA variances were higher in magnitude than SCA variances for all the characters studied indicating the predominance of the additive gene effects in their inheritance. The parent P2 (BG 009) appeared as the best general combiner for earliness; P1 (BG 006) for number of fruits, average single fruit weight and fruit yield; P4 (BG 027) for node number of first female flower and days to seed fruit maturity; P3 (BG 011) for fruit length and thickness of the fruit flesh; P5 (BG 033) for 100-seed weight; and P6 for number of nodes per main vine. The SCA effect as well as reciprocal effect was also significant for most of the important characters in different crosses.

The impact of linkage disequilibrium and epistasis in the studies of inheritance based on Hayman’s diallel and generation mean analysis

This simulation-based study assessed the impact of linkage disequilibrium (LD) and epistasis on Hayman’s diallel and generation mean analysis, assuming hundreds of genes, variable degree of dominance, and seven types of digenic epistasis. The diallel parents were 15 doubled-haploid lines from a high LD population. The generation mean analysis was based on seven generations, assuming association. Under low LD and no epistasis, the diallel analysis provided confident results about the inheritance of the quantitative trait and high correlation between number of recessive genes and Wr + Vr, but biased estimates of the dominance components and genetic parameters. The additional consequences of high LD under no epistasis were rejection of the additive-dominance model assuming high heritability and lower correlation. Assuming 100% of epistatic genes, for four epistasis types there was evidence of inadequacy of the additive-dominance model. Assuming 30% of epistatic genes, there was a tendency for accepting the additive-dominance model for low heritability traits and for rejecting for high heritability traits. Linkage and epistasis affects the estimates of the genetic components of the generation means. Even assuming 100% of interacting genes, for most epistasis types there was no statistical evidence of epistasis. Assuming positive partial dominance, the signs of the epistatic components do not allow discriminate complementary, recessive, dominant and recessive, duplicate genes with cumulative effects, and non-epistatic genic interaction. Negative epistatic components evidence dominant epistasis. When the additive x additive and dominance x dominance components are positive and the additive x dominance component is negative, there is duplicate epistasis.

Little heterosis found in Diploid Hybrid Potato

Hybrid potato breeding has become a novel alternative to conventional potato breeding allowing breeders to overcome intractable barriers (e.g. tetrasomic inheritance, masked deleterious alleles, obligate clonal propagation) with the benefit of seed-based propagule, flexible population design, and the potential of hybrid vigour. Until now, however, no formal inquiry has adequately examined the relevant genetic components for complex traits in hybrid potato populations. In this present study, we use a two-step modelling approach to estimate the relevant variance components to assess the magnitude of the general and specific combining abilities (GCA and SCA, respectively) in diploid hybrid potato (DHP). SCA effects were identified for all yield components studied here warranting evidence of non-additive genetic effects in hybrid potato yield. However, the estimated GCA effects were on average two times larger than their respective SCA quantile across all yield phenotypes. Tuber number GCAs and SCAs were found to be highly correlated with total yield's genetic components. Tuber volume appearing under-selected in this population. The prominence of additive effects found for all traits presents evidence that breeders can perform hybrid potato evaluation using the mid-parent value alone. Heterotic vigour stands be useful in bolstering simpler traits but this will be very dependent on the target market of a population. This study represents the first diallel analysis of its kind in diploid potato using material derived from a commercial hybrid breeding programme.

Implementation of partial diallel analysis to determine general combining ability and agronomic character genetic parameters of shade-tolerant maize lines

Information about combining ability and genetic parameters guide maize breeders in selecting parents and gene action of the desired trait. This study aims to determine the general combining ability of the yield characters of shading tolerant maize lines and the genetic parameters of their agronomic characters. This research was conducted at IP2TP Bajeng in December 2020-March 2021. The study was arranged in a randomized block design with three replications. The genotypes used were nine hybrids obtain from a partial diallelic (2x6). The results showed that line SHD3 showed good general ability for yield. High heritability values were shown by variables days to anthesis, days to silk, plant height, ear height, leaf length, leaf width, 100 grains weight and ear diameter.

Accounting for spatial trends in multi-environment diallel analysis in maize breeding

Spatial trends represent an obstacle to genetic evaluation in maize breeding. Spatial analyses can correct spatial trends, which allow for an increase in selective accuracy. The objective of this study was to compare the spatial (SPA) and non-spatial (NSPA) models in diallel multi-environment trial analyses in maize breeding. The trials consisted of 78 inter-populational maize hybrids, tested in four environments (E1, E2, E3, and E4), with three replications, under a randomized complete block design. The SPA models accounted for autocorrelation among rows and columns by the inclusion of first-order autoregressive matrices (AR1 ⊗ AR1). Then, the rows and columns factors were included in the fixed and random parts of the model. Based on the Bayesian information criteria, the SPA models were used to analyze trials E3 and E4, while the NSPA model was used for analyzing trials E1 and E2. In the joint analysis, the compound symmetry structure for the genotypic effects presented the best fit. The likelihood ratio test showed that some effects changed regarding significance when the SPA and NSPA models were used. In addition, the heritability, selective accuracy, and selection gain were higher when the SPA models were used. This indicates the power of the SPA model in dealing with spatial trends. The SPA model exhibits higher reliability values and is recommended to be incorporated in the standard procedure of genetic evaluation in maize breeding. The analyses bring the parents 2, 10 and 12, as potential parents in this microregion.

Diallel Analysis for Area, Chlorophyll and Temperature of Flag Leaf in Bread Wheat under Well Watered and Drought Stress Conditions

To study genetic analysis of some physiological traits of drought stress in wheat using diallel techniques, an experiment was performed on ten bread wheat genotypes as parents and their 45 F1 hybrids in a randomized complete block design with three replicates under well-watered and drought stress conditions at the Research Farm of Faculty of Agriculture, Sohag University, Egypt during season of 2018/19. The results showed significant differences between the genotypes (G), Parents (P), F1 crosses, P vs. F1, GCA and SCA under well-watered and drought stress in the flag leaf area (FLA), flag leaf chlorophyll content (FLCC) and flag leaf temperature (FLT), except FLCC for F1 crosses exhibited insignificant differences. The significant differences were found in the interaction of SCA × Env., in all studied traits and GCA × Env., for FLT., indicating the involvement of both additive and dominance gene action in their inheritance. The most desirable heterotic effects were considered as the largest positive heterosis estimates for FLA and FLCC, and the lowest negative for FLT. The parent numbers P9, P8 and P3 were the best general combiner for FLA under normal irrigation and drought stress. While the parents P2, P7 and P9 were the best general combiner for FLCC, under normal irrigation and (P1, P2 and P3) under drought stress. Therefor the parents P1, P4 and P5 were the best general combiner for FLT under normal irrigation, also the P3, P4 and P5 were the best general combiner for FLT under drought stress conditions. Under normal irrigation and drought stress conditions as well as the combined data, the additive genetic components of variation (VA) in F1 ’s was much greater than dominance component (VD), as expressed by the (VA/VD) ratio which was more than unity for the FLA, and FLT under normal irrigation and their combined. This indicates that the additive gene effects in F1 crosses are more important than dominance and plays the major role in the inheritance of these studied traits.

Combining Ability and Molecular Marker Approach Identified Genetic Resources to Improve Agronomic Performance in Coffea arabica Breeding

Plant breeding aims to develop cultivars with good agronomic traits through gene recombination and elite genotype selection. To support Coffea arabica breeding programs and assist parent selection, molecular characterization, genetic diversity (GD) analyses, and circulating diallel studies were strategically integrated to develop new cultivars. Molecular markers were used to assess the GD of 76 candidate parents and verify the crossing of potential F1 hybrids. Based on the complementary agronomic traits and genetic distance, eight elite parents were selected for circulating diallel analysis. The parents and 12 hybrids were evaluated based on 10 morpho-agronomic traits. For each trait, the effects of general and specific combining abilities, as well as the averages of the parents, hybrids, and predicted hybrids, were estimated. Crosses that maximize the genetic gains for the main agronomic traits of C. arabica were identified. Joint analysis of phenotypic and molecular data was used to estimate the correlation between molecular GD, phenotypic diversity (PD), phenotypic mean, and combining ability. The selection of parents that optimize the allele combination for the important traits of C. arabica is discussed in detail.

MANIFESTATION OF TRANSGRESSION BY MAIN QUANTITATIVE CHARACTERISTICS OF WINTER TRITICAL PRODUCTIVITY IN F2 HYBRID POPULATIONS

The research was conducted in 2014-2017 in the department of selection of fodder, grain ears, and industrial crops in the fields of scientific crop rotation of the Institute of Fodder and Agriculture of Podillya NAAS of Ukraine. A collection of 114 hexaploid specimens of different ecological and geographical origins was used as research material. Six varieties of winter triticale of different ecological and geographical origin and the manifestation of valuable economic features were used in crosses according to the scheme of full diallel analysis: Polovetske (UA0602494), Amos (UA0602627) originating from Ukraine; Kapryz (UA0601781), Tsekad 90 (UA0602066) - Russia; Dubrava (UA0602222) - Belarus and Pawo (UA0602555) - Poland. Only the best plants, which did not lag in growth and were normally developed, were selected for hybridization. The obtained generation F0 was sown in 2016, and generation F1 – 2017 manually in an experimental field with the same depth, which provides plants with the same area of nutrition. After full maturation, the plants were also collected manually in sheaves, structural analysis was performed on the main indicators of productivity. The frequency and degree of manifestation of positive transgressions in hybrids of the second generation (F2) of winter triticale were evaluated based on productivity: productive bushiness, number and weight of ear grains and grain weight from the plant. The best hybrids by degree and frequency of manifestation of positive transgression are selected. The degree of transgressions in productive bushiness averaged 65.3%, frequency - 43%; number of grains in the main ear - 7.4%, frequency - 15.3%; weight of grain in the ear - 13.8% at a frequency of 27, 7%; weight of grain from the plant - 91.5% with a transgression frequency of 52.7%. The best hybrid combinations of winter triticale on the basis of "productive bushiness" - Polovtsian / Caprice and Dubrava / Polovtsian (Tc = 100%), the maximum frequency of transgressions on this basis - hybrids Polovtsian / Caprice / Pawos and Pawo are selected and offered for use in the selection process. TC = 60); "Number of grains from the ear" - the maximum degree of transgressions was found in the hybrid Pawo / Polovtsian (Tc = 18.1%), the maximum frequency - in the hybrid Caprich / Pawo (Tch = 40); "Ear grain mass" - Pawo / Amos (Tc = 37.0%), the highest frequency of transgressions - in hybrids Amos / Dubrava and Kaprikh / Pawo (Tch = 50); "Grain weight from the plant" - Polovtsian / Amos (Tc = 37.0%), the frequency of transgressions - hybrids Polovtsian / Amos and Polovtsian / Caprice (Tc = 85%).