Genetic parameters controlling the inheritance of glaucousness and yield traits in bread wheat

Wheat breeders frequently use generation mean analysis to obtain information on the type of gene action involved in inheriting a trait to choose the helpful breeding procedure for trait improvement. The present study was carried out to study the inter-allelic and intra-allelic gene action and inheritance of glaucousness, earliness and yield traits in a bread wheat cross between divergent parents in glaucousness and yield traits; namely Mut-2 (P1) and Sakha 93 (P2). The experimental material included six populations, i.e. P1, P2, F1, F2, BC1, and BC2 for this wheat cross. A randomized complete block design with three replications was used, and a six parameters model was applied. Additive effects were generally more critical than dominance for all studied traits, except for plant height (PH) and grain yield/plant (GYPP). The duplicate epistasis was observed in spike length; SL, spikes/plant; SPP and days to heading; DTH. All six types of allelic and non-allelic interaction effects controlled SL, GYPP, DTH and glaucousness. All three types of epistasis, i.e. additive x additive, additive x dominance, and dominance x dominance, are essential in determining the inheritance of four traits (SL, GYPP, DTH and glaucousness). Dominance × dominance effects were higher in magnitude than additive × dominance and additive × additive in most traits. The average degree of dominance was minor than unity in six traits (glaucousness, grains/spike, spike weight, days to maturity, 100-grain weight and SL), indicating partial dominance and selection for these traits might be more effective in early generations. Meanwhile, the remaining traits (PH, SPP, GYPP and DTH) had a degree of dominance more than unity, indicating that overdominance gene effects control such traits and it is preferable to postpone selection to later generations. The highest values of narrow-sense heritability and genetic advance were recorded by glaucousness trait followed by SL and SPP, indicating that selection in segregating generations would be more effective than other traits.

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.

Inheritance of some quantitative traits in the hybrid generations ‘Kuboyar × Gagat’

Rice is an important food for humans. In the world, for food purposes white-grain rice varieties are mainly used, but there are varieties in which kernel pericarp is of red, brown, purple or black color. Such rice is more beneficial for health promotion. The current paper has presented the results of genetic analysis of the inheritance of a number of variable quantitative traits in rice hybrid populations of the first and third generations obtained by the hybridization of the varieties ‘Kuboyar’ and ‘Gagat’. The variety ‘Kuboyar’ is medium-sized, with a compact erect panicle, an oval caryopsis and white pericarp. The variety ‘Gagat’ is tall, with a long drooping panicle, a long kernel and black pericarp. The work was carried out on the territory of the OP ‘Proletarskoe’ of the Rostov region in 2018–2020. The analysis of the inheritance of some quantitative traits that have a direct impact on the rice productivity made it possible to establish new inheritance regularities. According to the trait ‘plant height’ there has been identified partial dominance of the largest values of the trait in the hybrids F2 and F3. Allelic differences of 3 pairs of genes were identified in parental forms. The trait ‘panicle length’ showed overdominance of the trait in F2, it was absent in F3, and there were digenic differences in parental forms. The trait ‘number of spikelets per panicle’ demonstrated overdominance of large values and positive transgression. According to the trait ‘1000-grain weight’, the hybrids of both generations were split by the digenic scheme in a ratio of 1:4:6:4:1. There was no dominance in the trait ‘kernel length’; the initial varieties had differences in 2 pairs of genes. According to the trait ‘kernel width’, there was identified incomplete dominance of smaller values, and there was monohybrid split. There have been selected the best plants F3 with a black pericarp, average values of the traits ‘plant height’, ‘panicle length’, ‘1000-grain weight’ and an increased number of grains per panicle for the further breeding process.

DYNAMICS OF HERITABILITY IN DIFFERENT CHARACTERS OF LETTUCE

ABSTRACT The lack of knowledge of the genetic parameters and the type of gene action results in difficulties to obtain varieties that combine agronomic and functional characteristics. The objective of this study was to determine the type of gene action associated with the contents of chlorophyll and agronomic characteristics in lettuce populations. The research was conducted at the Experimental Station of Vegetables, Monte Carmelo, Brazil. To perform the crosses and obtain the generations P1, P2, F1, F2, Bc1 and Bc2 the genotypes UFU-Albina#2, UFU-Albina#3, UFU-Lisa124#2#1, UFU-Crespa199#1#1 and UFU-Lisa217#5#2 were used as parents. The generations were evaluated for three characteristics: number of leaves, plant diameter and chlorophyll content. The parameters: genetic, phenotypic, environmental and additive variance, the dominance in F2, heritability in the broad and narrow-sense, the average degree of dominance based on averages, number of genes, the measure of the dominance deviations, additive effects and all interactions of ‘additive x additive’, ‘additive x dominant’ and ‘dominant x dominant’ type, were evaluated. Chlorophyll content was the most influenced by the environment. Plant diameter had the highest narrow-sense heritability for the cross UFU-Lisa-124#2#1 x UFU-Albina#3 (82.1%). The number of genes for the number of leaves varied from inconclusive to a minimum of 9 genes. The gene interactions for number of leaves were of overdominance type, while for plant diameter and for chlorophyll content the gene interactions were of partial dominance. The characteristics are suggested as being of polygenic or oligogenic nature.

Exploring the breeding potential of Iranian emmer wheats to increase durum wheat tolerance to drought

Emmer wheat (Triticum turgidum ssp. dicoccum) is one of the most promising gene sources for drought tolerance improvement of durum wheat (Triticum turgidum ssp. durum). Achieving desired results requires a conscious choice of crossing parents based on general and specific combining ability (GCA and SCA) and also understanding the genes action involved in controlling the desired traits. In this study a 12 × 12 full diallel cross was performed using four emmer and eight durum wheats. The 132 hybrid progenies along with their parental lines were field evaluated under water-stressed and non-stressed conditions. Based on the Griffing diallel analysis both GCA and SCA effects were highly significant for all measured traits under both water treatments indicating possibility of improvement for drought tolerance. In this respect, the amount of additive effect was higher than the non-additive suggesting the chance for genetic advancement through selection. Based on Hayman's graphical analyses under the two water conditions it was revealed that several grain yield component traits were under the control of partial dominance. In contrary, grain yield and most morphological traits showed either dominance or over-dominance gene action. Grain yield had a significant positive correlation with the number of kernels per spike, kernel diameter, grain weight per spike and harvest index. These traits also had greater share of additive effects, relatively high narrow-sense heritability and high Baker ratio suggesting effective indirect selection for grain yield. Most durum × emmer hybrids had grain yield and drought tolerance indices better than the parents indicating that Iranian emmer wheats have a great genetic potential for drought tolerance improvement of durum wheat.

Comparison of the F2 and F3 traits’ inheritance by the rice hybrid ‘Kontro x Kuboyar’

Rice is a very moisture-loving crop, therefore it suffers greatly from drought. However, in the world in recent years, there is an increasing shortage of fresh water, which makes the use of upland rice relevant. Therefore, rice varieties with a reduced demand for water supply, developed as a result of breeding work, are more profitable for agricultural producers than agrotechnical or reclamation measures. It is much cheaper to produce such rice with periodic irrigation. The purpose of the current study was to analyze genetically the main quantitative traits of the rice hybrid ‘Kontro x Kuboyar’ with the selection of the best forms for subsequent breeding for drought resistance. The study was carried out in 2019–2020 on the rice plots of the special subdivision ‘Proletarskoye’ belonging to of the Agricultural Research Center “Donskoy” in the Rostov Region. In the course of the study there has been made a genetic analysis of a number of quantitative traits that determine rice productivity. The character of traits’ inheritance in the second and third generations was identical. The inheritance of the trait ‘panicle length’ was characterized by partial negative dominance and monogenic differences in parental varieties. The trait ‘number of spikelets per panicle’ was inherited according to the type of negative dominance of smaller values of the trait and was determined by the interaction of two pairs of genes. The trait ‘1000-kernel weight’ was identified by the partial dominance of large values of the trait and monogenic differences in the parental varieties. The traits ‘kernel length’ and ‘kernel width’ were split according to the monohybrid scheme 1:2:1, and there was no dominance. From the third generation, the best early-maturing forms with optimal values of the traits ‘plant height’, ‘panicle length’, ‘1000-kernel weight’ and ‘the best kernel percentage per panicle’ were selected for the subsequent breeding of drought-resistant rice varieties.

Gene Action Studies in the Inheritance of Yield and Quality Attributing Traits in Diallel Cross of Cotton (Gossypium hirsutum L.)

A field experiment was conducted to evaluate the 45 F1 hybrids derived from 10×10 half diallel fashion along with ten parents and one standard check GN.Cot.Hy-14 were sown in randomized block design with three replications during kharif -2017 at Cotton Research Station, Junagadh Agricultural University, Junagadh. The genetic components of variation were determined for 12 characters viz., days to 50% flowering, days to 50% boll opening, plant height (cm), number of monopodia per plant, number of sympodia per plant, number of bolls per plant, boll weight (g), seed cotton yield per plant (g), ginning percentage (%), seed index (g), lint index (g) and oil percentage (%).The estimate of the components of variation revealed significant results for both additive (D) as well as dominance effects (H1 and H2) for all the characters except plant height non-significant H2 component, but in majority of traits (except plant height, lint index) H1 was higher than D indicating dominance components were important in the inheritance of seed cotton yield and its components. The average degree of dominance (H1/D)1/2 was found to be more than unity for all the traits (except plant height, number of monopodia per plant and lint index indicating partial dominance) indicating over dominance. Asymmetrical distribution of positive and negative genes in the parents was observed for all the traits. High estimates of heritability in narrow sense was observed for days to 50% flowering, days to 50 % boll bursting, number of monopodia per plant, ginning percentage (%), lint index (g) and oil content (%) suggesting that selection based on these attribute would lead to rapid improvement. Due to preponderance of non-additive gene effects of seed cotton yield per plant and most of its component traits, heterosis breeding would also be practically feasible in cotton.

Unique Transcriptome And Gene Expression Analysis of Flag Leaves of A Super-Hybrid Rice WFYT025

Background: The health and physiology of flag leaves are closely related to rice yield, and flag leaves play an important role in providing photosynthetic products during grain filling, many breeding studies have tried to improve the performance of flag leaves. However, there are few studies on the heterosis of rice flag leaves up to now. Results: Thus, the present research is focused on the flag leaves heterosis of a widely used late-cropping indica super hybrid rice combination WFYT025 in China using a high-throughput next-generation RNA-seq strategy under different environment with two stages, trying to find some genes related to photosynthesis, transpiration, and development of seeds. Mid-parent heterosis (MPH) and higher parent heterosis (HPH) were estimated for the heterosis of flag leaf. Under the environment of middle rice, the number of genes up-regulated in CHT025, WFB and WFYT025 were 892,1,273 and 819, down-regulated in CHT025, WFB and WFYT025 were 616,1934 and 2196, respectively. Among the SDGhps on the first day after flowering, 10.9% had a dominant effect, 41.81% had a partial dominant effect, 22.07% had an additive effect and the remaining 25.22% had an over-dominant effect. Meanwhile, on the tenth day after flowering, there were 491 genes, accounting for 27.16%, showed over-dominance; 222 genes, accounting for 12.28%, showed dominance; 760 genes, accounting for 42.04%, showed partial dominance; and 335 genes, accounting for 18.52%, showed additive effect. Conclusion: The co-expressed gene sets via weighted gene co-expression network analysis (WGCNA) were identified, and total of 5,000 highly expressed genes were divided into 24 co-expression groups. In the two stages, we found 9 identical transcription factors. Except for 5 reported TFs, the other 4 TFs may play an important role in grain number and photosynthesis heterosis.

A novel parent selection strategy for the development of drought-tolerant cotton cultivars

Drought is a devastating factor for crop production worldwide. Therefore, an experiment was conducted to study genetics for some agro-physiological traits in cotton under drought stress. The 13 parental cotton genotypes along with their 30 F1 hybrids were planted under normal and drought conditions. The mean performance of the genotypes was assessed through principal component and heat map analyses. The principal component analyses revealed 53.99 and 53.15% in the first two principal components of variability for normal and drought conditions, respectively. Heat map analysis revealed that three cotton genotypes i.e. FH-207 × NS-131, FH-207 × KZ-191 and S-15 × AA-703 attained higher values for all the traits except for canopy temperature under drought conditions. These crosses may proliferate to further filial generations to identify transgressive segregates for drought tolerance. The heritable differences of F̅1 and mid-parent showed dominance and non-additive gene action under drought conditions. Heritable differences between F̅1 and P̅1 showed over dominance and partial dominance under drought conditions. Heritable differences between F̅1 and P̅2 indicated negative over dominance and partial dominance for all traits under drought conditions. Proline contents and the bolls per plant showed high heritability and genetic advance through additive gene action. Therefore, these two traits can be used as a means of selection in future breeding programmes of drought tolerance.

A study of gene action for yield and quality traits of Basmati rice (Oryza sativa L.) following Hayman's graphical approach

The present study was conducted on 36 crosses obtained by carrying out a crossing program in nine Basmati rice genotypes following half-diallel mating design. Following, Hayman's graphical and numerical approach to comprehend the genetic system involved in the inheritance of traits, it was concluded that, out of 18 traits, only two traits viz., 100-grain weight, and aroma fulfilled the adequacy of additive-dominance model indicating absence of epistasis. Further, Vr/Wr graph was plotted and genetic components w ere estimated for these two traits only. By plotting Vr/Wr graph for 100-grain weight and aroma, partial dominance and over-dominance were observed in the inheritance, respectively. The ratio of KD/Kr implied influence of more of recessive alleles in inheritance of 100-grain weight among parents and dominant alleles for aroma genes among parents. Estimates of genetic components indicated the role of both additive and dominance effect in the inheritance of 100-grain weight and aroma. High heritability in narrow sense was observed for the traits.