Showing papers on "Diallel cross published in 2019"

Extensive impact of low-frequency variants on the phenotypic landscape at population-scale

Abstract: Genome-wide association studies (GWAS) allow to dissect complex traits and map genetic variants, which often explain relatively little of the heritability. One potential reason is the preponderance of undetected low-frequency variants. To increase their allele frequency and assess their phenotypic impact in a population, we generated a diallel panel of 3025 yeast hybrids, derived from pairwise crosses between natural isolates and examined a large number of traits. Parental versus hybrid regression analysis showed that while most phenotypic variance is explained by additivity, a third is governed by non-additive effects, with complete dominance having a key role. By performing GWAS on the diallel panel, we found that associated variants with low frequency in the initial population are overrepresented and explain a fraction of the phenotypic variance as well as an effect size similar to common variants. Overall, we highlighted the relevance of low-frequency variants on the phenotypic variation.

Analysis of genetic effects on a complete diallel cross test of Pinus koraiensis

Abstract: Thirty-four full-sib Pinus koraiensis families were used to evaluate and identify elite P. koraiensis material. Tree height (H) and diameter at breast height (dbh) were assessed. The results from variance analyses showed that familial variance sources for different traits in different growth years were extremely significantly different. The average phenotypic variation coefficients of H, dhb and volume (V) among families in different growth years ranged from 7.57 to 15.70, from 10.37 to 12.89 and from 24.44 to 28.13%, respectively. The family heritabilities of all traits ranged from 0.910 to 0.990, which are high values. A significant and positive correlation was observed among all traits, with values ranging from 0.43 to 0.99. According to the analyses of general and special combining ability, female parents F4 and F2 and male parents M7 and M13 had high levels of general combining ability for all three traits evaluated. Families PK05 (F9 × M14) and PK06 (F2 × M14) showed the highest and the lowest specific combining ability values in all traits evaluated. Using the comprehensive multiple-traits method to evaluate the families by traits in the 18th growth year at the rate of < 10%, we selected families PK40, PK05 and PK22 as elite families; the genetic gains for these families in H, dbh and V were 14.43, 11.29 and 24.72%, respectively. This study provides materials and basic theoretical knowledge that can be used to improve seed orchards and develop special hybrid seed orchards.

Inheritance of fruit yield and quality in melon (Cucumis melo L.) grown under field salinity stress.

Abstract: Cultivation of salinity-tolerant crops can help mitigate salinization threats to soil and fresh water resources. This study was conducted to investigate the quantitative genetic basis of yield, yield components, and quality-related traits of salinity-stressed melon (Cucumis melo L.) using 55 melon hybrids and their 11 parents (half diallel). The results of combined ANOVA revealed highly significant effects of salinity and genotype on all the traits studied. Salinity stress influenced the inheritance of all the traits. The lower values of variance components (mainly additive), GCA/SCA ratio, as well as broad- and narrow-sense heritabilities were estimated for saline conditions (ECW = 14 dSm−1) when compared with those obtained under non-saline conditions. Fruit weight was governed by additive effects in non-saline conditions, but largely governed by the dominant nature in saline conditions. Based on the results obtained, especially as reflected by fruit yield, it is possible to develop melon hybrids with higher salinity tolerance than is currently observed in tolerant cultivars. On the other hand, most of the traits contributing to fruit quality are found to be governed by additive effects, allowing for their further improvement through recurrent selection to develop new cultivars of high yield and good quality for cultivation under saline conditions.

Maize responsiveness to Azospirillum brasilense: Insights into genetic control, heterosis and genomic prediction

Abstract: Several studies have shown differences in the abilities of maize genotypes to facilitate or impede Azospirillum brasilense colonization and to receive benefits from this association. Hence, our aim was to study the genetic control, heterosis effect and the prediction accuracy of the shoot and root traits of maize in response to A. brasilense. For that, we evaluated 118 hybrids under two contrasting scenarios: i) N stress (control) and ii) N stress plus A. brasilense inoculation. The diallel analyses were performed using mixed model equations, and the genomic prediction models accounted for the general and specific combining ability (GCA and SCA, respectively) and the presence or not of G×E effects. In addition, the genomic models were fitted considering parametric (G-BLUP) and semi-parametric (RKHS) kernels. The genotypes showed significant inoculation effect for five root traits, and the GCA and SCA were significant for both. The GCA in the inoculated treatment presented a greater magnitude than the control, whereas the opposite was observed for SCA. Heterosis was weakly influenced by the inoculation, and the heterozygosity and N status in the plant can have a role in the benefits that can be obtained from this Plant Growth-Promoting Bacteria (PGPB). Prediction accuracies for N stress plus A. brasilense ranged from 0.42 to 0.78, depending on the scenario and trait, and were higher, in most cases, than the non-inoculated treatment. Finally, our findings provide an understanding of the quantitative variation of maize responsiveness to A. brasilense and important insights to be applied in maize breeding aiming the development of superior hybrids for this association.

Understanding the combining ability for physiological traits in soybean.

Abstract: Photosynthetic efficiency has become the target of several breeding programs since the positive correlation between photosynthetic rate and yield in soybean suggests that the improvement of photosynthetic efficiency may be a promising target for new yield gains. However, studies on combining ability of soybean genotypes for physiological traits are still scarce in the literature. The objective of this study was to estimate the combining ability of soybean genotypes based on F2 generation aiming to identify superior parents and segregating populations for physiological traits. Twenty-eight F2 populations resulting from partial diallel crossings between eleven lines were evaluated in two crop seasons for the physiological traits: photosynthesis, stomatal conductance, internal CO2 concentration, and transpiration. General combining ability (GCA) of the parents and specific combining ability (SCA) of the F2 populations were estimated. Our findings reveal the predominance of additive effects in controlling the traits. The genotype TMG 7062 IPRO is the most promising parent for programs aiming at photosynthetic efficiency. We have also identified other promising parents and proposed cross-breeding with higher potential for obtaining superior lines for photosynthetic efficiency.

Effects of Drought and Low Nitrogen Stress on Provitamin A Carotenoid Content of Biofortified Maize Hybrids

Abstract: Maize (Zea mays L.) hybrids with enhanced provitamin A (proVA) content have been deployed in sub-Saharan Africa, where low soil nitrogen and drought stress are common. The objectives of this study were to assess: (i) the effects of drought and low-N stress on grain proVA content of hybrids with enhanced proVA content, and (ii) the inheritance of proVA carotenoids under these stress conditions. An 11-line diallel cross (55 F1 crosses) was evaluated for carotenoid content and grain yield under optimum conditions, drought, and low-N stress. Compared with the optimum treatment, mean proVA was lower under both stress treatments. The consistency of genetic effects across stress treatments suggested that hybrids with improved proVA content can be developed for a broad range of environments, provided they are sufficiently adapted. General combining ability (GCA) was significant (P 85% of the variation among hybrids, whereas specific combining ability (SCA) effects were generally weak (P < 0.05), accounting for 5 to 15% of hybrid sums of squares across the three treatments. These results indicated that the inheritance of proVA was not affected by stress treatments. A negative correlation between grain yield and proVA carotenoids was detected, but the data suggested that it was caused by the genetic background of the germplasm used rather than pleiotropy. Our results provide insights that may help breeders design effective breeding strategies to develop proVA-enriched cultivars for resource-limited farming systems.

Haploid male fertility and spontaneous chromosome doubling evaluated in a diallel and recurrent selection experiment in maize.

Abstract: Mainly additive gene action governed inheritance of haploid male fertility, although epistatic effects were also significant. Recurrent selection for haploid male fertility resulted in substantial improvement in this trait. The doubled haploid (DH) technology offers several advantages in maize breeding compared to the traditional method of recurrent selfing. However, there is still great potential for improving the success rate of DH production. Currently, the majority of haploid plants are infertile after chromosome doubling treatment by antimitotic agents such as colchicine and cannot be selfed for production of DH lines. Improvement in haploid male fertility (HMF) by selection for a higher spontaneous chromosome doubling rate (SDR) has the potential to increase DH production efficiency. To investigate the gene action governing SDR in two breeding populations, we adapted the quantitative-genetic model of Eberhart and Gardner (in Biometrics 22:864–881. https://doi.org/10.2307/2528079 , 1966) for the case of haploid progeny from ten DH lines and corresponding diallel crosses. Furthermore, we carried out three cycles of recurrent selection for SDR in two additional populations to evaluate the selection gain for this trait. Additive genetic effects predominated in both diallel crosses, but epistatic effects were also significant. Entry-mean heritability of SDR observed for haploid progeny of these populations exceeded 0.91, but the single-plant heritability relevant to selection was low, ranging from 0.11 to 0.19. Recurrent selection increased SDR from approximately 5–50%, which suggests the presence of few QTL with large effects. This improvement in HMF is greater than the effect of standard colchicine treatment, which yields at maximum 30% fertile haploids. Altogether, the results show the great potential of spontaneous chromosome doubling to streamline development DH lines and to enable new breeding schemes with more efficient allocation of resources.

Genetic effects on the efficiency and responsiveness to phosphorus use in popcorn as estimated by diallel analysis.

Abstract: Agricultural expansion and the need for sustainable cultivation are challenges faced by researchers involved in the generation of new cultivars that can adapt to abiotic stress. Knowledge of the genetic effects of characteristics related to efficiency and responsiveness to phosphorus use must be considered when implementing methods to obtain better genotypes. The aim of this study was to characterize and select popcorn hybrids based on their efficiency and responsiveness to phosphorus use, and estimate their combining abilities and genetic effects via diallel analysis to implement improvement programs for sustainable agriculture. Eight contrasting inbred lines were used to obtain simple hybrids for diallel analysis. Twenty-eight diallelic hybrids plus the popcorn parental lines were evaluated at two different sites under two contrasting environments for soil phosphorus availability (6 × 6 lattice design). Grain yield, popping expansion, and volume of expanded popcorn per hectare were measured. A combined analysis of variance and a test of means were performed. The classification and utilization of the phosphorus use efficiency index, according to the grain yield performance of the hybrids under contrasting environments, was considered. Through model 2 of the Griffing's diallel analysis method, the general and specific combining abilities were estimated, along with their environmental interactions. The best strategy to obtain genotypes that are efficient and responsive to phosphorus involves exploring popcorn hybrids using genitors that result in the accumulation of additive genes that promote popping expansion. Hybrids P7 × L80, P7 × L59, P7 × L76, and P6 × L80 presented promising results and may be evaluated as cultivation options in phosphorus-deficient soils.

Formation of heterotic pools and understanding relationship between molecular divergence and heterosis in pearl millet [Pennisetum glaucum (L.) R. Br.].

Abstract: The present investigation was made to generate information on the heterotic pools amongst pearl millet hybrid parents. A set of 17 representative parents was selected from a diverse set of 147 hybrid parents using SSR based genetic distance (GD) and clustering pattern; 136 hybrids were developed in diallel fashion and evaluated at two locations in India. Moderate positive significant correlation (r = 0.37, p<0.01) and (r = 0.33, p<0.01) was found between GD and mid-parent heterosis (MPH) and better-parent heterosis (BPH), respectively, for grain yield for all the hybrids. Higher correlation between genetically closer individuals was observed for grain yield heterosis when the parents of B- and R- crosses had lesser genetic distance (<0.68 GD) in comparison to those parental combinations having GD higher than 0.68, indicating that the GD based predictions for grain yield are better when the parents are genetically related than when they are genetically diverse. In this study, all the pearl millet hybrid parents seems to exist in two broad-based heterotic pools; one each represented by seed and restorer parents as B × R hybrids showed highest mean heterosis for grain yield than either of B × B or R × R crosses. Further, four heterotic pools have been identified in this diverse set of hybrid parents of pearl millet, two each for seed parents (HPB1 and HPB2) and for restorer parents (HPR3 and HPR4). Among these, HPB1 × HPR3 was identified having the highest heterotic level, and could be further used to develop higher yielding pearl millet hybrids.

Diallel Analysis of Early Leaf Spot (Cercospora arachidicola Hori) Disease Resistance in Groundnut.

Abstract: Early leaf spot (ELS) is one of the major biotic constraints of groundnut production in West and Central Africa. A study using 6 × 6 F2 full diallel populations from six parents (NAMA, B188, PC79-79, QH243C, TS32-1, and CN94C) was conducted to assess the mode of inheritance of ELS resistance traits. The F2 and parents were grown in a randomized complete block design with three replications. Data was collected on ELS disease severity, and an area under disease progress curve (AUDPC) was estimated. The results revealed that additive and non-additive gene actions were involved in the inheritance of the ELS resistance traits, but additive gene action was predominant. Significant reciprocal cross effect was observed, suggesting cytoplasmic effect on ELS resistance. Graphical analysis also revealed the predominance of additive gene action for ELS resistance. The results suggest that early generation selection should be effective for ELS resistance. Looking at the distribution of array points along with the regression line, parental lines NAMA, PC79-79, and B188 would be suitable as good donors in an ELS disease resistance breeding program.

Molecular genetic studies on abiotic stress resistance in sorghum entries through using half diallel analysis and inter-simple sequence repeat (ISSR) markers

Abstract: Water deficit stress is considered as one of the most important environmental stresses which is more harmful to strategic crops, as it reduces the final crop yield by up to 40%. Therefore, the aim of this research is to evaluate some promising and superior sorghum entries for water stress tolerance and determine the most agro-morphological parameters and reasons responsible for drought tolerance in this regard. Fifteenth sorghum genotypes (five parents and their ten F1 crosses resulting from half diallel analysis) were used in this investigation under two levels of irrigation (normal and drought experiment). The recent genotypes were estimated through some physiological parameters related to water stress tolerance in sorghum; besides that, eight inter-simple sequence repeat (ISSR) primers were used to identify among the five sorghum parents and the highest five crosses resistance to water deficit conditions depending on the data calculated from all studied traits under both conditions. The following genotypes P1, P2, P3, P1 × P2, P1 × P3, P2 × P3, P2 × P4, and P3 × P4 confirmed high resistance to water deficit conditions under the drought treatment compared with the control. This high resistance was affirmed through the calculated data for all studied traits. The ISSR profile analysis showed 151 fragments as taxonomic divisions among the ten sorghum genotypes (38 of them were monomorphic and 113 polymorphic with 74.83% polymorphism). The entries (P1, P2, P3, P1 × P2, P1 × P3, P2 × P3, P2 × P4, and P3 × P4) were succeeded in achieving the highest concept of water deficit resistance under both conditions. Therefore, this work will be the nucleus for producing resistant sorghum varieties for drought stress in the future.

Diallel Analysis of Chilli Pepper ( Capsicum annuum L.) Genotypes for Morphological and Fruit Biochemical Traits.

Abstract: Chilli pepper is commercially cultivated as a spice and is also used for the extraction of a colouring agent. Here, we performed a diallel genetic study involving five chilli pepper varieties. Parents and their hybrid were evaluated for fifteen morphological and five biochemical traits over two crop seasons under open field conditions. Variation was recorded for all of the studied traits. Similarly, significant values for general combining ability (GCA) and specific combining ability (SCA) variance were obtained for all of the traits. The ratio of σ2 SCA/σ2 GCA indicates that non-additive gene effects were predominant for all the studied traits except for fruits plant-1. Based on SCA effects, cross combinations P2 × P5, and P4 × P5 were determined excellent for flesh thickness, yield components and vitamin C. These hybrids are recommended for multilocation testing to assess their suitability for commercial cultivation. Overall, this work presents useful information regarding the genetics of important morphological and biochemical traits in chilli pepper.

Genetic parameters and direct, maternal and heterosis effects on litter size in a diallel cross among three commercial varieties of Iberian pig

Abstract: The Iberian pig is one of the pig breeds that has the highest meat quality. Traditionally, producers have bred one of the available varieties, exclusively, and have not used crosses between them, which has contrasted sharply with other populations of commercial pigs for which crossbreeding has been a standard procedure. The objective of this study was to perform an experiment under full diallel design among three contemporary commercial varieties of Iberian pig and estimate the additive genetic variation and the crossbreeding effects (direct, maternal and heterosis) for prolificacy. The data set comprised 18 193 records for total number born and number born alive from 3800 sows of three varieties of the Iberian breed (Retinto, Torbiscal and Entrepelado) and their reciprocal crosses (Retinto × Torbiscal, Torbiscal × Retinto, Retinto × Entrepelado, Entrepelado × Retinto, Torbiscal × Entrepelado and Entrepelado × Torbiscal), and a pedigree of 4609 individuals. The analysis was based on a multiple population repeatability model, and we developed a model comparison test that indicated the presence of direct line, maternal and heterosis effects. The results indicated the superiorities of the direct line effect of the Retinto and the maternal effect of the Entrepelado populations. All of the potential crosses produced significant heterosis, and additive genetic variation was higher in the Entrepelado than it was in the other two populations. The recommended cross for the highest yield in prolificacy is a Retinto father and an Entrepelado mother to generate a hybrid commercial sow.

Combining Ability for Agromorphological and Physiological Traits in Different Gene Pools of Common Bean Subjected to Water Deficit

Abstract: Water stress is one of the main limiting factors for common bean crops, negatively affecting grain yield and seed quality. Thus, the objective of this study was to evaluate the inheritance of agromorphological and physiological traits related to drought tolerance in order to identify promising combinations. The experiment was carried out in a greenhouse with a partial diallel scheme between three drought-tolerant genotypes (IAPAR 81, BAT 477, and SEA 5), and nine cultivars widely grown in Brazil (BRS Estilo, IAC Alvorada, IPR Campos Gerais, IPR Uirapuru, IPR Nhambu, BRS Esteio, IPR Garca, BRS Radiante, and DRK 18), in a randomized block design with four replicates. The plants were grown in pots with substrate under 80% of pot capacity until they reached the stage R5, when water supply was restricted to 30% for 20 days in the pots under stress treatment. A wide variability for the agromorphological and physiological traits was observed. Water deficit reduced plant performance for most agromorphological traits and altered their physiological metabolism. Additive and non-additive effects are involved in the genetic control of the majority of agromorphological and physiological traits both under water stress and control (well-watered) conditions. The parental genotypes BAT 477 (group I) and IAC Alvorada, IPR Uirapuru, and BRS Esteio (group II) may be included in breeding programs aiming at improving drought tolerance in common bean since they present high positive general combining abilities for agromorphological traits. The crosses IAPAR 81 × IPR Campos Gerais, and SEA 5 × BRS Radiante resulted in the best combinations considering grain yield per plant and total dry biomass, when cultivated under water deficit.

Extensive impact of low-frequency variants on the phenotypic landscape at population-scale

Abstract: Genome-wide association studies (GWAS) allows to dissect the genetic basis of complex traits at the population level1. However, despite the extensive number of trait-associated loci found, they often fail to explain a large part of the observed phenotypic variance2–4. One potential source of this discrepancy could be the preponderance of undetected low-frequency genetic variants in natural populations5,6. To increase the allele frequency of those variants and assess their phenotypic effects at the population level, we generated a diallel panel consisting of 3,025 hybrids, derived from pairwise crosses between a subset of natural isolates from a completely sequenced 1,011 Saccharomyces cerevisiae population. We examined each hybrid across a large number of growth traits, resulting in a total of 148,225 cross/trait combinations. Parental versus hybrid regression analysis showed that while most phenotypic variance is explained by additivity, a significant proportion (29%) is governed by non-additive effects. This is confirmed by the fact that a majority of complete dominance is observed in 25% of the traits. By performing GWAS on the diallel panel, we detected 1,723 significantly associated genetic variants, with 16.3% of them being low-frequency variants in the initial population. These variants, which would not be detected using classical GWAS, explain 21% of the phenotypic variance on average. Altogether, our results demonstrate that low-frequency variants should be accounted for as they contribute to a large part of the phenotypic variation observed in a population.

Combining ability studies for yield and quality traits in aromatic genotypes of rice (Oryza sativa L.).

Abstract: The present investigation was aimed to study the general combining ability of eight aromatic genotypes of rice and specific combining ability of all possible crosses for grain yield and quality traits in 28 F1’s obtained by 8x8 on way Diallel mating design. The estimates of SCA variance were revealed greater than GCA variance for all the characters except days to 50% flowering, days to maturity, plant height, effective tillers/plant and kernel length after cooking. It showed that both the additive as well as non-additive genetic variance exhibited importance for expression of the characters studied. The Parents, Pusa -2517-2-51-1and Pusa Sugandh-5 studied were identified as best general combiner for both yield and quality traits for most of the characters. Crosses, Pusa-2517-2-51-1×Type-3 showed non additive effects for yield traits only. However, the cross Ranbir Basmati x Pusa Basmati-1 showed non additive effects for quality traits. Cross combination viz., Pusa Sugandh-5 x Pusa Basmati-1, Ranbir Basmati x Kasturi Basmati, Kasturi Basmati × Pusa-2517-2-51-1 and Pusa Sugandh-3 x Type-3 showed non additive gene action for most of the yield as well as quality traits. For those traits which showed high performance were under the control of dominance and dominance × dominance gene effects, heterosis breeding would be most effective. Thus, present study aims to develop hybrids performing better for both yield as well as quality traits.

Inheritance of grain yield and its related characters for 5×5 diallel cross of f1 bread wheat

Abstract: A full Diallel cross among five cultivars of common wheat (Triticum aestivum L.) with their twenty F1 progeny were evaluated at Kurdistan Reign-Iraq at two different locations, Kanipanka and Qlyasan, during the winter season of 2017-2018 using Completely Randomized Block Design (CRBD) with three replications. The mean squares of genotypes were highly significant for all studied characters. Parent Iba-95 at Kanipanka location produced highest value for grain yield/plant, while at Qlyasan location the highest value was provided by the Kauz parent. Maximum heterosis value for grain yield/plant at Kanipanka location produced by the reciprocal cross Klal×Kauz was 7.425%, while at Qlyasan location the diallel cross Hasad×Iba-95 reached 71.402%. Klal parent at both locations was the best general combiner for grain yield/plant and some yield components. The cross Aras×Iba-95 was found to be the best specific combiner for most characters at both locations. The inheritance of most characters is controlled by non-additive gene effect. Heritability in broad sense for most characters was moderate to high, while for narrow sense it was low to moderate. Grain yield/plant exhibited positive and significant correlation with most its important components at both locations. Maximum positive direct effect in grain yield recorded by weight of spikes/plant and biological yield/plant at both locations respectively.

Genetic variation and inheritance in a 9 × 9 diallel in silver birch (Betula pendula)

Abstract: A complete diallel cross was made among nine Betula pendula trees growing in a natural population and a trial was planted on agricultural soil at one site. This exceptional trial has provided estim...

Heterotic response and combining ability analysis in F1 diallel populations of Brassica napus L.

Abstract: Eight Brassica napus L. genotypes including Rainbow, Rustam Canola, Dunkled, Abasin-95, NIFA Gold, Durr-e-NIFA, Punjab Sarsoon and Faisal Canola, varied by genetic makeup and yield traits were crossed during 2014-15 in a 8 × 8 complete diallel fashion at the University of Agriculture, Peshawar, Pakistan. Parental genotypes and their 56 F1 hybrids were sown during 2015-16 in a randomized complete block design to evaluate through mean performance, heterosis and combining ability effects. Significant (p≤0.01) differences were observed among the parental genotypes and their F1 hybrids for all the studied traits. The F1 hybrids NIFA Gold × Rustam Canola, Rustam Canola × Punjab Sarsoon and Punjab Sarsoon × Abasin-95 exhibited best mean performance and maximum midand better-parent heterosis for plant height, 1000-seed weight and seed yield per plant. Combining ability analysis revealed significant (p≤0.01) mean squares due to general (GCA), specific (SCA) and reciprocal combining ability (RCA) for all the traits indicating the importance of additive, non-additive and maternal effects. For plant height and main raceme length, the mean squares due to GCA were greater in magnitude than SCA and RCA. However, for 1000-seed weight and seed yield per plant, the mean squares due to RCA were found greater followed by SCA and GCA. Results further enunciated that due to the preponderance of GCA and RCA effects, the contribution of additive and maternal effects was more important in the expression of these traits. Parental genotypes Abasin-95 and Punjab Sarsoon were found as best general combiners and performed better in combination with other genotypes for the majority of the traits. The F1 hybrids NIFA Gold × Rustam Canola, Rustam Canola × Punjab Sarsoon, Punjab Sarsoon × Abasin-95 and Dunkled × Rainbow exhibited best mean performance and renowned SCA for yield traits. The variances due to σSCA were higher than σGCA and σRCA. The ratios of σGCA/σSCA were noted to be less than unity which revealed that all the traits were controlled nonadditively and hence, the delayed selection in later segregating generations might be more effective. Based on the GCA and SCA effects and mean performance, the promising parental genotypes and F1 hybrids could be further utilized in future breeding programs to develop the rapeseed genotypes with good yield potential and oil quality traits.

Utilization of in Vitro Anther Culture in Spelt Wheat Breeding.

Abstract: The efficiency of in vitro anther culture was screened in a full diallel population of four spelt wheat genotypes and ten F1 hybrids. Genotype dependency was observed based on the data of embryo-like structures (ELS), green-, albino plantlets. In the diallel population and ten F1 hybrids, the green plantlets production ranged from 13.75 to 85.00 and from 6.30 to 51.00, respectively. The anther culture-derived plants of F1 hybrids were grown up in the nursery. At the harvest, 436 spontaneous doubled haploid (DH) plants were identified among the 1535 anther culture-derived transplanted and grown up individual plants. The mean of spontaneous rediploidization was 28.4% which ranged from 9.76% to 54.24%. In two consecutive years, the agronomic values of ‘Tonkoly.pop1’ advanced line were compared with seven DH lines of ‘Tonkoly.pop1’ in the nursery. The DH lines achieved competitive values in comparison with ‘Tonkoly.pop1’ advanced line based on the 11 measured parameters (heading date, plant height, yield, hardness, width and length of seed, TKW, hulling yield, flour yield, protein and wet gluten content). These observations presage the efficient utilization of anther culture in spelt wheat breeding.

Combining ability studies for yield and quality parameters in basmati rice (Oryza sativa L.) genotypes using diallel approach

Abstract: General and specific combining ability of six basmati rice varieties and their fifteen hybrids made through diallel mating without reciprocals for different yield and quality parameters were studied to select the general combiners for future domestic breeding programs. The Analysis of Variance showed that the mean squares due to general and specific combining ability were highly significant for all the traits indicating that both additive and non-additive gene actions were involved in the inheritance of fourteen yield and quality traits. Significant SCA effects for different characters indicated preponderance of non-additive gene actions in the inheritance of the characters under study. Different lines and hybrids were found as best general and specific combiners for different yield and quality traits, respectively. Thus, important specific cross-combiners can be used effectively in crop improvement programs to develop varieties, and further validation of specific genes to develop gene-based perfect markers in rice breeding.

Diallel analysis of some important Morpho-Phenological traits in bread Wheat (Triticum aestivum L.) crosses

Abstract: Wheat (Triticum aestivum L.) is the most important food crop. It offers a great wealth of material for genetic studies due to its wide ecological distribution. The effects of GCA and SCA of morpho-phenological traits i.e. days to emergence, days to flowering, days to maturity, flag leaf length, grain filling duration, spike weight per plant, stem weight and grain yield were studied utilizing an 8×8 half diallel cross according to Griffing’s method II of Fixed model (I). Kouhdasht, Mehregan, Karim, Line 17, N-80-19, Atrak, N-92-9 and Ehsan cultivars were evaluated based on a randomized complete block design (RCBD) with two replications at the research farm of Gonbad Kavous University during fall 2017-2018. The analysis of variance and effect of SCA were significant for all the characters which showed a significant variability among their parents for all studied traits. The analysis of variance indicated that the effect of GCA was significant for all traits except for days to maturity and grain filling duration (p≤0.05). The obtained results from the mean square ratio of GCA to SCA showed that non-additive genetic variance played a predominant role in the inheritance of most traits. Based on GCA and SCA effects obtained from biplot analysis on 8 parents, N-92-9×Ehsan, N-92-9×Kouhdasht, Mehregan×Atrak, Ehsan×Line 17, N-80-19×Mehregan and Karim×Karim were detected as the best hybrids for grain yield. Further studies in relation to the agronomic traits, can improve our knowledge about the wheat cultivars used in the present study and can direct future breeding programs.

Combining ability and heterosis of selected sweetpotato ( Ipomoea batatas L.) clones for storage root yield, yield-related traits and resistance to sweetpotato virus disease

Abstract: Designed crosses using genetically diverse and complementary genotypes is useful to develop sweetpotato clones with improved agronomic traits. The objective of this study was to determine combining ability and heterosis among selected sweetpotato clones for number of storage roots per plant (NRPP), storage root yield (SRY), dry matter content (DMC) and resistance to sweetpotato virus disease (SPVD) for breeding. Eight selected genotypes were crossed using an 8 × 8 half diallel mating design to generate 28 families which were evaluated along their parents under field condition at three sites using a 6 × 6 lattice design with three replications. General combining ability (GCA) and specific combining ability (SCA) effects were highly significant (P < 0.001) among families. Significant GCA × sites and SCA × sites effects indicated environmental effect on gene action and expression. Parental genotypes Simama and Gairo had positive and significant GCA effects for NRPP. The parents 03-03, Ukerewe and Simama had significant and positive GCA effects for SRY and DMC, respectively. Further, Ex-Msimbu-1 and Gairo displayed negative and significant (P ≤ 0.01) GCA effect for SPVD resistance. The genotypes Gairo, 03-03, Ukerewe, Simama and Ex-Msimbu-1 are promising parents for sweetpotato breeding to improve NRPP, SRY, DMC and resistance to SPVD. Further, the study selected best performing families namely: 03-03 × Simama, 03-03 × Resisto and Simama × Ex-Msimbu-1 which recorded the highest mean storage root yields of 16.1, 16.6 and 17.2 tons/ha combined with high DMC and resistant to SPVD for genetic advancement.

Combining Ability of Physiological and Yield Traits of Bread Wheat Diallel Crosses under Timely and Late Sowing Dates

Abstract: WHEAT (Triticum aestivum L.) is a vulnerable crop to heat stress. A set of 12 wheat genotypes were evaluated under timely and late sowing dates using physiological and yield traits during the two years of 2015/2016 and 2016/2017. Consequently, seven genotypes were used in a half-diallel mating system. The parents and their 21F1 hybrids were evaluated under timely and late sowing dates during 2018/2019. The results indicated that both chlorophyll absorbance at anthesis and flag leaf temperature depression at milk stage were strongly associated (r= 0.6; P<0.001) with grain yield under heat stress induced by late sowing date. Therefore, using these traits is highly recommended screening tools for heat stress tolerance in wheat breeding programs. Significant differences were observed between the parental genotypes for their GCA and between their crosses for SCA for all traits under heat stress. The additive constituent of gene action was predominant. Among the seven parents, 1, 4, and 6 were the best general combiners for grain yield, 1000 grain weight, chlorophyll absorbance at anthesis, flag leaf temperature depression and canopy temperature depression at milk stage under heat stress. The best specific crosses for grain yield were 6×9, 6×11 and 1×4, for flag leaf temperature depression at milk stage were 6×11, 6×9 and 10×11 and for canopy temperature depression at milk stage were 4×6, 1×4 and 6×11 under heat stress. Taking advantage of both additive and non-additive components requires using bi-paternal and multi-parental mating approaches in wheat breeding programs targeted to develop heat-tolerant varieties.

Genetic control of aluminum tolerance in tropical maize germplasm

Abstract: Aluminum (Al) toxicity is the most limiting factor to maize crop productivity in acid soils. Therefore, the understanding of inheritance of Al tolerance in maize is important for the developmentof more adequate procedures for Al tolerant genotypes selection. In this sense, the objectives of this study were to determine the inheritance, and the general (GCA) and specific combining ability (SCA) for Al tolerance in tropical maize. First, we evaluated diallel crosses of maize from landrace and hybrid germplasms for Al tolerance through the minimal solution methodology. The DIF data (root growth difference) were analyzed by Griffing diallel model. Later the additive-dominant genetic model proposed by Mather and Jinks (1971) was used to estimate the genetic effects. The results of the diallel analysis showed greater variability associated with the estimates of the SCA for both germplasm. The diallel crosses involving the V 06 (Dente de Ouro 2) landrace stood out by high SCA and GCA for Al tolerance. The generation mean analysis indicated quantitative inheritance of Al tolerance in this germplasm, with most of the variance explained by the additive effects. The heritability in the narrow sense varied from 47% to 71%, indicating the possibility of genetic gain with the selection of tolerant genotypes in F2 generation. Additive gene action associated with intermediate heritability and quantitative inheritance demonstrates the possibility of genetic gains with artificial selection for Al tolerance in this maize germplasm.