Non-additive Gene Effects Research Articles

Estimation of Genetic Variability and Character Association in Micro Mutant Lines of Greengram [<i>Vigna Radiata</i> (L.) Wilczek] for Yield Attributes and Cold Tolerance

Thirty genotypes of greengram including 22 mutant lines, two parents and two standard varieties along with four land races were evaluated in R.B.D. for yield and component traits. The PCV and GCV estimates were high for response to cold of 10, 30 and 40 days old seedlings of green gram at 10 oC temperature. Plant height and pods plant -1 had high heritability with high genetic advance indicating additive gene action. Characters like100-seed weight and seed pod -1 were with high-moderate heritability but low genetic advance indicating non-additive gene effect. Plant height, cluster plant -1 , Pods plant -1 , pod length and seeds pod -1 showed significant positive correlation with yield. Path-analysis showed that pods plant -1 had highest direct positive effects on yield followed by plant height. Positive correlation of most traits with yield was greatly influenced by indirect positive effect via pods plant -1 and plant height.

Studies on Combining Ability Through Line x Tester Analysis in Garden Pea(PIsum SativumL.)

This research was carried out to investigation the genetic structure of the 36 F1 garden pea hybrids established from 12 female parents (Line) and three male parents (Tester), to determine parents showing general combining ability (GCA) and determine crosses showing specific combining ability (SCA). Broad genetic variability was observed among the genotypes. Estimates of variance due to GCA and SCA and their ratio revealed predominantly non-additive gene effects for all studied traits. While line KS-156 and KS-256 were the best general combiners among the parents, KS-175 X E-6 was the best cross for seed yield. Hybrids generally showed grater yield potential than their parental genotypes.

Potencial de hibridação entre acessos de tomateiro para pré-melhoramento quanto à resistência à requeima

Resumo: O objetivo deste trabalho foi avaliar genitores com potencial de hibridação para o pré-melhoramento do tomateiro (Solanum lycopersicum) quanto à resistência à requeima. Foram utilizados seis acessos de tomateiro (BGH-2102, BGH-2117, BGH-2127, BGH-2130, BGH-2332 e BGH-2343) como genitores resistentes e 15 híbridos F1 originários destes genitores. Utilizou-se o delineamento de blocos ao acaso, com três repetições. As plantas foram inoculadas com uma mistura de esporângios de Phytophthora infestans, agente etiológico da requeima, na concentração de 5x103 esporângios mL-1. A área abaixo da curva de progresso da doença foi utilizada para avaliar a resistência. Realizou-se a análise dialélica, tendo-se considerado o efeito de genótipos como fixo. Estimou-se a capacidade geral e específica de combinação dos acessos. O padrão de resistência dos genitores e da maioria dos F1 foi o mesmo que o das testemunhas resistentes. Foram observados: variabilidade genética aditiva entre os genitores, predominância de efeitos gênicos não aditivos e desvios de dominância bidirecional no controle do caráter. A frequência de alelos favoráveis e divergentes para resistência à requeima é maior nos acessos BGH-2117, BGH-2127 e BGH-2343.

Breeding for components of earliness and seed yield in sesame

Sesame is an important oil crop not only in India but worldwide. Understanding of nature of inheritance of sesame plant characteristics is essential for planning of effective breeding strategies. Eight diverse genotypes of sesame were employed in a half-diallel mating to study combining abilities and assess potentials for earliness and seed yield improvement. The 28 F 1 and their eight parents were evaluated in randomized block design with three replications for six characters. Variances due to specific combining ability (SCA) and general combining ability (GCA) for all studied traits were significant. Predictability ratio revealed preponderance of non-additive gene effect for all the characters. Among the parent, AT 158 and AT 177 were good general combiner for earliness along with the former for seed yield and later for plant height. RT 54 for seed yield and days to maturity and ABT 33 for reproductive period and plant height were identified as good general combiner. Most good specific combination for seed yield involved average x low general combiner. Two crosses were identified for developing early maturing high yielding genotypes. Parents like AT 158, AT 177, RT 54 and ABT 33 could be utilized in multiple crossing programme and further intermating of segregants followed by recurrent selection could be an appropriate approach to select desirable recombinants for seed yield and earliness.

Evaluation of maize (<i>Zea mays</i> L.) accessions using line x tester analysis for aluminum and manganese tolerance

Soil acidity is a limiting factor severely affecting the growth and yield of maize. The present study aimed at estimating the breeding value of inbred lines and to assess the test-cross performance of the hybrid maize under acid soil conditions. A line x tester analysis involving 63 test-crosses generated by crossing 20 maize inbred lines with 3 testers and between testers themselves, and 1 standard check was investigated during the cropping season 2012 in two contrasted regions with aluminum and manganese toxicity in Cameroon. Both treatments, acid soil and non-acid soil, using dolomitic lime were conducted in a randomized complete block design with 3 replications. Seven hybrids producing high grain yield (4.27 to 9.88t/ha), with high specific combining ability (SCA) and slow rate of yield loss were discovered such as tolerant for both types of acidic soils. Likewise, four inbred lines (ATP-46, 87036, and Cam Inb gp117, C4SRRA7) with high general combining ability (GCA) were retained as good progenitors. The GCA and SCA effects showed that the tolerance to aluminum toxicity was controlled by additive effects of genes while on acid soil with manganese toxicity, the contribution of non-additive effects of genes was dominant.Keywords: Inbred lines, hybrids, acid soil, GCA, SCA, humid forest zones

English

The spotted stem borer, Chilo partellus, Swinhoe (Lepidoptera, Crambidae) is one of the most destructive insect pests of maize in tropical environments. However, the combining ability and heterotic orientation of the germplasm for grain yield and borer resistance is limited. The objective of this study was to determine combining ability and heterotic orientation of new maize inbred lines under C. partellus infestation. Sixty six (66) inbred lines were crossed to two single cross testers in a line x tester mating scheme. The 132 testcross hybrids and four checks were evaluated at three locations in Kenya under C. partellus infestation. General and specific combining ability effects were significant for C. partellus stem borer resistance traits and grain yield, suggesting the importance of both additive and non-additive gene effects for these traits. Heterotic classification of lines was done based on both heterosis and specific combining ability data. Based on heterosis for grain yield data at Embu, 15 lines were allocated to group A, 18 to group B and 12 to group AB. At Kakamega, 26 lines were oriented towards group A, 19 to group B and 9 to group AB.  At Kiboko, 15 lines were inclined towards group A, 18 to group B and 11 to group AB, whilst the remainder could not be classified. Based on the SCA estimates, at Embu, 10 lines revealed positive SCA effects with both testers and were considered to be AB-oriented while 8, and 1 lines were oriented towards A, and B, respectively. A similar trend was detected at Kakamega and Kiboko. The identified lines and heterotic groups would be used by hybrid maize programs where C. partellus stem borers occur exclusively or in league with other stem borers. Key words: Tropical maize, maize breeding, biotic and abiotic stresses tolerance.

ESTIMATION OF SOME GENETIC PARAMETERS FOR EARLINESS AND SOME VEGETATIVE TRAITS IN SOME HULLESS BARLEY GENOTYPES UNDER NORMAL AND WATER STRESS CONDITIONS

This investigation was carried out at Sakha Agricultural Research Station, ARC, Egypt during the two growing seasons (2010/2011 and 2011/2012). Seven lines and three testers were used to develop barley hybrids for earliness and vegetative traits under normal and water stress conditions. Data revealed that most of the variances due to genotypes, parents, crosses, parents x crosses, lines, testers and line x testers were highly significant for most studied traits under both conditions and their combined data. The water stress treatment decreased the mean of days to heading for parents and their hybrids. The parental Line-1, Tester-1 under all conditions and top cross no. 7 under normal and combined and cross no. 1 under stress were the earliest parents and crosses for days to heading. The stressed genotypes for water, matured earlier than genotypes grown under normal condition. The ratios of GCA/SCA were lesser than unity for all studied traits under all conditions, which mean that non-additive gene effects played an important role in the inheritance of these traits. In such cases, a bulk method would be fruitful to eliminate the effect of dominance in the advanced generation. Desirable significant GCA effects were showed by Line-1 under water stress and Tester-1 under all conditions for days to heading; Tester-1 under normal and combined for days to maturity; Line-2 under stress and Line-7 under normal condition for grain filling period; Line-4, Line-6 under both conditions and combined, Line-3 under normal, Line-7 under water stress, Tester-3 under both conditions and combined data for grain filling rate; Line-4 under both conditions and their combined data, Line-7 under water stress and combined data, Tester-2 under stress and combined data for flag leaf area; and Line-3 under normal, Line-2 and Line-7 under water stress for total chlorophyll content. Moderate phenotypic and genotypic coefficients of variability were obtained for grain filling rate and total chlorophyll content, and high for flag leaf area. Small differences between genotypic and phenotypic coefficients of variability were found for all studied traits under all conditions, indicating the presence of sufficient genetic variability for these traits, which may facilitate selection. Broad sense heritability percentages ranged from moderate to high with percentages ranged from 10.82% for days to maturity at combined data to 97.30% for grain filling rate under normal condition. These results indicate that genotypic variances played the major part of phenotypic variances. Narrow sense heritability percentages varied from low to moderate with percentages ranged from 0.92 % for grain filling period at combined data to 18.92% for grain filling rate under normal condition. The expected genetic advance (Δg) ranged from 0.02 for grain filling period at combined data to 0.36 for total chlorophyll conten under normal condition. While, the estimates of predicted genetic advance (Δg %) ranged from 0.04% for grain filling period at combined data to 7.41% for grain filling rate under stress condition. Generally, traits that showed high values of narrow sense heritability and expected genetic advance from selection should be used in breeding program where selection in the early segregating generations will be useful because additive gene action is more important than non-additive genetic components.

Integrating Crop Growth Models with Whole Genome Prediction through Approximate Bayesian Computation.

Genomic selection, enabled by whole genome prediction (WGP) methods, is revolutionizing plant breeding. Existing WGP methods have been shown to deliver accurate predictions in the most common settings, such as prediction of across environment performance for traits with additive gene effects. However, prediction of traits with non-additive gene effects and prediction of genotype by environment interaction (G×E), continues to be challenging. Previous attempts to increase prediction accuracy for these particularly difficult tasks employed prediction methods that are purely statistical in nature. Augmenting the statistical methods with biological knowledge has been largely overlooked thus far. Crop growth models (CGMs) attempt to represent the impact of functional relationships between plant physiology and the environment in the formation of yield and similar output traits of interest. Thus, they can explain the impact of G×E and certain types of non-additive gene effects on the expressed phenotype. Approximate Bayesian computation (ABC), a novel and powerful computational procedure, allows the incorporation of CGMs directly into the estimation of whole genome marker effects in WGP. Here we provide a proof of concept study for this novel approach and demonstrate its use with synthetic data sets. We show that this novel approach can be considerably more accurate than the benchmark WGP method GBLUP in predicting performance in environments represented in the estimation set as well as in previously unobserved environments for traits determined by non-additive gene effects. We conclude that this proof of concept demonstrates that using ABC for incorporating biological knowledge in the form of CGMs into WGP is a very promising and novel approach to improving prediction accuracy for some of the most challenging scenarios in plant breeding and applied genetics.

Nonadditive Effects of Genes in Human Metabolomics.

Genome-wide association studies (GWAS) are widely applied to analyze the genetic effects on phenotypes. With the availability of high-throughput technologies for metabolite measurements, GWAS successfully identified loci that affect metabolite concentrations and underlying pathways. In most GWAS, the effect of each SNP on the phenotype is assumed to be additive. Other genetic models such as recessive, dominant, or overdominant were considered only by very few studies. In contrast to this, there are theories that emphasize the relevance of nonadditive effects as a consequence of physiologic mechanisms. This might be especially important for metabolites because these intermediate phenotypes are closer to the underlying pathways than other traits or diseases. In this study we analyzed systematically nonadditive effects on a large panel of serum metabolites and all possible ratios (22,801 total) in a population-based study [Cooperative Health Research in the Region of Augsburg (KORA) F4, N = 1,785]. We applied four different 1-degree-of-freedom (1-df) tests corresponding to an additive, dominant, recessive, and overdominant trait model as well as a genotypic model with two degree-of-freedom (2-df) that allows a more general consideration of genetic effects. Twenty-three loci were found to be genome-wide significantly associated (Bonferroni corrected P ≤ 2.19 × 10(-12)) with at least one metabolite or ratio. For five of them, we show the evidence of nonadditive effects. We replicated 17 loci, including 3 loci with nonadditive effects, in an independent study (TwinsUK, N = 846). In conclusion, we found that most genetic effects on metabolite concentrations and ratios were indeed additive, which verifies the practice of using the additive model for analyzing SNP effects on metabolites.

English

Groundnut chlorotic rosette disease (GCRD) transmitted by the aphid, Aphis craccivora, is an important virus disease of groundnut in Africa. Breeding for host resistance remains the best strategy to minimize losses due to this disease. Nine cultivated groundnut genotypes with differential reaction to GCRD were crossed in an incomplete diallel mating design to determine the combining ability of GCRD resistance. The parents and 36 F2 populations were inoculated with veruliferous A. craccivora at the seedling stage and evaluated for disease reaction at two locations in Nigeria in 2012. Disease incidence (based on visual symptoms) was recorded three times at fortnightly interval using area under disease progress curve. General combining ability (GCA) and specific combining ability (SCA) effects for GCRD resistance were highly significant (P < 0.01), indicating that both additive and non-additive gene effects governed the inheritance of GCRD resistance. The Baker ratio was low (0.3) for GCRD indicating that non-additive gene effects was more important than additive gene effects in controlling GCRD resistance in these crosses. As a result, progeny performance could not be adequately predicted from GCA effects alone. Therefore, effective selection of superior genotypes would be achieved at advanced generations when maximum homozygosity is attained. Key words: Groundnut chlorotic rosette disease, area under disease progress curve, combining ability, additive and non-additive gene effects.

Inheritance of resistance to cassava green mite and other useful agronomic traits in cassava grown in Zambia

Cassava green mite (CGM) Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) is a major arthropod pest causing significant loss in the yields of storage roots and planting materials of cassava in Zambia. Its control has been mainly based on the use of exotic predatory mites as biological control agents, which unfortunately, have not established well in Zambia due to the lack of suitable host genotypes and harsh weather conditions. The current study was aimed at breeding cassava for improvement of morphological traits that are associated with resistance to CGM, which can also enable cassava genotypes to provide shelter and ensure continuous survival of natural enemies of CGM, and to determine the inheritance of these traits by assessing combining ability and therefore the type of gene action involved in their expression. Using a 5 × 5 half diallel mating design, full-sib cassava genotypes were generated out of which 300 were selected and evaluated in the field. Data were collected for CGM density, CGM leaf damage and cassava mosaic disease severity, plant growth habit, leaf morphological traits, storage root yield and root dry mass. Both general and specific combining ability effects were significant (P < 0.01) for the reaction of the F1 progeny to CGM, and for the various plant morphological traits that were measured, suggesting that both additive and non-additive gene effects play a role in the expression of the traits.

Inheritance of high iron and zinc concentration in selected bean varieties

Micronutrient malnutrition especially iron (Fe) and zinc (Zn) has disastrous consequences for the more vulnerable members of the human society, especially poor women and pre-school children in developing countries. The common bean (Phaseolus vulgaris L.), an important grain legume directly consumed by humans provides cheap and important quantities of protein and calories and is an excellent source of some minerals (Fe and Zn) and vitamins which qualify it as perfect food. Unfortunately, many of the adapted bean market class varieties are low in these nutrients. Therefore there is need for biofortification of these varieties with Fe and Zn through plant breeding and genetic engineering in order to contribute to improved health of bean consumers. The objective of this study was to determine the mode of inheritance of high Fe and Zn concentration in selected bean varieties. Six parents high and low in Fe and Zn were crossed following a full diallel crossing design. Populations were advanced from F1 to F2. F3 seed were analyzed for Fe and Zn concentration using X-ray fluorescence. The study showed that both additive and non-additive gene effects are important in determining the expression of high Zn and Fe concentration even though additive gene effects contributed more. Narrow sense heritability of Fe and Zn was high estimated at 71 % for Fe and 83 % for Zn. Significant maternal and reciprocal effects suggest also that cytoplasmic inheritance is involved in Zn and Fe concentration. Strong positive correlation between Fe and Zn concentrations (r = 0.75) was observed suggesting that these micronutrients are not independently inherited. The positive relationship between Fe and Zn plus the negative relationship observed between Zn and seed size (r = 56) suggest that Zn and Fe accumulation is controlled multigenically or oligogenically with some genes affecting the concentration of both minerals. The variability in seed mineral concentration among crosses was larger for Fe (47–77 ppm) than for Zn (28–38 ppm).

Generation Mean Analysis of Fibre Quality Characters in Upland Cotton (Gossypium hirsutum L.)

Generation mean analysis was carried out to estimate the nature and magnitude of gene effects for fibre quality traits in three crosses of upland cotton (Gossypium hirsutum L). The presence of epistasis was reflected by scaling tests and inadequacy of simple additive-dominance model for most of the characters studied. The results obtained revealed that the nature and magnitude of gene effects differed in different crosses and showed importance of additive as well as non-additive gene effects in the inheritance of different characters. In view of the parallel role of additive and non-additive gene effects in the inheritance of different characters, selection in the segregating generations should be delayed when dominance gene effects would have diminished or sophisticated selection procedures as recurrent selection and population improvement programmes may be followed. However, additive gene effects may be fixed with respect to some specific traits such as micronair value and fibre strength.

Combining Ability and Heterosis for Qualitative Traits in Chili Pepper (&lt;i&gt;Capsicum annuum&lt;/i&gt; L.)

Eight parents were crossed in half diallel design to develop 28 F 1 hybrids and these hybrids along with 8 parents like MS 341, SL 461, DL 161, SL 462, SD 463, PP 402, PP 403, VR 521 and four, commercial checks viz., CH-1, CH-3, Rudra and Soldier were evaluated for eight traits in a randomized complete block design (RCBD) with three replications at Punjab Agricultural University, Ludhiana, India. The results from present investigation revealed that the hybrids which were found superior on the basis of per se performance were also found best specific combiners as well as heterotic over the commercial checks. The present study also investigates that non-additive gene effects had greater role in controlling the inheritance of quality traits.

Genetic options for improving fodder yield and quality in forage sorghum

Improving yield and quality of fodder from forage sorghum is important, especially in the semi-arid tropics, where sorghum is a major source of fodder. The aim of this work was to understand the genetic basis of fodder yield and quality traits, and character associations, and to estimate combining ability of the parents. The experiment was carried out during 2 successive rainy seasons using 10 parents crossed in a half-diallel design. Significant differences among the genotypes for fodder yield, quality and cell wall constituents were observed. Important quality traits, crude protein and digestibility (IVOMD), were not correlated with fodder yield, indicating the potential to improve yield and quality simultaneously in forage sorghum. General combining ability and specific combining ability variances showed that, for almost all characters, both additive and non-additive gene effects were important, with a predominance of non-additive effects. Parental lines SEVS4, HC308 and UPMC503 were good general combiners for yield and quality. The brown midrib lines, EC582508 and EC582510, were good general combiners for low lignin and high IVOMD. Strategies for improving forage sorghum to suit animal and biofuel industries are discussed.Keywords: Digestibility, crude protein, ADL, diallel analysis, gene effects.DOI: 10.17138/TGFT(3)49-58

Inheritance of gynoecism and genetics of yield and yield contributing traits through generation mean analysis in bitter gourd

The phenotypic ratio of 3:1 (monoecious vs gynoecious) in bitter gourd confirmed the monogenic recessive inheritance of gynoecism trait. Further investigation on gene action in the cross DBGy 201 × S-2 and DBGy 201 × Pusa Do Mausami by generation mean analysis revealed duplicate epistasis for most of the traits including node at which first female flower appear, days to first flowering, days to first harvestable maturity, fruit length, fruit diameter, fruit weight and yield suggesting the possibilities of obtaining transgressive segregants in later generations. Moreover, significant additive and non-additive gene effect for traits like node at which first female flower appear, days to first flowering, days to first harvestable maturity and fruit diameter indicates use of reciprocal recurrent selection or bi-parental mating for improvement of these traits. Non-additive gene action was significant for number of fruits per plant, fruit length, weight and yield inferring heterosis breeding as the best option for obtaining higher gain in these characters.

Genetic analysis to identify good combiners for ToLCV resistance and yield components in tomato using interspecific hybridization

The interspecific hybridization for tomato leaf curl virus (ToLCV) resistance was carried out among 10 genetically diverse tomato genotypes (diversified by 50 SSR markers). Among the 10 parents, four susceptible cultivars of Solanum lycopersicum were crossed with six resistant wilds, such as S. pimpinellifolium, S. habrochaites, S. chemielewskii, S. ceraseforme, S. peruvianum and S. chilense in a line x tester mating design. All the 24 hybrids and their parents were grown in the field and glasshouse conditions to determine the general-combining abilities (GCA) and specific-combining abilities (SCA). The variances due to SCA and GCA showed both additive and nonadditive gene effects. Based on GCA estimates, EC-520061 and WIR-5032 were good general combiners while based on SCA estimates, PBC x EC-520061 and PBC x EC-521080 were best specific combiners for coefficient of infection and fruit yield per plant in both the environments. These lines could be selected and utilized in ToLCV resistance and high yield breeding programme for improving the traits.

English

A study was conducted during 2008 to 2009 in 12 environments in Nigeria, Benin Republic and Togo to evaluate genetic variation and heritability of yield and related traits in 48 rice genotypes. The experiments were laid out in a randomized complete block design (RCBD) with three replications. Genotypes differed significantly at p > 0.001 for all the traits studied, which implies that the genotypes contain adequate genetic variability. Phenotypic coefficients of variation (PCV) were higher than genotypic coefficients of variation (GCV) in all the characters across the 12 environments. High heritability estimates were obtained for days to flowering (91.37), days to maturity (86.86), plant height at maturity, number of tiller per meter square, panicle shattering, panicle threshability, panicle per meter and panicle length (72.21) suggesting that the traits are primarily under genetic control. High estimates of heritability, GCV and genetic advance (GA) observed for grain yield is an indication that selection for grain yield could be achieved through phenotypic performance. Furthermore, high estimates of heritability, GA and GCV recorded in these characters could be explained by additive gene action. Low estimates of heritability, GCV and GA recorded for grain yield and number of grains per panicle could be due to non-additive gene effect suggesting that these traits were less responsive to specific environment influences. Grain yield recorded highly significant positive correlation with panicle length (0.28), leaf width (0.40), grain length (0.30), number of panicles per meter square (0.19) and1000-grain weight (0.17). It correlated negatively with basal leaf sheath coloration (-0.33) and grain width (-0.20) in the 12 environments. The current study indicated that more number of tillers, panicles per meter square, long panicles, high number of primary and secondary branch panicles and large 1000-grain weight are important yield related traits and could be used for selection in rice breeding programs. Key words: Correlation coefficients, heritability, phenotypic coefficients, rice, variability, yield components.

Variability and heritability analysis in F4 genotypes of Brassica rapa L.

A field experiment was conducted in the experimental field of Genetics and Plant Breeding Department, Sher-e Bangla Agricultural University, Dhaka, Bangladesh to study variability in 10 F4 lines obtained through intervarietal crosses along with 8 released varieties of Brassica rapa. Significant variation was observed among all the genotypes for all the characters studied. Considering genetic parameters high genotypic co-efficient of variation (GCV) was observed for number of secondary branches per plant, siliquae per plant, yield per plant, whereas days to maturity showed very low GCV. High heritability with low genetic advance in percent of mean was observed for days to maturity which indicated that non-additive gene effects were involved for the expression of this character and selection for such trait might not be rewarding. High heritability with moderate genetic advance in percent of mean was observed for plant height and days to 50% flowering indicating that this trait was under additive gene control and selection for genetic improvement for this trait would be effective. Considering, inter genotypic variability, heritability, and genetic advance, % coefficient of variation and other agronomic performance G2, G14, G18, G1, G9, G12, G16, G17 may be considered to be better parents for future uses in hybridization programme. DOI: http://dx.doi.org/10.3329/bjar.v39i2.20426 Bangladesh J. Agril. Res. 39(2): 227-241, June 2014

Osmoregulation capacity in Bulgarian durum wheat

The phenotypic variation in osmotic adjustment (OA) capacity of five Bulgarian winter durum wheat genotypes and their progenies was determined using a modified method based on the measurement of seedling growth suppression after three-day exposure to osmotic stress induced by 1 mol/L sucrose. The genetic parameters of the studied trait in a diallel crossing scheme, including the selected genotypes and the microsatellite polymorphism at 43 loci, were determined. The old Bulgarian cultivar Apulicum 233 and all hybrid combinations involving this genotype showed higher OA. In the heritability of osmoregulation ability, the non-additive gene effects (specific combining ability) strongly predominated over the additive ones and had a significant impact on the observed high heterosis effect. Distinct polymorphisms were identified between the studied genotypes. Cluster analysis of the phenotypic data obtained from a multiyear test under water-limited conditions and the molecular data, both based on Euclidean distance, showed similar grouping of the genotypes with specific separation of cultivar Apulicum 233 (high OA) in a single cluster. Principal component analysis revealed not only interrelationships between the important agronomic and morpho-physiological traits in Bulgarian durum wheat under water-limited conditions, but also presence of relations between them and some microsatellite loci located near or within known quantitative trait loci (QTLs) for these traits. Further studies based on segregating population between genotypes with contrasting levels of OA will allow mapping QTLs for phenotypic traits expressed under water deficit and isolation of genes that can be used as potential markers in marker-assisted selection for drought tolerance.