Specific Combining Ability Values Research Articles

Enhancing yield and oil content in oilseed rape hybrids: Insights from line × tester and SIIG approaches.

The production of high-oil-yielding hybrid varieties is a primary objective in oilseed rape (Brassica napus L.) breeding programs. Biometric genetic experiments such as line × tester provide valuable insights into the genetic structure of traits associated with high oil yield. In this study, 21 winter hybrids of oilseed rape were evaluated, which were generated by crossing three restorers with seven CMS lines. The experiment was conducted using a line × tester experiment based on a completely randomized block design. Phenological, agronomic, yield, and oil yield components were assessed in this study. The ideal genotype selection index (SIIG) methodology was also employed to identify superior hybrids based on all studied traits simultaneously. Significant differences were observed between the obtained hybrids and the check cultivars. Heritability analysis revealed that phenological traits were primarily controlled by additive effects, while agronomic and qualitative traits were mainly influenced by non-additive gene effects. Both broad-sense and narrow-sense heritability exhibited a wide range, underscoring the importance of genetic variance. Notably, the hybrids T1 × L5, T1 × L6, and T3 × L1 showed significant specific combining ability values of 394.74, 541.73, and 1236.79, respectively, making them the top specific combinations for increasing seed yield. Based on the SIIG index, hybrids T3 × L1, T1 × L5, T1 × L3, and T2 × L3 emerged as high-oil-yielding hybrids with desirable agronomic traits. The identified superior hybrids by line × tester and SIIG approaches hold promise for the development of high-yielding oilseed rape cultivars with desirable agronomic traits in oilseed rape breeding programs.

Analysis of Genetic Architecture for Ten Genotypes of Bread Wheat Using Half Diallel Crosses Under Nitrogen Stress

This study included 10 genotypes of bread wheat are M45, Yakora, Giza168, Sids 12, SK95, Misr2, Giemiza 9, Sahel 1, Sids14, and Silano. The genotypes (parents and F1 crosses) were cultivated at the research station of the Department of Field Crops of the College of Agriculture at the University of Kirkuk, during the season (2021-2022) in two separate experiments on sufficiency and insufficiency of the nitrogen element using a Randomized Complete Block Design (R.C.B.D) and with three replications, to estimate the general and specific combining ability, gene action and some genetic parameters. The results of the statistical and genetic analysis showed that there are highly significant differences for the general and specific combining ability values and that the ratio of the combining ability variance components to the specific combining ability variance components was less than the one for nitrogen sufficiency and insufficiency for all the studied traits. Sids14 variety excelled in its desirable effects of general combining ability, followed by Sr. (Sids12). The hybrid (M45 × Sids14) had the highest desired values for the effects of the special combining ability at nitrogen levels for all the traits studied, followed by the cross (Sahel 1 × Sids 12) also for all the traits studied except for The number of spikes plant-1 when there was insufficient nitrogen. The heritability broad sense was high with sufficient and insufficient nitrogen, while heritability narrow sense was high with sufficient nitrogen in the number of grains spike-1 and grains yield plant-1 (gm) and medium in The number of spikes plant-1 and the weight 1000 grains (gm) and the biological yield in the insufficient amount of the nitrogen element, the heritability narrow sense was medium in all studied traits. The average degree of dominance was greater than one when nitrogen was sufficient and insufficient, which indicates the existence of Over dominance, and the expected genetic advance as a percentage was low except for the number of grains spike-1 when nitrogen was sufficient and the grains yield plant-1 (gm) when nitrogen was insufficient, as it was medium. (11.908 and 12.250), respectively, these parents that are superior in the general combining ability with high phenotypic significance can be included in wheat breeding programs to produce hybrids that are superior in the specific combining ability that can be invested in the following generations with in the breeding programs to reach the best promising varieties with future nitrogen insufficiency.

A Study on the Specific Combining Ability in Several Inbred Lines of Maize

Maize is a cereal crop essential to fulfill the need for food and support global food security programs. Maize hybrid varieties play a very significant role in increasing maize production. Objectives of the research were to obtain a tester, which is consistent in identifying inbred lines with a high specific combining ability, and to obtain prospective crossed-hybrids that have the potential assembling to be maize hybrid varieties. The grain yield showed that the specific combining ability values ranged from -3682.2 to 5251.7. Crosses that have high and positive specific combining ability included lines of JG-11, JG-18, JG-34, JG-01, JG-40, JG-B0, JG-19, and JG-02 with a tester of JG-T00; lines of JG-20, JG-01, JG-03, JG-42, JG-02, JG-46, and tester of JG-T14; lines of JG-24, JG-08, JG-23, JG-26, JG-21, JG-07, and JG-06 with a tester of JG-T15; lines of JG-38, JG-40, JG-35, JG-36, JG-01, JG-51, JG-17, JG-B0, and JG-08 with tester of JG-T22; and lines of JG-07, JG-01, JG-26, JG-24, and JG-18 with tester of JG-T37. There were combinations of 9 crosses between inbred lines and the best testers, including JG-06XJG-T15, JG-51XJG-T22, JG-49XJG-T22, JG-B0XJG-T22, JG-35XJG-T22, JG-38XJG-T22, JG-17XJG-T22, JG-36XJG-T22, and JG-49XJG-37, which are potential as prospective maize hybrids that have high productivity.

Effects of the combining ability on mirador chili (Capsicum annuum L.) populations native to Veracruz, Mexico

Objective: To evaluate the effects of the general and specific combining abilities on the agronomic traits of the native populations of mirador chili and to identify potential genotypes for the genetic improvement of this crop. Design/Methodology/Approach: The general and specific combining abilities were calculated to determine the agronomic traits and yield of five mirador chili populations, using Griffing’s method 2, model I, which includes parental lines and direct crosses. Results: The P1, P4, and P3 genotypes recorded the highest and positive values. They also recorded a significative difference regarding the general combining ability. Meanwhile, the P1×P5 and P4×P5 crosses recorded the highest specific combining ability values. Study Limitations/Implications: We were not able to establish diverse evaluation environments and genomic selection studies using molecular markers. Findings/Conclusions: Information about the yield potential of five mirador chili was generated. These results are important for the development of a genetic improvement program and for the selection of the method that will be used.

COMBINING ABILITY ANALYSIS FOR MATURITY AND YIELD ATTRIBUTES IN SWEET CORN ACROSS ENVIRONMENTS

Early maturity and genotype by environment interaction (GEI) have always been challenging concerns for breeders in selecting appropriate parents for breeding programs. The presented study aimed to investigate early maturity and the dimension of gene action, as well as, assess the performance of half-diallel populations using eight advanced sweet corn inbred lines and their 28 F1 hybrids with two commercial checks for maturity and yield-related traits in the spring of 2018 at the Nowshera (plain) and Swat (hilly) areas, Khyber Pakhtunkhwa, Pakistan. Analysis revealed significant differences among the genotypes for the studied traits over both locations. General combining ability (GCA) effects were significant for all the traits at both the agro-climatic conditions, except 100-kernel weight, with the specific combining ability (SCA) effects relevant for grain yield at both locations. The GCA-SCA ratio for studied traits indicated dominance gene action, which also gained support by higher values of SCA than GCA variances. Based on the results, the identified inbred lines SWTS-1-8 and SODS-1 serve as good general combiners for traits like earliness and grain yield attributes, making them better parents to improve the stated characteristics in sweet corn. However, the F1 hybrids, i.e., NARCCCRI-19 × CCRI-34 at Nowshera and CCRI-34 × SODS-1 at Swat, showed the best specific combiners for maturity. Likewise, F1 hybrids, i.e., SWTS-1-4 × SWTS-1-8 and SWTS-1-8 × CCRIS-34, emerged as desirable for grain yield at Nowshera and Swat, respectively. The inbred lines for the mentioned hybrids can be a source of germplasm improvement, breaking through undesirable linkages in future sweet corn breeding programs.

Heterosis and Combining Ability Estimate on Yield and Yield-Related Traits in a Half Diallel Crosses of Kenaf (Hibiscus Cannabinus L.) in Malaysia

ABSTRACT Understanding heterosis and combining ability among distinct kenaf (Hibiscus cannabinus L.) genetic resources is crucial for developing hybrid kenaf. An investigation was conducted on 36 F1 combinations produced from nine parental genotypes of kenaf in a diallelic scheme using Griffing diallel analysis technique 2, model I. Highly significant F-test values revealed the presence of variability for all the 15 quantitative traits for general combining ability (GCA) and specific combining ability (SCA) except days to 1st flowering. The magnitude of GCA variance was considerably higher than that of SCA variance for plant height, stem middle diameter, stem top diameter, days to flowering, number of pods, number of seeds and 1000 seeds weight, showing the predominates of additive gene for these traits. Narrow-sense heritability of 50.93% in the combined environments showed that seed number was the most heritable trait, whereas days to 1st flowering and 1000 seed weight had moderate heritability. Parents P1, P3 and P4 had the most dominant alleles for most traits studied. Considering SCA and heterosis values, the hybrids H3, H4, H9, H11, H23, H29 and H35 had high heterotic for fiber and seed yield.

COMBINING ABILITY ANALYSIS FOR VARIOUS MORPHOLOGICAL TRAITS IN SUNFLOWER (HELIANTHUS ANNUUS L.)

The present research was conducted in the Department of Plant Breeding and Genetics, University of Agriculture Faisalabad. Six lines and four testers were sown, and 24 crosses were generated. The seeds of these crosses were sown in a randomized complete block design (RCBD) with three replications and data for several morphological traits, including the number of days to flowering, plant height, number of whorls per head, head diameter, number of seeds per head, number of leaves per plant, achene yield per plant, 100-seed weight, oil content and protein content were recorded. Data were analyzed using analysis of variance and line × tester analysis. General combining ability (GCA) and specific combining ability (SCA) for traits mentioned above were evaluated. Lines with crosses showing high values of GCA and SCA were selected for further breeding programs. The recorded data were further subjected to analysis of variance, GCA and SCA to determine genetic variability and association among the characters. The results showed that the parental lines A-1, A-2, A-7 and A-8 showed good potential for most of the traits so that they could be taken to further breeding programs. The crosses A-5×A-10 and A-2×A-7 could be used for hybrid development.

Exploring the quantitative genetics of essential oil components in Coriandrum sativum L. under different water regimes

Coriander is one of the most popular essential oil (EO) source in Apiaceae family and economically important. This study aimed to evaluate the genetic combining ability and inheritance nature in coriander for EO components. A set of 4 × 4 one-way diallel crosses were performed between four genetically divers genotypes. The plant materials (hybrids + parents) were evaluated under well-watered (WW) and water deficit stressed (WDS) irrigation regimes. Linalool (65.96% in WW; 69.45% in WDS) and geranyl acetate (12.92% in WW; 15.58% in WDS) composed a large percent of the total EO content in both irrigation regimes. WDS had an increasing effect on linalool, geranyl acetate, o-cymene and geraniol content. Significant genotypic and genotype × irrigation regime effects observed for EO components which are due to differences in the genome alleles content and alleles action. The significant general combining ability (GCA) and specific combining ability (SCA) effects for EO components reveal the presence of both additive and dominance gene actions. Genetic control pattern of o-cymene, γ-terpinene and citronellol in WDS regime were similar to WW while the preponderance of additive gene effects increased for α-pinene and linalool. In conclusion, consideration the GCA and SCA values and inheritance nature of the EO components, selection for high linalool, α-pinene and geranyl acetate content in segregating generations derived from H1×4 (a hybrid derived crossing between parent 1 and parent 4) hybrid should be delayed to F3 generation.

Combining Abilities, Heterosis, Growth Performance, and Carcass Characteristics in a Diallel Cross from Black-Bone Chickens and Thai Native Chickens.

Simple SummaryBlack-bone chicken is classified as a healthy food due to its naturally bioactive ingredients; however, the limitation of a slow growth rate results in longer times to raise it to market weight. Crossbreeding is a tool used to produce superior breeds. The present study therefore determined the combining abilities and heterosis for better growth performance and maintained the color of black-bone chickens to gain desirable antioxidant properties (melanin and carnosine) in crosses between Hmong black-bone (HB), Chinese black-bone (CB), and Thai native (TN) chickens. The results indicate that crossing between the TN sires and CB dams had the best potential to promote careers for farmers on a commercial scale.The purpose of this study was to determine the combining abilities and heterosis for the growth performance and carcass characteristics in crosses between Hmong black-bone (HB), Chinese black-bone (CB), and Thai native (TN) chickens using a mating system diallel crossing. Nine crossbred chickens including HB × HB, CB × CB, TN × TN, HB × TN, TN × HB, CB × HB, HB × CB, TN × CB, and CB × TN, were tested. The total data were 699 recorded at the beginning of the experiment to 595 recorded in weeks 14 of age. Body weight (BW), average daily gain (ADG), feed conversion ratio (FCR), and survival rate (SUR) were recorded. Heterosis and combining ability regarding general combining ability (GCA), specific combining ability (SCA), and reciprocal combining ability (RCA) were estimated. The study found that CB had the greatest BW and ADG at all weeks (p < 0.05) except for hatch, while those of HB were the lowest. The highest GCA was found in CB; meanwhile, GCA was significantly negative in HB of all ages. Crossing between TN × CB had the greatest BW from 8 weeks of age, which was related to positive SCA and RCA values. However, the RCA value of TN × CB was lower than the SCA value of CB × TN. The yield percentages of the carcass in CB (87.00%) were higher than those in TN (85.05%) and HB (82.91%) (p < 0.05). The highest breast and thigh meat lightness (L*) values were obtained in TN (p < 0.05), while those of CB and HB were not different (p > 0.05). In the crossbreed, the yield percentage of the carcass was highest in TN × CB (89.65%) and CB × TN (88.55%) (p > 0.05) and was lowest in TN × HB (71.91%) (p < 0.05). The meat and skin color of the breast and thigh parts in the crossbreed had the lowest lightness in HB × CB (27.91 to 38.23) (p < 0.05), while those of TN × CB and CB × TN were insignificant (p > 0.05). In conclusion, crossing between the TN sires and CB dams has the preferable potential to develop crossbred Thai native chickens for commercial use based on their high growth performance.

Heritability and Combining Ability of Some Vegetative and Yield Characteristics of Promising Arabica Coffee Varieties in Indonesia

Breeding for high yielding and good quality arabica coffee is the direction of the coffee breeding program in Indonesia. Hybridization becomes the important step to select promising genotypes from the genetic variability to achieve those goals. This research aimed to study heritability and combining ability of vegetative and yield characteristics of arabica coffee offspring. This research was conducted in randomized complete block design with three replications at Andungsari Experimental Station, East Java. The materials consisted of five parents of arabica coffee namely BP 542A(P1), P88(P2), S795(P3), HDT(P4), GEISHA(P5), and ten F1 hybrids as the offspring. The results showed that the narrow-sense heritability of leaf width was categorized as high. P3 and P5 varieties had the highest general combining ability (GCA) value for internode length, cluster number, and cherries number. These results indicated that both parental lines had potential as parents for the breeding program. The highest value of specific combining ability (SCA) for cherry size and leaf size was shown in crossing combination of P1×P3 and P2×P3. While, the crossing combination of P3×P4 showed the highest SCA value for cluster number, internode length, and cherries number per branch. From this crossing combination, high yielding promising lines can be obtained.

Genetic Analysis for Resistance to Sclerotinia Stem Rot, Yield and Its Component Traits in Indian Mustard [Brassica juncea (L.) Czern & Coss.

Understanding the mode of gene action that controls seed yield and Sclerotinia stem rot resistance in Indian mustard is critical for boosting yield potential. In a line × tester mating design, ten susceptible lines and four resistant testers were used to conduct genetic analysis. The significance of general combining ability (GCA) and specific combining ability (SCA) variances revealed that both additive and non-additive gene actions were involved in the inheritance of Sclerotinia stem rot resistance and yield attributing traits. In addition to 1000-seed weight and number of primary and secondary branches/plant, the genotypes RH 1569 (line) and DRMR 2035 (tester) appeared to be the strongest general combiners for Sclerotinia stem rot resistance. RH 1657 × EC 597317 was the only cross among several that demonstrated a significant desired SCA value for Sclerotinia rot resistance. Regarding SCA effects for yield and component traits, the cross RH 1658 × EC 597328 performed best, with a non-significant but acceptable negative SCA effect for resistance. DRMR 2035, RH 1222-28, RH 1569, RH 1599-41, RH 1657, RH 1658, and EC 597328 are promising genotypes to use as parents in future heterosis breeding and for obtaining populations with high yield potential and greater resistance to Sclerotinia stem rot disease in Indian mustard, based on GCA effects of parents, per se performance, and SCA effects of hybrids. Days to 50% flowering, number of primary branches/plant, main shoot length, and 1000-seed weight all had a high genotypic coefficient of variability (GCV), broad-sense heritability (h2bs), and genetic advance as percent of the mean (GAM) values, as well as significant and desirable correlations and direct effects on seed yield. As a result, these traits have been recognized as the most critical selection criterion for Indian mustard breeding programs.

Combining ability and heterotic pattern in relation to F1 performance of tropical and temperate-adapted sweet corn lines

The aims of this study were: to assess the genetic relationship of supersweet corn populations; and to establish the heterotic pattern of 49 supersweet (sh2) corn inbreds on F2S5 generation based on molecular marker data and specific combining ability. Forty-nine inbreds were evaluated using 20 SSR molecular markers, which were allocated into heterotic groups according to the discriminant principal component analysis. Twelve inbreds were crossed in a complete diallel scheme. The 81 entries (hybrids developed, parental lines and three commercial checks) were evaluated in a triple partial balanced lattice design (9 × 9) during the growing seasons of 2016/2017 and 2017. The general combining ability (GCA) and specific combining ability (SCA) were estimated. The SCA values were used to set the heterotic patterns of the parental lines as well. Commercial yield without husk (CYWH) and ear length (EL) were more informative to set the heterotic groups. Additive and non-additive effects were important on the genetic control of the evaluated traits. However, for five of the six traits, the non-additive/dominance genetic effects showed to be more important in both environments. In fact, the hybrids developed among tropical by temperate germplasm had better performance than those ones developed within the temperate germplasm itself. SSR based-genetic distance demonstrate to be a reliable predictor as significant correlation was obtained between genetic distance with hybrid performance (for length of ears, ear height and CYWH) and SCA for all observed traits. The non-additive genetic effect that predominantly controlled all traits was the feasible explanation for the good prediction.

Combining ability and heterosis to root-knot nematode resistance on seven genotypes of kenaf using full diallel cross analysis

A full diallel cross is confirmed to be able to advocate kenaf breeders to select breeding materials, such as inbred lines that produce the best combination with heterosis properties. The results of this study provided information about general combining abilities (GCA) of parents, specific combining ability (SCA), as well as heterosis values. This study aims to estimate the combining abilities and heterosis values of root-knot nematodes in kenaf originated from the full diallel cross. Semi-field research was conducted in an experimental garden located at Karangploso Balittas, from November 2018 to January 2019. The variance of GCA values was higher than SCA values for the number of root knot, reproductive factors, and number of egg mass. In contrast, the variance of GCA values was lower than SCA values for the number of second-stage juvenile (J2) and the number of egg per egg mass characters. KR4, K45, and KR15 genotypes indicated negative GCA values on all characters tested. Meanwhile, KR1, Kin2 and DS028 genotypes signified susceptibility with a positive GCA value. The crossbreeding combinations showed negative SCA values on the number of second-stage juvenile, the number of egg mass and the number of egg per egg mass characters of resistance to root-knot nematodes (M. incognita), i.e. KR6 x DS028. KR4, KR5 and KR15 genotipe was quite consistent with negative GCA and SCA values, as well as heterosis values for characters of resistance to root-knot nematodes on kenaf roots on the number of second-stage juvenile (J2), the number of egg mass and the number of egg per egg mass characters tested. Genotype of KR4 x KR5 and its reciprocal have negative heterobeltiosis values on number of second-stage juvenile, egg mass, and the number of eggs per egg mass evaluated characters

Estimation of the specific combining ability (SCA) of eight bitter gourd (Momordica charantia L.) inbred lines in the sixth generation

Estimating the Specific Combining Ability (SCA) of bitter gourd (Momordica charantia L.) inbred lines for breeding F1 hybrid cultivars was performed at the Research and Development Center for Hi-tech Agriculture in Ho Chi Minh City from September to December 2019. The objective of the study was to select the outstanding hybrid combinations from diallen method to produce F1 hybrid cultivars. The results from estimating the SCAs based on the productivity characteristic of 28 hybrid combinations produced from eight bitter gourd I6 inbred lines (Q16, Q65, Q80, Q86, Q75, Q06, Q81 and Q87) following diallen method showed that four promised hybrid combinations (Q65/Q80, Q86/Q75, Q06/Q81 and Q81/Q87) performed over 10% higher SCA values and heterosis than the control, and they were less susceptible to infectious diseases. Fruit characteristics and yield of four hybrid combinations included fruit length of 16.0 to 17.6 cm; fruit width of 6.2 to 6.8 cm; 132.2 to 151.7 g/fruit and average yield of 4.1 to 4.3 tons/1000 m2.

PARENTAL SELECTIONS IN SORGHUM (SORGHUM BICOLOR L.) ON THE BASIS OF HETEROSIS AND COMBINING ABILITY IN ASSOCIATION WITH SSR DIVERSITY IN SUB-TROPICAL PLAINS OF UTTARAKHAND, INDIA

Selection of genetically diverse and complementary parents for important key traits is most difficult task in any hybrid breeding programme. The objective of this study was to estimate heterosis and relative combining abilities with associated SSR diversity for identification of unique sorghum genotypes. A total of forty crosses and thirteen parental lines including five cytoplasmic male sterile (CMS) lines and eight pollinator lines with two standard check varieties were phenotyped using six agro-morphological traits and genetic diversity was estimated by using five polymorphic SSR markers. Sorghum genotypes were crossed with CMS lines using a line × tester mating design and 40 hybrids, 13 parents and two check varieties were field-evaluated using alpha lattice design with three replications. General combining ability (GCA), specific combining ability (SCA) and heterosis for grain yield and other associated attributes were determined. SSR diversity estimates were ranged from 0.54 to 0.90. Among CMS lines, 11A2 and MR750A2 and among pollinators, UPC2 and M35-1 were reported as best general combiners. A2 cytoplasm was found to be more efficient to produce more heterotic combination with experimental lines. Cross, 11A2 x UPC2 gave best results of heterosis for most of the characters. MR750 A2 x UPC2, 11A2 x UPC2, ICSA467 x UPC2, ICSA467 x CS3541, ICSA 467 x RS29, ICSA 467 x M35-1 and 11A2 x M35-1 revealed significant and positive values of heterosis, SCA and GCA. However, no direct correlation was detected with heterosis and molecular diversity for most of the characters. These results may be used for the exploitation of hybrid vigor in sorghum breeding programmes

Reciprocal differences and combining ability for growth and yield components in cacao (Theobroma cacao L.): a case of recommended cacao varieties in Ghana

The inappropriate use of cacao clones either as female or male parents in seed gardens have been suggested as some of the reasons for the low yields of cacao hybrid varieties grown in West Africa. The concept of reciprocal effects in cacao crosses has not been well studied. To investigate the impact of maternal effect on growth and yield traits, reciprocal differences and combining abilities of recommended cacao parents in Ghana were evaluated. Six clones, comprising four important seed gardens clones used across West Africa and two clones previously used as standards in international breeding projects were crossed in a 6 × 6 complete diallel mating design to produce 30 F1 progenies. These progenies were tested in the field using a random block design with four blocks and elementary plots containing 20 plants. Growth and yield traits including stem cross-sectional area in juvenile stage, jorquette height, bean weight, number of beans per pod and bean yield were monitored over a 6-year period. Mean squares of general combining ability (GCA), specific combining ability (SCA) and reciprocal effects were significant for almost all the traits except jorquette height in SCA. This indicates that additive and non-additive gene effects are important in the inheritance of the traits. The presence of reciprocal differences for all traits suggests the influence of maternal effects in controlling the traits. Manual pollinations for commercial seed production should, therefore, follow established protocol and clones recommended as female and male parents used strictly as recommended. One of the standard clones, AMAZ15/15 had significant positive GCA effect for yield, and consistently produced progenies with high SCA values. It could be added to parental clones currently used in producing cacao varieties in the seed gardens in Ghana and other West African cacao growing countries.

Genome-wide dissection of hybridization for fiber quality- and yield-related traits in upland cotton.

SUMMARYAn evaluation of combining ability can facilitate the selection of suitable parents and superior F1 hybrids for hybrid cotton breeding, although the molecular genetic basis of combining ability has not been fully characterized. In the present study, 282 female parents were crossed with four male parents in accordance with the North Carolina II mating scheme to generate 1128 hybrids. The parental lines were genotyped based on restriction site‐associated DNA sequencing and 306 814 filtered single nucleotide polymorphisms were used for genome‐wide association analysis involving the phenotypes, general combining ability (GCA) values, and specific combining ability values of eight fiber quality‐ and yield‐related traits. The main results were: (i) all parents could be clustered into five subgroups based on population structure analyses and the GCA performance of the female parents had significant differences between subgroups; (ii) 20 accessions with a top 5% GCA value for more than one trait were identified as elite parents for hybrid cotton breeding; (iii) 120 significant single nucleotide polymorphisms, clustered into 66 quantitative trait loci, such as the previously reported Gh_A07G1769 and GhHOX3 genes, were found to be significantly associated with GCA; and (iv) identified quantitative trait loci for GCA had a cumulative effect on GCA of the accessions. Overall, our results suggest that pyramiding the favorable loci for GCA may improve the efficiency of hybrid cotton breeding.

Study of combining ability of meadow clover varieties for breeding purposes in the conditions of the Volga-Vyatka region

The article presents the results of research work on the assessment of general combining ability (GCA) and specificcombining ability (SCA) in 14 varieties of meadow clover (Trifolium pratense L.) of various ecological and geographicalorigin (Russia, Belarus). The study was aimed at identifying the best varieties according to productivity indicators for inclusion into the breeding process in the conditions of the Volga-Vyatka region. The study of initial cultivars and their hybridforms F1 was carried out in the field experiment of 2009 with two-year use of grass stand (2010, 2011). The characteristics ofcultivars according to the main morphological and biological characteristics (winter hardiness, length of the vegetative period, plant height, grass stand vigour) and economically significant indicators (collection of raw and dry phytomass, seed yield)in comparison with the zoned Dymkovsky variety are given. All varieties showed high winter hardiness in the conditions of theKirov region (more than 79 %). By productivity of green mass the varieties Karmin, Trio, Stodolich (Russia) were selected.They provided significantly high productivity for 2 years of grass stand use (5.52-5.81 kg/m2, +2.01-2.30 kg/m2to standard)and were characterized by medium value of GCA (104.2-109.6 %) and very high SCA (123.7-139.3 %). According to the totalcollection of dry phytomass, the best varieties were Karmin and Gefest (Russia) with a significantly high level of productivity(1.28; 1.29 kg/m2, +0.49; 0.50 kg/m2to standard), medium GCA (102.4; 103.2 %) and very high SCA (133.3; 134.4 %). By seedyield, the most productive Russian varieties are Stodolishchensky, Trio and Svetlyachok (74.2-82.6 g/m2, +8.8-17.2 g/m2tostandard) with very high GCA (125.5-139.8 %) and SCA value of medium and high level (106.6-118.7 %). According to theresults of the study, for further breeding work the following meadow clover cultivars of Russian research institutes breeding were included as components of new polycross populations: early-matured Karmin and Trio, late-matured Gefest andSvetlyachok.

Sources, Spectrum, Genetics, and Inheritance of Phaseolus vulgaris Resistance Against Xanthomonas citri pv. fuscans.

Common bean (Phaseolus vulgaris) is one of the most consumed agricultural products in the world. Its production is affected by common bacterial blight (CBB) caused by Xanthomonas citri pv. fuscans and X. phaseoli pv. phaseoli. In this work, we investigated the spectrum, genetics, and inheritance of common bean resistance to X. citri pv. fuscans. Inoculation of nine selected cultivars with an X. citri pv. fuscans strain showed that BRS Radiante and IAPAR 16 were resistant. These two cultivars were also resistant to six X. phaseoli pv. phaseoli strains of different geographic origins, demonstrating their broad-spectrum resistances. BRS Radiante sustained smaller X. citri pv. fuscans populations than two susceptible cultivars. Stomatal densities of IAPAR 16 and BRS Radiante were significantly higher than or not different from susceptible cultivars. BRS Radiante showed the lowest general combining ability values and the combination BRS Radiante × Carioca MG the lowest specific combining ability (SCA) values, revealing the capacity of BRS Radiante to increase resistance to X. citri pv. fuscans. Positive and negative parental SCA values indicated dominant and recessive genes involved in X. citri pv. fuscans resistance. Resistance of the BRS Radiante × Carioca MG cross segregated in a 9:7 ratio in the F2 population, indicating that it is governed by two complementary dominant genes. Maximum likelihood analysis showed that the resistance of BRS Radiante to X. citri pv. fuscans is conferred by a gene of major effect with contribution of additional polygenes. This study contributes with important knowledge on the resistance against CBB in Brazilian common bean cultivars as well as with molecular tools for confirmation of common bean hybrids.

Genetic analysis of Agronomic Traits of Wheat under Terminal Drought Stress

Seven wheat genotypes (Sirvan, Zarin, Pishgam, Karim, Baran, Heidary, and Rizhav) were crossed in diallel mating to develop 42 F1's hybrids. The resultant hybrids along with parents were evaluated during cropping season 2015-16 at agriculture and natural resources Pardis of Tehran University, Iran, using RCB design with 3 replications under drought stress and normal field conditions from the booting stage till physiological maturity. General combining ability (GCA) and specific combining ability (SCA) for agronomic traits were determined. The main objective of the research was the identification and proper selection of best-performing wheat parental genotypes and best F1's hybrids, based on GCA and SCA estimates. Significant differences were observed among the wheat genotypes for all the reported traits in this article. Results for combining ability analysis indicated that mean squares of GCA and SCA effects were significantly high for most of the traits. The estimates of σ2gca and σ2sca and its ratio (σ2gca/σ2sca) indicated that non-additive genetic expression was dominant for most of the traits studied, then the heterosis breading is a useful program, however selection on superior hybrids should be postponed to the next generation for these traits in recombination program. It is concluded that Zarin, and Baran are recommended as the best general combiners for a future wheat breeding program. The maximum values of SCA observed in flag leaf length in normal and peduncle length in drought condition related to crosses of Rizhav with other parents. So, it is suggested these series of crosses can be down to improve these traits at the mentioned condition