High General Combining Ability Effects Research Articles

Exploration of Diallel Method for Assessing Heterosis and Combining Ability in Maize (Zea mays L.)

During the Kharif season of 2018 and Rabi season of 2018-19, an experimental study was conducted. The selection of seven maize genotypes was based on quantitative traits, growth duration, suitability for the Kharif season, and yield. These genotypes were then crossed in a half diallel mating design, resulting in the production of 21 single-cross hybrids. The cultivation of these hybrids, along with the seven parental inbred lines, totaling 28 genotypes, followed a randomized block design. Each plot had dimensions of 23.10m by 1.0m and maintained a plant density of 240 plants per plot. To assess the quantitative traits, observations were recorded from five randomly selected plants per plot. The analysis of variance indicated significant genetic variability among the genotypes, particularly in traits such as days to 50% germination, silking, maturity, plant height, number of leaves per plant, biological yield, cob ear weight, number of rows per cob, and number of seeds per cob. This variability was attributed to both additive and non-additive genetic components, as evident from significant variances due to general combining ability (GCA) and specific combining ability (SCA). The GCA/SCA ratio was less than unity for most traits. For most traits, parental lines P1, P2, and P4 exhibited high GCA effects. Additionally, F1 hybrids P4x P3, P3x P1, P5x P3, and P7 x P5 were found to be desirable in terms of yield and related traits. In terms of yield, seven crosses (P1 x P6, P2 x P7, P2x P5, P1 x P2, P3x P4, P5 x P7, and P3 x P5) outperformed the check hybrid, demonstrating their potential for future breeding programs aimed at enhancing maize yield.

Combining Ability Studies on Growth and Improved Leaf Yield Traits in Mulberry, Morus spp.

The study was conducted to evaluate combining ability for growth, quality and yield parameters in mulberry at the field germplasm existed at the Department of Sericulture, UAS, GKVK, Bangalore. Twenty one F1 hybrids was developed by crossing seven lines with three testers according to line x tester design. and assessed using randomized complete block design with three replications. Results revealed that analysis of general combining ability showed the higher magnitude of specific combining ability (SCA) variance than general combining ability (GCA) variance for most of the characters, which indicates the presence of non- additive gene action for most of the traits except for number of branches per plant, number of leaves per plant, and single leaf area. Among seven lines, M. cathyana, MI-47, M. laevigata, MI-494 were found to be best general combiners and in testers V1, MI-66 were found best general combiners with high GCA effects. Among twenty one crosses, BC-259 × MI-66, M. indica × MI-66, M. laevigata × V1 and M. indica × C-776 were found to be superior performers with high SCA effects.

The Combining Ability for Grain Yield and Some Related Characteristics in Rice (Oryza sativa L.) Under Normal and Water Stress Conditions.

Drought is considered a major threat to rice production. This study aimed to determine the effects of drought stress on the estimates of heterosis and the combining ability of rice genotypes for the number of days to 50% heading, plant height, number of panicles per plant, panicle length, number of filled grains per panicle, and grain yield per plant. Field experiments were conducted at the Rice Research and Training Center, Kafr El Sheikh, Egypt, during the rice-growing season in 2018 and 2019. Eight rice genotypes (Giza178, Giza179, Sakha106, Sakha107, Sakha108, WAB1573, NERICA4, and IET1444) were crossed in a half-diallel cross in the rice-growing season in 2018, which yielded a wide range of variability in numerous agronomic traits and drought tolerance measurements. In 2019, these parents and their 28 F1 crosses were produced by employing a three-replication randomized complete block design under normal and water stress conditions. The results showed remarkable differences across the studied genotypes under normal and water stress conditions. Under both conditions, Sakha107 was the best general combiner for earliness and short stature. Giza179 and Sakha108 were the best general combiners for grain yield per plant and one or more of its characteristics. Furthermore, in both normal and water stress conditions, Giza179 exhibited the highest general combining ability effects for all attributes that were evaluated. Under normal and water stress conditions, the Giza179 × Sakha107 cross demonstrated substantial and desirable specific combining ability effects on all the examined traits, which suggested that it could be considered for use in rice hybrid breeding programs. Therefore, we recommend that these vital indirect selection criteria to be considered for improving rice grain yield under drought conditions.

Estimation of parameters of genetic variation of spring durum wheat (Triticum durum Desf.) on the basis of “number of grains from the main spike”

Aim. To assess the combining ability, features and nature of the inheritance of the trait “number of grains from the main spike” in varieties of spring durum wheat for their further involvement in breeding programs. Methods. The investigations were carried out at the V. M. Remeslo Institute of Wheat of NAAS of Ukraine. Varieties (‘Zhizel’, ‘MIP Raiduzhna’, ‘Kharkivska 27’, ‘Kharkivska 39’, ‘Spadshchyna’, ‘Kuchumovka’, ‘Tera’) of domestic breeding were involved in crossings according to the full diallel scheme (7 ´ 7). Parental components and F1 were studied in the field in 2016, 2017. Results. The analysis of variance of combining ability showed a significant advantage in general combining abili­ty (GCA) effects. The mean square of the specific combi­ning ability (SCA) was significantly inferior to the GCA, but was significant in both years of the study. Consistently high GCA effects in 2016, 2017 were determined in the variety ‘Tera’ (gi = 1.35; 2.37). Non-alelic gene interaction was not found, which made it possible to analyze the main parame­ters of genetic variation. In two years of investigations, in the phenotypic manifestation of the number of grains from the main spike, dominant effects (H1 and H2) survived over additive ones (D). The average degree of dominance indicated overdominance (H1/D). The indicator of the ave­rage degree of dominance in loci () also indicated overdominance. Dominance was significantly oriented. Dominant effects of genes increased the number of grains, while recessive effects decreased them. At least one group of genes has been identified that has led to dominance. In general, dominant genes (F > 0) or groups of genes dominated quantitatively in cultivar investigated. A high coefficient of heritability in a broad sense (H2 = 0.88; 0.90) indicates a significant phenotypic conditionality to genetic factors. The coefficient of heritability in a narrow sense (h2 = 0.31; 0.38) indicates the average contribution of the additive effects of genes over the dominant ones. Conclusions. The identified breeding and genetic features on the basis of the “number of grains from the main spike” trait make it possible to predict the effectiveness of selections aimed at increasing the trait in the newly hybrid material. However, due to the predominance of dominant effects and overdominance in the genetic control of a trait, selection in later generations will be more effective. Varieties ‘Kharkivska 27’, ‘Kharkivska 39’ and ‘Tera’ should be used as genetic sources to increase the trait “number of grains from the main spike”.

Genetics of dual resistance to african stem borer, busseola fusca and spotted stem borer, Chilo partellus in sorghum

African stem borer, Busseola fusca Fuller (Noctuidae) and spotted stem borer, Chilo partellus Swinhoe (Crambidae) cause more than 40 % of grain yield loss in cereals and bothpests co-exist in mid-altitudes in Kenya. Development of sorghum with dual resistance to B. fusca and C. partellus has been difficult due to the inadequate understanding of inheritance of resistance traits to the two species. The objective of this study was to investigate the genetics of dual resistance to the two insect species in sorghum. Thirty sorghum populations derived from crossing sorghum lines with varying levels of resistance to the two insect species were studied. The experiments were conducted in two separate sites at Embu and Kiboko in Kenya with two replications per site. North Calorina Design II mating design was used. Artificial infestation with first instar neonates of each pest species was done at 30 days after planting in both sites. Data collected included sorghum damage due to the two borer species and agro-morphological traits. Genetic analyses were performed using line x tester method using Genstat statistical software. Data analyses revealed that general combining ability (GCA) and specific combining ability (SCA) effects were significant for foliar and stem damage traits, indicating that additive and non-additive gene effects conditioned resistance to B. fusca and C. partellus. Sorghum lines ICSA 464, ICSB 474, ICSB 464 and ICSA 472 and ICSB 473 exhibited desirable high negative GCA effects to B. fusca and C. partellus. These parents could be used in development of sorghum with dual resistance to B. fusca and C. partellus thus contributing to sustainable integrated management of these two stem borer species in sorghum via host plant resistance management.

Combining ability study for yield and quality traits in cucumber (Cucumis sativus L.)

Seven cucumber (Cucumissativus L.) genotypes (3 lines and 4 testers) were crossed in a line × tester mating design. The resultant 12 hybrids and their parents were evaluated using Randomised Block Design with two replications during Kharif 2018. Sufficient genetic variability was observed for all the characters under study. In this study, the parents L2 (Koradacherry local), T2 (Orathanadu local) and T3 (Aipatti local) exhibited high positive GCA (General Combining Ability) effects for yield related traits and high negative GCA effects for earliness characters. The parent T2 identified in this study may be used in multiple crossing programme to isolate high yielding varieties. Among the hybrid combinations, L2xT3, L1xT2 and L3xT4 expressed the maximum positive significant SCA (Specific Combining Ability) effects for yield and yield associated characters. In the above cross combinations one parent was a good combiner and the other was an average/poor combiner; hence the hybrids can be exploited for transgressive selection.

Combining ability and heterosis for some canola characteristics sown on recommended and late planting dates using biplot

Canola (Brassica napus L.) is one of the most efficient oil-producing crops in arid and semi-arid regions of the world. In the current study, ten winter canola genotypes [seven genotypes as lines (Zarfam (L1), Talaye (L2), SLM046 (L3), Geronimo (L4), Modena (L5), Opera (L6) and Symbol (L7)] and three genotypes as testers [Okapi (T1), Licord (T2) and Orient (T3)] and their F1 hybrids (21 hybrids) were evaluated to determine the genetic parameters for grain yield, oil content, meal and seed glucosinolate contents under two different planting date [recommended (late September) and late planting (late October)]. According to combined analysis of variance there were significant differences among the genotypes for most studied traits. The genotype main effect and genotype × environment interaction (GGE) biplot method was used for analyzing line × tester design data. Among the lines, L5 showed high negative general combining ability (GCA) effect for meal glucosinolate content in both conditions whereas L1, L5 and L6 revealed high negative GCA effects for seed glucosinolate content in both planting date. From the results, it could be concluded that, hybridization between T1×L1, T1×L6 or T3×L5 is an efficient approach to release genotypes with low seed and meal glucosinolate content. Furthermore, to develop canola cultivars with higher seed and oil yield, hybridization between T1×L7 or T2×L7 is highly recommended. Improved oil content will be achieved if T1×L5, T2×L5 or T3×L6 hybrids are implemented into the breeding programs.

Combining Ability and Genetic Control of Pod Yield and Component Traits in Dolichos Bean

ABSTRACTThe major limitation of dolichos bean (Dolichos lablab L.) improvement is the narrow genetic base for useful traits present in available germplasm that may be overcome through interspecific hybridization. Five diverse genotypes involving two each of indeterminate and semi-indeterminate, and one determinate type, were crossed in a 5 × 5 half diallel mating design to estimate combining ability, mode of gene action, and extent of heterosis for 12 quantitative traits. The preponderance of additive genetic effects was evident for pod weight and number of pods/inflorescence; additive and non-additive gene effects for number of pods/plant, and non-additive gene action in expression of days to 50% flowering, raceme length, number nodes/inflorescence, number inflorescences/plant, number flower buds/inflorescence, pod length, pod diameter, pod thickness, and pod yield/plant. The parents “BCDB 10” and “BCDB-2” were identified as potential donors for breeding. The crosses “BCDB-2×BCDB-15” and “BCDB-10×BCDB-5” exhibited high heterobeltiosis for pod yield/plant to the extent of 114.26 and 86.63%, respectively. They could not be exploited at the commercial level. These crosses involved one parent having high general combining ability effects for pod yield and other important horticultural traits that could produce desirable transgressive segregants in subsequent generations.

Combining Ability of Yellow Lines Derived from CIMMYT Populations for Use in Subtropical and Tropical Midaltitude Maize Production Environments

ABSTRACTThe introduction and utilization of new maize (Zea mays L.) germplasm from sources, such as the International Maize and Wheat Improvement Center (CIMMYT), can be valuable for broadening the genetic base of breeding populations through the introgression of new alleles. Twenty‐five inbred lines, derived from CIMMYT breeding populations, were selected on the basis of grain color, resistance to turcicum leaf blight, and per se line performance in Yunnan. To use the lines effectively, information on their performance in hybrid combinations and on general combining ability (GCA) and specific combining ability (SCA) needed to be obtained. The objectives of this study were (i) to evaluate these lines for grain yield (GY) in hybrid combinations and determine GCA of parental lines and SCA of crosses between the 25 introduced lines and six testers using North Carolina Design II; and (ii) to classify the lines into different maize heterotic groups. The field testing at three locations identified crosses with lines from Cateto and Population 147 (P147) as having significantly higher GY than those from SA3 and other introduced populations, and the high GY was largely attributable to their high positive GCA effects. Lines from the same population were not necessarily classified into same maize heterotic group. Lines selected at S4 or a later generation would be expected to have more stable GCA effects than lines selected in earlier generations.

Exploring genotypic variations for improved oil content and healthy fatty acids composition in rapeseed (Brassica napus L.).

Development of new genotypes having high oil content and desirable levels of fatty acid compositions is a major objective of rapeseed breeding programmes. In the current study combining ability was determined for oil, protein, glucosinolates and various fatty acids content using 8 × 8 full diallel in rapeseed (Brassica napus). Highly significant genotypic differences were observed for oil, protein, glucosinolates, oleic acid, linolenic acid and erucic acid content. Mean squares due to general combining ability (GCA), specific combining ability (SCA) and reciprocal combining ability (RCA) were highly significant (P ≤ 0.01) for biochemical traits. Parental line AUP-17 for high oil content and low glucosinolates, genotype AUP-2 for high protein and oleic acids, and AUP-18 for low lenolenic and erucic acid were best general combiners. Based on desirable SCA effects, F1 hybrids AUP-17 × AUP-20; AUP-2 × AUP-8; AUP-7 × AUP-14; AUP-2 × AUP-9; AUP-7 × AUP-14 and AUP-2 × AUP-9 were found superior involving at least one best general combiner. F1 hybrids AUP-17 × AUP-20 (for oil content); AUP-2 × AUP-8 (for protein content); AUP-7 × AUP-14 (for glucosinolates); AUP-2 × AUP-9 (for oleic acid); AUP-7 × AUP-14 (for linolenic acid) and AUP-2 × AUP-9 (for erucic acid) were found superior involving at least one best general combiner. As reciprocal crosses of AUP-14 with AUP-7 and AUP-8 were superior had low × low and low × high GCA effects for glucosinolates and oleic acid, respectively therefore, these could be exploited in future rapeseed breeding programmes to develop new lines with good quality. © 2016 Society of Chemical Industry.

Heterosis y aptitud combinatoria, para rendimiento y calidad forrajera, en poblaciones de maíz.

Twenty-eight crosses among eight populations of maize forage were evaluated in two environments (Celaya, Gto. y Gómez Palacios, Dgo. México) according with yield and quality forage. This study was carry out to determine the heterotic patterns of the populations and to identify the better populations. Sintético Forrajero and Tuxpeño Bajío populations were the best heterotic pattern, which showed the greater diversity for all traits studied. The highest forage yield was showed for cross between this two populations, 30.85 t/ha and 14.6% of heterosis. In addition, the highest general combining ability effect by forage yield over environments was of the Tuxpeño Bajío population. This suggests that Sintético Forrajero and Tuxpeño Bajío populations are the best option to begin a program of recurrent reciprocal selection. The yield of dry matter and protein was not correlated (0.06); besides, protein had very little variation between maiz forage populations.

Genetic variation in sorghum as revealed by phenotypic and SSR markers: implications for combining ability and heterosis for grain yield

AbstractHybrid breeding relies on selection of genetically unrelated and complementary parents for key traits. The objective of this study was to examine genetic variation and identify unique sorghum genotypes using phenotypic and simple sequence repeat (SSR) markers and to determine their relationships with combining ability and heterosis for grain yield. A total of 32 landraces and four cytoplasmic male sterile (CMS) lines were phenotyped using 25 agro-morphological traits and genotyped with 30 polymorphic SSR markers. The landraces were crossed with four CMS lines using a line × tester mating design. The 128 hybrids, 36 parentals and four check varieties were field-evaluated using a 12 × 14 alpha lattice design with three replications. General combining ability (GCA), specific combining ability (SCA) and heterosis for grain yield were determined. Genetic distance estimates ranged from 0.39 to 0.60 and 0.50 to 0.79, based on phenotypic and SSR markers, respectively. Landraces 72572, 75454, 200654, 239175, 239208, 244735A and 242039B and CMS lines ICSA 743 and ICSA 756 displayed positive and significant GCA effects for grain yield. Based on the SCA effects of yield, lines were classified into three heterotic groups aligned to the different cytoplasmic systems of testers. Lines with high GCA effects rendered hybrids with highly significant SCA effects with high mid-parent heterosis (MPH) for grain yield. Both marker systems were effective in demarcating sorghum genotypes that provided desirable cross-combinations with high combining ability effects and MPH for grain yield. The selected genotypes are recommended as potential parents for sorghum hybrid breeding in moisture stress environments.

Estimating Combining Ability Effect of the Indian and Exotic Lines of Tomatoes by Partial Diallel Analysis

Eight nearly homozygous, horticulturally superior and optimally divergent lines of tomato having Indian and exotic adaptability were used for carrying out half diallel design to study General Combining Ability (GCA) and Specific Combining Ability (SCA) estimates for fruit weight, polar and equatorial diameter, locules fruit-1, pericarp thickness and fruit firmness. The variances due to both GCA and SCA were significant, suggesting that both additive and non additive genetic variance were involved for genetic control of the character fruit polar and equatorial diameter, and locules number in F1 and F2 generations. However, the variance due to GCA was more pronounced for fruit weight, pericarp thickness and firmness as a result of additive gene action. Due to their high general combining ability effects, exotic parents Ec 490130 and Ec 177371 producing firm fruited small to medium sized tomato fruits having constant expression of GCA effects over the generationsregarded as best general combiners. The crosses GT 1 x Ec 490130 and Ec 490130 x Ec 398704 having high x high and high x low combinations, respectively in F1. While in F2, GT 1 x Ec 177371 and H 24 x Ec 490130 having high x high and high x low combining lines were considered as best crosses for greater fruit firmness. Therefore, heterosis breeding in F1 and selection of desirable lines in F2 generation is recommended for further improvements were suggested for future hybridization programmes.

Performance of testers with different genetic structure for evaluation of maize inbred lines

The objective of this study was to evaluate four maize testers for identification of superior inbreed lines in testcross. The four testers evaluated are cultivars with narrow or wide genetic base (single-cross hybrids and open pollinated varieties) and two kernel types (flint or dent). SynD and SynF testers are open pollinated varieties with dent and flint kernels, respectively, and FSH and DSH testers are single-cross hybrids with flint and dent kernels, respectively. SynD tester showed the biggest genetic variance among the maize inbreed lines in crosses. The effects of general combining ability (GCA) for lines and specific combining ability (SCA) for lines x testers were significant, whereas GCA effects for testers were not significant. SynD and SynF testers identified the largest number of lines with higher GCA. The DSH and FSH testers showed suitable to identify lines with high SCA. It was concluded that SynD and SynF testers are adequate to identify inbreed lines with high GCA effects, and it's possible to identify new lines with high heterotic potential in each one of the four testers.

Combining ability analysis for within-boll yield components in upland cotton (Gossypium hirsutum L.)

Cotton is an important cash crop worldwide, accounting for a large percentage of world agricultural exports; however, yield per acre is still poor in many countries, including Pakistan. Diallel mating system was used to identify parents for improving within-boll yield and fiber quality parameters. Combining ability analysis was employed to obtain suitable parents for this purpose. The parental genotypes CP-15/2, NIAB Krishma, CIM-482, MS-39, and S-12 were crossed in complete diallel mating under green house conditions during 2009. The F₀ seed of 20 hybrids and five parents were planted in the field in randomized complete block design with three replications during 2010. There were highly significant differences among all F₁ hybrids and their parents. Specific combining ability (SCA) variance was greater than general combining ability (GCA) variance for bolls per plant (9.987), seeds per boll (0.635), seed density (5.672), lint per seed (4.174), boll size (3.69), seed cotton yield (0.315), and lint percentage (0.470), showing predominance of non-additive genes; while seed volume (3.84) was controlled by additive gene action based on maximum GCA variance. Cultivar MS-39 was found to be the best general combiner for seed volume (0.102), seeds per boll (0.448), and lint per seed (0.038) and its utilization produced valuable hybrids, including MS-39 x NIAB Krishma and MS-39 x S-12. The parental line CIM-482 had high GCA effects for boll size (0.33) and seeds per boll (0.90). It also showed good SCA with S-12 and NIAB Krishma for bolls per plant, with CP- 15/2 for boll size, and with MS-39 for seeds per boll. The hybrids, namely, CP-15/2 x NIAB Krishma, NIAB Krishma x S-12, NIAB Krishma x CIM-482, MS-39 x NIAB Krishma, MS-39 x CP-15/2, and S-12 x MS-39 showed promising results. Correlation analysis revealed that seed cotton yield showed significant positive correlation with bolls per plant, boll size and seeds per boll while it showed negative correlation with lint percentage and lint per seed. Seed volume showed significant negative correlation with seed density. Seeds per boll were positively correlated with boll size and negatively correlated with bolls per plant lint percentage and lint per seed. Similarly, lint per seed exhibited positive correlation with lint percentage and boll size showed significantly negative correlation with bolls per plant. Presence of non-additive genetic effects in traits like bolls per plant, seeds per boll, lint per seed, seed cotton yield, and lint percentage is indicative of later generation selection or heterosis breeding may be adopted. For boll size, seed volume and seed density early generation selection may be followed because of the presence of additive gene action. The parental material used in this study and cross combinations obtained from these parents may be exploited in future breeding endeavors.

Genetic analysis of resistance to nematodes in inbred maize (Zea mays L.) and maize hybrids

Nematodes cause substantial grain yield loss in susceptible maize (Zea mays L.) cultivars. This study was conducted to estimate general combining ability (GCA), specific combining ability (SCA) and genetic effects associated with nematode resistance in maize. The 30 F1 hybrids generated from a 6 × 6 diallel and two local checks were evaluated in 2009 at three sites in Uganda. A split plot design was used with nematode treatments serving as whole plots and the hybrids as subplots but arranged in an 8 × 4 spatially adjusted alpha-lattice design. The experiment was replicated three times. Results showed GCA to be important for the reduction of P. zeae and Meloidogyne spp. densities and increase of root mass, with a contribution of 72 to 93% of the phenotypic variance. Inbreds MP709 and CML206 had the highest GCA for Pratylenchus zeae resistance, whereas for grain yield, it was CML444, CML312 and CML395 that were outstanding. The SCA influenced plant height and grain yield under nematode infestation, contributing 43 and 58% of the phenotypic variance, respectively. Observed reciprocal differences due to maternal effects also played a role in influencing the grain yield under nematode infestation. Overdominance genetic effects explained the non-additive variance recorded for the plant height, grain yield, number of root lesions, and P. zeae and Meloidogyne spp. densities under nematode infestation. The parents MP709, CML206, 5057, and CML444 contributed most of the dominant genes for the P. zeae resistance in all their crosses. The parent CML444 contributed most of the dominant genes for improved grain yield in all of its crosses. The high GCA effects among some parents support their utility in breeding of widely adapted nematode-resistant cultivars. The dominant genes and SCA effects would favour pedigree and various sib tests to improve grain yield under nematode pressure.

Combining Ability of Early‐maturing White Maize Inbreds under Stress and Nonstress Environments

Maize (Zea mays L.) hybrids resistant to Striga hermonthica (Del) Benth and tolerant to drought are vital to the sustainability of productivity of the maize‐based farming systems of West and Central Africa (WCA). Thirty‐six diallel crosses derived from nine early maturing white maize inbreds were evaluated under drought, well‐watered, striga‐infested, and striga‐free conditions at five locations in Nigeria between 2007 and 2009. The objective was to examine the combining ability, performance and stability of the inbreds, and to identify the heterotic groups. Additive and nonadditive gene actions were important in the control of the inheritance of drought tolerance and striga resistance in the inbreds. General combining ability (GCA) mean squares of grain yield and other traits were larger than those of specific combining ability (SCA), indicating that additive gene action was more important in the inheritance of drought tolerance. The GCA mean squares for striga damage rating at 8 and 10 weeks after planting (WAP) were about six and five times greater than those of the SCA, indicating that additive gene action played a major role in the inheritance of the striga traits. The GGE biplot analysis revealed that TZEI 4 and TZEI 5 were the most promising inbreds in yield performance and stability across the test environments. Two heterotic groups were identified; [TZEI 7, TZEI 19, TZEI 2, TZEI 4] and [TZEI 5, TZEI 3]. Tester TZEI 3 was the closest to the ideal tester. Entry TZEI 7 had the highest GCA effects and TZEI 2 the lowest.

Heterosis and combining ability for resistance to powdery mildew in adult melon plants

With 4 tables Abstract To estimate the heterosis, general combining ability (GCA) and specific combining ability (SCA) for resistance to powdery mildew, 30 F1 hybrids developed in a 6 × 5 line × tester mating design were evaluated both under the greenhouse and field conditions. Predominance of non-additive variance over additive variance in the inheritance of resistance to powdery mildew was detected. Inbred lines IIHR 681, IIHR 352, IIHR 190, RM 43, IIHR 121 and IIHR 122 demonstrated consistently high and negative GCA effects. There was a strong correlation between GCA effect and mean per cent disease index (PDI) of parent that would permit the use of the mean performance of the parental lines to predict the value of a resulting hybrid. Six hybrids, that is, Arka Jeet × IIHR 122, Punjab Sunehri × IIHR 190, RM 43 × IIHR 121, IIHR 681 × IIHR 616, IIHR 352 × IIHR 616 and IIHR 352 × IIHR 718 which involved one or both the parents with good GCA effects exhibited low mean PDI with negative mid-parent heterosis and negative SCA effects.

Combining ability analysis in Brassica juncea L. for oil quality traits

This study was conducted in Brassica juncea L. for the determination of good combiners for quality associated traits using 8 x 8 diallel during 2004 - 2005 and 2005 - 2006. Analysis of variance revealed highly significant differences (p
0.01) for all the studied traits. Components of combining ability analysis showed that general combining ability (GCA) was highly significant (p
0.01) for oil percentage (%) and glucosinolates (iMolg-1) whereas the rest were non-significant. Specific combining ability (SCA) effects were highly significant for all traits except for oleic acids. Reciprocal combining ability (RCA) effects were highly significant (p
0.01) for all traits except for oleic acid which was significant at (p
0.05). The SCA effects were higher than RCA for oil %. The GCA effects were of greater magnitude than the SCA effects for glucosinolate, erucic acid and protein content. The parental genotypes NUM009, NUM123, NUM105 and NUM117 and their hybrids NUM009x NUM123, NUM103x NUM105, NUM113x NUM124 and NUM103x NUM120 had high GCA and SCA effects, respectively and therefore these could be exploited for further selection of high yielding progenies. The overall study reveals the importance of both additive and non-additive genetic variability suggesting the use of integrated breeding strategies which can efficiently utilize the additive as well as non-additive genetic variability.

Interference of genotypes x environments interaction in the genetic control of resistance to Asian rust soybean

The objectives of this work were to identify parents resistant to Asian soybean rust using diallel crosses, obtain information on the genetic control of soybean resistance to the pathogen and verify whether the combining ability estimates interact with the environment (year or time of assessment). The F1 generation was obtained in a greenhouse from crosses between five contrasting parents for the trait resistance to soybean rust, in a complete diallel without reciprocals. Two rust-severity assessments were carried out on individual soybean plants of 25 treatments (parents and F2 and F3 populations) in 2006/2007 and 2007/2008, in an experimental field at Embrapa Soja, Londrina, PR, Brazil. Additive effects predominated in the genetic control of soybean resistance to Asian rust, and the interaction of the segregant populations with the environment, although significant, did not alter the genetic parameter's general combining ability (GCA) and specific combining ability estimates, indicating that estimates obtained in one year and one assessment can be extrapolated to others. BR01-18437 inbred line is resistant to Asian rust and showed high GCA effects. This line should be used as parent if the objective is the resistance to Phakopsora pachyrhizi.