SCA Variance Research Articles

Line x Tester Analysis of Combing Ability for Seed Yield and Its Contributing Traits in Soybean [Glycine max (L.) Merrill

Hybridization in Line x Tester mating design was conducted with seven lines and three diverse testers in soybean to understand the nature of gene action, combining ability of the parents (gca) and to assess the potential for the exploitation of heterosis (sca) in hybrids. Data on eleven quantitative characters viz., days to 50% flowering, plant height (cm), number of branches per plant, number of pods per plant, number of seeds per pod, pod length (cm), 100-seed weight (g), seed yield per plant (g), biological yield per plant (g) and harvest index (%) were collected on 21 hybrids and their 10 parents. The ratio of GCA variance to SCA variance is less than unity indicated that non additive genetic effects were predominant for control of most of the seed yield and its attributing characters. Among the lines, AUKS 238, RKS 18, RVS 2011-10 were found high gca effects which are use as general combiner parents for enhancing yield potential by assembling the favourable genes and crosses with sca effects such as AUKS 224 x JS 20-98 and RVS 2011-10 x NRC 150 were found to be superior for seed yield and yield components. These crosses may be utilized for heterosis breeding as well as for isolating the superior recombinants in advance generation for seed yield.

Deciphering the estimates of combining ability and heterosis for selecting superior parents and hybrids in rice (Oryza sativa L.)

Twenty F1s, parents and checks viz., MTU 1010 and RNR 15048 were assessed for grain yield and its contributing attributes to study combining ability and heterosis. The mean of hybrids was greater than that of the parents except for days to 50% flowering and plant height. For majority of the investigated characters, the analysis of variance indicated considerable variations among parents and hybrids. Degree of dominance was more than unity for majority of traits including grain yield. For the examined characters, SCA variances were equal to GCA variances, indicating the dominance of additive and non-additive gene activity. The traits days to 50 % flowering, plant height, panicle length, test weight, kernel length and kernel length/breadth ratio showed additive gene action whereas the remaining traits showed non-additive gene action. The gca effects revealed that among the lines IR 72 had significant gca effects in desired direction for yield and yield attributing traits. Among the 20 hybrids, MTU 1001 x Akshyadhan was found to be a good specific combiner for grain yield per plant. Similarly, the hybrids NLR 34449 x IR10N270 and IR 72 x IR10N270 were found to be good specific combiners for grain yield and yield contributing characters. The standard heterosis of these three hybrids was positively significant over the check varieties MTU 1010 and RNR 15048. Based on mean, sca and heterosis estimates, MTU 1001 x Akshyadhan, NLR 34449 x IR10N270 and IR 72 x IR10N270 were identified as promising hybrids. Keywords: Combining ability, gene action, heterosis and hybrid rice

Study on gene action, combining ability and heterosis for different traits in Indian mustard (Brassica juncea L. Cxern & Coss)

Abstract Combining ability and heterosis was investigated in mustard hybrids obtained from 7 × 7 half diallel cross. Twenty one F1s along with seven parents were evaluated in Randomized Complete Block Design. The combined analysis of variance revealed very significant differences among the parents for all morphological variables with the exception of secondary branches and siliqua length, indicating wide diversity among the parental material used in the present study. Significant GCA and SCA variance indicated additive and non-additive gene action across all the characters. The SCA variance components were larger than the GCA variance components for most traits indicating the prevalence of non-additive gene effects. Jawahar mustard × PM-30, showed a significantly positive SCA and better parent heterosis for seed yield per plant whereas five hybrids (Kranti × PM-30, Gujarat Mustard-3 × Pusa Mahak, Jawahar Mustard × PM-30, Jawahar Mustard × Pusa Mahak and PM-30 × Pusa Mahak) exhibited significant positive SCA effect for number of siliqua/ plant. Jawahar Mustard × PM-30, Varuna×Jawahar Mustard, Gujarat Mustard-3 × PM-30, exhibited highly significant heterosis over the mid-parent. Keywords: Brassica juncea, GCA, SCA, gene action, Heterosis

General and Specific Combining Ability for Fruit Yield Using Diallel Population of Ridge Gourd (Luffa acutangula (Roxb.) L.)

An experiment was conducted using 7 x 7 diallel population of ridge gourd to study the general and specific combining ability (GCA and SCA) of parents and their hybrids for 17 yield traits in a randomized complete block design with three replications. Data on 17 characters were subjected to analysis of GCA and SCA variances and their effects. The GCA and SCA variance were found highly significant for all the characters except days to first female flowering. Low magnitude of σ²g/σ²s ratio was observed for all the traits other than days to first male flowering, days to first female flowering, fruit length (cm), fruit width (mm), individual fruit weight (g). On the other hand, σ²g/σ²s ratio was more than 1.0 for days to first male flowering, days to first female flowering, fruit length (cm), fruit width (mm) and individual fruit weight (g). The general combining effects (GCA) of the parents revealed that none of the parent was found to be good general combiner for all the characters. However, in the present investigation, parent P3 was observed to be one of the best general combiner as it has shown significant GCA effects in desirable direction for number of fruits per plant and fruit yield per plant. It also observed significant GCA effects for parameters related to earliness viz., days to first male flowering, node number of first female flower and days to first harvest. Similarly, parent P5 was also good general combiners for fruit length, fruit width and individual weight of fruit, parent P6 and P7 were also good general combiners for fruit length, individual weight of fruit except fruit width. The parent P2 and P4 were also good general combiners for number of fruits per plant. The estimate of SCA effects revealed that none of the crosses was consistently superior for all the characters. The highest yielding hybrid (P3 x P4) had registered the highest SCA effect for fruit yield per plant. Similarly, the cross combinations P6 x P7, P3 x P6, P3 x P7, P1 x P5, P2 x P6, P4 x P5 were observed as good specific combinations for fruit yield per plant. The hybrid P2 x P6 was good specific combiner for days to first male flowering, hybrid P3 x P4 for sex ratio followed by P4 x P5 and P5 x P7. Hybrid P1 x P4, P6 x P7, P3 x P6 and P2 x P4 were found as good specific combinations for fruit length, P4 x P6 and P3 x P4 for fruit width. The hybrids P3 x P6, P6 x P7, P3 x P4, P2 x P4 and P1 x P5 were observed as good specific combinations for individual fruit weight.

Gene action and heterosis studies for grain Fe and Zn content in rice (Oryza sativa L.)

Development of rice genotypes possessing high yielding potential; with increased grain iron content is the need of the hour to tackle hidden hunger. Considering the above said fact, genetical analysis was conducted in six improved cultivars along with 15 potential crosses thereof. Analysis of variance for combining ability revealed significant differences in GCA and SCA variances for grain yield as well as for iron and zinc content, indicating the possibility of realization of development of iron fortified varieties with higher yielding potential. The preponderance of additive gene action for these two important characters i.e., iron and zinc content indicate that selection will be highly rewarding for genetic improvement pertaining to these two traits. The genotype Gouri was found to be very good combiner for both grain yield (0.93) and iron content of grain (2.04). Similarly, genotype Sebati was found as a very good combiner for both grain yield (0.13) and zinc content of grain (0.65). Some of the superior crosses identified concerning both grain yield and grain iron content were Birupa / Pradeep, Sebati / Gouri, Sebati / Pratap, Gouri / Pradeep and Pratap / Pradeep. Hence, these specific crosses can be used in further breeding programme for the improvement of both grain yield as well as grain iron content. The crosses viz., Bhanja / Pratap and Bhanja / Sebati were found to be superior crosses for both grain yield and grain zinc content.

Assessment of gene action and combining ability for advancement of yield andits attributing traits in pansy (<i>Viola </i>× <i>wittrockiana </i>Gams.) through diallel mating design

Pansy is one of the most important bedding winter annual for sub-tropical climatic conditions. Twenty-eight F1 hybrids of pansy were evaluated in randomized block design with three replications, to study the combining ability for vegetative and floral characters. The analysis of variance indicated significant variability among all the genotypes for all the characters. The ratio of genetic component of variance indicated the equal importance of additive and non-additive gene action in governing the flower yield and its component traits of pansy. Estimates of general combining ability effects showed that parents Pa-64-1-5-14, Pa-62-4-12-18, Pa-63-1-7-25 and Pa-32-8-7-6 were good general combiners for most of the traits except stalk length and flower size. The specific combining ability effects showed that for yield traits the best cross combinations were Pa-64-1-5-14 × Pa-62-4-12-18, Pa-13-1-2-3 × Pa-47-1-3, Pa-11-1-3-7 × Pa- 62-4-12-18, Pa-64-1-5-14 × Pa-63-1-7-25 and Pa-11-1-3-7 × Pa-64-1-5-14. The study on gene effect of different characters indicated the predominance of non-additive gene effects for most of the characters. The gca variances was higher for branches number, flower size, days from bud initiation to flowering and flowers number than sca variances, indicating additive gene action, and progeny selection will be effective for the genetic improvement of these traits.

Combining Ability Studies for Yield and Yield Attributes in Bajra

In this study combining ability and gene action were studied in eight quantitative attributes in pearl millet using seven male sterile lines and three restorers which were crossed in Line x Tester design. Analysis of variance for combining ability revealed significant differences among mean squares for lines, testers and lines x testers for all the characters except for spike girth, lines for spike length and lines x testers for days to maturity. These results are indicative of importance of both additive and non-additive genetic variances in the expression of these traits. The ratio of GCA variance and SCA variance indicated the predominance of non-additive gene action for all the eight characters studied, i.e. days to 50% flowering, days to maturity, plant height, number of productive tillers per plant, spike length, spike girth, dry fodder yield and grain yield. Among the lines, ICMA12222 and ICMA 94444 and the tester ICMR 07555 displayed high GCA effect for grain yield per plant. Significant and positive SCA effect for grain yield per plant was displayed by the cross ICMA 12222 x ICMR 07666 followed by ICMA 98444 x ICMR 07555, ICMA 98111 x ICMR 07555 and ICMA 88006 x ICMR 08111. These crosses have been identified as best combiners to give higher grain yield hybrids and could be further evaluated to confirm their stable superior performance.

Genetic analysis of tolerance to combined drought and heat stress in tropical maize.

Simultaneous occurrences of heat and drought stresses have a detrimental effect on growth, development and yield of maize. Heat and drought is expected to worsen maize yield losses under climate change. Selecting CDHS tolerant maize hybrids creates great opportunity for sustainable maize improvement in the tropics. The objective of current investigation was to dissect the genetic basis of CDHS tolerance in tropical maize and to determine performance of single cross hybrids under CDHS. Ninety six single-cross hybrids resulted from crossing 12 tassel blast tolerant and 12 tassel blast susceptible lines along with two Striga resistant commercial hybrids, a heat tolerant and a heat susceptible check hybrids were evaluated under FIRR, MDRTS and CDHS using 25x4 alpha lattice design with two replications. The results showed significant genetic variation for FIRR, MDRTS and CDHS tolerance among maize hybrids. The majority of single crosses that showed improved grain yield over their respective standard checks under MDRTS also exhibited improved grain yield over the same checks under CHDS, indicating development of CHDS tolerance hybrids. Significant and positive genotypic and phenotypic correlation of grain yield under MDRTS and CDHS implicated common genetic mechanisms controlling yield under MDRTS and CDHS. Stress tolerance indices YI, GMP, MP, HM and STI were identified as best selecting indices under both stresses. GCA variances were larger than SCA variances in each testing environment for most studied traits indicating the impotence of additive gene action than non-additive gene action to control these traits. Majority of stress indices and SCA effects demonstrated that hybrids HB18, HB41, HB91 and HB95 were high yielder under MDRTS and CDHS. Hybrids HB41, HB91 and HB95 and their parents' scored minimum tassel blast. Parents 19 and 7 were well general combiner for grain yield and early maturity under MDRTS and CDHS indicting their valuable source of genes for hybridization. The current findings revealed that CDHS tolerance hybrids can reduce expected yield losses and maintain maize productivity in CDHS prone areas. Promising hybrids should be tested further under various drought and CHDS for commercialization.

Heterosis and combining ability in intraspecific (G. hirsutum L.) and interspecific (G. hirsutum L. × G. barbadense L.) cotton hybrids

The inheritance of most important economic characters, heterosis and combining ability were studied in six interspecific (G. hirsutum L. × G. barbadnese L.) and three intraspecific hybrid combinations. There were found different types of inheritance of productivity, boll weight and lint percentage and fiber length in the individual crosses. The genetic variance for productivity and fiber length was mainly non-additive, while for lint percentage it was additive. Although non-additive genetic variance prevailed for productivity and fiber length, only individual crosses showed positive heterosis, outperforming the better parent. Of the female forms, the cultivar Helius was identified as a very good general combiner for productivity. From the male forms the cultivar Ashkabat emerged as a very good general combiner for productivity, boll weight and lint percentage. The cultivars Mytra (female), Karshinski-2 and C-6037 (male) were determined as very good general combiners for fiber length. All these cultivars, with the exception of C-6037, had low SCA variances, their high GCA was mainly due to additive gene effects, and they were very suitable for synthetic selection. The cross Helius × Ashkabat was found to be most valuable for the selection of productivity because of the highest mean performance and the highest level of heterosis with high SCA effects. All intraspecific hybrids were found to be most promising for improving lint percentage. The interspecific cross combinations Mytra × C-6037, Helius × C-6037 and Mytra × Karshinski-2, having the longest fibers, the first two with high SCA effects were most valuable for fiber length improvement.

Combining ability and gene action studies in castor (Ricinus communis L.)

The present study of combining ability and gene action studies will be helpful in identifying better combiners to yield superior hybrids along with selection protocol for the trait of interest. Analysis of variance studies revealed that significant variation exists in the material understudy. Higher estimates of SCA variance were observed than the GCA variance except for seed yield indicating preponderance of non-additive gene action in governing the traits. Significant gca effects were observed in SKP-84 and ICS-142 for seed yield and PPL-1001, SKI-215, DCS86, PCS-327 and Kiran for oil content. Significant sca effect was observed for the crosses viz., M-574 x Kiran, PPL1001 x SKI-215 and SKP-84 x JI-244 for total yield.

Combining ability studies in castor (Ricinus communis L.) under irrigated and un-irrigated environments

Forty eight hybrids developed through L x T design (four females and 12 males) were evaluated under irrigated and unirrigated environments for computing estimates of general and specific combining ability effects for 14 quantitative and qualitative charactersincluding castor(Ricinus communisL.)seed yield.Combining ability analysis revealed that gca variances were significant, only for few characters, under both environments; whereas sca variances were significant for all the characters in both the environments, reiterating the preponderance of non-additive gene action in the inheritance of these characters. The female parents, SKP-84 and SKP-49 and male parents viz.,JI-224,JI-244,JI-260, SKI-160, SKI-202 and SKI-232 were superior and consistent general combiners for seed yield and other yield contributing characters. For oil content, the parents SKP-49, SKI-202, SKI 232 and JI-260 were superior general combiners under irrigated environment, whereas under the un-irrigated situation, SKP-84, JP-82, JI 263 and JI-258 were the good general combiners. The hybrids which recorded high sca effects forseed yield wereGeetha x JI-224 and SKP-49 x JI-227 under irrigated and un-irrigated environments, respectively. Looking to the importance of both additive and non-additive gene action in the inheritance of various characters, a breeding strategy involving biparental matings coupled with reciprocal recurrent selection may be employed for simultaneous improvement of the characters.

Estimation of Combining Ability for Flowering and Yield Attributes in Bhendi (Abelmoschus esculentus (L.) Moench)

The present study on general combining ability effects and specific combining ability effects involves seven parents viz., G1 (Arka Anamika), G2 (Aruna), G3 (Varsha Uphar), G4 (Pusa-5), G5 (MDU-1), G6 (Kashi Kranti), G7 (Ankur-41) with their 21 F1 hybrids through half-diallel mating system. The present investigation was undertaken using Randomized Block Design with three replications. The combining ability effects were estimated for seven characters viz., days to first flowering, days to first fruit harvest, fruit length, fruit girth, fruit weight, number of immature seeds per fruit and fruit yield per plant. The results showed that gca effects of parents and sca effect of hybrids were significantly differed. The SCA variance was higher than the GCA variance that indicates the presence of preponderance of non-additive gene action for all the seven traits i.e., presence of preponderance of non-additive gene action for all characters except number of nodes per plant. Among the parents, G3 was found to be a good general combiner based on the per se performance and gca effects for its flowering and yield traits. Among the 21 F1 hybrids, the crosses G3 x G5 and G4 x G6 were superior on the basis of per se performance and sca effect for flowering and yield attributes. Hence, these hybrids were used for further exploitation of heterosis.

Genetic effects and heterosis for seed yield and physio-biochemical traits in chickpea (Cicer arietinum)

A 8-parent diallel analysis was taken to investigate the genetic effects and heterosis for seed yield and 6 physiobiochemical characters in chickpea (Cicer arietinum L.) under timely and late sown conditions at research farm of Rajasthan Agricultural Research Institute, Durgapura, Jaipur, Rajasthan during winter (rabi) seasons of 2020–21 and 2021–22. Significant disproportion of GCA and SCA variances depicted that both additive and non-additive gene action plays a vital role for genetic control of all the traits. Though the relative amount of GCA/SCA was less than unity for all traits under study signifying that non-additive gene plays a key role under the environments studied. The parents CSJ-515, CSJD-884 and RSG-963 emerged as good general combiners for seed yield, additionally theparents CSJ 515 and RSG 963 were considered as good general combiners for CC and PV, whereas parent CSJD-884 for MSI, TCC and PC. The crosses CSJD 884 × RSG 963, CSJD 884 × RSG 973, CSJD 884 × Avrodhi, CSJD 884 × HC 5, RSG 963 × CSJ 515, RSG 974 × HC 5 and CSJ 515 × HC 5 showed consistent SCA effect and heterobeltiosis for seed yield and one or more heat tolerant physio-biochemical traits and projected that these crosses would provide enviable transgressive segregate for heat tolerance.

Combining ability and gene action studies for yield and fibre traits in Gossypium arboreum using Griffings numerical and Haymans graphical approach

BackgroundFor the purpose of utilising hybrid vigour to produce possible hybrids with a suitable level of stability, the knowledge of gene activity and combining ability is a crucial prerequisite before choosing desirable parents. The present study was carried out with six parents crossed in full diallel fashion and generated 30 F1 hybrids. These hybrids were evaluated in two replications in Randomized Block Design at Department of Cotton, TNAU for combining ability and gene action. Diallel analysis was carried out according to Griffing’s method-I (parents + F1 + reciprocals) and model-I and Hayman’s graphical approach by using INDOSTAT software.ResultsAnalysis of variance for combining ability indicated that mean square values of GCA, SCA and reciprocals were highly significant for all the traits except for the uniformity index. RG763 and K12 showed highly positively significant GCA effects for most of the yield traits while PA838 and K12 for fibre quality traits, so they were found as best general combiners. PAIG379 × K12 and PDB29 × K12 for yield traits, and PDB29 × PA838, RG763 × PA838, and CNA1007 × RG763 cross combinations for fibre quality traits could be recommended for future breeding programms.ConclusionThe results of both Griffing’s and Hayman’s approaches showed that non-additive gene action predominates as SCA variance was bigger than GCA variance, so heterosis breeding is thought to be a more fruitful option for enhancing GCA of many traits.

Study of Combining Ability in Association with Heterosis in Rice (Oryza sativa L.)

In the current investigation, eight lines KNM 12444, KNM 12469, KNM 12472, KNM 13449, KNM 13555, KNM 13568, KNM 14913 and KNM 14985 were crossed with four testers namely Aganni, IBT MRR 24, INRC 3021 and WGL 1119 in Line by Tester mating design during rabi season of 2021-22. The resultant 32 F1’stogether with parents and two commercial checks, KNM 118 and KNM 1638 were evaluated for their combining ability and heterosis at Agricultural Research Station, Kunaram during kharif season, 2022.The analysis of variance for combining ability specified that significant differences were observed due to lines, testers, F1’ hybrids and various interactions indicating the existence of wider adaptability in the material examined. The ratio of gca to sca variances showed that non-additive gene action was predominant in the inheritance of panicle length, plant height, number of productive tillers/plants, grain yield per plant, kernel length, kernel L/B ratio and incidence of gall midge, whereas, preponderance of additive gene action was noticed for 1000 grain weight, days to 50% flowering, number of filled grains per panicle, kernel breadth, hulling percentage, milling percentage and head rice recovery. The gca effects of the parents revealed that, the line KNM 13555 and the testers Aganni, IBT MRR 24 were found to be the best general combiners for single plant yield and its components. Based on the significant sca effects, per se performance, standard heterosis and gall midge incidence, KNM 12469/Aganni followed by KNM 13555/INRC 3021, KNM 13568/IBT MRR 24, KNM 12472/Aganni and KNM 13449/Aganni were identified as promising for single plant yield, its components, quality traits and gall midge incidence. Hence, these parents and F1 hybrids may be further tested for future crop improvement programme.

Genomic prediction in hybrid breeding: I. Optimizing the training set design

Key messageTraining sets produced by maximizing the number of parent lines, each involved in one cross, had the highest prediction accuracy for H0 hybrids, but lowest for H1 and H2 hybrids.Genomic prediction holds great promise for hybrid breeding but optimum composition of the training set (TS) as determined by the number of parents (nTS) and crosses per parent (c) has received little attention. Our objective was to examine prediction accuracy (r_{a}) of GCA for lines used as parents of the TS (I1 lines) or not (I0 lines), and H0, H1 and H2 hybrids, comprising crosses of type I0 × I0, I1 × I0 and I1 × I1, respectively, as function of nTS and c. In the theory, we developed estimates for r_{a} of GBLUPs for hybrids: (i)hat{r}_{a} based on the expected prediction accuracy, and (ii) tilde{r}_{a} based on r_{a} of GBLUPs of GCA and SCA effects. In the simulation part, hybrid populations were generated using molecular data from two experimental maize data sets. Additive and dominance effects of QTL borrowed from literature were used to simulate six scenarios of traits differing in the proportion (τSCA = 1%, 6%, 22%) of SCA variance in σG2 and heritability (h2 = 0.4, 0.8). Values of tilde{r}_{a} and hat{r}_{a} closely agreed with r_{a} for hybrids. For given size NTS = nTS × c of TS, r_{a} of H0 hybrids and GCA of I0 lines was highest for c = 1. Conversely, for GCA of I1 lines and H1 and H2 hybrids, c = 1 yielded lowest r_{a} with concordant results across all scenarios for both data sets. In view of these opposite trends, the optimum choice of c for maximizing selection response across all types of hybrids depends on the size and resources of the breeding program.

Evaluation of General and Specific Combining Ability for Yield and its Attributing Traits in Bread Wheat (Triticum aestivum L.)

In order to investigate the general and specific combining ability (GCA and SCA) and gene action for yield and its contributing traits in common wheat, 10 lines and 4 testers were crossed using line × tester mating design at the Crop Research Center of SVP University of Agriculture and Technology, Meerut, Uttar Pradesh, India. The experimental material was raised under Randomized Block Design with three repetitions during rabi season of 2019–20 and 2020–21. The variance due to cross vs parent was highly significant for all the traits. Estimates of SCA variance for harvest index, plant height, biological yield per plant, 1000 grain weight, days to 50% blooming, grain yield per plant, days to maturity and number of productive tillers per plant, were higher than those of GCA variance, depicting the prevalence of non-additive gene action. GCA variance was found to be higher than SCA variance for the remaining characteristics, reflecting additive gene action. Based on GCA four parents were found promising (UP1109, DBW187, HD3237, PBW226, RAJ3777). On the basis of SCA, 9 crosses (HD3237 × WR544, RAJ 3777 × HD3086, DBW187 × HD3086, DBW187 × PBW226, K9162 × WH1105, PBW373 × WH1105, K9162 × PBW226, UP2628 × WR544, UP1109 × PBW226) were identified good specific combiner for grain yield per plant. In present study non-additive type of gene action was more pronounced, which can be utilized by pedigree method, biparental mating and selection in later generation.

Efficient Genomic Prediction of Yield and Dry Matter in Hybrid Potato.

There is an ongoing endeavor within the potato breeding sector to rapidly adapt potato from a clonal polyploid crop to a diploid hybrid potato crop. While hybrid breeding allows for the efficient generation and selection of parental lines, it also increases breeding program complexity and results in longer breeding cycles. Over the past two decades, genomic prediction has revolutionized hybrid crop breeding through shorter breeding cycles, lower phenotyping costs, and better population improvement, resulting in increased genetic gains for genetically complex traits. In order to accelerate the genetic gains in hybrid potato, the proper implementation of genomic prediction is a crucial milestone in the rapid improvement of this crop. The authors of this paper set out to test genomic prediction in hybrid potato using current genotyped material with two alternative models: one model that predicts the general combining ability effects (GCA) and another which predicts both the general and specific combining ability effects (GCA+SCA). Using a training set comprising 769 hybrids and 456 genotyped parental lines, we found that reasonable a prediction accuracy could be achieved for most phenotypes with both zero common parents (ρ=0.36-0.61) and one (ρ=0.50-0.68) common parent between the training and test sets. There was no benefit with the inclusion of non-additive genetic effects in the GCA+SCA model despite SCA variance contributing between 9% and 19% of the total genetic variance. Genotype-by-environment interactions, while present, did not appear to affect the prediction accuracy, though prediction errors did vary across the trial's targets. These results suggest that genomically estimated breeding values on parental lines are sufficient for hybrid yield prediction.

ESTIMATION OF HETEROSIS AND COMBINING ABILITY EFFECTS FOR YIELD AND FIBER QUALITY TRAITS INCOTTON (GOSSYPIUM HIRSUTUM L.)

Cotton (Gossypium hirsutum L.) is an important cash crop worldwide, including Pakistan. Cotton is the fibre crop that plays a vital role in Pakistan's economy. Cotton devotes a major part to enhancing foreign exchange earnings and contributes 65 percent of total annual earnings by exporting the raw material and finished products of cotton. Identifying the parents with higher yield contributing traits is essential to enhance the economic yield. The diallel mating design was used because it is the best tool to discriminate between good and bad combiners. All crosses showed significant results except the number of monopodial branches, internodal distance and first fruiting branch node. Traits that showed significant variability were further analyzed for combining ability effects and gene action related to yield contributing traits. From parents NIAB-777 and Tipo-1 showed superior general combiners for most of the traits. Among the crosses NIAB-777 × Tipo-1, C-1 × Tipo-1 and C-1 × Shahkar exhibited high SCA. SCA variance for most of the genotypes was better than GCA and RCA variance. The information devised is really helpful in selecting suitable parents and hybrids for further breeding programs.

English

Twenty-one crosses developed from the frame of line × tester analysis along with ten parents were grown in two replicates experiment. Data on days to flowering, days to maturity, plant height, number of pods/plant, number of primary branches, number of secondary branches, number of tertiary branches, number of seeds per pod and seed yield per plant (g), revealed high significant differences exist among lines, testers and crosses for all traits studied. The ratio value of general combining ability variance to specific combining ability variance suggests the preponderance of non-additive type as well as additive gene action for some traits. Genotype Pusa-362 was the best general combiner for days to flowering. Genotype ICCL-87322 was identified as the best general combiner for the number of seeds per plant. Genotype BG329 was identified as the best general combiner for seed yield per plant (g) followed by KPG-59. Genotype PG-92-4 recorded desirable and significant GCA across five traits consistently. Cross PG-92-4 X Pant-186 recorded five significant SCA in the positive direction for secondary branches, number of tertiary branches, number of pods per plant, seed yield per plant and hundred seed weight. This cross is considered the most important compared to other materials under study. The proportional contribution of line × tester interaction was evident for most of the traits followed by the contribution of maternal lines. Days to flowering, days to maturity, primary branches, secondary branches, tertiary branches, pod per plant, seed per pod and seed yield per plant (g) recorded higher SCA variance suggesting non-additive gene action exit in expressing of these traits. The presence of a high SCA effect suggests that heterosis breeding can be exploited. Selection for those characters should be undertaken in later generations when these traits are fixed in homozygous lines. Key words: Chickpea, Cicer reticulatum, combining ability, gene action, heritability.