Significant GCA Effects Research Articles

Combining Ability and Gene Action for Grain Yield and Attributing Traits in Maize (Zea mays L.) Subjected to Drought Stress

Background: Maize production is subdued by many impediments that cause yield minimization. Among various biotic and abiotic stress factors, one significant cause of yield reduction in maize is drought stress. Methods: A set of 15 inbreds which were crossed with 3 narrow base testers in line × tester mating design, and resulting 45 F1s along with the parent inbreds and 3 commercial checks were then, in RCBD, subjected to drought stressed and well-watered conditions to assess their genetic worth during spring 2021. Result: The ANOVA unraveled significant mean sum of squares due to lines, testers and line × tester in pooled analysis for all the ten traits. The inbred EI-2188-2 followed by EI-2448 and EI-03-3 contained fair per se performance and significant high GCA effects over the environments for grain yield/plant, proline content and cob length whereas the cross EI-2448-1 × EI-2156 was found most promising hybrid with significant and high SCA effects across the environments regarding grain yield/plant, proline content and cob girth. Prevalence of non-additive type of genetic variance in governing most of the traits suggests adoption of heterosis breeding will be rewarding for improving yield and drought tolerance. Heterotic pooling of the highlighted inbreds and utilization of the superlative hybrids in further breeding programmes for drought tolerance is proposed.

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

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.

Identification of Potential Tropical Maize Inbred Lines with Early Maturity for Drought-Prone Environments

The present study was undertaken during October, 2020–January, 2021 at Maize Research Centre, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana state, India to identify potential inbred lines and hybrids with early maturity and high yield through combining ability analysis and heterosis. Six lines and four testers were crossed in L×T design to obtain 24 crosses. Evaluation of these crosses and their parents for combining ability revealed significant differences due to lines, testers and their crosses indicating the existence of wider variability among the material used in the study. Maize line MGC 434 (91 days), two testers GP-170 and PFSR-56 (91 days), and one hybrid MGC-445×PFSR-132 (83 days) were identified as early duration genotypes. Four lines MGC-444 (-3.13), MGC-440 (-2.71), MGC-439 (-1.96) and MGC-445 (-0.46) with significant negative GCA effects were identified as best general combiners for early maturity. Eight hybrids, MGC-439×BML-14 (-4.99), MGC-445×PFSR-56 (-4.65), MGC-461×PFSR-56 (-3.65), MGC-445×PFSR-132 (-3.60), MGC-434×BML-14 (-2.32), MGC-439×GP-170 (-2.10), MGC-440×PFSR-56 (-2.07) and MGC-440×GP-170 (-1.01) with significant negative SCA effects were considered as best cross combinations with early maturity. The inbred parents and cross combinations with early maturity identified in the study can be utilized for development of hybrids suitable to drought prone environments.

Heterosis and Diallel Analysis for Grain Yield, Yield Attributes and Physiological Traits in Barley (Hordeum vulgare L.)

The present study was carried out during November–April, 2019–2020 and 2020–21 with eight diverse barley genotypes and their developed 28F1s (half diallel, excluding reciprocals) to ascertain gene effects, hetrosis and correlations for grain yield, yield attributes and physiological traits under water limited conditions of Bundelkhand region. Days to heading and days to maturity exhibited general mean values of 86 days and 127 days, respectively. The parental genotypes, DWRB180, RD2794 and RD2899 showed early spike emergence and maturity. The cross combinations, namely DWRB160 /DWRB180, DWRB180/RD2907 and BH946/RD2552 were promising for flag leaf length and width. The GCA effects were significant and prevalent for all the characters, except days to heading, plant height and tillers count. The parents, DWRB160 (5.29**) and BH902 (1.59**) depicted high GCA effects for 1000 grain weight. The parents, DWRB180, RD2552, and BH946 exhibited significant positive GCA effects for leaf area index and chlorophyll fluorescence, whereas the genotypes, RD2907, BH946 and RD2899 showed higher GCA effects for chlorophyll content. Grain yield exhibited significant positive correlations with flag leaf width (0.60**), tillers per meter (0.35*), grains per spike (0.39*), harvest index (0.53**), chlorophyll content (0.69**), leaf area index (0.49**) and chlorophyll fluorescence (0.68**). The parents, BH946, DWRB180 and RD2907 and the hybrids, RD2552/DWRB180, BH902/RD2794, DWRB160/DWRB180 and BH946/RD2907 were found promising for yield and yield attributes in the dry agro-ecology of Bundelkhand region. The crosses, DWRB160/BH902 and DWRB160/BH946 can be explored for developing superior segregants for malt barley breeding.

GENETIC EVALUATION FOR SEED YIELD AND ITS COMPONENT TRAITS IN SUNFLOWER (HELIANTHUS ANNUUS L.) USING LINE × TESTER APPROACH

Sunflower is a vital oilseed crop, but yield improvement remains a major objective. Exploring germplasm and exploiting non-additive gene action can help overcome yield limitations and identify superior parental lines and crosses for hybrid development through GCA and SCA. Four parental lines (A-1, A-2, A-3, and A-4) were crossed with three testers (B-1, B-2, B-3) in a line × tester fashion to generate F0 seeds. These seeds were planted using a randomized complete block design (RCBD) with three replicate plots in the field to ensure unbiased results. Data on various growth and yield parameters is collected and analyzed using Analysis of variance and combining ability analysis. Lines A-3 and A-4 and tester B-3 demonstrated consistently positive GCA effects for several traits, signifying their broad genetic value for hybrid development. The hybrid A-4 × B-1 emerged as the top performer, exhibiting exceptional SCA effects in days to flowering, seed yield per head and height of the plant, indicating exceptional compatibility between these parental lines. Lines A-3 and A-4 displayed significant positive GCA effects for key parameters like head diameter and seed yield. Tester B-3 also contributed to enhanced yield traits in hybrid combinations. Lines A-3 and A-4, tester B-3, and hybrid A-4 × B-1 emerged as promising parents for sunflower hybrid development due to their superior GCA and SCA effects. These findings offer valuable resources for future breeding programs that enhance sunflower yield and productivity.

Combining ability analysis of Cucurbita moschata D. in Côte d'Ivoire and classification of promising lines based on their gca effects.

Cucurbita moschata varieties grown in Africa have very low yield. They have been neglected, and totally ignored in agricultural research programs. However, interest in their fruits, seeds, flowers and leaves is growing nowadays due to their nutritional and medicinal potentials. That growing interest has prompted plant breeders and agronomists to develop research programs for their improvement. A complete diallel cross analysis of four parental lines, Long, Zouan-H, Oval, and Soubre and their twelve F1 hybrids, was carried out in a farming environment at the University Nangui Abrogoua, Abidjan, Côte d'Ivoire. The four parental lines and the F1 hybrids were evaluated for their general performances, combining abilities, potency ratio and heterosis effects. The investigated traits included plant height, and eleven fruit- and seed-related characters. The analysis of variance showed significant differences for all traits studied. In addition, the diallel model yielded highly significant gca effects of the female parents. The gca effects of the male parents were significant for all traits except plant height, length of the fruit, width of the fruit and length of the seed. Highly significant sca effects were observed in the crosses for all the traits. Strong maternal effects were observed for the weight and diameter of the fruit, weight of the pulp, number of seeds per fruit, weight of the fresh seeds and 100-seed weight. The general predictive ratio approached the value 1 for all the traits except weight of the fresh seed and width of the dry seed. Most of the characters under this study are predominantly determined by the effects of additive genes. But, weight of the fresh seed and width of the dry seed may be controlled by non-additive genes. Mid-parent heterosis was significant for all measured traits in the crosses, except the length of the fruit. And better-parent heterosis was significant for all traits except plant height, number of fruits per plant and length of the fruit. Gene expression is described by a super-dominance for many traits, and partial dominance for some other traits in all twelve F1 hybrids. Classification of the parental lines based on the effects of their general combining ability grouped the Soubre lines as promising contributors to fruit yield. The parental lines Long and Oval formed another group likely on the basis of the small size of their fruits, the small pulps, the smaller number of fruits per plant and the large number of seeds per fruit. However, Long would be a candidate parent for the development of cultivars with longer vegetative growth. The parental line Zouan-H formed the third group and it was mostly characterized by its large number of seeds per fruit and relatively large fruits.

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 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.

Heterosis and Combining Studies for Growth, Yield and Quality Traits in Garden Pea (Pisum sativum L.)

The present study entitled “Line × Tester analysis in garden pea” was undertaken to estimate the extent of heterosis and combining ability effects for growth, yield and quality traits in pea. Experimental materials comprise five lines viz., Arka Uttam, IIHR-48, IIHR-34, IIHR-41, Arka Tapas and three testers viz., Arka Ajith, Arka Sampoorna and Arka Priya with their fifteen crosses along with one check Arka Pramodh. The parents and hybrids were randomized separately and sown using a Randomized Block Design with two replications during 2019-20. The results revealed that the female parent Arka Tapas recorded a significant GCA effect for most growth and yield parameters. The cross Arka Tapas × Arka Priya exhibited a high percentage of mid-parent (38.74 %), better parent (16.70 %) and heterosis over the commercial check (9.96 %) for the character pod yield per hectare.

Hybrid breeding for fall armyworm resistance: Combining ability and hybrid prediction

AbstractFall armyworm (FAW, Spodoptera frugiperda) emerged as a major lepidopteran pest destroying maize in sub‐Saharan Africa. A diallel mating design was used to generate 210 experimental hybrids from 21 lines. Experimental hybrids and four checks were evaluated in two locations. Commercial checks suffered higher foliar and ear damage compared to the top 15 hybrids. Mean squares associated with the genotypic variation were higher than genotype‐by‐environment interactions for foliar and ear damage traits. Heritabilities were moderate to high. Significant correlations were observed between grain yield (GY) with ear rot (−0.54) and ear damage (−0.45). Positive and significant GCA effects were observed for GY in seven parental lines, which were developed from multiple insect resistance breeding programmes. CKSBL10153 has the highest GCA value for GY and shows significant GCA effects for foliar and ear damage traits. These lines were identified as the ideal combiners for GY and FAW resistance and are therefore recommended for utilization as testers in the development of FAW‐resistant three‐way cross‐hybrid maize with correlated response for increased GY. GCA and marker‐based prediction correlations of GY were 0.79 and 0.96, respectively. Both GCA effects and marker‐based models were effective in predicting hybrid performance for FAW resistance.

Combining ability for rancidity and associated traits in pearl millet (Pennisetum glaucum)

AbstractPearl millet occupies an important place in attaining nutritional security in marginal areas; however, as it develops off‐flavours, it is less preferred by food industry. The objective of the current study was to determine the variations in rancidity‐related traits and estimate the combining ability of inbreds and hybrids for these traits under varied environmental conditions. In this study, 32 hybrids were developed from eight lines and four testers using line × tester mating design and evaluated along with parents and checks 86M86 and HHB 67 for yield and rancidity‐associated traits in three environments. The hybrids L7T2 and L6T1 are identified as promising hybrids for grain yield and rancidity. Higher variance due to specific combining ability and predictability ratio for grain yield and rancidity‐associated characters indicate the predominance of non‐additive gene action. The tester T1 recorded a significant negative GCA effect with low alcoholic acidity. A significant and positive SCA for grain yield was observed in L3T1 and L7T2, whereas for rancidity in L5T4. Alcoholic acidity showed a significant positive association with 1000 seed weight, lipase and lipoxygenase in parents and negative association with 1000 seed weight in hybrids.

Heterotic Classification of Inbred Lines of Maize Based on Combining Ability for Kernel Yield

Grouping of maize inbred lines into heterotic groups is an initial step in exploitation of heterosis. Hence a field study was conducted to classify 27 inbred lines into two heterotic groups by evaluating the performance of 54 crosses along with lines and testers in a simple lattice design. The 27 inbred lines were crossed to two broad based heterotic testers. Highly significant differences were noticed for kernel yield per plant, days to anthesis, days to silking and plant height among all the genotypes. One cross PI 330 × LM 13 was found to be promising among the crosses. Highly significant GCA and SCA effects for kernel yield per plant was recorded. Five inbred lines were identified as good general combiners for kernel yield per plant while nine test crosses were found to be good specific combiners. Out of 27 inbred lines, the testers could classify 15 inbred lines into heterotic groups based on GCA and SCA effects and mean kernel yield per plant. The study demonstrated the applicability of combining ability effects in classifying the inbred lines.

Combining Ability of Cowpea (Vigna unguiculata (L) Walp) Genotypes for Resistance to Cowpea Bacterial Blight in Uganda

The low productivity of cowpea is partly attributed to a number of constraints including diseases such as cowpea bacterial blight (CoBB). Cowpea bacterial blight has the capacity to cause up to 92% yield loss under severe infections. The objective of this study was to determine the combining ability for resistance to CoBB among cowpea genotypes in Uganda. Nine selected parents were crossed to produce 63 progenies. F1 progenies were evaluated and data gathered included days to 50% flowering, CoBB disease scores and grain yield. The mean squares for rAUDPC due to GCA and SCA effects were significant (P≤0.001) and non-significant respectively. The broad sense coefficient of genetic determination (BCGD) and narrow sense coefficient of genetic determination (NCGD) were 44.3% and 29.1% respectively for rAUDPC. Parents WC 26 (-0.023) and NE 31 (-0.035) had highly significant negative GCA effects for rAUDPC and were therefore good general combiners for this trait. Crosses SECOW 3B x ACC 26 X SECOW 1T and WC 26 x NE 32 had negative significant SCA effect for rAUDPC with a values of -0.073 and -0.06, respectively while Crosses ACC 26 x SECOW 1T x NE 40 (-0.07) and NE 40 x WC 26 (-0.06) had significant negative reciprocal effects for rAUDPC. This study revealed that genetic inheritance for cowpea bacterial blight was controlled predominantly by additive gene effects. Parents WC 26 and NE 31 identified as good general combiners for resistance to CoBB could be utilized as sources of resistance while Crosses SECOW 3B x ACC 26 X SECOW 1T, WC 26 x NE 32, ACC 26 X SECOW 1T x NE 40 and NE 40 x WC 26 that were the best specific combiners for resistance to CoBB could be put under further evaluation as potential varieties.

Heterosis and Combining Ability Analysis in Maize Using Line X Tester Model

Twenty-two lines were crossed with 2 testers in a Line × Tester mating design in 2017-18 and the resulting 44 crosses along with the lines, testers and three checks i.e., BARI Hybrid Maize 9 (BHM 9), 981 and Elite were evaluated in a alpha lattice design with two replications, during rabi, 2018-19. Highly significant differences were found among the genotypes for all the characters studied. Parent and parents vs crosses were significant for all the characters except ASI indicating greater diversity in the parental lines of the traits. Three lines (viz., BMZ 55, BMZ 53, BMZ 4) showed significant negative GCA effect for both days to 50% tasseling and silking, indicating good general combiners for earliness. BMZ 15, BMZ 55, BMZ 53 and BMZ 68 showed significant negative GCA effects for both plant and ear height. BIL 79, Pinacle 17 and BIL 182 exhibited desirable significant positive GCA for grain yield. Considering desirable GCA effects those parents could be used extensively in hybrid breeding program to accumulate those favorable genes. However, two cross combinations BIL 182 x CML 429 and BIL 79 x CML 429 were found promising considering SCA effect, mean performance and could be utilized for enhancing hybrid production. Considering BHM 9 as check, the percent standard heterosis for grain yield varied from -52.6 to 0.6%. None of the crosses showed significant positive heterosis for grain yield except BIL 79 × CML 429.
 Bangladesh J. Agril. Res. 46(3): 261-274, September 2021

Inheritance of Secondary Metabolites Associated With Cowpea Resistance to Flower Bud Thrips

Plant secondary metabolites are part of defense mechanism that form host plant resistance. Understanding the inheritance of secondary metabolites is preliquisite for conducting an effective plant breeding program. The objective of this study was to determine the mode of inheritance of secondary metabolites associated with resistance of cowpea to flower bud thrips. Five cowpea genotypes with varying level of resistance to flower thrips were crossed in full diallel method 1. The F2 were evaluated for secondary metabolites and flower thrips damage in field and screen house. The results confirmed genotype TVU-3804 as resistant, and TVU-9820 and TVU-201 as susceptible to flower bud thrips. Flavonoids, antioxidants, proteins and reducing sugars had significant (p < 0.001) GCA and SCA effects indicating the importance of additive and dominance effect in controlling resistance of flower bud thrips. In addition, significant reciprocal observed for crosses such as Lori Niebe × Sanzi and Sanzi × TVU-3804 for flavonoids and antioxidants is an indication that maternal effect is key in governing resistance of cowpea to thrips. The broad sense heritability was low for secondary metabolites except flavonoid which had moderate value, an indication that delaying selection to a later generation would yield better results while breeding for resistance to flower thrips based on secondary metabolites. The results of this experiment showed that it is possible to use secondary metabolites to breed for improved cowpea resistance to flower bud thrips.

Combining ability study on yield and its contributing traits in maize (Zea mays L)

Experimental material consisted of 25 lines, 2 testers and their 50 crosses along with standard checks viz., Palam Sankar Makka-2 and PSCL 4640 were evaluated using Randomized Block Design with two replication during Kharif 2020. Genotype mean square was significant for days to 50% tasseling, days to 50% silking, days to 75% brown husk, ear height (cm), plant height (cm), ear length (cm), ear circumference (cm), kernel rows/cob, kernels/row, 1000-kernel weight (g), shelling (%) and grain yield (q/ha) which indicated the presence of sufficient genetic variability in the material studied. Also the ratio of GCA variance to SCA variance was less than unity for all traits indicated preponderance of non-additive gene action. Among lines, KI-3 exhibited higher grain yield followed by KI-7 and CML 140. These lines also exhibited highest significant GCA effect for grain yield and were identified as promising parents. KI-7 × LM 13, CML 140 × LM 13, CML 139 × LM 13, CML 162 × LM 13 and KI-3 × LM 14 exhibited maximum SCA effect for most of traits. These promising cross combinations need to be evaluated in multi-location trials over the years to assess their suitability in different agro-climatic zones of the State.

Genetic Analysis of Agronomic and Fall Armyworm-Resistance Traits in Maize Hybrids with Varying Levels of Resistance to Stem Borers

Stem borer (SB) and more recently, fall armyworm (FAW) are serious economic pests in maize production in sub-Saharan Africa. It is hypothesized that SB-resistant germplasm may confer resistance against FAW. However, the performance of SB-resistant lines in hybrid combinations and the inheritance of FAW-resistant traits under variable FAW infestations have not been reported. This study was conducted to (i) obtain information on the inheritance of agronomic and FAW-resistant traits under variable FAW infestations; (ii) identify hybrids combining high grain yield (GYLD) and stability under FAW infestations; and (iii) determine the effects of FAW damage on GYLD. Three SB-resistant lines (1393, CKSBL10060 and CML 331) as testers and six open-pollinated varieties (OPVs) as lines were crossed in a line tester scheme to generate eighteen test crosses. The test crosses together with two tester × tester crosses and two checks were evaluated under artificial FAW infestation (AI), natural infestation (NI) and pesticide-protected condition (PC) in Nigeria. Additive and non-additive effects were significant for GYLD, most agronomic and FAW-resistant traits under AI and NI, except ear damage (EDAM) scores under NI, whereas only the non-additive effect was significant for GYLD under PC. Two testers (1393 and CKSBL10060) combined significant and positive GCA effects for GYLD with desirable GCA effects for FAW-resistant traits under AI and NI, whereas CML 331 combined significant and negative GCA effects of GYLD with undesirable GCA effects of FAW resistance under the test conditions. Three OPVs (AWR SYN-W2, AMATZBR-WC4 and TZB-SR) had a significantly positive GCA effect for GYLD and a desirable GCA effect for either leaf damage (LDAM) or EDAM score under AI. The FAW LDAM and EDAM significantly reduced GYLD under AI but not under NI. Three test crosses (AMATZBR-WC4 x CKSBL10060, TZB-SR x CKSBL10060 and TZBR Comp 1-WC2 × 1393) combined high yield with stability and FAW tolerance across the test conditions and thus were recommended for further testing.

Combining ability of common bean (Phaseolus vulgaris) genotypes for root traits across diverse environments

AbstractRoot system architecture is important for common bean (Phaseolus vulgaris) adaptability to diverse environments. Beans employ complex adaptive root mechanisms for coping with multiple stresses in production environments. Understanding genetic control of root traits is central to improvement of common bean for adaptation to marginal environments. The objectives of this study were to (i) determine combining ability of root and agronomic traits and (ii) estimate the heritability and genetic correlation of root and agronomic traits in common bean. Four bean lines with superior root traits were crossed with four locally adapted varieties in a North Carolina II mating scheme to generate 16 crosses. The 16 F1s were selfed and advanced to F2 generation. Eight parents and their F2 progenies were evaluated in an alpha‐Lattice design with two replications. General and specific combing ability mean squares were significant (p ≤ .05) for all traits measured. General predictability ratios ranged from .47 to .68 across locations suggesting that both additive and non‐additive gene action modulate root traits and seed yield. Positive and significant (p ≤ .05) phenotypic and genetic correlations revealed significant association between root traits and yield. Moderate to high heritability estimates of between .43 and .67 were realized. Such estimates point to possible deployment of a successful selection programme. Genotype AFR398 displayed significant positive GCA effects among its crosses for both root and agronomic traits hence a potential candidate genotype for inclusion in a bean genetic improvement programme for marginal environments.

Genetic Variability, Diversity, Heterosis and Combining Ability in Sponge Gourd [Luffa cylindrica (Roem.) L.

This experiment was conducted at Mandouri farm, Horticultural Research Station, Bidhan Chandra Krishi Viswavidyala (BCKV), West Bengal, India during March, 2014 to July, 2018. The objectives of the research were to determine genetic variability, phenotypic performance and diversity for yield and 17 yield attributing traits of the 45 sponge gourd germplasm. To study the heterosis and combining ability of parental lines with half diallel analysis for earliness and yield contributing characters. PCV (phenotypic coefficient of variation) was higher than GCV (genotypic coefficient of variation) for all the traits studied. Higher PCV and GCV were recorded for traits namely number of primary branches plant-1, number of fruiting nodes on main stem, sex ratio (male/female), fruits plant-1 and fruit yield plant-1. Based on Mahalanobis’ D2 statistic, the genotypes of sponge gourd were grouped into 7 different clusters. Fruit yield plant-1, weight of fruit and number of fruiting nodes on main stem had maximum contribution towards genetic divergence. Among the parents, Patna Local, IC-336759 and IC-284795 showed high significant positive GCA effects as well as per se performance for yield and yield related attributes. Additive as well as non-additive gene action regulating the different traits. The traits under non additive gene action. The magnitude of standard heterosis was found in desirable direction for early and yield traits viz., days to first pistillate flower appearance in the cross IC284795×Patna Loca (-23.07%), for 50% flowering in the cross IC-284795×Patna Local (-18.89%), sex ratio in the cross IC-336759×Patna Local (-53.41%), for number of fruit vine-1 in the cross IC-284795×Patna Local (34.56%) and average fruit weight in the cross IC336759×Patna Local (110.09%). Promising germplasm Patna Local may be subjected for regional yield trail along with released variety with a view to develop new variety of sponge gourd. The superior hybrids can be exploited for hybridization programme.