Combining Ability Analysis and Association of Yield and Yield Components among Selected Rajmash (Phaseolus vulgaris L.) Lines

Legumes are the important constituents of vegetarian Indian diet. They are important source of protein and calories. On average, pulses contain 22 to 24 per cent protein as against 8 to 10 per cent in cereals. Rajmash (Phaseolus vulgaris L.) is the third most important grain legume in the world and regarded as “Grain of hope” since it is an important component of subsistence agriculture and feeds about 300 million people in tropics and 100 million people in Africa alone (Kull et al., 2003). In India, Rajmash is mainly produced by resource-poor, small and marginal farmers in the traditional cropping system which includes rotation with vegetables and intercropping of climbing/ pole type beans with grain amaranth, potato and maize during the rainy season in the mountains/hills while as a sole crop of bushy types during winters (Rana et al., 2011). Rajamsh considered to be a very rich source of protein and vitamins. It also provides with carotenoids like beta-carotene, neoxanthin, lutein and violaxanthin. It also contains antioxidant capacity and hence helps to rid of harmful radicals which cause damage to cardiovascular system. It is rich source of dietary fiber which protects the mucosa in the colon by reducing exposure to toxins. It has rich source of zea-xanthin, a dietary carotenoid that gives protective UV filtering function. Its dry seed contains 21.1 per cent protein, 69.9 per cent carbohydrates, 1.7 per cent fat, 381 mg calcium, 425 mg phosphorus and 12.4 mg iron per 100 g of edible part (Ali and Kushwaha, 1987). The nutritional composition of tender Rajmash is moisture 12.0 g, protein 22.9 g, fat 1.3 g, minerals 3.2 g, crude fiber 4.8 g, carbohydrates 60.6g, energy 346 Kcal, calcium 260 mg, phosphorus 410 mg, iron 5.1 mg/100 g. of edible portion (Gopalan et al., 2012). It has both carminative and reparative properties against constipation and diarrhea, diuretic, dropsy, dysentery and kidney resolvent respectively. Targeted breeding programs are crucial for addressing the complex and evolving challenges in agriculture, food production and ecosystem conservation, with broad implications for global food security, economic development and environmental sustainability. Top of Form So, there is an urgent need to organize a strong and efficient breeding programme to develop high-yielding and good-quality varieties of Rajmash.
 
From a genetic standpoint, the most crucial step in the hybridization program is the selection of superior parents to produce new genotypes with desirable characteristics (Ahmad et al., 2006). A high-performance genotype may not inevitably create better hybrids and transgressive segregants when employed in hybridization (Sharma et al., 2022). The yielding potential of the genotypes will be greatly affected if grown under different environmental conditions. The genotype which performs better in varied climatic situations will be an ideal one. (Patel et al., 2021a and Sharma et al., 2022b). Different types of breeding designs, like diallel, test crosses, bi-parental, line x tester and multiple crosses, are used to evaluate breeding material (Nduwumuremyi et al., 2013). The primary goal of these designs is to assess the GCA and SCA impacts on parental lines, the SCA and heterosis of crossings and the heredity of the traits (Sharma and Shadakshari, 2021 and Singh et al., 2022). Line × tester analysis is a modified version of the top cross design, is usually used for determining combining ability (GCA and SCA), identifying parental lines based on hybrid performance and estimating various sorts of gene activities (Kempthorne, 1957). Generally seed yield is a quantitative trait that is governed by polygenes in bean (Arunga et al., 2010). Selection based on seed yield alone is usually not effective, whereas selection along with yield components could be more efficient and reliable (Kwaye et al., 2008). Consequently, information on the association between seed yield and its components and among the yield characters themselves can improve the efficiency of selection in plant breeding programs (Muhammad et al., 1994; Shimelis, 2006; Kwaye et al., 2008). The objectives of this study are to determine the combining ability of yield and yield components (days to flowering, days to maturity, number of primary brancheses per plant, plant height, number of pods per plant, number of seed per pod, pod length, seed yield per plant and 100 seed weight,) among cross-combinations of ten selected parents.

The experiment was conducted at Pulses Research Station, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar during Rabi-2022-23. The experimental material consisting of 31 entries including 10 parents (seven females as lines and three males as testers) and resultant 21 crosses were raised in a Randomised Block Design with three replications. Procedure for hybridization is given in Fig 1. Each entry was grown in single row of 2m length with 15 cm spacing between plants, the rows were spaced 45 cm apart. Parents are grown along with F1 and parents are utilized for calculating combining ability and heterosis analysis. Recommended agronomic practices and plant protection measures were adopted to raise healthy crops. The observations on days to flowering, days to maturity, number of primary branches per plant, plant height, number of pods per plant, number of seed per pod, pod length, seed yield per plant and 100 seed weight were recorded for five randomly selected plants in each entry and in each replication. The data were compiled for analysis of the variance of different traits using the method suggested by Panse and Sukhatme (1967). Combining ability was analyzed suggested by Kempthorne (1957) using TNAUSTAT software. Phenotypic correlation coefficients between all the traits were computed according to Know and Torrie (1964).

The mean square due to genotype was found significant for all traits (Table 1). This indicates that experimental material possessed considerable variability and there were possibilities to improvement of various traits under study through heterosis breeding. In a breeding programme, once the appropriate parents and potential crosses are identified, the next important step is to adopt a suitable breeding strategy for the management of generated variability which largely depends upon type of gene action in the population for the traits under genetic improvement (Cockerham, 1961; Sprauge, 1966). The estimate of gca variance was greater than that of the sca for all characters except NPB, NPP, NSP and SYP. The ratio of gca variance to sca variance was greater than unity for DTF, DTM, PH, PL and HSW which indicates preponderance of additive gene action and found less than unity for NPB, NPP, NSP and SYP which indicate preponderance of non-additive gene action. In view of parallel role of both additive and non-additive genetic effects determining the inheritance of different characters, the population breeding approach in the form of biparental crosses followed by modified recurrent selection may likely result in greater genetic improvement by exploiting both additive and non-additive genetic variances. These results are similar to the results obtained by (Patil Atul et al., 2013; Selvakumar et al., 2014; Dias et al., 2016).



Per se performance of parents and hybrids for different characters are detailed in Table 2. An estimate of GCA effects of the ten genotypes for nine characters showed that SKAU-R-19, RR-21-01, TRCR 3 and RKR 1033 were the best combiners for seed yield per plant (Table 3). Apart from seed yield SKAU-R-19 also reported best for days to earlier flowering, days to maturity, plant height, number of pods per plant, 100 seed weight.

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The genotypes TRCR 3, TRCR 2, SKAU-R-19 and GR 1 were superior in early flowering, as indicated by their highly significant and negative general combining ability (GCA) effects. In addition, for days to maturity, similar effects of GCA were shown by parents viz, TRCR 3, TRCR 2, SKAU-R-19, RR-21-01 and RKR 1033. The minimum number of days to flowering and maturity is preferred to reduce the crop growth period. The kidney bean growers require short-duration hybrids, because such hybrids reduce the incidence of insect pest, disease attacks, adverse environmental effects and reduce the cost of cultivation. For days to flowering and days to maturity line TRCR 3, TRCR 2 and SKAU-R-19 exhibited significant negative gca effect for both these traits. Therefore, these lines could be used in the synthesis of early maturing hybrids.

For number of primary branches per plant TRCR 3, IPR-205-19 and RKR 1033 good general combiners.  Lines TRCR 3, TRCR 2, SKAU-R-19, RR21-01, RR-21-12. and tester RKR 1033 and HUR are good combiners for plant height. As reduced plant height promotes resistance to lodging, there is also a huge interest in the development of semi-dwarf hybrids. Therefore, these lines and testers can be used in breeding programme for development of dwarf type hybrids. Based on their highly significant and positive GCA effects lines IPR-205-19, SKAU-R-19, RR-21-01, RR-21-12 and tester RKR 1033 are found to be the best combiners for number of pods per plant. These identified lines and testers with positive GCA effect could be used in further breeding programme to synthesis hybrids with more number of pods per plant thus inturn contributing to increased seed yield. IPR-205-19 is a good combiner for number of seeds per pod and TRCR 3, TRCR 2 for pod length. If pod length increases, the number of seeds per pod also increased thus contributing to increased seed yield. The seed weight of a genotype serves as an indicator to the expression of end product. Lines TRCR 3, TRCR 2, SKAU-R-19 and tester GR 1 are identified as good general combiner for 100 seed weight. These results are in conformity with previous reports by (Ceyhan et al., 2014; Sen et al., 2019 and Sharma and Shadakshari, 2021).

SCA effects represent non-fixable components of variation, which are dominance, additive × dominance and dominance × dominance. Selecting crosses with positive and desirable SCA effects, indicating that the hybrid has better performance than expected from the average of the parents. Out of the 21 cross combinations, five crosses, namely SKAU-R-19 × RKR 1033, IPR-205-19 × HUR, RR-21-01 × RKR 1033, RR-21-12 × GR 1 and RR-21-01 × HUR, were found to be positive and significant specific combiners for seed yield per plant (Table 4). Askander et al., (2018) and Sharma et al., (2023) also recorded good combiner for seed yield per plants.

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For days to flowering none of the crosses showed significant SCA effects in the desirable direction. Two crosses SKAU-R-19 × RKR 1033 and SKAU-R-19 × GR 1 showed significant negative SCA effects for days to maturity. IPR-277-19 ´ RKR 1033 recorded significant positive SCA effect for number of primary branches per plant. For Plant height, high-negative SCA effects were displayed by the crosses TRCR 3 × GR 1, TRCR2 × HUR, IPR-205-19 × RKR1033, IPR-277-19 × HUR, SKAU-R-19 × GR 1, SKAU-R-19 × HUR, RR-21-01 × GR 1 and RR-21-12 ´ HUR. Six crosses SKAU-R-19 × RKR 1033, IPR-205-19 × GR 1, TRCR 3 × RKR 1033, RR-21-01 × HUR, RR-21-12 × GR 1 and TRCR 2 × GR1 recorded significant positive SCA effect for number of pods per plant. Similar results were observed by Bishnoi et al., (2018), Thangraj et al., (2018) for days to maturity, plant height and number of pod per plant. TRCR 2 × GR1 for number of seeds per pod. A positively significant SCA effects for pod length was recorded by PR-277-19 × GR 1. Where none of the crosses are for 100 seed weight. Best five crosses on basis of SCA effect for seed yield per plant are shown in Fig 2 and Fig 3 and 4 are depicting morphology of parents and their promising F1s.

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The performance of different crosses based on SCA is used to construct the gene action. High SCA effects resulting from crosses involving both parents with good general combiners (e.g., SKAU-R-19 × RKR 1033 and RR-21-01 × RKR 1033 for seed yield per plant) may be attributed to additive × additive gene action whereas high SCA effects derived from crosses including good × poor general combiners (e.g., RR-21-01 × HUR for seed yield per plant) may be due to favorable additive effects of the good general combiner parent and epistatic effects of the poor general combiner. In crosse IPR-205-19 × HUR involving poor × poor general combiners, dominance × dominance interaction might be playing major role in the inheritance of these characters.

The various quantitative characters were studied and their relations with yield as well as among themselves were examined by using correlation analysis. Correlation coefficients between yield and its components are presented in Table 5. Significant desirable correlations were observed for DF, DM, NBP, NPP, PL and HSW with seed yield per plant. The very strong significant positive correlations was recorded between days to flowering with days to matrity (0.65) and number of pod per plant with seed yield and moderataly strong significant positive correlation was recorded between pod length with 100 seed weight. Number of pods per plant, pod length, 100-seed weight showed significant positive correlation with seed yield per plant and among themselves indicating that simultaneous selection for this character would result in improvement of high yielding Rajmash bean genotypes. Similar, findings were reported by Asati and Singh (2008), Karasu and Oza (2010), Pandey et al. (2013), Sharma and Sridevi (2016) and Patel et al. (2021b). Positive correlation between pod length and number of seeds per pod indicates that with longer pods more space is provided for seeds increases yield. However, there are generally negatively significant correlations between seed yield and days to flowering and days to maturity.

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The general assessment of the results from these studies indicates that yield and its contributing traits are under the control of additive and non-additive genes. To utilize both types of gene actions, a breeding program involving some inter-mating in segregating generations to infuse genes in a population, like the diallel selective mating system or multiple crossings or mass selections followed by inter-mating might be helpful in breaking yield barriers in this crop. Five crosses, namely SKAU-R-19 × RKR 1033, IPR-205-19 × HUR, RR-21-01 × RKR 1033, RR-21-12 × GR 1 and RR-21-01 × HUR, were found to be positive and significant specific combiners for seed yield per plant. Hence, these crosses were identified as potential for getting good transgressive segregants for seed yield per plant and its component traits and suggested for further evaluation in future breeding programme.

Authors declare there is no conflict of interest to disclose.