Assessment of genetic variability, correlation and path analysis for yield and yield-attributing traits in French bean (Phaseolus vulgaris L.)

Introduction

French bean (Phaseolus vulgaris L.) is a diploid (2n = 22), herbaceous annual legume of the family Leguminosae, commonly known as kidney bean, snap bean or Rajmash in India (Schoonhoven and Voyset, 1991) [17] . It originated from Phaseolus aborigineus, with South Mexico and Central America as primary centres of origin and Peru and Ecuador as secondary centres (Vavilov). The crop grows best at 15-25 °C, while temperatures below 10 °C or above 35 °C cause flower drop and yield reduction (Duke and Kumar, 2022) [6] . In India, French bean is an important vegetable and cash crop grown mainly for tender pods, covering about 2.56 lakh ha with a production of 2.52 million tonnes (NHB, 2021). In Chhattisgarh, it occupies nearly 9.235 thousand ha (Anonymous, 2024) [1] . Major producing regions include Africa, the Americas, Eastern Asia and parts of Europe (Dursun, 2007) [7] . The crop also improves soil fertility through biological nitrogen fixation and contributes to food and nutritional security. French bean is nutritionally rich, containing 1.7 g protein, 4.5 g carbohydrates, 1.8 g dietary fibre and 0.1 g fat per 100 g of edible portion, along with essential vitamins and minerals (Sardana et al., 2000) [16] . Improvement in yield and quality depends on the magnitude of genetic variability present in the germplasm (Verma et al., 2014; Devi et al., 2012) [20,4] . Estimates of genotypic and phenotypic variability, heritability and genetic advance assist in assessing selection efficiency, while correlation and path coefficient analyses help identify important yield-contributing traits for effective breeding programmes (Shukla et al., 2006; Raffi and Nath, 2004; Buys et al., 2002) [18,14,2] . Therefore, the present study was undertaken to evaluate diverse French bean genotypes for morphological, growth, yield and quality traits, to assess genetic variability and trait associations, and to identify superior genotypes and key yield-determining characters for varietal improvement under Chhattisgarh conditions.

Materials and Methods

Location and traits: The present study was conducted at the Horticulture Research cum Instructional Farm, Department of Vegetable Science, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.) during the Rabi season of 2024-25.

The experimental field had clay-loam soil with a pH of 7.09. The experiment was laid out in a Randomized Block Design (RBD) with three replications, using a plot size of 3m × 3 m and a spacing of 50 cm × 40 cm. A total of 26 genotypes of French beans, maintained by the Department of Horticulture, IGKV, Raipur, were used as planting material. Healthy seedlings of all genotypes were transplanted and uniformly managed following standard cultural practices. Data were recorded for 20 characters, including growth traits (germination percentage, plant height (45 DAS and 65 DAS), number of primary branches (45 DAS and 65 DAS), number of secondary branches (45 DAS and 65 DAS), number of leaves per plant (45 DAS and 65 DAS), days of first flower initiation, days of 50% flower initiation, days of first pod harvest, days of last pod harvest, number of pod per plant, pod length (cm), pod width (cm), pod weight (g), pod yield per plant (g), pod yield per plot (kg) and total yield (q/ha). The observations provided comprehensive information on morphological, yield, and quality traits of the 26 genotypes under Chhattisgarh conditions.

Statistical analysis:

Statistical analysis was carried out on the mean values of five competitive plants randomly selected from each genotype in every replication, following the procedure outlined by Panse and Sukhatme (1967) [13] . The genotypic and phenotypic coefficients of variation were estimated using the method described by Lush (1940) [10] , while broad-sense heritability was calculated as per Hanson et al. (1956) [8] . Expected genetic advance (GA) was determined following the approach suggested by Johnson et al. (1955) [9] . The genotypic and phenotypic correlation coefficients among different traits were computed according to Miller et al. (1958) [11] . Further, the genotypic correlation coefficients were partitioned into direct and indirect effects through path coefficient analysis, as originally proposed by Wright (1921) [22] and subsequently elaborated by Dewey and Lu (1959) [5] .

Results and Discussion

The results of analysis of variance (ANOVA) for all the characters studied are presented in Table No.1.Highly significant differences (at 1% level of significance) were observed among the twenty-six French bean genotypes for all growth, phenological, and yield-related traits, including germination percentage, plant height, number of primary and secondary branches, number of leaves, flowering and harvesting traits, pod characteristics, and yield parameters. The presence of significant variation for these traits indicates a wide range of genetic variability among the genotypes, providing sample scope for selection and improvement in French bean. The phenotypic coefficient of variation (PCV) was higher than the genotypic coefficient of variation (GCV) for all twenty characters studied ( [3] , Singh and Singh (2013) [19] , Verma et al. (2014) [20] and Ramandeep et al. (2017) [15] . Germination percentage showed significant positive association with pod weight (0.587, 0.581), pod width (0.501, 0.496), number of pods per plant (0.410, 0.318), pod yield per plant (0.465, 0.447), pod yield per plot (0.532, 0.533) and total marketable yield per hectare (0.449, 0.452), while its association with plant height was non-significant. Plant height at 65 DAS exhibited strong positive correlation with number of leaves per plant (0.977, 0.977), number of secondary branches (0.808, 0.806), number of pods per plant (0.649, 0.611), pod length (0.672, 0.656), pod yield per plant (0.598, 0.570) and total marketable yield per hectare (0.641, 0.643). Similarly, number of primary and secondary branches showed highly significant positive association with pod yield per plot (0.782, 0.782; 0.798, 0.799), pod yield per plant (0.749, 0.739; 0.807, 0.816), number of pods per plant (0.645, 0.606; 0.801, 0.808) and total marketable yield per hectare (0.743, 0.744; 0.828, 0.830). Among yield components, number of pods per plant recorded the highest positive association with total marketable yield per hectare (0.911), followed by pod yield per plant (0.949, 0.950), pod yield per plot (0.932, 0.933), pod weight (0.873, 0.875), pod width (0.863, 0.864) and pod length (0.836), indicating their importance as reliable selection criteria for yield improvement in French bean. PW PWT PYP PYPL TY GP -0.0148 0.0002 -0.0069 -0.0044 -0.0011 -0.0054 -0.0028 -0.0051 -0.0049 -0.0061 -0.0045 -0.0074 -0.0087 -0.0069 -0.0079 0.4487** PH -0.0002 0.0193 0.0084 0.0156 0.0188 0.0072 0.0117 0.0104 0.0036 0.0125 0.0130 0.0118 0.0087 0.0115 0.0098 0.6415** PB 0.0150 0.0139 0.0320 0.0231 0.0167 0.0173 0.0148 0.0123 0.0054 0.0206 0.0195 0.0235 0.0225 0.0240 0.0250 0.7429** SB -0.0126 -0.0343 -0.0306 -0.0424 -0.0365 -0.0195 -0.0226 -0.0239 -0.0123 -0.0340 -0.0311 -0.0326 -0.0301 -0.0342 -0.0338 0.8276** NOL 0.0066 0.0852 0.0455 0.0750 0.0872 0.0352 0.0536 0.0480 0.0179 0.0614 0.0612 0.0591 0.0460 0.0577 0.0507 0.7024** NFI -0.0018 -0.0019 -0.0027 -0.0023 -0.0020 -0.0050 -0.0026 -0.0020 -0.0012 -0.0023 -0.0022 -0.0026 -0.0025 -0.0026 -0.0027 0.5132** NOFFI -0.0058 -0.0186 -0.0141 -0.0163 -0.0188 -0.0161 -0.0306 -0.0187 -0.0054 -0.0174 -0.0169 -0.0165 -0.0167 -0.0182 -0.0165 0.5915** NFPH 0.0063 0.0098 0.0070 0.0104 0.0101 0.0075 0.0112 0.0183 0.0045 0.0110 0.0097 0.0102 0.0096 0.0109 0.0099 0.5935** NLPH -0.0024 -0.0013 -0.0012 -0.0021 -0.0015 -0.0017 -0.0013 -0.0018 -0.0071 -0.0024 -0.0018 -0.0024 -0.0022 -0.0024 -0.0023 0.3134** NPP 0.0583 0.0922 0.0917 0.1138 0.1000 0.0662 0.0807 0.0852 0.0486 0.1421 0.1105 0.1149 0.1172 0.1276 0.1227 0.9109** PL 0.0519 0.1141 0.1034 0.1243 0.1191 0.0734 0.0938 0.0894 0.0430 0.1319 0.1697 0.1348 0.1116 0.1331 0.1296 0.8362** PW -0.0152 -0.0186 -0.0223 -0.0233 -0.0205 -0.0158 -0.0163 -0.0169 -0.0101 -0.0245 -0.0241 -0.0303 -0.0257 -0.0258 -0.0254 0.8625** PWT 0.0848 0.0651 0.1017 0.1025 0.0762 0.0717 0.0791 0.0758 0.0453 0. Path coefficient analysis, as proposed by Wright (1921) [22] , was used to partition correlation coefficients into direct and indirect effects in order to assess the true contribution of individual traits to total marketable yield, with greater emphasis on genotypic path coefficients as phenotypic associations are influenced by environmental factors (Table No. 5). At the genotypic level, pod yield per plant showed the highest direct positive effect on total marketable yield per hectare (0.325), followed by pod yield per plot (0.2397) and pod length (0.1697), while pod weight (0.1446), number of pods per plant (0.1421), number of leaves per plant at 65 DAS (0.0872), number of primary branches at 65 DAS (0.032), plant height (0.0193), days to first pod harvest (0.0183) and days to first flower initiation (0.0183) also exhibited positive direct effects. In contrast, germination percentage (-0.0148), number of secondary branches at 65 DAS (-0.0424), days to first flower initiation (-0.005), days to 50% flowering (-0.0306), days to last pod harvest (-0.0071) and pod weight (-0.0303) exerted negative direct effects. Pod yield per plant further showed strong positive indirect effects via pod yield per plot (0.3031), number of pods per plant (0.2918) and pod weight (0.2832), while pod length contributed indirectly through pod width (0.1348), pod yield per plant (0.1331) and number of pods per plant (0.1319); however, delayed flowering traits such as days to 50% flowering had negative indirect effects through pod yield per plant (-0.0182) and plant height (-0.0186). Overall, the results highlight pod yield per plant, pod length and pod weight as major determinants and reliable selection criteria for yield improvement in French bean.

Summary

The present investigation revealed substantial genetic variability among the French bean (Phaseolus vulgaris L.) genotypes for yield and yield-attributing traits. High estimates of GCV, PCV, heritability and genetic advance were recorded for characters such as number of pods per plant, pod yield per plant, pod yield per plot, average pod weight and total green pod yield, indicating predominance of additive gene action and effectiveness of direct selection. Correlation and path coefficient analyses revealed that pod yield per plant, number of pods per plant, pod weight, pod length and plant height exerted positive and direct effects on total yield, whereas delayed flowering traits showed negative effects. Overall, pod yield per plant, pod weight and number of pods per plant emerged as reliable selection criteria for yield improvement. On the basis of overall performance, genotypes, 2024/FBB VAR-4, 2023/FBB VAR-1, 2022/FBB VAR-6 (bush type) and 2024/FBP VAR-3 (pole type) were identified as superior and can be effectively utilized as promising varieties in future French bean breeding programmes for yield enhancement.

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