Correlation and Path Analysis Studies of Pod Yield and its Component Traits in Mungbean [Vigna radiata (L.) Wilczek] Genotypes

Pulses compliment the daily human diet of Indians along with cereals. They are rich source of proteins with satisfactory proportion of carbohydrates. Among pulses, mungbean [Vigna radiata (L.) Wilczek] also known as green gram is an ancient pulse crop widely cultivated in India. It is a diploid species with chromosome number 2n=2x=22 belongs to the family Leguminosae (Fabaceae), sub-family Papilionaceae and botanically recognized as Vigna radiata (L.) Wilczek and it is essentially a self-pollinated crop. Mungbean is native of South Asia (India). Vigna radiata var. sublobata is the probable progenitor of mungbean. High protein, easy digestibility and low flatulence production made the crop more acceptable by the people world over. Because of short duration, wide adaptation, low water requirement and photo insensitiveness, it can be grown in various crop rotation practices. It is primarily grown in India, Pakistan, Bangladesh, Sri Lanka, Nepal and other Southeast Asian countries (Singh et al., 2015).
       
Mungbean is short day, warm season crop mainly grown in arid and semi-arid regions. It is a drought resistant crop with ability to grow under harsh climate and medium to low rainfall conditions and requires fewer quantities of inputs to grow well and mature. It grows on a variety of soils including black, red lateritic, gravelly and sandy soils with well drained fertile sandy loam soil of pH between 6.2 to 7.2 is the best for mungbean cultivation. Water logged and saline soils are not suitable for mungbean cultivation (Sharma, 2016). Estimates of genetic parameters provide an indication of the relative importance of the various types of gene effects affecting the total variation of a plant character. Therefore, the present study was conducted to assess genetic variability, heritability and genetic advance in mungbean genotype during kharif season under rainfed in Rajasthan. So that promising genotypes could be identified for breeding programme to develop high yielding varieties of mungbean.
               
Studies of correlation allow breeders to understand the strength of the relationship between different characters as well as the direction of changes expected during selection. Correlation and path analysis will determine the magnitude of association between yield and its components and also bring out relative importance of their direct and indirect effects, thus providing an obvious understanding of their association with seed yield. Path analysis is standardized partial regression coefficient which splits the correlation coefficient into the measure of direct and indirect effect and measure the direct and indirect contribution of each independent variable on the depend variable (Wright, 1921).

The investigation was conducted during Kharif, 2019 under rainfed conditions at experimental field of Agricultural Research Station, Agriculture University, Mandor, Jodhpur, Rajasthan. The material comprised of 38 genotypes/varieties of mungbean which were sown by adopting randomized block design (RBD) with three replications is presented in Table 1. Each genotype was sown in 4 m length of five rows with the spacing of 30 cm between rows and 10 cm from plant to plant. The recommended agronomic practices were followed to raise a good crop. Observations were recorded on days to 50% flowering, days to maturity, plant height (cm), number of pods per plant, pod length (cm), number of branches per plant, number of seeds per pod, 100 seed weight (g), seed yield per plant (g), harvest index (%) and protein content (%). The estimates of correlation and path coefficient analysis were calculated by using data.
 

Analysis of variance revealed highly significant difference among for all eleven characters Table 2. The phenotypic and genotypic correlations between seed yield and its contributing traits for 38 genotypes/varieties were estimated and are presented in Table 3. In general, for most of the characters under study, the genotypic correlation coefficients were higher in magnitude than phenotypic correlation coefficients. High genotypic correlations as compared to their phenotypic counterparts indicated strong inherent association between the characters studied and its expression is lessened due to influence of environment. Among the eleven characters studied under this experiment, only five traits viz., plant height, number of pods per plant, number of branches per plant, number of seeds per pod and 100 seed weight exhibited significant positive association at both genotypic and phenotypic levels with seed yield per plant. The correlations of seed yield per plant (g) was positive and significant at both level with characters viz., plant height, number of pods per plant and number of branches per plant (Patel et al., 2014; Kapadia et al., 2015; Muthuswamy et al., 2019 and Ahmad and  Belwal, 2020), number of seeds per pods (Singh et al., 2009; Pulagmpalli and Lavanya, 2017; Kumar et al., 2018; Muthuswamy et al., 2019), 100 seed weight (Raturi et al., 2015;  Kumar et al., 2018 and Ahmad and  Belwal, 2020). The correlations of seed yield per plant (g) with days to 50% flowering and pod length were highly positive and significant at genotypic level.
 

 

       
The seed yield per plant was dependent character and output of direct and indirect effects of independent characters (variables) like days to 50% flowering, days to maturity, plant height (cm), number of pods per plant, pod length (cm), number of branches per plant, number of seeds per pod, 100 seed weight (g), harvest index (%) and protein content (%). The direct and indirect contribution of each character towards seed yield per plant is presented in Table 4, Fig 1. Results of path coefficient analysis of different characters contributing towards seed yield per plant showed that number of pods per plant (0.7520) had highest positive direct effect on seed yield per plant followed by number of seeds per pod (0.4033), pod length (0.2178), 100 seed weight (0.2130), plant height (0.1599) and days to maturity (0.1474) at genotypic level. These finding were supported the observations made earlier by (Rao et al., (2006); Ahmad and Belwal, 2020). Whereas, days to 50% flowering (-0.4150) had the highest negative direct effect on seed yield per plant followed by protein content (Kumar, 2011), harvest index (Gadakh et al., 2013) and number of branches per plant (Aqsa et al., 2010; Muthuswamy et al., 2019) at genotypic level.
 

 

               
At phenotypic level, highest direct positive effect on seed yield per plant was observed for number of pods per plant had the highest positive direct effect on seed yield per plant followed by 100 seed weight, number of seeds per pod, plant height. Direct negative effect on seed yield per plant was also observed for days to maturity had the highest negative direct effect on seed yield per plant followed by protein content, harvest index, days to 50% flowering, pod length and number of branches per plant.

Correlation relieved that seed yield per plant was positive significant correlation with plant height, number of pods per plant, number of branches per plant per plant, number of seeds per pod and 100 seed weight at both levels. The traits days to 50% flowering and pod length showed positive significant correlation with seed yield per plant at genotypic level only. Protein content exhibited negative significant correlation with seed yield per plant at genotypic level only. The selection for plant height, number of pods per plant, number of branches per plant per plant, number of seeds per pod and 100 seed weight may bring simultaneous improvement in seed yield. Path coefficient analysis revealed that the highest positive direct effect on seed yield exerted by number of pods per plant, followed by number of seeds per pod, 100 seed weight and plant height, therefore may be used for further improving yield attributes breeding programme of mungbean.

The authors are thankful to the Sitaram Kumhar, Sesame Breeder, Agricultural Research Station (Agriculture University, Jodhpur) and Department of Genetics and Plant Breeding, Agriculture University, Mandore, Jodhpur for providing the valuable genotypes to carry out this study.

None.