M. PARAMESH*, D.M. REDDY, M. SHANTHI PRIYA, M. REDDI SEKHAR, P. SUDHAKAR, K.H.P. REDDY AND S.J. MALLIKARJUNA
Department of Genetics and Plant Breeding, S.V. Agricultural College, Tirupati.
An experiment was carried out to know the nature and magnitude of association among various yield and drought related traits using thirty one mungbean genotypes. Estimates of correlations revealed that seed yield had positive and significant correlation with number of pods per plant, number of clusters per plant, number of seeds per pod, days to 50% flowering, days to maturity, plant height and SLA. Whereas, seed yield showed non-significant but positive association with SCMR, RI and CSI. From the present study it is evident that improvement in seed yield and drought tolerance in green gram could be brought through selection of component characters like number of pods per plant, number of clusters per plant, number of seeds per pod, days to 50% flowering, days to maturity, plant height, SLA, SCMR, RI and CSI.
Mungbean, Correlation, Seed yield.
Mungbean (Vigna radiata (L.) Wilczek) is an important pulse legume and ranks third after chickpea and pigeon pea in India. It is a cheap and rich source of vegetable protein and therefore, commonly used as a supplement to the normal diet of many people. Mungbean occupies an important position due to its high seed protein content (22 to 24%) and ability to restore the soil fertility through symbiotic nitrogen fixation. It is rich in essential amino acids specially lysine, which is deficient in most of the cereal grains. Despite of its importance, greengram production and productivity levels are low in India as this crop is mainly grown in marginal lands and are affected by various biotic and abiotic stresses. Among the stresses, drought is considered as the most important factor to reduce the productivity level. Since seed yield and drought tolerance are the most complex traits and expression of these traits largely depends upon the interplay of a number of their component traits. Being this intricacy, the direct selection is never effective for genetic enhancement and knowledge of correlation is always helpful in the short listing of desirable component traits. Correlation studies provide reliable information on nature and extent of relationship between different characters and is of great value to plant breeders as it will helps in assessing the scope of simultaneous improvement of two or more characters at a time. Hence, the present investigation is aimed to study the correlation coefficients of a number of yield and drought related components in mungbean, in order to design the selection criteria to improve yield coupled with drought tolerance in mungbean.
Thirty one mungbean genotypes belonging to varied geographical regions were collected and sown in a randomized block design (RBD) with three replications during rabi, 2013-14 at wet land farm of Sri Venkateswara Agricultural College, Tirupati. The inter and intra- row spacing adapted was 30cm x 10cm. Each genotype was sown in three rows of 3m length and observations were recorded on five randomly selected plants in each replication for characters viz., plant height, number of clusters per plant, number of pods per cluster, number of pods per plant, number of seeds per pod, hundred seed weight, harvest index, SPAD Chlorophyll Meter Reading(SCMR), Relative Water Content (RWC), Relative Injury (RI), Chlorophyll Stability Index (CSI), Specific Leaf Area (SLA), chlorophyll content and seed yield per plant. However, the data for days to 50% flowering and days to maturity were recorded on plot basis. Recommended cultural practices and plant protection measures were followed to raise a healthy crop.
Genotypic and phenotypic correlations were calculated as per the procedure described by Johnson et al., (1955).
The results based on analysis of variance revealed that the genotypes differed significantly for all the characters indicating the existence of considerable amount of variation among the genotypes studied. Based on mean performance, the genotypes LGG 450, KM 122, GIVT 203, TM 96-2 and MGG 350 showed superior performance for yield and yield contributing traits (Table 1). For drought tolerance parameters, the genotypes WGG 2, MGG 347, EC 396117, MGG 350 and Asha showed better performance (Table 1). The phenotypic and genotypic correlation coefficients between all pairs of characters were presented in Table 2. Genetic correlation between different characters of plant could arise because of linkage, pleiotropy or developmentally induced functional relationships. For a rational approach towards the improvement of yield and drought tolerance, selection has to be made for their components traits since both of these traits are complex in nature. The genotypic correlations were greater than the corresponding phenotypic correlations in all most all the cases, indicating the preponderance of genetic variance in expression of different characters (Table 2). Seed yield per plant possessed highly significant positive correlation with number of pods per plant, number of clusters per plant and number of seeds per pod. This indicates that selection based on these characters may result in improved yield. Similar kind of results were also reported by Narasimhulu et al., (2013), Srikanth et al., (2013) and Singh and Kumar (2014). Seed yield per plant also showed significant positive correlation with days to 50% flowering, days to maturity, pods per cluster, plant height and SLA. Whereas, seed yield showed non-significant but positive association with SCMR, RI and CSI. On contrary, seed yield per plant exhibited non-significant negative correlation with relative water content and chlorophyll content. Similar results were also reported by Hossain et al., (2010) and Swathi (2013) for RWC.
The inter-se correlations among yield and drought related traits revealed that, days to 50% flowering showed positive association with days to maturity, plant height, clusters per plant, seeds per pod and pods per plant. Similarly, days to maturity with plant height, clusters per plant, seeds per pod, pods per plant, SCMR and chlorophyll content; plant height with clusters per plant,seeds per pod and pods per plant; clusters per plant with seeds per pod and pods per plant; pods per cluster with SLA, RI and CSI; seeds per pod with pods per plant, SCMR and chlorophyll content; pods per plant with SLA; 100 seed weight with RWC and SCMR; harvest index with RI and CSI; SLA with RI and CSI and RI with CSI, showed positive and significant association suggesting the interdependency of these characters on each other.
Days to 50% flowering had positive and significant association with days to maturity at both genotypic and phenotypic levels which is of an important component in identifying and deciding the duration of the crop. Thus, it indicated that flowering time was an important indicator of maturity. Both these traits i.e. days to 50% flowering and days to maturity were also found to have positive and significant correlations with plant height, clusters per plant, seeds per pod and pods per plant and negative associations with number of pods per cluster. These results are in accordance with the earlier findings of Sirohi et al., (2007) and Singh and Kumar (2014).
In case of drought related traits, RWC showed significant positive association with SCMR and negative association with SLA. Similarly, SCMR also showed negative association with SLA. SLA showed significant positive association with RI and CSI and negative association with SCMR and chlorophyll content. Similar results were also observed by Swathi (2013). Hence, for selecting drought tolerant genotypes the traits viz., RWC, SLA, SCMR and CSI may be effective.
In conclusion, from the present study it is evident that improvement in seed yield and drought tolerance in green gram could be brought through selection of component characters like number of pods per plant, number of clusters per plant, number of seeds per pod, days to 50% flowering, days to maturity, plant height, SLA, SCMR, RI and CSI.