Stability Analysis for Agro-morphological and Physio-biochemical Traits in Mungbean [Vigna radiata (L.) Wilzeck] under Arid Environment

Mungbean/green gram is an ancient pulse crop widely cultivated under different agro-ecological situations in India mainly during Kharif and summer seasons. It is a diploid species having chromosome number (2n=22) belongs to family Leguminosae (Fabaceae), sub-family Papilionaceae and is botanically recognized as Vigna radiata (L.) Wilczek. Mungbean is a native of South Asia (India). Vigna radiata var. sublobata is the probable progenitor of mungbean. It is essentially a self-pollinated crop (Singh et al., 2015).
       
Mungbean is largely cultivated in arid and semi-arid areas. It is drought tolerant and has ability to grow under harsh climate and medium to poor rainfall situations. It is tolerant to moisture stress and heat as well. It has ability to cultivate under low input conditions. It is grown on a variety of soil including black, red lateritic, gravelly and sandy soils. Well-drained fertile sandy loam soil with a pH between 6.2- 7.2 is the best for mungbean cultivation (Sharma, 2016).
       
Mungbean is an important dietary component for vegetarians of the country. It is the potential source of protein (about 24 per cent), essential minerals and vitamin-B (vitamin-C in sprouting grains). It is an economical source of protein and provides nutritional safety to vegetarians. Mungbean is eaten in the form of Dal, sprouts and green pods as a vegetable. It is also used in the preparation of several food products like Papad, Namkeen, Mangori, Dal vada, etc. Mung Ki Dal Ki Khichadi made with mungbean Dal and rice is easily digestible and therefore, always recommended by doctors for sick people. Mung Ki Dal Ka Halwa is a very famous sweet prepared from mungbean in India (Sharma, 2016).
       
Genotype and its interaction with the prevailing environment is the basic factor determining the final yield. The genotype x environment interaction is particularly important in the expression of quantitative characters, which are controlled by polygenes and are greatly modified by environmental influences. Thus, in order to have unbiased estimates of various genetic components, it is imperative that the experiment must be repeated over different environments. The evaluation of genotype x environment interaction gives an idea of the stability or buffering ability of the population under study. Genotype x environment interaction is of common occurrence and often creates manifold difficulties in interpreting results and thus hampers the progress of breeding programme aiming at the further genetic improvement of crop plants. Hence, the knowledge of magnitude and nature of genotype x environment interaction is very useful to a breeder for proper understanding and assessment of his material (Sprague, 1966). The present investigation was therefore, undertaken to identify the stable genotype and appropriate sowing time of mungbean.
 

The experimental material consisting of thirty five genotypes (including 21 germplasm and 14 released varieties) were procured from NBPGR, Regional Station, Jodhpur; Rajasthan Agricultural Research Institute, Durgapura, Jaipur; Agricultural Research Station, Sriganganagar and Agricultural Research Station, Mandor, Jodhpur is given in Table 1. A field experiment was conducted at Swami Keshwanand Rajasthan Agricultural University, Bikaner during summer-2019 and Kharif-2019. The experimental material consisted of 35 genotypes of mungbean was evaluated in randomized block design with three replications accommodating 3 meter long two rows per replication at 30 cm spacing under sprinkler irrigated situation in four different environments created by four different dates of sowing viz., (i) summer season: (A) early sowing (06, March) and (B) late sowing (20, March); (ii) Kharif season: (C) early sowing (06, July) and (D) late sowing (20, July).  Observations were recorded for seventeen characters viz., days to 50 per cent flowering, days to maturity, plant height, number of pods per plant, number of seeds per pod, pod length, 100-seed weight, biological yield per plant, harvest index, chlorophyll-a, chlorophyll-b, total chlorophyll content, membrane stability index, relative water content, proline content, protein content and seed yield per plant to study the stability parameters of mungbean genotypes. The observations were recorded on individual plant basis on five randomly selected plants from each genotype of each replication for all traits except day to 50 per cent flowering and days to maturity. Day to 50 per cent flowering and days to maturity were recorded on whole plot basis. The mean values of different genotypes for all the characters were subjected to analysis of variance separately for individual environment as well as for pooled data to determine the significance of differences among genotypes, environments and genotype x environment interaction described by Panse and Sukhatme (1985). Stability parameters were estimated according to the model of Eberhart and Russell (1966).

The analysis of variance indicated significant difference among genotypes in each environment for all seventeen traits studied (Table 2). Pooled analysis of variance also exhibited significant differences among genotypes and environments for all characters under study (Table 3) which indicate the high degree of variability among genotypes as well as in environments. Significant G x E interactions revealed the varying performance of genotypes in different environments for all characters except pod length. Similar findings were earlier reported by Lal et al., (2013), Win et al., (2018), Wankhede and Najan (2019), Baraki et al., (2020) and Singh et al., (2020) in mungbean.
 



       
The mean squares due to E+ (G x E) were found to be significant for all the traits except days to flowering, days to maturity, 100-seed weight and total chlorophyll content. Environments (linear) were found significant for all characters representing the presence of variability among environments; thereby, indicating the effect of environment on performance of genotypes. Linear component of G x E interaction was found significant for plant height, number of pods per plant, number of seeds per pod, biological yield per plant, chlorophyll-a, proline content and protein content indicated that the performance of genotypes with reference to seed yield and above mentioned component characters is predictable. Pooled deviation (non-linear) was found non-significant for all traits indicated that the performance of genotypes can be predicted on the basis of these traits (Table 4). These results are accordance with the earlier finding of Singh et al., (2009), Kuchanur et al., (2018) and Baraki et al., (2020) in mungbean.
 

       
On the basis of mean performance over environments, highest seed yield was observed in GM 4 followed by RMG 344, RMG 62, IC 39492, SML 832, Keshwanand Mung 1, MUM 2, IC 39269, IC 102821, IC 102857, MH 2-15, Samrat, IC 103059 and IC 39328 (Table 5). Mungbean is a self-pollinated crop therefore; all above mentioned varieties/genotypes could directly be used for cultivation under irrigated normal soil and water situation of arid zone as well as in future breeding programme to develop superior varieties. Similar findings were earlier reported by Kuchanur et al., (2018), Baraki et al., (2020) and Samyuktha et al., (2020) in mungbean.
       


In current study, genotype IC-39269 exhibited stable performance for number of seeds per pod, biological yield and harvest index in all four environments; whereas, IPM 02-3, MH 2-15 and RMG-344 were found stable for seed yield under favourable environment i.e. Kharif season; and genotype IC 103059 for stressed environment i.e. summer season (Table 6). None of the genotype was found stable for wider adaptability for seed yield; whereas, genotype IC-39269 was found stable for number of seeds per pod, biological yield and harvest index. All these traits were also positively correlated and directly contributed towards seed yield. Therefore, genotype IC-39269 may indirectly be considered as stable genotype for wider adaptability for seed yield also. The genotypes exhibited stable performance under favourable environment i.e. Kharif season were Sweta and IC-39492 for days to maturity; RMG-344, IC-39328, GM-4 and MH 2-15 for number of pods per plant; IC-102792, IC-39399, IC-102857, IC-39454 and IC-39409 for biological yield; whereas, variety RMG-344 for days to maturity; SML-668 for number of seed per pod and pod length; IC-39409 for number of seed per pod and 100-seed weight were found stable for stressed environment i.e. summer season. Seed yield potential obtained under different environments indicate that early sowing in Kharif i.e. July 6^th was most appropriate sowing time to achieve the highest seed yield of mungbean. The results confirmed the findings of Raje and Rao (2004), Nath (2012), Win et al., (2018), Wankhede and Najan (2019) and Samyuktha et al., (2020) in mungbean.
 

 

Pulses are an integral part of human diet part to fulfill the nutritional significance of vegetarians. Looking the significance and increasing demand of pulses for human consumption, International Pulse Day is celebrated on 10th February ever year to invite attention of researchers, policy planners, consumers and industry towards pulses. Mungbean is one of the widely adapted and high potential pulse crop largely cultivated in arid and semi-arid areas. Results revealed that Mungbean genotypes used in the investigation are of diverse nature. On the basis of mean performance over environments, genotypes namely; GM 4, RMG 344, RMG 62, IC 39492, SML 832, Keshwanand Mung 1, MUM 2, IC 39269, IC 102821, IC 102857, MH 2-15, Samrat, IC 103059 and IC 39328 performed relatively better and provided higher seed yield. Therefore, the potential of these genotypes may be explored for mungbean improvement programme besides their commercial cultivation. Seed yield potential obtained under different environments indicates that first week of July was most appropriate sowing time to achieve the highest seed yield of mungbean.