Genetic and Phenotypic Insights into Seed Characteristics for Enhancing Yield Potential in Mungbean [Vigna radiata (L.) Wilczek]

Pulses are an important source of staple protein for vegetarians which constitute a major population of the country. Mungbean is also known as green gram, an ancient pulse crop widely cultivated under different agro-ecological situations in India mainly during Kharif and summer seasons (Kumar et al., 2024). 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 (Anita et al., 2022). Mungbean is a native of South Asia (India). Vigna radiata var. sublobata is the possible progenitor of mungbean. It is basically a self-pollinated crop (Singh et al., 2015).
       
After chickpea and pigeon pea in terms of production and area, mungbean is the third most significant pulse crop in India. India is a major producer of mungbean and at the same time India identified as the largest consumer of mungbean in the world (Sneha et al., 2020). In India, the total area covered under mungbean is 4.607 million hectares with a production of 2.448 m tons and a productivity of 513 kg/ha in the country during 2017-18 to 2021-2022 (Directorate of Pulses Development, 2022). Currently, the realized average productivity of mungbean is well below the economic level (Rahmianna et al., 2021).      
       
Pulses play an important role in supplying the needs of food in human society, especially in developing countries. Determination of physical and mechanical properties of seeds and agricultural products is important in designing of harvesting, handling and processing equipment, transport, yield and store of the crop. Physical parameters of seed affect vegetative growth and are frequently related to yield, market grade and harvest efficiency. Some physical properties of seeds viz., 100-seed weight, seed volume and seed size are the important characteristics for designing equipment for the transportation of agricultural produce (Peleg, 1985). Genetic variation is the cause for variation in the size of seed between varieties. Many researchers investigated the variation on seed size for seed germination following seedling emergence and related agronomic aspects in mungbean. Generally, the larger seed has better field performance than the small seed. The 100-seed weight is one of the important characters and represents the size, quality and density of seeds which are also affected by environment and genetic factors (ICARDA, 2005). Therefore, it is essential to achieve basic scientific information about these seed characteristics.
       
High yield is the basic objective of all crop breeding programmes. In any program aimed at genetic improvement of yield, existence of variability is the basic requirement (Azam et al., 2018). The available genetic variability for the traits of interest, especially yield and its attributes are to be exploited by mungbean breeders in order to broaden and strengthen genetic potential. Yield is a complex character and depends upon the action and interaction of a number of factors. The relative contributions of these different characters to seed yield can be estimated by correlation analysis. However, correlation studies do not provide an exact picture of the relative importance of direct and indirect influence of each of them. The path coefficient analysis further allows the partitioning of correlation coefficients of yield-related characters into their direct and indirect effects (Gogoi et al., 2024).
       
Keeping all these points in view, the present study was planned to assess genetic variability, heritability, genetic advance, correlation and path coefficient for seed yield and its contributing seed traits in mungbean in order to identify the most promising traits of interest and genotypes to be considered in future mungbean crop improvement programmes.

The experimental material consisting of thirty-five genotypes 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. Field experiments were conducted at College of Agriculture, Bikaner, Swami Keshwanand Rajasthan Agricultural University, Bikaner, Rajasthan 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 (6^th March 2019) and (B) late sowing (20^th  March 2019); (ii) Kharif season: (C) early sowing (6^th  July 2019) and (D) late sowing (20^th July 2019). All the recommended package of practices was adopted to raise a good crop. The observation for seed yield was recorded on individual plant basis on five randomly selected plants from each genotype of each replication.


       
The laboratory experiment was conducted from the harvested seeds with same 35 genotypes of mungbean for three replications of each mungbean genotype under completely randomized design (CRD) studied at room temperature at Department of Biotechnology, Swami Keshwanand Rajasthan Agricultural University, Bikaner, Rajasthan during Kharif-2020. The data on seven seed parameters viz., 100- seed weight, seed volume, true density, bulk density, porosity, water absorption capacity and water absorption index studied at room temperature were estimated and recorded. The procedure adopted to record the observations for each character is given below:
 
100-seed weight (g)
 
Well dried 100-seeds were counted from bulk seeds of each genotype and weighed on electrical balance.
 
Seed volume (µl/seed)
 
Seed volume was measured by ‘Liquid displacement technique’ (Shepherd and Bhardwaj, 1986). Water was used to determine seed volume. For each mungbean genotype 100-seeds were weighed and put into a 100 ml measuring cylinder containing 15 ml (initial reading) of water that could completely cover all the seeds. Seed volume was calculated according to Mohsenin (1986) by using the formula:
 

  

 
True density (g/cm³)
 
True density was determined using the ‘Toluene displacement method’ (Mohsenin, 1986; Singh and Goswami, 1996). Toluene (200 ml) was filled in a 500 ml graduated measuring cylinder and 100g seeds were immersed in it. The amount of toluene displaced was recorded. The true density was estimated as the ratio of sample mass to the volume of displaced toluene.
 
Bulk density (g/cm³)
 
Bulk density was determined following the method reported by Singh and Goswami (1996) and Gupta and Das (1997) by filling a 500 ml cylinder with seeds from a height of 15 cm at a constant rate. Excess seeds were levelled off with a metal rod and then the contents were weighed. Bulk densities were calculated as the ratio of the mass of the sample to the volume of the container and expressed in gcm^-3. Tests were carried out without tapping the cylinder and compacting the seeds.      
 

        

The analysis of variance revealed significant differences among genotypes for all seven seed traits which indicate the presence of good amount of variability in the genotypes and scope of selection for genetic improvement of mungbean (Table 2). The results confirmed the findings of Adlan (2019) in mungbean, Get et al., (2019) in lentil, Pal et al., (2020) and Meena et al., (2021) in mothbean.


       
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 3). 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 Baraki et al., (2020), Samyuktha et al., (2020) and Kumar et al., (2024).


       
High GCV and PCV were found for water absorption capacity, water absorption index, porosity and seed yield per plant. Include the lowest and highest values for all traits. Therefore, high degree of heritable genetic variability in these seed traits reveals the good scope of selection for these traits (Table 4). Similar findings were earlier reported by Adlan (2019) in mungbean and Get et al., (2019) in lentil. High heritability coupled with high/moderate genetic advance as per cent of mean was observed for water absorption capacity, water absorption index, porosity, seed volume, 100-seed weight, true density and seed yield per plant. These traits are governed by additive gene action and therefore, may be improved through direct selection. These results are accordance with the earlier finding of Adlan (2019) in mungbean, Get et al., (2019) in lentil, Pal et al., (2020) and Meena et al., (2021) in mothbean.      

 
       
The traits namely; 100-seed weight, true density, porosity, water absorption capacity and water absorption index had significantly positive correlation with seed yield per plant (Table 5). Positive direct effect on seed yield per plant was observed for water absorption index and 100-seed weight at both phenotypic and genotypic levels; whereas, true density at phenotypic level and porosity and bulk density at genotypic level (Table 6). The residual effect was found high for seed traits at both phenotypic and genotypic levels which indicate that seed traits were also contributed to seed yield but major contribution came from other traits like agro-morphological and physio-biochemical traits (Fig 1). These findings are in accordance as reported by Adlan (2019) in mungbean, Pal et al., (2020) and Meena et al., (2021) in mothbean.

Highly significant differences were found among all genotypes for all seed traits studied. The high degree of genetic variability along with high heritability and high genetic advance as per cent of mean were observed for water absorption capacity, water absorption index and porosity which reveals that these characters were under the control of additive gene action and therefore, form the basis of selection for mungbean improvement programme. Among seed traits, water absorption index and 100-seed weight had positive correlation with seed yield and directly contributed towards seed yield which can help in the improvement of seed yield in mungbean.

The present study was supported by Prof. (Dr.) N.K. Sharma, SKRAU, Bikaner; for the best guidance and support. I am also extremely grateful to Dr. Om Veer Singh, Principal Scientist and Officer-In-Charge, NBPGR, RS, Jodhpur; Prof. (Dr.) B.R. Chaudhary, Hon’ble Vice-Chancellor, Agriculture University, Jodhpur; Prof. (Dr.) O.P. Khedar, O/I, MULLaRP, RARI, Durgapura, Jaipur and Prof. (Dr.) Vijay Prakash, ARS, Sriganganagar for providing valuable research material for my Ph.D. research experimentation.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

The authors declare that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript.