Legume Research

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Legume Research, volume 46 issue 4 (april 2023) : 395-402

Interspecific Hybridization Between Vigna radiata and Vigna mungo Towards the Broadening of Genetic Base for MYMV Disease Resistance and Generating Variability

A. Mahalingam1,*, N. Manivannan2
1Regional Research Station, Tamil Nadu Agricultural University, Vriddhachalam-606 001, Tamil Nadu, India.
2Centre of Excellence in Molecular Breeding, Centre for Plant Breeding and Genetics, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.
  • Submitted26-08-2020|

  • Accepted03-03-2021|

  • First Online 10-04-2021|

  • doi 10.18805/LR-4495

Cite article:- Mahalingam A., Manivannan N. (2023). Interspecific Hybridization Between Vigna radiata and Vigna mungo Towards the Broadening of Genetic Base for MYMV Disease Resistance and Generating Variability . Legume Research. 46(4): 395-402. doi: 10.18805/LR-4495.
Background: The main cause for low yield in greengram is its susceptibility to Mungbean Yellow Mosaic Virus (MYMV) which is the most prevalent and destructive viral pathogen cause 85% yield lose. Inter specific hybridization between Vigna radiata and Vigna mungo could be an alternate approach to develop MYMV resistant genotypes in greengram which leads to additional source of creating variability for desirable attributes including yield, nutritional quality, biotic and abiotic stresses.

Methods: The present investigation was carried out at National Pulses Research Centre (NPRC), Tamil Nadu Agricultural University, Vamban during 2016-2017. Interspecific hybridization has been effected between Vigna radiata var. VBN (Gg)2, VBN (Gg) 3 (as females) and Vigna mungo Var. Mash 114 (as male) during Summer 2016. The interspecific F1 hybrids, F2 and F3 populations were evaluated during Kharif 2016, Rabi 2016-17 and summer 2017 respectively. The F2 and F3 populations were evaluated for days to 1st flowering, days to maturity, plant height (cm), number of branches / plant, number of clusters / plant, number of pods / clusters, pod length (cm), number of seeds / pod, number of pods / plant, single plant yield (g.). The MYMV resistance has been confirmed under infector row method using CO 5 as susceptible check variety. Phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV), Heritability (h2) in broad sense, genetic advance as per cent of mean, Skewness and Kurtosis were estimated for yield and yield components.

Result: Four true F1 plants were recovered in Vigna radiata var. VBN (Gg)2 x Vigna mungo Var. Mash 114 cross combination. The fertile F1 had the shallow lobbed leaf of Vigna radiata var. VBN (Gg)2 and black colour seed of Vigna mungo var. Mash 114 with pollen fertility of 42.0 per cent and crossability of 12.50%. Most interestingly all the four interspecific F1 plants were free from MYMV disease. In F2 generation, only one healthy plant was survived which had a pod, stem and branching behaviour of blackgram and greengram characters of lobbed leaf and green seed colour. In F3 generation, number of branches per plant, number of clusters per plant, number of pods per plant, pod length and seed yield per plant had high GCV, high PCV, high heritability coupled with high genetic advance as per cent of mean. Present study suggests that MYMV resistant cultivars of greengram can be explored through interspecific hybridization with Vigna mungo var. Mash 114 as a source of resistance and the hidden transgressive segregants can be recovered in F3 generation.
Greengram [Vigna radiata (L.) Wilczek], also known as mungbean, green bean, mash bean, golden gram and green soy which is an important source of dietary protein across Asia. It is widely cultivated in tropical and sub tropical regions as mono crop as well as in the intercropping systems. Almost 90% of the world’s greengram production comes from Asia, and India is the world’s largest producer. In India greengram is cultivated in an area of 4.32 million ha with an annual production of 2.17 million tones and productivity of 502 kg/ha. In Tamil Nadu, greengram is being cultivated in an area of 1.68 lakh ha with a production of 0.51 lakh tonnes and productivity of 300 kg/ha (Anonymous, 2018). The main cause for low yield is its susceptibility to pests and diseases of which Mungbean Yellow Mosaic Virus (MYMV) is the most prevalent and destructive viral pathogen produces typical yellow mosaic symptoms. The symptoms appear in the form of small irregular yellow specs and spots along the veins, which enlarge until leaves were completely yellowed. Diseased plants were stunted with fewer flowers and pods that bear smaller, occasionally shrivelled seeds in severe cases and other plant parts also become completely yellow. Depending on the severity of the MYMV disease infection, the yield penalty may reach up to 85% (Haq et al., 2010). MYMV disease is being transmitted by white fly Bemisia tabaci and its control is often based on limiting the vector population with insecticides, which are ineffective under severe whitefly infestations (Malathi et al., 2008). The use of resistant varieties is the most desirable strategy to manage the disease in an economical and environmentally friendly way.

Interspecific hybridization is one of the methods of creation of genetic variability and widening of genetic base of a crop species. Continuous breeding efforts for improvement of greengram [Vigna radiata (L.) Wilczek] and blackgram [V. mungo (L.) Hepper] had exhausted the available variability and only limited improvement is possible. Both of these species have some desirable characters like, greengram has early maturity, erect growth habit and long pods with more number of seeds/pod and blackgram possess non shattering pods with synchronous maturity, more clusters/plant, pods with large seeds and comparatively more durable resistance to yellow mosaic virus, which can be transferred in them via wide hybridization (Singh, 1990). Mahalingam et al., (2019) reported that, interspecific hybridization between Vigna radiata and Vigna mungo could be an alternate approach to develop MYMV resistant genotypes in greengram. In view of these considerations the present investigation was under taken with the objective of developing high yielding and MYMV resistant genotypes through interspecific hybridization between Vigna radiata var VBN (Gg) 2, Vigna radiata var VBN (Gg) 3 and Vigna mungo var. Mash 114.
Parental materials
 
The present experiments were carried out at the National Pulses Research Centre (NPRC), Tamil Nadu Agricultural University, Vamban, Pudukkottai during the year 2016-2018. The experimental material comprising of two distinguished cultivated species viz., Vigna radiata var. VBN (Gg)2, VBN (Gg) 3 and Vigna mungo var. Mash 114. Vigna radiata var. VBN (Gg)2 is a high yielding variety with tri lobbed leaves and shiny green colour seeds having susceptibility to Mungbean Yellow Mosaic Virus (MYMV) disease whereas, VBN (Gg)3 is a high yielding variety with ovate leaves and green colour dull seeds but highly susceptible to MYMV disease. Vigna mungo var. Mash 114 a derivative from wild progenitor Vigna mungo spp. silvestris is highly resistant to MYMV disease with determinate plant type and synchronized maturity having a lanceolate leaves and black colour seeds.
 
Screening for yellow mosaic virus symptoms
 
The three vigna species (Vigna radiata var. VBN (Gg)2, VBN (Gg) 3 and Vigna mungo var. Mash 114 were evaluated for their MYMV disease resistance during Rabi 2015-16 season following the infector row method, where in two test rows alternating with one infector row of the susceptible variety (CO 5 blackgram). The plants were maintained properly by providing row to row and plant to plant spacing of 30 cm and 10 cm respectively. No insecticides were sprayed in order to maintain the natural whitefly population in the experimental field. The scoring of test materials was done only when the 80% of infector rows showed MYMV disease incidence. The rating scale suggested by Singh and Singh (1988) was adopted as given below:

   

Based upon the MYMV disease score, the greengram plants were classified into five categories viz., resistant (R), moderately resistant (MR), moderately susceptible (MS), susceptible (S) and highly susceptible (HS).

Hybridization of MYMV susceptible and resistant vigna species
 
Vigna mungo var. Mash 114 has been used as donor parent (male) for MYMV disease resistance while the susceptible Vigna radiata var. VBN (Gg)2 and VBN (Gg) 3 were taken as female parents for hybridization. The crossing block consisted of four rows of female parent and two rows of male parent spaced at 50 ´ 30 cm during Summer 2016. The emasculation and pollination was done on the same day following bud pollination technique. Hybridization was effected during morning 7-9.30 am. The hybridized seeds were collected and dried for F1 evaluation.

Evaluation of F1 hybrid for MYMV resistance

The interspecific F1 hybrids developed were evaluated during Kharif 2016. The F1 seeds were planted at a spacing of 50 × 50 cm on either side of F1s parental lines were raised. F1s were evaluated for days to 1st flowering, days to maturity, plant height (cm), number of branches/plant, number of clusters/plant, number of pods/clusters, pod length (cm), number of seeds/pod, number of pods/plant, single plant yield (g), pollen fertility (%), pod setting percentage and MYMV resistance.

Evaluation of F2 and F3 population for yield parameters and MYMV resistance

F2 and F3 populations developed were evaluated during Rabi 2016-17 and summer 2017 respectively. The F2 and F3 seeds were planted at a normal spacing of 30 × 10 cm. On either side of F2 and F3 populations MYMV susceptible blackgram variety CO 5 was raised as infector row. The F2 and F3 populations were evaluated for days to 1st flowering, days to maturity, plant height (cm), number of branche/plant, number of clusters/plant, number of pods/clusters, pod length (cm), number of seeds/pod, number of pods/plant, single plant yield (g) and MYMV resistance. Phenotypic coefficient of variation (PCV %) and genotypic coefficient of variation (GCV %) were calculated by the method suggested by Burton (1952). Heritability (h2) in broad sense was calculated as suggested by Lush (1940) and expressed in percentage. Genetic advance and genetic advance as per cent of mean was estimated by the method formulated by Johnson et al., (1955).
Screening of Vigna species for MYMV symptoms

The field evaluation of three different Vigna species under infector row method, the vigna radiata var. VBN (Gg) 2 and VBN (Gg) 3 showed moderately susceptible and susceptible reaction with a disease score of 5 and 7 respectively to mungbean yellow mosaic virus (MYMV) disease. Whereas the vigna mungo var. Mash 114 was free (0 score) from MYMV disease. The F1 interspecific hybrid plants were also free from MYMV disease (0 score). Similarly the only survived F2 plant also free from MYMV disease (Table 3). In F3 generation, 23 single plants were found to be free from MYMV disease.
 
Cross compatibility and performance of F1 hybrid
 
Crosses between species of the same or different genera have contributed immensely to crop improvement, gene and genome mapping, understanding of chromosome behaviour and evolution in crops like rice, wheat, maize, sugarcane, cotton, tomato, etc (Sharma, 1995). Stalker (1980) elaborated the gaps between hybridization and utilization, along with approaches for the utilization of wild species in food legumes. However, it is well recognized that gene transfer through wide crosses is a long and tedious process, due to lack of homology between chromosomes of participating species in the crosses, pre and post zygotic crossability barriers between wild and cultivated species. In the present investigation, fifteen and three crossed pods were harvested from 120 and 74 flower buds that were pollinated in VBN (Gg) 2 × Mash 114 and VBN (Gg) 3 × Mash 114 crosses with a crossability percentage of 12.50 and 4.05 respectively. The hybrid germination of 40.0% and hybrid pollen fertility of 42.5% was recorded in VBN (Gg) 2 × Mash 114 cross combination (Table 1). 

Table 1: Pod set, crossability, pollen fertility and germination percentage of parents and F1 hybrids of interspecific cross of Vigna radiata x Vigna mungo.



In Vigna radiata var. VBN (Gg) 2 × Vigna mungo var. Mash 114 cross combination, among the 20 crossed seeds sown during kharif 2016 only eight plants have germinated. Most interestingly, four plants were found to be a true interspecific F1 hybrid plants. Among the four true interspecific F1 hybrid plants three were sterile and one was partially sterile with pollen fertility of 42.5%. Phenotypically the F1 plants are intermediate in expression. The F1 plant had the greengram features of shallow lobbed leaf shape and flowering characters. Determinate plant type, pod length (4.5 cm), seed colour (black), days to 1st flowering (36 days), days to maturity (69 days), number of seeds per pod (3-4) were similar to blackgram features (Table 2).

Table 2: Morphological features of F1 hybrid plant between Vigna radiata var. VBN (Gg)2 x Vigna mungo var. Mash 114.



In VBN (Gg) 3 × Mash 114 cross combination, among the five crossed seeds sown none of them have germinated (Table 1). The observed failure of germination of the hybrid seeds have resulted from the loss of seed viability which could have been caused by series of factors such as poor seed preservation technique, unfavourable germination condition and the presence of lethal alleles in hybrid genotype (Saccardo et al., 1992). Egawa (1988) reported that all the 56 seeds from a V. mungo × V. radiata cross and 5 seeds from a V. umbellata × V. radiata cross failed to germinate. The reasons for failures of interspecific crosses in Vigna are poorly understood (Chen et al., 1983), several factors such as specific cross combination, genetic divergence and environment have influenced the low success rate. Furthermore, pre and post fertilization barriers such as pollen pistil incompatibility (Chowdhury and Chowdhury, 1977), embryo abortion (Ahn and Hartmann, 1977; Fatokun et al., 1997) and hybrid failure and breakdown (Chen et al., 1983) have also been responsible for the low success rates and failure of crosses.

A number of studies undertaken on crossability among different Vigna species have been reviewed by Dana and Karmakar (1990) and Singh (1990). Most reports indicate that V. radiata produced successful hybrids as seed parent with V. mungo, V. umbellata and V. angularis, although their reciprocal cross hybrids were not viable. However, by using sequential embryo rescue methods, the reciprocal hybrids between V. mungo and V. radiata could be successfully produced (Gosal and Bajaj, 1983; Verma and Singh, 1986). V. mungo was also successfully crossed with V. delzelliana (Chavan et al., 1966), V. glabrescens (Dana, 1968) and V. trilobata (Dana, 1966).

Chances of success can be increased through in vitro pollination and fertilization followed by embryo rescue technique (Fatokun and Singh, 1987; Chen et al., 1977). Pollination methods such as cut style and style grafting can also be employed alongside the bud pollination technique (Van Tuyl and De Jeu, 1997).

The results of crossability in the cross VBN (Gg) 2 × Mash 114 is in agreement with the findings of different interspecific crosses of Blakeslee (1945), Burton (1952), Bhatnagar et al., (1974), Ahuja and Singh (1977), Chen (1989), Ganeshram (1993).  The average pollen fertility in F1 hybrid plants were reported by Stebbins (1958) and Rego et al., (2000). 

In the present study, the four F1 hybrid plants between VBN (Gg) 2 × Mash 114 were free from MYMV disease and the single plant of F2 generation was also free from MYMV infestation (Table 3). Results of MYMV reaction of F1 and F2 generation clearly showed that, there is a great scope for the development of MYMV resistant cultivars of greengram through greengram × blackgram interspecific hybridization.

Table 3: Mean performance of parents, F1 and F2 generation.


 
Performance of F2 and F3 population
 
In the F2 population of Vigna radiata var. VBN (Gg) 2 × Vigna mungo var. Mash 114 cross combination only one plant survived. The F2 plant had the greengram feature of long pod (7.3 cm) and blackgram feature of determinate plant type with single plant yield of 9.5 grams (Table 3 and Fig 1). The hidden variability has been observed in F3 generation for all the quantitative traits studied. In the present study, wider range of variability has been recorded for plant height (30 to 89 cm), number of branches per plant (1-7 branches), number of clusters per plant (2-70 clusters), number of pods per cluster (1-4), pod length (5.1 to 8.4 cm), number of seeds per pod (3-10 seeds), pods per plant (2-161 pods) and single plant yield (0.31 to 49.8 grams). Among the 31 F3 single plants, 23 plants were free from MYMV disease infection (Table 4 and Fig 2). 

Table 4: Performance of F3 individuals of interspecific cross between Vigna radiata var. VBN (Gg) 2 x Vigna mungo var. Mash 114.



Fig 1: Generation and evaluation of Vigna radiata var. VBN (Gg) 2 x Vigna mungo var. Mash 114 interspecific cross combination.



Fig 2: Variations in the F3 generation.


 
Variability parameters in F3 generation
 
In the present investigation of F3 interspecific progenies between greengram and blackgram, all the traits studied have recorded more variability among the progenies. The traits viz., number of branches per plant, number of clusters per plant, number of pods per plant, pod length and seed yield per plant were recorded high PCV and GCV among the interspecific progenies of F3 generation (Table 5). The traits viz., plant height and number of pods per clusters were recorded high PCV along with moderate GCV. The traits number of seeds per pod and 100-seed weight were recorded moderate PCV and low GCV. High heritability was recorded by the traits viz., plant height (87.15%), number of branches per plant (91.96%), number of clusters per plant (99.75%), number of pods per plant (99.12%), pod length (99.74%) and seed yield per plant (99.91%). Moderate heritability percentage was recorded by number of pods per cluster (30.61%) and 100-seed weight (45.45%). Low heritability percentage was recorded by the trait number of seeds per pod (25.00%). In case of genetic advance as per cent of mean all the nine traits were recorded higher values among the interspecific derivatives of greengram and blackgram. In case of skewness and kurtosis all the traits studied among the interspecific derivatives were showed mesokurtic nature and no skewness has been shown. High heritability coupled with high genetic advance indicated that most likely the heritability is due to additive genetic effects and the selection may be effective. This also suggested that the variation in the environment played relatively limited role in influencing the inheritance of these characters and thus the response to selection would be higher.

Table 5: Variability parameters among the F3 interspecific derivatives between greengram and blackgram for yield and yield component traits.

The success in the improvement of cultivated variety for yield, quality, resistance to biotic and abiotic resistance largely depends upon the natural variability present in the population. Through hybridization among the selected genotypes, it is possible to reshuffle desired characteristics provided the segregating generations contain large variability. Selection for quantitative characters is generally taken up in the early segregating generations mostly from F2 generation onwards. For characters like grain yield the selection is continued till the material become homozygous. Because, such characters are controlled by large number of genes and huge number of population has to be raised for making the selection effective. This is not always true, because the effective selection was known to restricted by close linkages between desirable and undesirable component characters and these undesirable linkages delay the utilization of full recombination potential (Mike, 1985). Present investigation also revealed that, in F2 generation only one plant was survived with poor yield and the hidden variability was released only in F3 generation. Interspecific hybridization between Vigna radiata and Vigna mungo the variability for yield and yield component traits and MYMV resistance can be expected in F3 generation and the selection pressure can be applied till F8 or F9 generation in order to attain homozygous breeding line.

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