Evaluation for the Resistance of Green Gram (Vigna radiata L.) Germplasm against Macrophomina phaseolina

Green gram is one of the most important legumes; it is cultivated in almost all parts of the country, the green gram is susceptible to approximately 26 diseases worldwide, (Charles. 1978). Among them, dry root rot caused by Macrophomina phaseolina is of most importance in reducing crop yields, especially in the arid zone of the world (Hoes., 1985). Dry root rot poses a serious threat to green gram growing areas around the world, as well as in Pakistan, which can lead to crop loss of up to 100% in epidemic situations (Iqbal et al., 2010). Macrophomina phaseolina a soil-borne pathogen causes severe disease in various crops in India, reducing crop yields, (Pandey et al., 2018). Macrophomina phaseolina is highly destructive that infects plants through the soil. The pathogenic fungus Macrophomina phaseolina causes dry root rot/charcoal rot in many plant species. Dry Root Rot/ Macrophomina blight has been a major restraint on the high production of green gram in recent years. The management of DRR is challenging as the pathogen is soil and seed-borne pathogen. Therefore, the use of chemicals is undesirable and even impractical as a long-term solution to crop health. Using host plant resistance can be a good alternative to disease management. Traditional methods of dealing with these diseases are difficult due to the predominantly subterranean habit and the strong competitiveness of the pathogen. Hence, the resistance of the host plant is one of the excellent ways to overcome dry rot root of green gram, it is a cost-effective and eco-friendly way of disease management.

Location of experiments
 
The experiment was conducted during the 2017 Kharif season at the experimental field, College of Agriculture, Swami Keshwanand Rajasthan Agricultural University, Bikaner.
 
Observations recorded
 
The crop was properly observed to record the first appearance of the disease after germination and the observation was taken at the time of maturity of a crop by randomly selecting 20 plants from each germplasm according to the method described (Anonymous, 2004). The incidence of the disease was recorded at maturity and the PDI was calculated as follows:

Layout and sowing

In this experiment, 25 germplasm of green gram, namely Samrat, Ganga-1, Ganga-8, V-7240, PM-106, RMG-10, V-3890, RMG-4, RMG-40, RMG-5, RMG -8, RMG-26, PM-116, PM-111, PM-105, OUM-112, OUM-7, OUM-115, BPMR-1, HUM-9, V-3219, V-1082, MH-2-15, IPM-02-03 and Pusa Vishal were collected from ARS, Sri Ganganagar and germplasm were screened in Macrophomina phaseolina sick plot during Kharif-2017, Macrophomina phaseolina sand maize meal inoculum was applied to the field in sufficient amounts to maintain the sick plot before planting green gram germplasm, each germplasm was planted in three rows of 5 m in length, maintaining a distance between plants of 10 cm, the incidence was recorded on a scale from 0 to 9 (Nene et al., 1981). The package of practices recommended for increasing yields was followed.

Screening of germplasm of green gram against M. phaseolina
 
Twenty-five green gram germplasm against Macrophomina phaseolina was selected under artificial inoculation in the field, the incidence of DRR was recorded using a rating scale from 0 to 9 (Nene et al., 1981). Based on disease reaction, green gram germplasm was grouped into different categories, namely, highly resistant (HR), Resistant (R), Moderately resistant (MR), Moderately Susceptible (MS), Susceptible (S) and highly susceptible. (HS) (Table 1). None of the germplasm was recorded as highly resistant, i.e. four germplasms, IPM-02-03, G-2, MH-2-15 and MUM-2 were classified as resistant. Fifteen other germplasm, namely RMG-4, RMG-5, RMG-8, RMG-10, PM-105, PM-106, PM-111, PM-116, V-1082, V-3219, V-3940, V-7240, G-8, Pusa Vishal and Samrat were moderately resistant, five germplasm were moderately susceptible, i.e. BPMR-1, RMG-14, OUM-7, OUM -112, OUM-115 and the remaining germplasm RMG-26 was susceptible (Table 2).




 
Twenty-five green gram germplasm was tested against M. phaseolina under artificial inoculation in the field. The reaction to the disease was recorded according to a standard rating scale. None of the germplasm was highly resistant (HR), while four germplasm, namely MUM-2, MH-2-15, G-2 and IPM-02-03 were classified as resistant (R). Another fifteen germplasm were classified as moderately resistant. (MR), five germplasm were moderately susceptible and one remaining germplasm of RMG-26 was susceptible (S) (Table 3).


 
Choudhary et al., (2011), tested twenty-five of green gram germplasm to determine the source of Macrophomina phaseolina resistance to DRR in the field. The three germplasm MSJ-118, KM 4-44 and KM 4-59 were resistant to dry root rot. Similarly, Haseeb et.al., (2013) tested twenty-seven green gram germplasm against M. phaseolina in the field under artificial inoculation, No one is immune from dry root rot, germplasm such as Azari 2006, NM 2006 and AUM 9 was found to be resistant.

Resistant germplasm can be used in a crop improvement program after further testing with a large number of virulent M. phaseolina strains. The IPM99-125 germplasm has higher plant survival can be beneficial in green gram breeding programs to create germplasm that is resistant to DRR, (Pandey et al., 2020).
 
Among 26 genotypes, 2 (MNUYT-317 and NM-2011) were highly resistant, 10 were moderately resistant (Mung-12004, MNUYT-317, Mung-12007, MNUYT-201, MNUYT-219, AZRI-2006, Mung - 12002, MNUYT -318, MNUYT-207 and MNUYT-107, (Akhtar and Shoaib, 2018). Thombre and Kohire (2018) found that BPMR-145 was resistant and two more germplasm JL-781 and Kopargaon were susceptible.
 
Most workers collected germplasm against Macrophomina phaseolina and at the time of selection found resistant or moderately resistant germplasm. We also found germplasm to be resistant and moderately resistant to Macrophomina phaseolina and these can be used for crop improvement programs after further testing and these results are confirmed by the previous findings.
 
 

Out of 25 genotypes screened, four genotypes viz., MUM-2, MH-2-15, G-2 and fifteen genotypes were moderately resistant against M. phaseolina. The resistant genotypes recognized in the present investigation could be utilized as potential donors for future resistance breeding programme for dry root rot in green gram.

Authors are grateful to the Agricultural Research Station, Sri Ganganagar for providing seed of germplasm and Department of Plant Pathology, Swami Keshwanand Rajasthan agricultural university, Bikaner for providing an experimental field for the studies.