Screening Of Mung Bean Germplasm Biology Essay

Published: Last Edited:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

Mungbean {VIgna radiata (L.) Wilczeck} also known as green gram belongs to family fabaceae is a widely consumed pulse crop of South Asia. Mung bean is grown in kharif season in Pakistan. It acquires an ability of adopting diverse cropping pattern due to development of short duration and uniform maturing varieties (Haqqani et al., 2004).In Pakistan, during 2006-2007 the are under mung bean cultivation was 217.8 thousand hectares produced 138.5 thousand tones with average yield of 636 kg/hectare (Anonymous, 2008).

Mungbean constitute important nutrients including protein, carbohydrates, minerals, vitamin B, fibers and lipids. Seed is used as a whole, husked and dehusked form in different ways, as dhal, in curries, soup preparation, noodles, bread and different kinds of sweets. Easy digestibility and absence of flatulence causing factors increased its importance. Moreover, it is also used in medicines for curing different ailments (Engel, 1977; Singh et al., 1988; Thirumaran and Seralathan, 1988; Bashir, 1994). Despite great nutritional value, mungbean is subjected to prone different biotic stresses in which diseases are the most important. Among them, Charcoal rot by Macrophomina phaseolina ( Tassi.) Goid is a serious and threatening one (Bashir and Malik, 1988). The pathogen is soil-borne and survives in microsclerotial form in soil (Dhingra and Sinclair, 1977). Its growth and survival can be triggered by low moisture contents, high temperature, heat and different physiological stresses (Papavizas, 1977; Dhingra and Sinclair, 1978). Severity of charcoal rot disease results in appearance of severe symptoms, usual tan colored stem turns grey from ground level to upwards with presence of black sclerotia on infected portion. It also causes wet rot of sprouts during germination process. Wilting and premature death is commonly seen in infected plants (Seraffin, 2008).

Different management strategies have been adopted to control the disease such as application of different chemicals, antagonists and crop rotation method by reducing sclerotial level in soil (Franci et al., 1988; Pineda, 2001; Chaudhary et al, 2004).

The chemical management of this disease is not cost-effective due to its soilborne nature. These chemicals lead to health hazards and ecological effluence due to frequent use. But these strategies could not successful due to their feasibility under specific conditions. So, cultivation of resistant varieties seems to be useful method in disease management. It is cheaper and pertinent method besides time consumption. Resistant response in different crops against disease may be due to decreased level of certain chemicals as compared to susceptible ones (Songa et al., 1997; Smith and Carvil, 1997). Therefore, in this regard, present study aimed to screen out resistant mungbean germplasm against charcoal rot disease and this information is essential for plant breeders for obtaining durable and resistant lines of mungbean against this disease.


Materials and Methods

Isolation of Macrophomina phaseolina

Stem tissues of mungbean bearing fungal sclerotia and characteristics charcoal rot symptoms were collected for isolation of the pathogen. The tissues were cut into small pieces of 5-10 mm length and 2-3 mm thickness. Surface was bleached with 1% sodium hypochlorite (NaOCl) for 2 minutes to eliminate secondary invaders and then rinsed in three successive changes of sterile distilled water prior to plating. These pieces were placed on chloroneb mercury rose bengal agar (CMRA) medium (Meyer et al., 1973).The Petri dishes containing infected tissue were incubated in dark at 26±2°C for 6 days.

Preparation of sorghum inoculants for M. phaseolina

Seeds of the sorghum were moistened, air dried under room temperature and placed in conical flasks. The mouth of each flask was plugged with cotton wool and wrapped in aluminum foil before autoclaving at 15 psi (121°C) for 20min. After cooling, the flasks were inoculated with 4 mm mycelial plug from a 7 days old culture of M. phaseolina and incubated at 26±2°C for 15 days for the colonization of sorghum seeds with the pathogen. One hundred colonized sorghum seed were plated on PDA at 26±2°C and after five days the cultures were examined under the microscope for the presence of the pathogen. The number of seeds showing the mycelial presence of the pathogen was counted. The percentage recovery of M. phaseolina from the inoculants was calculated.

Screening of mung germplasm for charcoal rot Resistance.

One hundred mung germplasm accessions were planted at National Agricultural Research Centre (NARC) in artificially inoculated soils in the field and green house during 2008 in kharif season. Each genotype was planted in a single row of 4m length. Plant to plant and row to row distance was maintained at 10cm and 30cm respectively. Plots were inoculated with inoculum @ 2g per meter of row. In the green house 2-3 sorghum seeds infected with M. phaseolina were placed around each seed of mungbean sown in pots. Five seeds were planted in each pot. Data was recorded on 1-9 disease ratting scale (Abawi and Pastor-Corrales, 1990), where, 1 = no symptoms on plants (highly resistant): 3 = (resistant): 5 = (tolerant): 7 = (susceptible) and 9 = (highly susceptible).


The results revealed that all genotypes differed in their response to charcoal rot disease. The disease severity of various genotypes ranged from 1-9 in green house as well as in the field. Out of one hundred accessions, fourteen genotypes, 013987, 013992, 014026, 014033, 014062, 014098, 014218, 014219, 014245, 014253, 014255, 014256, 014257 and 014258 with disease ratting score '1' were highly resistant whereas 18 genotypes with disease ratting score '3' were found as resistant. 35 Genotypes with disease rating '5' acted as tolerant lines whereas rest of 33 genotypes with rating scale '7' and '9' showed either susceptible or highly susceptible behavior (Table-1). The disease response under field conditions showed that out of 100 genotypes, 34 genotypes, 013987, 013992, 014026, 014033, 014062, 014098, 014149, 014173, 014184, 014218, 014219, 014220, 014222, 014223, 014239, 014240, 014241, 014243,014245, 014253, 014255, 014256, 014257, 014258, 014259, 014262, 014263, 014293, 014294, 014297, 014307, 014308, 014309 and 014310 appeared as highly resistant with disease score '1', whereas thirty were resistant, twenty three tolerant, 8 genotypes were susceptible and 5 acted as highly susceptible lines. As shown in scatter plot diagram (fig-1) there was a strong linear relationship between these two stages. Twelve groups were found which indicate different combinations of genotypes on the basis of disease severity. Fifteen genotypes (13987, 13992, 14026, 14033, 14062, 14098, 14218, 14219, 14245, 14253, 14255, 14256, 14257 and 14258) were highly resistant at both seedling and maturity at the point (1, 1) on X and Y-axis. 7 genotypes showed resistant reaction with disease score "2" at (2, 2) on X and Y-axis, While five were found to be highly susceptible at (5, 5) on X and Y-axis with disease rating "5". The disease severity was less at reproductive stage as compared with the seedling stage. High relationship was observed between these two stages. It was concluded that charcoal rot of mungbean gave high level of infection at seedling stage under greenhouse conditions therefore it was recommended to screen out large number of mungbean germplasm at greenhouse level to minimize the labour and resources.


Charcoal rot caused by Macrophomina phaseolina is highly devastating disease of the most cereal crops which infect the plants both at seedling and maturity stages. In our results most of the genotypes were found susceptible at seedling stage under greenhouse condition and only five genotypes (014227, 014228, 014284, 014285 and 014286) were susceptible under field conditions at maturity stage. This may be due to un-even distribution of inoculum in the field because in the pots under greenhouse conditions the inoculum is uniform and the micro-climate is distributed evenly that's why the number of genotypes in greenhouse are more susceptible to this disease as compared to filed.

The soil in the field are rich with organic mater that's why there is an abundant number of bacteria and actinomycetes which have antagonistic affect on M. phaseolina. Therefore the propagules density may be affected. Due to which the disease tri-angle (host-pathogen-environment) cannot be established. Sometimes the diseased debris cannot be decomposed properly in the soil and exposed to sunlight and remain in such conditions. The propagules cannot multiply in the soil and disease escape was occurred, while the conditions are uniform in case of glass house. We used sterilized soil which gives the pathogen maximum chance to flourish. There will be no competition between pathogen and the soil micro flora.

During this study different reaction groups were formed. Fifteen genotypes were found highly resistant at both seedling and maturity stages. Songa et al (1997) evaluated 313 common bean accessions against charcoal rot under field conditions and found fifty lines resistant. Ashraf et al (2005) screened 56 chickpea lines for resistance against this disease. Only one genotype was to be resistant against charcoal rot. 53 accessions of beans were evaluated by Pastor and Abawi (1998) Twenty two genotypes classified as resistant and remaining found tolerant to susceptible.

This indicates that the factors for resistance against charcoal rot do not protect the host against the pathogen but they retard the growth of the fungus. Therefore the crop is governed by polygenic genes which resist the pathogen in the field, which needs to be investigated in detail. However the large numbers of genotypes are investigated to find out the resistant sources of mung bean germplasm against charcoal rot.

Table.1. level of resistance/susceptibility of Mungbean germplasm against charcoal rot

Disease Reaction




Highly resistant (HR)


F =34





013987,013992,014026,014033,014062, 014098,014149,014173,014184,014218, 014219,014220,014222,014223,014239,





Resistant (R)


F =30






013953,013954,013956,013961,013962, 014075,014089,014119,014121,014123, 014125,014148,014213,014224,014233, 014234,014235,014237,014247,014249,



Tolerant (T)


F =23

013953,013954,013971,014044, 014063,014064,014073,014075,

014119,014121,014123,014125, 014213,014220,014223,014232, 014237,014239,014240,014247,


014270,014277,014287,014288, 014290,014292,014303,014304,


013955,013971,014035,014044,014063, 014064,014073,014133,014221,014232, 014251,014252,014274,014275,014276, 014287,014292,014298,014301,014302, 014303,014304,014311

Susceptible (S)


F =8





014043,014225,014226,014278,014279, 014280,014281,014283,

Highly susceptible (HS)


F =5


014226,014227,014228,014274, 014278,014279,014280,014281,




Analysis of Variance

Source of Variation




























Fig- 1: Correlation of disease reaction between seedling and maturity stage of mungbean

Fig-2: Precipitation, Temperature and R.H% at NARC during the kharif season 2007.