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PATHOGENIC VARIABILITY IN COLLETOTRICHUM TRUNCATUM ,A LEAP SPOTTING PATHOGEN OF URDBHAN (VIGNA MUNGO (L.)HEPPHR)
RP KAUSUAL and RAJAN SHARNA

Department of Plant Pathology, Himachal Pradesh Krishi Vishvavi-dyalaya, Palampur - 176 062 (11.P.) INDIA

Background and objectives
Urdbean (vigna mungo) is an edible grain legume of majority of population of Asia, prized for its ripe proteinous grains. The yields are limiting because of virulent attack of Colleto-trichum truncatum among others especially in high rainfall areas. Since the pathogen infects most of the leguminous hosts, study on pathogenic variation in the fungus is essential for successful breeding of resistant legume varieties.


Materials and methods
Virulence pattern of the isolates of C.truncatum was studied on indigenously developed differential set of 12 urdbean lines and also on selected 11 related edible legume hosts.


Results and Conclusions
Based on the reaction of the test isolates on the urdbean differentials, they were grouped in 6 pathotypes. Isolates CT 1, CT 4 and CT 11 were grouped in pathotype 1, IV and VI respectively. Isolates CT 2, CT 5 and CT 8 were grouped as pathotype II; CT 3, CT 6 and CT 9 as pathotype III and CT 7 and CT 10 as V. Pathotype III was most virulent attacking all the differentials and IV and VI as least virulent pathotypes.
Isolates were also grouped into 6 pathogenic groups based on their reaction on related legume hosts. CT 1 was designated pathogenic group 'a' ; CT 2, CT 5 and CT 11 were grouped as ‘b’ and CT 3 and CT 8 as 'c'. Isolate CT 4 was designated pathogenic group ‘d', CT 6 and CT 9 were grouped in ‘e’ and CT 7 and CT 10 in ‘f'. Among different legume hosts, broadbean (vicia faba) was highly susceptible. Cultivar 'Parbhat’ of redgram (Cajanus cajan) was highly resistant while Upas 120 war susceptible to all the pathogen isolates. Bhardwaj and Singh [1] found variation in 4 isolate of C.truncatum obtained from different hosts. Manandhar et al. [2] also found pathogenic variation in this pathogen isolated from soybean.


References
1.Bhardwaj CL, Singh BM, 1986. Indian Journal. of Mycology and Plant Pathology 16, 139-41. 2.Manandhar JB, Hartman GL, Sinclair JB, 1988. Plant Disease 72, 56-59.