Differentiating thirty three isolates of rice sheath blight pathogen (Rhizoctonia solani Kahn) by hyphal anastomosis and cultural characteristics.
1990
Than H. | Mew T.W.
Differentiation of Rhizoctonia solani (Rs) isolates into anastomosis groups in relation to types of anastomosis has been recognized. Rs isolates, prevalent in rice ecosystem, were studied to distinguish the relationship among each other on the basis of types of hyphal anastomosis on glass slides coated with 1.5% water agar and types of fusion between the two colonies on potato dextrose agar (PDA) plates. Perfect fusion, without killing reaction associated with vegetative compatibility between the two closely related isolates were found showing indistinct fusion with the same isolates. In perfect fusion, with killing reaction relating to vegetative incompatibility between the two less closely related isolates showed clearing zone formation at the meeting area between the two colonies on the plates. These results revealed belongingness of Rs isolates within an anastomosis group, less relationship among most of the isolates, existence of similar isolates at distinct places, and presence of more than one type of anastomosis group in rice plant. In addition, examination of types of colony fusions on the PDA plates was found useful to detect the types of anastomosis for larger number of Rs isolates in a shorter time. Differentiation of Rs isolates on the basis of sixty-five attributes determined by hyphal growth, number of sclerotia formed, size of sclerotia, pigmentation, formation of aerial mycelium, and pseudosclerotia on a variety of media were used for cluster analysis of UPGMA. There was no significant relationships among the isolates. Out of ten clusters formed, cluster 2 comprising 36% of isolates was the largest cluster. The results indicated that majority of Rs isolates under rice ecosystems were less related to each other, but can be grouped on the basis of cultural characteristics.
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