Pestalotiopsis versicolor: A Causal Agent of Rice Collar Rot. N. Iboton Singh, Department of Plant Pathology, College of Agriculture, Central Agricultural University, Iroisemba, Imphal-795 001, India.. R. K. Tombisana Devi, and L. Nongdren Khomba Singh, Department of Plant Pathology, College of Agriculture, Central Agricultural University, Iroisemba, Imphal-795 001, India. Plant Dis. 79:1186. Accepted for publication 19 July 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1186B.
During September and October of 1992 and 1993, rice plants (Oryza saliva L.) from all of 43 fields surveyed in Imphal, Thoubal, and Bishnupur districts of Manipur suffered from a collar rot disease. Disease incidence ranged from 65 to 100% and yield losses were 25 to 45%. Symptoms that first appeared at the collar joining the leaf blade and leaf sheath consisted of small brown lesions that expanded and covered the whole collar region. Lesions sometimes extended down the sheath and the blade, turning them dark brown to black. Subsequent rotting caused the leaf blade to separated from the sheath and drop off. In severe cases, several leaves on the same plant dried up and fell. Surface-disinfested collar tissue plated on potato-dextrose agar (PDA) yielded Pestalotiopsis versicolor (Speg.) Steyaert. The identity of the fungus was confirmed by the International Mycological Institute (IMI 356490). The pathogenicity of the fungus was determined by placing a drop of 4 x l03 conidia per ml at the collar regions of 20 rice plants incubated in perforated polyethylene bags. Three days after inoculation, 90% of the rice plants produced disease symptoms that were identical to those occurring in nature. Necrotic tissues, from artificially induced rice collar rot, were plated on PDA and consistently yielded P. versicolor. This is the first report of P. versicolor on rice collar in India. Recognition of this disease is important because symptoms can be easily mistaken for those of rice collar rot caused by Ascochyta oryzae Cattaneo (1,2).References: (1) P. Kanjanasoon. Int. Rice Commission Newsl. 2(3):22, 1992. (2) N. I. Singh and R K. T. Devi. Int. Rice Res. Newsl. 15:27, 1994.