Occurrence of abnormal rice kernels associated with the infestation of white tip nematode, Aphelenchoides besseyi

Abstract

Recently with the increased infestation of white tip nematodes in paddy rice in this country, occurrence of diseased rice kernels with black wedge-shaped spots, a new type of damage in rice production, has widely been observed. These kernels bear a striking resemblance to “black eye-spot of rice grains” which were caused by a bacterial disease as reported in 1941 by Miyake and Tsunoda. The white tip nematodes were, however, found to be the primary cause of the black wedged rice, as a result of some observations made in paddy fields of commercial growers and of a field experiment done by inoculating the nematodes. In addition to the primary role of the nematodes, necessity of the secondary action by saprophytic microorganisms, such as Enterobacter agglomerans, for black discoloration process was ascertained by duplicated inoculation experiments of these organisms. Diseased kernels showing similar symptom were recognized among the nematode-infected rice grains produced in Thailand, and it was suggested that “L type” pecky rice occurring in Louisiana, Texas, and Arkansas (Douglas, 1950) is possibly identical to this disease primarily caused by the nematodes.