Evaluation of Resistance to Leaf Blight Disease of Rice Varieties in Suphanburi Province

Abstract

         Bacterial blight disease is caused by the bacteria Xanthomonas oryzae pv. oryzae (Xoo), the gram-negative bacteria. It has been considered an important rice disease since there was a severe outbreak causing damage in rice growing areas, especially in irrigation areas. Rice with severe damage rice yield with sever damage is reduced by 20-30 percent and may be as high as 60 percent in susceptible areas. The objective of this research was to evaluate the resistance to bacterial leaf blight disease characteristics of 13 varieties of rice in Suphanburi province. 13 varieties of rice were transplanted 1 pot per plant 3 replications in Suphanburi province experimental greenhouse. Random samples of rice leaves with bacterial blight were collected to isolate pure bacteria using the tissue transplanting technique. Morphological examination revealed that the colonies were round and convex, smooth, greasy, mucilaginous, and produced yellow pigment. It was a Gram-negative bacteria. It had a rod shape and was approximately 0.5-0.8 x 1.0-2.0 µm. in size. Testing for disease reactions according to Koch's postulation method found that the symptoms were watery wounds, subsequently. Later, It turned gray in long lines along the edge of the leaf. Preparing bacterial suspensions were prepared from pure cultures to assess resistance characteristics. 13 varieties of rice were transplanted test bacterial blight disease using the clipping method. Disease symptoms were assessed by scoring the area of damaged leaves at 21 days after inoculation. The results of the study found that four varieties that showed highly resistance (HR) were strain R2006 had 1 percent of infected rice leaf area, while strains R3001, R3018, and R3021 had 2 percent of infected rice leaf area. The results of this experiment can be used as information to support rice breeding work in Thailand to develop good rice varieties with resistance to leaf blight disease. It could be an alternative for farmers to increase rice production.