Characterization of resistance in rice to bacterial blight.

Abstract

Infection from strains of Xanthomonas campestris pv. oryzae on IR8, IR20 and IR1545 by the leaf clipping, pin-pricking and spray methods of inoculation suggested that neither lesion length nor disease score were affected.The incubation period was varied by methods of inoculation, but not by varietal resistance.Breeding lines derived from TKM 6 for Xa4 and DZ192 for xa5 sources of resistance were consistent with respective bacterial strains of the same virulence group, at maximum tillering stage of plant growth.The resistance was not complete. Significant differences in virulence between group 1 strains to TKM 6 and its derivatives and group 2 strains to TKM 6, DZ192 and their derivatives were observed.The effect of leaf age, as well as plant age, to infection varied from young to old, but the significant lesion length was observed only in compatible rice cultivar and bacterial strain combinations. The lesion length of breeding lines having "adult plant" resistance, such as IR1695 and IR944, gradually decreased from vegetative stage to repro ductive stage against strains of all virulence groups evaluated.Lesion length of cultivars of moderate susceptibility comparable to partial resistance, was decreased significantly when inoculum dosage was lower, while the lesions on lines with adult plant resistance were not different from IR 8, the check variety.

Developmental control of Xa21‐mediated disease resistance in rice

“…oryzae (Xoo), the causal agent of bacterial leaf blight, is developmentally controlled (Goel & Gupta 1990; Kim et al . 1987; Mew et al . 1981; Mew 1987; Ogawa 1993; Yeh et al .…”

Resistance of Rice toXanthomonas oryzaepv.oryzaein Nepal

“…LL, AUDPC, disease development over time, and dose-response curves reflected differences in resistance of IR24, Sabitri, and Laxmi. Previous studies also suggested that an appropriate dose of inoculum and the test of a rice cultivar at the proper growth stage is important in evaluating rice cultivar resistance to BB (15,16). The strains of X. o. oryzae from Nepal are virulent on most of the resistance genes that are currently used in rice breeding programs…”

“…The principal criterion used previously for evaluation of rice cultivar-X. o. oryzae interaction was lesion length (LL) measured 30-40 days after clip inoculation of the leaves (15,16). One way of evaluating this interaction is to monitor inoculum doses of the pathogen needed to elicit a certain response in the host (8).…”

Xanthomonas Oryzae Pv. Oryzae. An Overview of Bacterial Blight Disease of Rice Caused By

“…The paint brush method of inoculation was found to be less effective as compared to other two methods but it was more similar to natural infection. Mew et al (1981) compared the needle prick, clip and spray technique and found that neither lesion length nor disease score were affected by inoculation method, although the incubation period was longer in spray inoculated plants than in other plants. The pin-prick method of inoculation developed by Muko and Yoshida (1951) and Yoshida and Muko (1961) proved most suitable for quantitative determination of causal bacterium.…”

“…Crop growth stages with reference to resistance were studied by few research workers. Mew et al (1981) reported that leaf and plant age influenced the infection which varied from young to old plants. Noda (1982) observed that the reaction of cultivars at different growth stages found to be helpful in classifying the pathogen isolates into different groups.…”