RICE SCIENCE ›› 2007, Vol. 14 ›› Issue (4): 302-310 .

• Research Paper • Previous Articles     Next Articles

Host Active Defense Responses Occur within 24 Hours after Pathogen Inoculation in the Rice Blast System

WANG Zhong-hua1, JIA Yu-lin 2, LIN Hui 3, Adair INTERN 3, Barbara VALENT 4, J. Neil RUTGER5   

  1. 1 Institute of Biotechnology, Zhejiang Wanli University, Ningbo 315100, China; 2 USDA-ARS Dale Bumpers National Rice Research Center, P. O. Box 1090, Stuttgart, AR 72160, USA; 3 Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701, USA; 4 Department of Plant Pathology, Kansas State University, 4024 Throckmorton Plant Science Center, Manhattan, KS 66506-5502, USA; 5 USDA-ARS Dale Bumpers National Rice Research Center, P. O. Box 1090, Stuttgart, AR 72160, USA
  • Received:2006-09-12 Online:2007-12-28 Published:2007-12-28
  • Contact: WANG Zhong-hua, or JIA Yu-lin
  • Supported by:

    the Special Foundation of Education Bureau in Zhejiang Province (Grant No. 20050218), the Arkansas Rice Research and Promotion Board and Adair Internship for their financial support.

Abstract: Phenotypical, cytological and molecular responses of rice to the fungus Magnaporthe grisea were studied using rice cultivars and lesion mimic plants. The cultivar Katy was susceptible to several virulent M. grisea isolates, and a Sekiguchi like-lesion mimic mutant of Katy (LmmKaty) showed enhanced resistance to these isolates. Lesion mimic phenotype of LmmKaty was rapidly induced by virulent M. grisea isolates or by avirulent ones only at high levels of inoculum. Autofluorescence (a sign of an active defense response) was visible under ultraviolet light 24 h after localized inoculation in the incompatible interaction, whereas, not evident in the compatible interaction. Autofluorescence was also observed in LmmKaty 20 h after pathogen inoculation, indicating that rapid cell death is a mechanism of LmmKaty to restrict pathogen invasion. Rapid accumulations of defense related (DR) gene transcripts, phenylalanine ammonia lyase and ß-glucanase, were observed beginning at 6 h and were obvious at 16 h and 24 h after inoculation in an incompatible interaction. Rapid transcript accumulations of PR-1 and chitinase had occurred by 24 h after inoculation in an incompatible interaction. Accumulations of these transcripts were delayed in the compatible interaction. These results indicate that host active defense responses occur 24 h after pathogen inoculation and that LmmKaty exhibits enhanced resistance to M. grisea. It is suggested that the autofluorescence and expression of the DR genes after heavy inoculation are important cytological and molecular markers respectively for early determination of the host response to M. grisea in the rice blast system.

Key words: rice (Oryza sativa), lesion mimic mutant, disease resistance, cytology, defense response, Magnaporthe grisea