Link to home

Mediation of Partial Resistance to Rice Blast Through Anaerobic Induction of Ethylene

August 2004 , Volume 94 , Number  8
Pages  819 - 825

Manjul P. Singh , Fleet N. Lee , Paul A. Counce , and Julia H. Gibbons

University of Arkansas, Rice Research and Extension Center, Stuttgart 72160

Go to article:
Accepted for publication 5 March 2004.

The correlation between anaerobic soil conditions and increased resistance to rice blast disease has long been observed without benefit of an adequate explanation. We researched flood depth, dissolved oxygen (DO), and ethylene relative to expression of partial blast resistance in cvs. M-201, Newbonnet, LaGrue, Mars, and Cypress. Cultivar blast index (BI) and flood DO decreased with increasing flood depth. BIs were positively correlated with DO. Total leaf blast lesions were 3.4 and 3.2 times greater in cvs. M-201 and LaGrue growing in a 5.0-μl liter-1 DO nutrient solution than when growing in a 0.1-μl liter-1 DO solution. Treatment with 0.25 mM ethephon, which releases ethylene, lowered BIs of Newbonnet, LaGrue, and Cypress growing upland when applied drench, foliar, or foliar-drench. If flooded, BIs of ethephon-treated cultivars were decreased by drench and foliar-drench applications only. BIs of upland plants were unchanged, whereas BIs of analogous flooded plants increased following treatment with 0.31 mM aminoethoxyvinylglycine (AVG), an ethylene biosynthesis inhibitor. We hypothesize that varying anaerobic conditions mediate production of phytohormones, particularly ethylene, which modify expression of inherent partial blast resistance in these rice cultivars.

Additional keywords: field resistance, hormone, host-pathogen interaction, Magnaporthe grisea, Oryza sativa.

The American Phytopathological Society, 2004