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Title: Rice resistance to blast caused by leaf surface moistening prior to inoculation

Author
item Baker, Con
item ROMANOVA, T - Moscow Agricultural Academy
item AVER'YANOV, A - Moscow Agricultural Academy
item PASECHNIK, T - Moscow Agricultural Academy
item LAPIKOVA, V - Moscow Agricultural Academy

Submitted to: Russian Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2009
Publication Date: 12/1/2009
Citation: Baker, C.J., Romanova, T.S., Aver'Yanov, A.A., Pasechnik, T.D., Lapikova, V.P. 2009. Rice resistance to blast caused by leaf surface moistening prior to inoculation. Russian Journal of Plant Physiology. 56:(3):389-393.

Interpretive Summary: Fungal diseases of crops cause major losses for farmers each year. Many of these fungal diseases start by the germination of the fungal spore in a droplet of water or dew on the leaf surface. During our studies of spore germination of the rice blast fungus on rice, we observed that when water droplets, without spores, were placed on leaves for several hours prior to adding spores, the disease symptoms were noticeably less severe. This is the first report of this phenomenon of ‘reduced severity’ by water and also indicates the biochemical mechanisms that may be involved. Better understanding of the biochemical basis for plant resistance to disease will lead to improved strategies to improve plant health and reduce losses. This information will be of use to plant scientists who are devising new strategies to improve disease resistance in plants.

Technical Abstract: Effect of water droplets placed onto rice (Oryza sativa L.) leaves before inoculation with blast fungus Magnaporthe grisea (Hebert) Barr on disease severity and superoxide radical generation by the leaves was investigated. The leaves were inoculated by placement of spore suspension droplets. One day before, droplets of distilled water were placed to the same sites as inoculum. It was found, that such a pretreatment decreased frequency of susceptible type lesions 2 to 2.5 times and increased that of symptomless outcome 1.5 times in comparison with the non-treated control. Besides, the pretreatment enhanced superoxide radical generation in diffusates of healthy leaves of susceptible cultivar and in diffusates of infected leaves of resistant cultivar one day post inoculation. It is suggested that water contacting with leaf surface for rather long time washes out from its cells compounds possessing properties of plant endogenous elicitors. The latter induce superoxide radical formation by plants and, as a consequence, their disease resistance. This may be interpreted as plant adaptation to high humidity, which usually favors infections.