Application of systemic acquired resistance theory as biological control to manage rice blast disease (pyricularia grisea) at the Mekong Delta of Vietnam

Studies on application of systemic acquired resistance (SAR) to control rice blast disease (Pyricularia grisea) in Mekong delta have been done since 1997, under support by DANIDA, Denmark. Studies found that there were 18 SAR agents, two microorganisms, Flavimoras oryzihabitans and Colletotrichum sp., extracts from five plants Kalanchoe blossfeldiana, Ageratum conyzoides, Acanthus ebracteatus, Psidium guajava and Derris triifolia; 11 non pesticide chemicals as copper chloride, dipotassium hydrogen phosphate, oxalic acid, benzoic acid, natrium silicate, natrium tetraborate, humic acid, salicylic acid, chitosan, glucosamine and saccharin. Among them, rice leaves induced with copper chloride and Colletotrichum sp. were found that there was an increasing of catalase and phenylalanine ammonia-lyase (PAL) enzymes and PR-Proteins e. g. beta -1,3-glucanase, peroxidase and chitinase. Copper chloride, dipotassium phosphate, oxalic acid and natrium tetraborate were also proved their SAR ability by increasing number of fluorescent epidermal cells walls beneath appressoria of fungal pathogen, under fluorescent microscope. Under microscopy, rice leaves induced by copper chloride were also proved its SAR ability by increasing in number of accumulation of polyphenol in cells around appressoria of the pathogen. Application of SAR agent to control rice blast disease was done in experimental farm and in armer fields. Copper chloride, oxalic acid, dipotassium hydrogen phosphate, natrium silicate, natrium tetraborate and Flavimonas oryzihabitans, were used as SAR agents under seed soaking and leaf spraying, Leaf blast disease incidence of the crops were decreased from 54 percent to 70 percent down and node blast incidence were decreased also from 7 percent to 34 percent down, to compare with control one. Grain yields of SAR treatments were increased from 20 to 27 percent to compare with control one. However, other experiments were proved that SAR ability of each SAR agent was depended to race of athogen. Further studies should be done to have a mixed product, to combine many SAR agents, to overcome the obstacle