2008 APS Annual 

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APS Abstract of Presentation

New strategy to enhance rice resistance to fungal pathogens
T. XU (2), M. Liu (2), Z. Sun (4), G. E. Harman (1), M. Lorito (3), S. L. Woo (3)
(1) Department of Horticultural Sciences, Cornell University, Geneva, NY, USA; (2) Department of Plant Protection, Zhejiang University, Zhejiang, China; (3) Institute of Plant Pathology, Napoli University, Tritici, Italy; (4) Key Laboratory for Rice Biology, Ministry of Agriculture, China National Rice Research Institute, Hangzhou 310006
Phytopathology 98:S174

Rice sheath blight (Rhizoctonia solani) and blast (Magnaporthe grisea) are two serious diseases in China. Resistance breeding is a key strategy to control the diseases. However, rice cultivars with broad spectrum, high level and durable resistance to the pathogens have been difficult to obtain by traditional breeding due to the lack of resistant germplasm to R. solani and the high genetic diversity of M. grisea. Trichoderma strains were demonstrated to encode proteins with high antifungal activity against a wide range of plant pathogenic fungi. The potential of the biocontrol agent Trichoderma strains and their genes encoding for fungal cell wall degrading enzymes (CWDE) to enhance rice resistance against the pathogens was investigated in greenhouse. The disease severities of blast and sheath blight on rice cultivar Yuanfengzao pretreated by seed coating with T. harzianum NF9 were significantly reduced and the rice seedlings exhibited a moderate resistance to both of the pathogens. Agrobacterium mediated transformation of rice with three genes encoding for CWDE, ech42 (endochitinase), nag70 (exochitinase) and gluc78 (exo-1,3-beta-glucanase) from Trichoderma atroviride was conducted with transformation rates ranging from 24.6 to 55.5%. A total of more than 1,800 independently regenerated plantlets in seven different populations were obtained. The results from Southern blot analysis of the PCR-positive plants further confirmed that the exogenous genes were inserted into rice genome. Enhanced resistance to blast was found in all types of regenerated plants, while a few lines expressing ech42 appeared to be immune to this pathogen. The expression of the ech42 gene increased resistance to sheath blight and the expression level was correlated with disease resistance. In addition, exochitinase enhanced the positive effect of endochitinase on disease resistance when two genes were co-expressed in transgenic rice. This work was supported by the Sino-Italy Joint Research Project (2006DFA32900).


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