Tissue culture and transformation of introducing genes useful for pest management in rice
Sheath blight (SB), caused by Rhizoctonia solani K¨¹hn, is a major rice disease internationally and in the southern rice area of the Unites States, including Louisiana. Breeders have incorporated partial resistance into commercial rice varieties to control the disease, but a higher level of resistance is needed. It has been demonstrated that the pathogenesis-related (PR) proteins ¦Â-1, 3-glucanase and chitinase are components of effective defense mechanisms for protecting plants against fungal pathogens. This research was conducted to co-transform the ¦Â-1, 3-glucanase, chitinase and bar genes into the rice variety Taipei 309 using the hpt gene for resistance to hygromycin B as a selective marker. Transformed calli and regenerated plants were screened with hygromycin B, and the plants were then further tested for resistance to Liberty herbicide and Rhizoctonia solani. Methods were developed to screen transgenic plants for resistance to hygromycin B and Liberty herbicide using dip and cut in toxicant solutions. Five of 99 plants in the field test and 51 of 55 plants in greenhouse test were highly resistant to Liberty herbicide. The tooth-pick inoculation method was used to test transformed plants for SB resistance. Seventeen transgenic plants in the field test and 10 transgenic plants from greenhouse tests were highly resistant to SB. Fourteen of the17 SB resistant plants were also resistant to hygromycin B, one of the plants was highly resistant to Liberty herbicide, and 9 of the 17 SB resistant plants had moderate resistance to Liberty. Panicle blight, caused by Burkholderia glumae, has been an important bacterial disease in rice worldwide and in Louisiana. No effective pesticides are available to control this disease. The PR protein thionin is reported to control certain bacterial diseases in plants. In this study, the thionin production, bar, and hpt genes were co-transformed to the rice variety Lafitte. Resistance to hygromycin B, Liberty herbicide, Xanthomonas oryza and B. glumae were expressed in selected transformed Lafitte plants. This research has created, through transformation, new sources of resistance to two major rice pathogens that cause major losses to rice. These resistances can be transferred to commercial varieties by conventional breeding methods.
rice tissue culture, transformation, pathogenesis-related proteins, chitinases, glucanases
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