Wide hybridization for rice improvement
1994
Chairerg Maneephong (Kasetsart Univ., Bangkok (Thailand). Faculty of Agriculture. Dept. of Agronomy)
Wide cross between cultivated rice, Oryza sativa and wild Oryza spp. was made after screening for disease and insect resistance. O. minuta G.S.No.5510 showed resistance to green leafhopper and brown planthopper. Other seven accessions of different species have highly resistance to brown planthopper. Rate of seed sets ranged from 0-44.03 percent depending on parents of cultivated and wild species used. Embryo rescue of F1 plant was made at 11-13 days after pollination on 1-4-strength Murashige and Skoog medium devoid of auxin and allowed to germinate in the dark. The rate of embryo rescue ranged 20-100 percent depending on the two parents. The F1 hybrid between O. sativa and the wild species O. minuta, O. officinalis and O. spontanea were intermediate between the two parents in some respects but showed a preponderance of the traits of wild species. They were robust and extremely vigorous. All of them were completely sterile. Colchicine treatment on the tip of F1 plant showed poor result. Adding colchicine solution into medium cultured the young F1 plant gave some fertile F1 plants after transfered to grow in the soil and set seed. Vegetative multiplication of F1 plants for use in screening insect resistance was done by adding benzyladenine (BA) 15 mg/l in the medium culturing the young F1 plantlet. Four tillers per plant were produced at this BA concentration. Another method is node multiplication by cutting nodes of vigorous F1 plants and transplanted in wet sand. Backcrosses were made by using F1 plants as female and the respective cultivated parents as male. The seed set of backcross ranged from 0-5.68 percent depending on parents used. Backcrossed progenies will be examined cytologically and will be tested for brown planthopper resistance. After that they will be backcrossed 3-4 times to get the cultivated rice background plus brown planthopper resistant gene from wild species.
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