DIFFERENTIAL RESPONSE OF RICE VARIETIES TO THE BROWN PLANTHOPPER IN INTERNATIONAL SCREENING TESTS

This paper discusses results of International Rice Brown Planthopper Nursery (IRBPN) screening tests conducted in 1975-79 with special reference to understanding biotype variations in BPH and identifying sources of genetic resistance to these biotypes. The number of rice varieties tested ranged from 41 in 1975 to 162 in 1979 and included several traditional tall varieties and improved semidwarf breeding lines. Varieties containing the BPH-resistant genes Bph 1, bph 2, Bph 3, and bph 4 were included. A uniformly high susceptibility to BPH at different sites indicated a major distinction between BPH populations in South Asia (Bangladesh, India, and Sri Lanka) and those in the rest of Asia. Biotype differences of lower order within BPH populations common in East and Southeast Asian countries were also evident. Biotype differences were also evident at different sites in India, since reactions at Pantnagar were different from those at other sites. It was found that varieties which showed similar resistance patterns at the IRRI in the Philippines did not necessarily show similar patterns at other sites. PTB33, Suduru Samba, and Sinna Sivappu were found to be resistant at almost all test sites. Several improved breeding lines derived from PTB33 showed promise in all the regions of Asia and the Solomon Islands. Genes conveying BPH resistance in PTB33 seem to be different in South Asia from those in other parts of Asia, as evident from the different reactions of the semidwarf selections derived from that variety. Differences between field and greenhouse reactions for several varieties were observed, but more detailed studies are needed to provide genetic interpretation for these differences. Further international collaboration is recommended for follow-up breeding and genetic studies to develop varieties with genetic resistance to BPH in different countries. The report concludes with suggestions for breeding such varieties. A description of IRBPN"s screening and scoring procedures and a 7-item list of references (1971-79) are appended.