Development of Management Strategies to Control Major Soybean Virus Diseases in the North Central States

Objective 1. Identify/understand the virus problems in the North Central States A. We plan to monitor virus incidencelidentity in soybeans in KY and IL (for IL, collaboration with John Russin, Southern illinois University). The focus will be on BPMV, S:NfV,AMV and TSV. ELISA-based methods will be used for virus identification. Because recent studies indicated considerable diversity among BPMV isolates, we will examine representative isolates from the participating states for diversity using cloned cDNA probes representing two estabJished subgroups ofBPM\1 strains. We have developed an efficient slot-blot nucleic acid hybridization protocol, 'which we will use for this purpose. ?JreIIlatively, reverse transcription (RT)-polymerase chain reaction RT-PCR methods will be used in cenain situations (e.g., viruses for which efficient/reliable ELISA protocol are not available. For example, luteoviruses, TSV, etc.). B. Mecha.nism of beetle cransmission of BPYIV. Previous studies have shown that removal of certain critical amino acids at the surface of the virus particle may lead to failure of transmissibility by che beetle vectors. We plan to study the beetle transmissibility of various coat protein. mutants of BPMV in an attempt to shed some light on the mechanism of beetle transmission. Full-length cDNA cIones of BPMV are available in our laboratory, and PCRbased methods will be used to generate the desired mlltants. . Objective n. Development and implementation of virus disease control strategies A. Short-term control strategies. We plan to continue our studies on Identification of the primary sources of BPMV in the soybean fields early in the ~eason with emphasis on identification of alternative leguminous hosts that may serve a..c:; reservoirs ofBPMV. Over-wintered beetles that emerge in the spring will be collected from alfalfa/red clover fields as well as from leguminous weeds growing near the cultivated fields (the host range of BPMV is very limited and include mainly leguminous hosts). The beerle~ will be tcsted for BPMV content by ELISA and for their abiJity to transmit BPMV to healthy assay plants. Leaf samples from such leguminous plao.ts showing beetle-feeding site:s will also be collected and tested for BPMV by ELISA. B. Cultivar development. We have generated in previous studies transgenic soybean lines exprcssing BPMV capsid polyprotein. A homozygous transgenic soybean line (Jack 183-2) chat showed resistance to systemic infection with subgroup I of BPMV strains has been 0 r~ ~) selected for further evaluation. We plan to evaluate the Jack 183-2 line for ~sistance to ioiection Wltb subgroup II strains and possibly othc=rgenetically distinct strains, as may be revealed in the proposed studies under objective 1. W~ a1:;o plan to constrUct additional plane transformation Vec[urs containing the viral genes coding for the individual coat proteins, movement protein and Ri'\lA-dependem RL~Apolymerase, Our long-range goal is to produce broad transgenic resiscance to all known BPMV strains rbat can be incorporated into desired soybean culrivars.