RESPONSE OF SOYBEAN ACCESSIONS FROM PROVINCES IN SOUTHERN CHINA TO PHYTOPHTHORA-SOJAE

Phytophthora rot, caused by Phytophthora sojae, is a damaging disease of soybean (Glycine max (L.) Merr.) throughout the soybean-producing r egions of the world. The discovery of new sources of resistance in soy bean is vital in maintaining control of Phytophthora rot, because race s of the pathogen have been discovered that can attack cultivars with commonly used resistance genes. The objectives of this study were to i nvestigate the distribution and diversity of Phytophthora-resistant so ybean in southern China and identify sources that confer resistance to multiple races for implementation into breeding programs. Soybean acc essions obtained from southern China were evaluated for their response to races 1, 3, 4, 5, 7, 10, 12, 17, 20, and 25 of P. sojae using the hypocotyl inoculation technique in the greenhouse at Urbana, Illinois in 1996 and 1997. Accessions were identified that confer resistant res ponses to multiple races of the pathogen. These accessions may provide sources of resistance for control of Phytophthora rot of soybean in t he future. The majority of the accessions with resistance to eight or more of the ten races tested were from the provinces of Hubei, Jiangsu , and Sichuan in southern China. Based on the evaluated accessions, th ese provinces appear to be valuable sources of Phytophthora-resistant soybean.