Abstract: Phytophthora root rot caused by Phytophthora sojae is a destructive disease for soybean [Glycine max (L.) Merr.] in soybean production regions of the world. Utilization of resistant varieties is the most economical and environmentally safe method for controlling this disease. A total of 48 soybean cultivars, which mainly used in Huang-Huai Valley, were analyzed to study their resistance to P. sojae by identifying seedlings with 7 stains of P. sojae. The resistance to P. sojae varied among different cultivars, which were divided into 8 groups at 0.682 similarity coefficient. The results showed that there exist the rich resistant soybean resources to P. sojae in Huang-Huai Valley. Most known plant disease-resistance (R) genes include nucleotide binding site (NBS) or leucine-rich repeats (LRRs) and serine/threonine protein kinase (STK) in their encoded products domains. Two primers, XLRRfor/XLRRrev and Pto-kin1/Pto-kin2, were designed on the loci of these conserved domains. By polymerase chain reaction (PCR) and denatured polyacrylamide-gel electrophoresis techniques, disease resistance gene analogues (RGA) amplified on 48 soybean materials. The RGA analysis of 48 cultivars produced 53 amplification bands, 39 of them (73.6 %) showed polymorphic, and they were divided into 7 groups at 0.746 similarity coefficient. Although there was no parallelism relationship in groups be-tween two different types of the clustering, the cultivars with broad resistance spectrum, such as Fengshouhuang, Kefeng 36, and Jimoyoudou could be clustered into the same group. The result indicated RGAP (resistance gene analog polymorphism) technique, combining the resistant spectrum, provides a useful and efficient way to improve the efficiency of parent selection in soybean breeding and to accelerate the process of developing soybean cultivars with resistance.

Key words: Soybean, Resistance gene analogue (RGA), Polymorphism, Resistance identification