EFFECT OF BRASSINOSTEROIDS ON SOYBEAN RESISTANCE TO PHYTOPHTHORA SOJAE

Peroxidase(POD)and phenylalanine ammonialyase(PAL)are defensive enzyme for soybean Phytophthora root rot.To elucidate the effect of Brassinosteroids(BR)on soybean re- sistance to Phytophthora root rot and identify the resistance of a soybean mutant.Two soybean cultivars Williams(sensitive)and Ludou 4(resistant),and a pair of soybean mutant(Dongze 11) with its wild type(Dongnong 42)were adopted as materials.The soybean seedlings were treated with Brassinosteroids(BR)or/and inoculated with Phytophthora sojae and the changes in activi- ties of POD and PAL were investigated.The POD and PAL activity in plants inoculated with Phytophthora sojae were significantly higher than those without inoculation,which showed the Phytophthora sojae induced the systemic resistance of soybean plants.The activity of POD and PAL were also increased when treated with BR,which suggested that BR might have some resist- ant effect on Phytophthora root rot.The identification results showed Dongnong 42 was suscepti- ble and the mutant was mid-type,their resistance to Phytophthora root rot were enhanced when treated with BR.