This study investigated the effect of CaCl 2 and Ca(NO 3 ) 2 on fungal growth of Phytophthora sojae isolates, disease reduction on two cultivars of Glycine max (L.) Merr. cv. Chusei-Hikarikuro (black soybean) and cv. Sachiyutaka (white soybean) and zoospore release. A concentration of 20-30 mm CaCl 2 or 30 mm Ca(NO 3 ) 2 led to a slight decrease of the growth rate of two isolates on PDA; however, 0.4 and 4 mm of CaCl 2 and Ca(NO 3 ) 2 increased growth. The application of 4 mm CaCl 2 or more than 4 mm Ca(NO 3 ) 2 before inoculation greatly inhibited infection in the two soybean cultivars. Disease suppression recorded in laboratory experiments using pathogen mycelium was because of the response of plant tissues rather than a direct inhibition of pathogen hyphal growth by the application of calcium. Furthermore, Ca(NO 3 ) 2 was more effective than CaCl 2 . The calcium contents in plants increased at the time of inoculation. The extent of disease reduction was related to an increased calcium uptake by plants of the two cultivars, except for some cases involving cv. Chusei-Hikarikuro. Results showed that the effective element in reducing Phytophthora stem rot was calcium and that differences existed between the two cultivars in terms of the mechanisms of calcium uptake and the effect on disease suppression. The presence of 4-30 mm CaCl 2 and Ca(NO 3 ) 2 decreased the release of zoospores from isolates on lima bean agar, although 0.4 mm CaCl 2 and Ca(NO 3 ) 2 significantly induced zoospore release. These results suggest the possibility of applying a solution containing more than 4 mm of calcium to decrease the incidence of disease in agricultural fields by the inhibition of zoospore release.

Since 1987, Phytophthora root and stem rot of soybean [Glycine max (L.) Merr. cv. Tanbakuro], caused by Phytophthora sojae Kaufman and Gerdemann, has been increasing in the Sasayama, Nishiwaki, and Kasai regions in Hyogo, the most famous soybean (cv. Tanbakuro)-producing areas in Japan. In 2002 to 2004, 51 isolates (one from each field) of P. sojae were recovered from 51 fields in Hyogo. These isolates were tested for virulence on six Japanese differential soybean cultivars used for race determination in Japan, and three additional ones containing four Rps genes used in Indiana, USA. Race E was the most prevalent from 2002 to 2004, followed by races A, C, D, and four new races (proposed as races K, L, M, and N). Interestingly, none of the new races had high virulence on the Japanese differential cultivars, compared with other races in each area. One (race N) was avirulent on all six soybean differentials. There was a difference in race distribution on each of three individual areas; race E seemed to be a major component of the P. sojae population in Sasayama, whereas race A and the new race M were the most prevalent in Nishiwaki and Kasai, respectively. Rps6 (cv. Altona) and Rps1a + Rps7 (cv. Harosoy 63) were infected by 90.2% and 33.3% of all isolates, respectively. However, Rps1d (cv. PI103091) was not susceptible to any of the 51 isolates, nor was cv. Gedenshirazu-1. These two soybean cultivars were considered to be potential sources of resistance to breed new resistant cultivars with the desirable characteristics of cv. Tanbakuro for this region.

A cDNA clone of a novel cytochrome P450, CYP76A4, was isolated from Petunia hybrida. The cDNA clone contained an open reading frame (ORF) encoding a predicted 510 amino acid polypeptide. The CYP76A4 cDNA was expressed in yeast Saccharomyces cerevisiae AH22. Recombinant yeast microsomes containing the CYP76A4 hemoprotein were found to catalyze (!-1)-hydroxylation of lauric acid.