PRODUCTION AND GERMINATION OF OOSPORES OF ALBUGO-CANDIDA

To facilitate genetic studies with Albugo candida, a reliable procedur e was developed to produce and germinate oospores under controlled env ironmental conditions. Race 2 or race 7 were inoculated into plants of Brassica juncea and B. rapa at the seedling stage to produce oospores in senescent cotyledons, and at the early bud stage to produce oospor es in hypertrophic stems and floral parts (stagheads). Although germin ation of oospores produced in cotyledons was unsuccessful, high percen tage (greater-than-or-equal-to 80%) germination of oospores formed in hypertrophic stems and floral parts was consistently obtained by agita ting oospores for up to 24 h in sterile distilled water containing a 1 -2% mixture of beta-glucuronidase and aryl sulfatase followed by 3 day s of washing on a rotary shaker at room temperature and 15 h of chilli ng at 13-degrees-C. The effectiveness of the enzymes on stimulation of oospore germination depended on stages of oospore maturity. Aging of mature stagheads for 2 weeks increased oospore germination. Chilling w as also a key factor for stimulating oospore germination.