掘氏疫霉卵孢子萌发研究

ON THE GERMINATION OF OOSPORES OF PHYTOPHTHORA DRECHSLERI

掘氏疫霉(Phytophthora drechsleri)种内菌株直接交配产生的卵孢子分别用0.1%KMnO_4处理20分钟和0.3%H_2O_2处理2分钟在S+L培养基上(26℃)培养7天萌发率>70%。H_2O_2是本研究首次报道的一种刺激掘氏疫霉卵孢子萌发的处理剂,其效果略优于KMnO_4。用KMnO_4和H_2O_2处理均可有效地抑制卵孢子悬浮液中菌丝片段及菌丝膨大体的萌发生长。在一定时期内卵孢子萌发率随卵孢子保存时间的增加而增加,保存30天和45天的卵孢子分别用KMnO_4和H_2O_2处理萌发率最高。卵孢子保存期间有无光照对萌发率无显著影响,但卵孢子荫发时给予光照对萌发有明显的促进作用,保存30天的卵孢子在光照下萌发率为60—70%,在黑暗中仅0—16%。卵孢子萌发过程中的光照条件以黑光灯8小时,日光灯16小时交替连续照射7天效果最好,其次为黑光灯单独连续光照,以日光灯单独照射效果较差。所测定的6种培养基中以S+L培养基对卵孢子萌发的效果最好,其次为V_(?)+L和WA+L。蜗牛酶、纤维素酶、土壤浸出液和黄瓜果提取液对掘氏疫霉卵孢子萌发无明显刺激作用。

Oospores from the crosses of intraspecific isolates of Phytophthora drechsleri were treated with 0.1% KMnO_4for 20 min.and 0.3% H_2O_2 for 2 min. respectively and incubated on S+L medium at 26℃ for germination, more than 70% oospores germinated after 7 days by continuously exposing oospores to black light for 8 hr and fluoresent light for 18hr alternately.H_2O_2 was a new effective agent for stimulation the oospore germination of Phytophthora drechsleri,Higher germination rates were obtained from oospores treated with H_2O_2 than that with KMnO_4.Treated with KMnO_4 and H_2O_2 also prevented the germination of residual mycelial fragments and hyphal swellings in oospore suspension. Germination rate of oospores increased with the age of culture, reaching about 70% at 30-day-old when treated with KMnO_4 and 77% at 45-day-old with H_2O_2. Illumination was not essential during oospore storage for maturation. The-germination rates of oospores were prominently enhanced when light was supplied during oospore germination on S+L medium, the germination rates reaching about 60-70% when oospores at the age of 30 days under light and only 0-16% when light was omitted. The best illumination condition for oospore germination was black light and fluoresent light alternately,followed by mono-illumination with black light. The best medium for oospore germination tested was S+L medium. Lecithin was effective for oospore germination of P. drechsleri. No prominent stimulation to oospore germination of P, drechsleri was observed when oospores treated with snailase, cellulase as well as soil and cucumber fruit extracts.