温度对油菜黑胫病菌(Leptosphaeria biglobosa)假囊壳和子囊孢子发育的影响

Effect of temperature on pseudothecia development of Leptosphaeria biglobosa in oilseed rape(Brassica napus)stubbles

油菜黑胫病是双球小球腔菌(Leptosphaeria biglobosa)引起的一种真菌病害,在油菜产区广泛发生。为了解我国特定气候和栽培条件下的流行规律,通过室内试验和田间试验探讨了温度对罹病油菜茎秆上L.biglobosa假囊壳和子囊孢子发育的影响。室内试验结果表明:在保证环境水分(湿度)充足的条件下,温度影响L.biglobosa假囊壳和子囊孢子的发育进程。在4℃下培养105 d,成熟假囊壳比例仍低于1%,而在10、15、20和25℃下分别培养66.5、57.9、34.5和47.3 d后,成熟假囊壳比例达到50%。可见,10~25℃较4℃更适合L.biglobosa假囊壳和子囊孢子发育。武汉的田间试验结果表明:L.biglobosa越夏后(8月底),在平均气温26℃和平均降雨量为2.7 mm/d的条件下,经过56.3 d成熟假囊壳的比例达到50%。L.biglobosa越秋后(10月底),在平均气温为12℃和平均降雨量为1.5mm/d条件下,仅需28.1 d成熟假囊壳的比例即达到50%。可见秋末冬初的环境条件较夏末秋初更加适合L.biglobosa假囊壳和子囊孢子发育。研究结果还表明:L.biglobosa子囊孢子在水琼脂培养基上培养2 h后(20℃)萌发率达到100%,萌发方式是两端细胞先萌发,中间细胞后萌发,子囊孢子能直接侵染油菜子叶,引起坏死病斑。

Blackleg of oilseed rape is caused by ascomycetous fungus Leptosphaeria biglobosa.To better understand the life cycle and epidemiological characteristics in China,temperature effects were studied on development of pseudothecia and ascospores of L.biglobosa in oilseed rape stubbles by induction of pseudothecia formation under constant temperatures from 4 to 25℃in indoor experiment,and under fluctuated temperatures in field experiment.Indoor results showed that temperatures(ranging from 4 to 25℃)greatly affected maturation of pseudothecia and ascospores of L.biglobosa.At 4℃,the percentage of mature pseudothecia was lower than 1%after incubation for 105 d.However,under 10,15,20 and 25℃,50%pseudothecia matured after incubation for 66.5,57.9,34.5 and 47.3 d,respectively.It suggested that L.biglobosa was more adapted to 10 to 25℃than to 4℃for the development of pseudothecia and ascospores.Field results in Wuhan showed that over the summer(at the end of August),half of pseudothecia matured after 56.3 d under26℃(on average)with 2.7 mm/d rainfall.After autumn,half of pseudothecia of L.biglobosa matured after 28.1 d at 12℃(on average)with 1.5 mm/d rainfall.L.biglobosa appeared to be more adapted to the weather conditions in autumn-winter than to that in summer-autumn in Wuhan.Results also showed that ascospores of L.biglobosa germinated rapidly at 20℃on water agar and 100%ascospores germinated in 2 h.The ascospore germination started in the terminal cells,followed by the internal cells.Ascospores of L.biglobosa could directly infect the intact cotyledons of roilseed rape,and form necrotic lesions.