Study On Biological Characteristics Of Leptosphaeria Biglobosa In Oilseed Rape

Blackleg is one of the important diseases in the rapeseed production. This disease is relatively serious in the United States, Australia, Canada, Europe and other places. Pathogens of blackleg have two species:strong pathogenicity(Leptosphaeria maculans) and weak pathogenicity(Leptosphaeria biglobosa). In this study strains collected from different provinces were identified through ITS analysis to determine the type of blackleg strain in our country. Temperature, humidity, illumination time, different carbon and nitrogen sources and different rape varieties leaf juice which could influence L. biglobosa conidium germination were tested, providing theoretical basis for prevention and control of rape blackleg. Five defense enzymes peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), polyphenol oxidase (PPO) and phenylalanine ammonia enzyme (PAL) of different resistant varieties changed after infected by L. biglobosa, which revealed plant physiological and biochemical aspects of the defense mechanism. Detailed results were as follows:1. The sequences of19strains were analyzed. They had high sequence homology with the known strains of L. biglobosa, showing that the strains in our country belonged to Leptosphaeria. The19strains were identified as weak type L. biglobosa.2. The temperature, moisture and illumination time had different influences on conidium germination of blackleg fungus. Temperature, moisture and illumination time were positively correlated with conidium germination rate. Temperature which was from21to27℃and moisturizing time which was more than24h and illumination time which was more than12h were conducive to conidium germination.3. Different carbon and nitrogen sources and different rapeseed varieties leaf juice had different influences on conidium germination of blackleg fungus. The glucose and soluble starch as carbon source were beneficial to conidium germination. Maltose and fructose inhibited conidium germination and fructose was the last one suitable as carbon source. Calcium nitrate as the nitrogen source was conducive to conidium germination, with sodium nitrate and ammonium chloride coming second, and urea had strong inhibition for conidium germination. Relatively speaking, nitrate nitrogen was in favor of the germination of the conidia than ammonium nitrogen. Based on the results of different varieties leaf juice to cultivate blackleg pathogen, we speculated that Qingza2and Dehezayou8were relatively resistant to L. biglobosa; and Ganliangyou2, Huashuang5, Chuheza1and Qingyou14were weakly resistant. To further determine the varieties’ resistance requires pathogenicity determination.4. Rapeseed plants were infected by blackleg fungus, to some extent the activity of PAL and PPO increased. The enzyme activity of resistant varieties Shibao and Qingza2increased more than the activity of susceptible cultivar Drakka, showing that the resistance to blackleg had a direct relationship with the activity of the PAL and PPO, and the activity of PAL and PPO of disease-resistant varieties was high. The activity of POD and CAT of resistant varieties Shibao, Qingza4and susceptible cultivar Drakka increased. The enzyme activity of Shibao and Qingza4were significantly higher than that of Drakka’s, showing that the resistance to blackleg had a direct relationship with the activity of the POD, CAT and SOD, and the activity of POD, CAT and SOD of resistant varieties was high.