| Sclerotinia stem rot of oilseed rape (SSR) is one of the most common fungal disease of rapeseed with losses of 10%-30% frequently reported. In these years, losses caused by SSR in this area have increased because of the lightened and simpilfied cultivation(LSC). There are no sclerotinia-resistant rape varieties and control is reliant on use of fungicides which have been known to have adverse effects on food. Therefore, the concerns about pesticide residues have prompted interest in agricultural measures and biological control. In order to characterize epidemics of SSR in field and evaluate the efficacy of Coniothyrium minitans in two types fields (cotton-rapeseed succession fields and rice-rapeseed succession fields) in Hubei province under LSC, we investigated the occurrence of SSR in fields, efficacy of C. minitans in suppression of SSR.Firstly, the survival of sclerotinia in different depth of soil in the indoor test simulation was studied. The results showed the sclerotinias were buried in the depth of 1-9cm have 100% survival for 18 consecutive months. The sclerotinias survived 20 days under flooded condition in indoor in autumn, survived 45 days under flooded condition in indoor in winter. The occurrence of SSR in field was investigated during 2008-2010 growing seasons in Wuxue County and Huanggang County. In cotton-rapeseed succession fields, the number of apothecia was generally higher than in rice-rape succession fields, and the subsequent disease severity on leaf and stem was obviously higher except Huanggang County in 2009.The study demonstrated that apothecia in cotton-rapeseed succession fields was appeared in early March, peak time was in late march or early April. The occurrence of SSR had no obvious difference with above two types of fields. Disease appeared on leaf in fields in mid-March, disease appeared on stem in end of March or early April. The correlation analysis between disease incidence and 5 climatic factors (daily minimum temperature, maximum temperature, daily average temperature, daily rainfall and rainy days) during the blooming period showed that there was no statistic difference (P＜0.05).Laboratory tests showed disease suppression on leaf and stem with applications of C. minitans at 107 conidia/ml was 60%,68.8%respectively. Inhibitory effect on sclerotinia germination with applications of C. minitans at 106 conidia/ml was obviously. But with increasing concentration of the sclerotinia, inhibitory effect was decreased. The field studies indicated that with increased spore concentrations of C. minitans (C. minitans at concentrations of 105,106, or 107 conidia/ml), efficacy was increased in the both types of succession fields. Efficacy of C. minitans at concentrations of 105 conidia/ml was significantly lower than that of 106, or 107 conidia/ml in most conditions (P<0.05). Efficacy of C. minitans between 105 conidia/ml and 106 conidia/ml has not significant difference (P<0.05). There was at least one efficacy between 106 conidia/ml and 107 conidia/ml has not significant difference with fungicide or be significantly higer than fungicide (P<0.05).In demonstration field trials (2008-2010), control effect by C. minitans sprayed in seedling stage at concentrations of 106 to 107 conidia/ml was not good, mean disease index control effect was 12.8%, mean disease incidence effect was 0. Efficacy of C. minitans at 106conidia/ml-107 conidia/ml sprayed at early bloom was much better. The level of control effect in all demonstration field trials was 2 or 3 level.Based on the results of this studys, paddy-upland rotation can reduce SSR, Coniothyrium minitans was an effective antagonist and biocontrol agent of the plant pathogen Sclerotinia sclerotiorum.
|
PDF Full Text Request