甘蔗新品种(系)苗期白条病人工接种抗性鉴定与评价

Identification of resistance to leaf scald in newly released sugarcane varieties at seedling stage by artificial inoculation

由白条黄单胞杆菌(Xanthomonas albilineans)引起的甘蔗白条病是甘蔗生产中的重要细菌性病害之一,选用抗病品种是甘蔗白条病防控最经济、最有效的措施。为明确国内甘蔗新品种(系)对白条病菌的抗性水平,本研究选用抗白条病品种LCP 85-384和感白条病品种新台糖20号为对照种,对我国各育种单位新选育的49个甘蔗新品种(系)进行苗期人工接种抗白条病鉴定。研究结果显示,从白条病菌Xa-FJ1菌液接种后第7天开始,随着时间的推移,甘蔗品种白条病病情指数不断提高,到接种后21~28 d时,各品系的病情指数进入平稳增长时期。对接种后的病叶进行病原菌分离和叶片总DNA的提取,利用甘蔗白条病菌特异性引物XAF1/XAR1进行PCR检测和鉴定,结果证实白条病菌Xa-FJ1通过人工接种方式成功侵染供试材料。基于病情指数评价甘蔗抗病性水平,将51份供试材料划分为抗、中抗、感、高感4个不同抗病等级。抗病至中抗水平的品种(系)有19份,占37.3%,其中抗病等级只有3份,分别为粤甘50、福农09-7111和中蔗10号;感病至高感水平的品种(系)有32份,占62.7%。上述抗性鉴定结果表明,本研究参试国内新选育的甘蔗品种(系)苗期对白条病的抗性水平没有达到高抗的品种(系),建议加强甘蔗白条病抗病基因资源的挖掘和利用。

Sugarcane leaf scald caused by the pathogen of Xanthomonas albilineans is one of important bacterial diseases.The utilization of sugarcane resistant varieties is the most economical and effective measure for control of this disease.In this study,to identify the level of resistance to leaf scald for domestic sugarcane varieties,a total of 49 newly-released sugarcane varieties from different sugarcane breeding institutions in China were identified upon 3–5 fully expanding leaf stage by artificial inoculation with Xa-FJ1 strain.The leaf scald resistant variety LCP 85-384 and the leaf scald susceptible variety ROC20 were used as controls.Our results indicated that the disease indexes of these varieties were continually increased from the 7th day post-inoculation(dpi),while the disease indexes reached a steady plateau at 21–28 dpi.These re-isolated pathogenic bacteria in leaf tissues of the inoculated plants were detected by PCR assay with the XAF1/XAR1 primers specific to X.albilineans.PCR results confirmed that the pathogen Xa-FJ1 was successfully infected with all the tested varieties after inoculation.Based on the disease indexes,51 sugarcane varieties were divided into four different groups,resistant,medium resistant,susceptible,and high susceptible grades.Of all the tested varieties,37.3%(19/51)varieties were resistant or medium resistant to leaf scald,among which only three varieties(Yuegan 50,Funong 09-7111,and Zhongzhe 10)reached resistant levels.Meanwhile,62.7%(32/51)varieties were susceptible or highly susceptible to leaf scald.Our results revealed the lack of high resistance germplasms in the newly released varieties in China,and it is urgent to create more germplasm resources resistant to leaf scald.