水直播条件下黑龙江省不同稻区稻瘟病菌致病性分析

为明确水直播条件下黑龙江省不同稻区稻瘟病菌Magnaporthe oryzae的致病性分化情况，以24个抗瘟单基因系品种为寄主，来源于2017—2018年黑龙江省水直播稻田的242株稻瘟病菌菌株为接种体，采用离体划伤方法接种，记录病斑反应型，计算有效致病菌株率和抗性频率，并进行聚类分析。结果显示，在水直播条件下，2017年，黑龙江省南部和中东部稻区稻瘟病菌菌株对抗瘟单基因系品种的有效致病菌株率介于8.33%~95.83%和20.83%~95.83%之间，无毒基因出现频率分别为575次和622次；2018年，南部和中东部稻区稻瘟病菌菌株对鉴别体系的有效致病菌株率介于29.17%~95.83%和20.83%~91.67%之间，无毒基因出现频率分别为536次和571次。2017年，黑龙江省南部和中东部稻区稻瘟病菌菌株的致病性相似系数介于0.15~1.00和0.14~1.00之间，以致病性相似系数0.40为阈值，可将菌株分别划分为5个类群和6个类群；2018年，南部和中东部稻区菌株的致病性相似系数介于0.15~0.93和0.26~1.00之间，以致病性相似系数0.40为阈值，可将菌株分别划分为5个类群和4个类群。2017年，抗瘟单基因系品种对黑龙江省南部和中东部稻区稻瘟病菌菌株的抗性频率介于11.29%~88.71%和10.77%~86.15%之间，其中抗瘟单基因系品种IRBL9-W（Pi-9）和IRBLz5-CA（Pi-z5）抗性表现最好；2018年，抗瘟单基因系品种对南部和中东部稻区菌株的抗性频率介于10.34%~82.67%和15.79%~85.96%之间，其中抗瘟单基因系品种IRBL9-W（Pi-9）和IRBLz5-CA（Pi-z5）抗性表现最好。表明水直播条件下黑龙江省稻瘟病菌致病性分化剧烈，稻瘟病菌整体致病力较强，但仍有部分水稻种质抗性较好且相对稳定，基因聚合后抗性会得到进一步提升。

Pathogenicity of Magnaporthe oryzae from different rice growing regions of Heilongjiang Province under water direct seeding

In order to clarify the pathogenicity of Magnaporthe oryzae from different rice growing regions of Heilongjiang Province under water direct seeding, the 24 blast-resistance of monogenic rice lines were inoculated with 242 M. oryzae isolates in 2017-2018 with the method of scratch in vitro, the reaction type of disease spot was recorded, the disease incidence of M. oryzae isolates and the resistance frequencies of blast-resistance of monogenic rice lines were calculated, the cluster analysis were conducted. The results showed that the disease incidence of M. oryzae isolates from southern and east-central rice growing regions of Heilongjiang Province under water direct seeding were 8.33%-95.83% and 20.83%-95.83%, respectively, and the occurrence frequency of avirulence genes were 575 and 622 times in 2017, respectively. The disease incidence of M. oryzae isolates from southern and east-central rice growing regions of Heilongjiang Province under water direct seeding were 29.17%-95.83% and 20.83%-91.67%, respectively, and the occurrence frequencies of avirulence genes were 536 and 571 times in 2018, respectively. The similarity coefficient of M. oryzae isolates from southern and east-central rice growing regions of Heilongjiang Province were 0.15-1.00 and 0.14-1.00, respectively, and the M. oryzae isolates were divided into five and six pathogenicity groups in the level of 0.40 similarity coefficient in 2017, respectively. The similarity coefficient of M. oryzae isolates from southern and east-central rice growing regions of Heilongjiang Province were 0.15-0.93 and 0.26-1.00, respectively, and the M. oryzae isolates were divided into five and four pathogenicity groups in the level of 0.40 similarity coefficient in 2018. The reference frequencies of blast-resistance of monogenic rice lines to M. oryzae isolates from southern and east-central rice growing regions of Heilongjiang Province were 11.29%-88.71% and 10.77%-86.15%, the best blast-resistance of monogenic rice lines were IRBL9-W (Pi-9) and IRBLz5-CA (Pi-z5) in 2017, respectively. The reference frequencies of blast-resistance of monogenic rice lines to M. oryzae isolates from southern and east-central rice growing regions of Heilongjiang Province were 10.34%-82.67% and 15.79%-85.96%, furthermore, the best blast-resistance of monogenic rice lines were IRBL9-W (Pi-9) and IRBLz5-CA (Pi-z5) in 2018. The results indicated that the pathogenicity differentiation of M. oryzae isolates were intense, and the pathogenicity of M. oryzae isolates was stronger, but some high-resistance rice germplasm was stable resistance and the blast-resistance will be improved after gene pyramiding to M. oryzae isolates.