西瓜专化型尖孢镰刀菌的分离鉴定及水稻根系分泌物对其生长的影响

利用尖孢镰刀菌选择性培养基从西瓜枯萎病发病部位分离出病原菌，通过Booth＇s镰刀菌分类鉴定标准和专化型试验，确定该菌株为西瓜专化型尖孢镰刀菌（Fusarium oxysporum f．sp．niveum）。以该菌株为材料，研究水稻根系分泌物对其生长的影响。结果表明，2个水稻品种ELIO和4007的根系分泌物均能显著抑制其孢子萌发和孢子产生。当根系分泌物的加入量为1．5mL时，ELIO和4007对孢子萌发的抑制率分别为37．8％和41．0％；当加入20mL水稻根系分泌物时，ELIO和4007对孢子产生的抑制率达到96．3％和76．4％。水稻根系分泌物对西瓜尖孢镰刀菌孢子产生过程的抑制作用主要发生在孢子萌发阶段和孢子在尖孢镰刀菌瓶状小梗上的生成阶段，而对菌丝营养生长没有影响。西瓜与旱作水稻间作的盆栽试验表明，间作系统中西瓜苗的鲜重和株高分别提高了186．0％和80．5％。单作西瓜枯萎病发病率为66．7％，死亡率为44．4％，而间作处理中西瓜均生长正常。间作条件下，西瓜根际土壤中的尖孢镰刀菌数量显著降低，与单作根际土壤相比减少了91％。表明：水稻根系分泌物能显著抑制西瓜专化型尖孢镰刀菌生长，采用旱作水稻与西瓜间作能有效缓解西瓜枯萎病的发生。

Identification of the Fusarium oxysporum f.sp.niveum and the effects of rice root exudates on its growth

The pathogen of wilt disease was isolated from the infected watermelon plants using selective medium. According to the symptoms, morphology and pathogenicity, the pathogen was identified as Fusariurn oxysporum f. sp. niveum. Rice root exudates of both ELIO and 4007 were collected to investigate the effects of them on the spore development of F. oxysporum f. sp. niveum. The absolute value of influence ratio to spore germination of F. oxysporum f. sp. niveurn was 37. 8% and 41.0%, with adding 1.5 mL root exudates of ELIO and 4007, respectively. The absolute value of influence ratio to F. oxysporum f. sp. niveurn reproduction reached 96. 3% and 76. 4%, with adding 20 mL root exudates of ELIO and 4007, respectively. Pot experiments were carried out to investigate the effect of intercropping with aerobic rice on Fusariurn wilt in watermelon. The results showed that fresh weight and plant height of watermelon seedlings increased by 186.0% and 80. 5% in intercropping system, respectively, compared with those in mono-cropping system. 66. 7% of watermelon were infected with wilt disease and 44. 4% died after 40 days of transplanting in mono-cropped soil, but those were normally grown in intercropping system. The density of F. oxysporum decreased 91% in intercropped rhizosphere soil compared with mono-cropped soil after 40 days of transplanting. It is suggested that intercropping with aerobic rice alleviated Fusariurn wilt in watermelon, by restraining the spore reproduction and spore germination of F. oxysporum f. sp. niveum through the production of rice root exudates.