高粱花黑穗病生物学特性及侵染途径研究

 高粱花黑穗病(Ustilago Kenjiana Ito)是我国高粱上发生的一种病害,对产量影响轻微。冬孢子萌发适温是25-30℃,在水滴里萌发率最高,最适pH是6.0-6.5。在不同营养液里以酵母汁及花粉汁里萌发率最高,在人工培养基上病菌生长最适温度是25℃,最适pH是5.9.碳源以葡萄糖、半乳糖、甘露糖和果糖里生长最佳。氮源以蛋白胨和天冬素生长最好.菌瘿黑冬孢子变褐后不经休眠即可萌发。冬孢子在室外可存活一年半,在土壤里经一冬便丧失生活力,室内能存活三年.以冬孢子接种土壤和种子均未发病,属于花器局部侵染,当年侵染当年发病的非系统侵染病害.冬孢子在高粱孕穗或尚未开花的小花护颖与外颖缝隙中侵入子房,而不是在开花期或开花后侵入,也不是从柱头、花柱或其它部位侵入,当年尚能重复侵染.

BIOLOGICAL CHARACTER AND INFECTION OF KERNEL SMUT OF SORGHUM (USTILAGO KENJIANA ITO)

Kernel smut of sorghum caused by Ustilago Kenjiana.It is much less common than other smuts of sorghum.The optimun temperature for teliospore(Chlamydospore) germination is 25-30℃,pH value lies 4.5-9.1 with the obtimum pH6.0-6.5。The germination needs high relative humidity,the highest germination percentage is in water,and sharply decrease below 98.5%.The best nutrient for germination is yeast extract and the pollen extract.The favourable temperature for fungi growth is 25℃,with pH value 5.9.Among 15 carbon source,glucose,galactose,fructose mannitol are the best,among 5 nitrogen sources the best are peptone and asparagine.Under suitable conditions the teliospore may germinate directly without dormancy.The viability of teliospores varies with different storage conditions.It remains for three years in outdoor for more than one and a half year,and less than where one year while in soils.There is no infection cccurred with seed inoculation nor soil inoculation.So it is not the seedling systemic infection.but of local infection limited to individual flowers in an inflorescence,Where the kernel smut gallsformed in current season.The infection cccured during the florescence period but before single flower is in flowering.The germ tubepenetrate through between glumes into the ovary.but not through the stigma,style nor other parts of the flower.The incubation period is 12-13 days,and it can reinfect with the newly matured teliofpores during the growing season.