马铃薯腐烂茎线虫侵入甘薯部位以及在植株内的种群动态

在自然环境条件下,采用人工接种的方式对马铃薯腐烂茎线虫侵入甘薯部位以及在甘薯植株内的种群动态进行研究。结果表明,马铃薯腐烂茎线虫自甘薯秧苗的基部侵入,逐步向上迁移危害。在移栽后4周,线虫仅在地下茎下部3 cm部分危害;移栽后8周,线虫扩展到地下茎接近地面部位;移栽后10周,线虫扩展到地上茎部分;移栽后12周,线虫已转移到新结甘薯块根上危害;但未发现线虫侵入甘薯须根。在装有500 g沙壤土的塑料管中移栽甘薯秧苗,在接种量为每克土壤含1~2头线虫时,24 d后秧苗的发病率为40%,发病指数低于10,60 d后发病率达到100%,病指为20~24,120 d后的病指为52~60;在接种量为每克土壤含16~64头线虫时,24 d后秧苗的发病率为60%~80%,发病指数为20,60 d后发病率为100%,发病指数为40~48,120 d后的发病指数达60~100;在接种量为128~256头/克土时,24 d后的秧苗发病率已达100%,发病指数为20,96 d后其病指高达100。线虫在甘薯内的数量随接种时间的延长呈指数增长趋势。在低剂量接种处理,每克土壤含1~2头线虫时,线虫在移栽60 d以前,秧苗内线虫数量较少,单茎数量在49~56头之间,而此时高剂量接种处理线虫数量已达200头以上。在植株生长后期,其茎内的线虫数量又出现下降趋势。

The Infection and Dynamics of Ditylenchus destructor in Sweet Potato

The penetration and dynamics of Ditylenchus destructor in sweet potato were studied in a natural filed condition with an inoculation method.The results showed that the nematodes penetrated to the seedling from its tip(6 cm deep from soil surface) and then migrated to upside in the seedling.The nematodes could migrate in underground stem closing to ground 8 weeks later.The nematodes reached to the aerial stem of a plant and caused damage 10 weeks after transplanting.The nematodes migrated to the new tuber roots and caused the damage 12 weeks after transplanting,but the nematodes were not extracted from the fiber roots.The nematode dynamics in the sweet plants were determined with a series of inoculation densities.The disease incidences were 40% and disease indexes were 10 in the treatments of 1 g soil containing 1-2 nematodes in 24 d after transplanting (DAT),and disease incidences reached to 100% in 60 DAT,the disease indexes were 52-60 in 120 DAT,while the disease incidences were 60%-80% and disease indexes were 20 in the treatments of 1 g soil containing 16-64 nematodes in 24 DAT,and the disease indexes reached as high as 60-100 in 120 DAT.The disease incidences reached 100% in 24 DAT and disease indexes were 100 in 96 DAT in the highest inoculation densities(256 nematodes per gram soil).Generally,the numbers of nematodes increased in the plants with both of increasing nematode densities and culture times.The numbers of nematode per stem were 49-56 in the treatments of 1 g soil containing 1-2 nematodes in 60 DAT,while its numbers were more than 200 in the treatments 1 g soil containing more than 16 nematodes.The numbers of nematode started to decline in 96 DAT in the treatments of 1 g soil containing more than 2 nematodes.Our studies determined the nematodes penetration site D.destructor to the sweet potato seedling and the linear relation between the numbers of nematode in the soil and disease indexes.Our data provided more information in the selection of control strategy and measure for managing D.destructor in sweet potato.