野生和栽培茭白二化螟感病率与微生物多样性分析

Morbidity of Chilo suppressalis in Wild and Cultivated Water Oat(Zizania latifolia)and Microorganism Diversity in Dead Insects

为了明确茭白二化螟的感病死亡率以及携带的优势微生物种类,本文在野生茭白和栽培茭白中共采集二化螟越冬幼虫6000余头,发现二化螟的感病死亡率分别为19.98%和17.00%,二者之间没有显著差异,表明栽培措施没有影响昆虫病原菌的流行。采用18S rRNA和16S rRNA测序方法对死虫标本中的真菌和细菌组成和丰度进行了研究,结果表明95%以上个体的优势真菌为白僵菌,相对丰度在90%以上,没有检出绿僵菌;优势细菌科为肠杆菌科、肠球菌科、根瘤菌科和丛毛单胞菌科,丰度分别为19.37%、17.37%、7.04%和5.04%,含昆虫病原细菌的芽胞杆菌科和梭菌科细菌的丰度只有1.44%和0.41%,表明细菌不是致死的主要原因。本研究证明白僵菌是越冬期茭白二化螟的优势病原菌。因此,在茭白田中开展以菌治虫首选使用白僵菌。

Water oat Zizania latifolia is an aquatic vegetable in China,with high nutritional value and good taste.In recent years,the vegetable has been cultivated increasingly.However,water oat is susceptible to insect pests among which Chilo suppressalis is one of the most serious.Insect pathogens are effective biological control agents of pest insects.In order to find effective insect pathogens that prevail in water oat field,6039 overwintering C.suppressalis larvae were collected from wild and cultivated water oat,and were observed for the mortality due to insect pathogens,which revealed no difference in pathogenic mortality of 19.98%in wild water oat and of 17.00%in cultivated water oat,indicating that farming practices do not affect the prevailing of insect pathogens.Microorganism community in the dead specimens(>1000)were identified by high-throughput sequencing of 18S rRNA and 16S rRNA gene.Results showed that 96.67%of dead specimens from wild water oat were predominated by Beauveria fungi,and 100%of dead specimens from cultivated water oat were predominated by this genus.Except for one sample,the abundance of Beauveria in each specimen was more than 90%.Metarhizium fungi were not detected in any of the specimens.Enterobacteriaceae,Rhizobiaceae,Enterococcaceae and Comamonadaceae were the top four bacteria family with abundances of 19.37%,17.37%,7.04%and 5.04%,respectively.Insect pathogenic bacteria were seldom reported in those four dominant families.Bacillaceae and Clostridiaceae that most likely contain insect pathogenic bacteria were only 1.44%and 0.41%in abundance.This study shows that biocontrol agent against C.suppressalis in water oat field.