The Population Genetic Variation Analysis of Bitter Gourd Wilt Caused byFusarium oxysporumf. sp.momordicaein China by Inter Simple Sequence Repeats (ISSR) Molecular Marker

Abstract

Abstract： The bitter gourd fusarium wilt caused by Fusarium oxysporum f.sp. momordicae 11 (FOM) was a devastating disease in China and leading to great economic losses every year. A total 12 of 152 isolates, which have the typical Fusarium oxysporum characteristics with abundant 13 microconidia and macroconidia on the white or ruby colonies, were obtained from diseased plant 14 tissues with typical fusarium wilt symptoms. The BLASTn analysis of rDNA-ITS showed 99% 15 identity with F. oxysporum species. Among the tested isolates, three isolates infected tower 16 gourd, and five isolates were pathogenic to bottle gourd. However, they were all pathogenic to 17 bitter gourd. Based on the molecular and morphologic results, the isolates were identified as FOM. 18 For genetic variation analysis, forty ISSR primers were screened and eleven primers were used in 19 PCR amplification. Totally, 121 loci were detected, of which 52 loci were polymorphic at rate of 20 42.98%. The POPGENE analysis showed that Nei's gene diversity index (H) and Shannon's 21 information index (I) were 0.0902 and 0.1478, respectively, which indicated that the genetic 22 diversity for the tested 152 isolates was relatively low. It also means that each geographical 23 population was a relatively independent unit. While the value of coefficient of gene differentiation 24 (Gst=0.4929 > 0.15) pointed to the genetic differentiation was mainly among populations. The 25 strength of gene flow (Nm=0.5143<1.0) was weaker, indicating that gene exchanges were blocked 26to some degree. The dendrogram based on ISSR markers showed that the eight geographical 27 populations were clustered into four groups at the threshold of genetic similar coefficient 0.96. 28Fujian, Jiangxi and Guangdong populations were clustered into GroupⅠ. Group Ⅱ contained 16We are grateful to Dr. Zhengdong Chen for their tremendous efforts in sample collection. We

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“…This result is also con rmed by the Gst value (diversity among populations). Zang et al (2018) proposed that Gst is an important parameter to measure whether genetic differentiation exists among populations. When the Gst value falls between 0.05 and 0.15, the genetic differentiation is considered as the medium.…”