Development of Pathogenicity and <scp>AFLP</scp> to Characterize <i>Fusarium oxysporum</i> f.sp. <i>momordicae</i> Isolates from Bitter Gourd in China

Abstract

Abstract Bitter gourd ( M omordica charantia L.) cultivated in C hina is regarded as an important vegetable crop and is of considerable economic importance. However, it is susceptible to fusarium wilt, which causes heavy economic losses. Forty‐eight isolates were isolated from diseased bitter gourd plants that displayed typical fusarium wilt symptoms. Based on the morphological features, the r DNA internal transcribed space ( ITS ) sequences, pathogenicity and host biotypes, all of the isolates tested were pathogenic to the susceptible bitter gourd plants species (cv. ‘ G uinongke No. 2’) and were identified as F usarium oxysporum f. sp . momordicae ( FOM ). Our results classified different isolates as slightly, moderately or highly virulent. Among the isolates tested, 43 isolates slightly infected bottle gourd ( L agenaria siceraria var. clavata ), whereas they did not infect other species from the family C ucurbitaceae . Genetic diversity among 48 isolates was characterized using amplified fragment length polymorphism ( AFLP ) analysis. The number of bands amplified by each primer pairs ranged from 41 to 66, with sizes ranging from 200 to 500 bp. A total of 366 bands were observed, out of which 363 were polymorphic (99.14%). The N ei's genetic identity of the six geographical populations varied from 0.7362 to 0.9707. The mean N ei's gene diversity index ( H = 0.2644) and the mean S hannon's information index ( I = 0.4071) at species level were higher than ones at populations level, indicated that the variation within populations was greater than that among populations. The N ei's GST (0.5103) and gene flow ( N m = 0.4923) revealed that genetic differentiation was mainly among populations and few gene exchanges. The dendrogram obtained from AFLP marker showed that there was a good correlation between isolates from different geographical locations and their pathogenicity. The AFLP marker effectively distinguished the high virulent isolates from the less virulent isolates. The highly virulent isolates were distinctly separated in different clusters, which indicated a significantly high correlation with the geographical origin in the AFLP dendrogram. The pathogenicity and molecular marker analysis confirmed the presence of variation in virulence as well as genetic diversity among the FOM isolates studied.