Genetic diversity and structure of the Fusarium oxysporum f.sp lini populations on linseed (Linum usitatissimum) in China

The genetic diversity of specific Fusarium oxysporum f.sp. lini from six provinces in China was investigated using molecular markers, inter-simple sequence repeats (ISSR). Based on the morphological features and the internal transcribed spacer (ITS) sequences, 96 isolates were identified as Fusarium oxysporum. The 96 isolates were amplified by PCR with 12 ISSR primers. The number of bands amplified by each primer ranged from 43 to 142, with sizes ranging from 250 to 4,500 bp. A total of 800 bands were observed, out of which 797 were polymorphic (99.62%). The percentage of polymorphic loci varied from 17.25% in Gansu and Inner Mongolia to 33.75% in Sinkiang. Nei's gene diversity index (h) ranged from 0.0428 in Gansu to 0.0666 in Sinkiang, and Shannon's information index (I) ranged from 0.0675 in Gansu to 0.1117 in Sinkiang. The genetic identity using the Nei's genetic identity varied from 0.9643 between the populations from Hebei and Gansu to 0.9844 between the populations from Sinkiang and Shanxi. Unweighted pair group mean analysis (UPGMA) cluster analysis, as indicated by the Nei's genetic distance, showed the distances ranging from 0.0158 between the populations from Sinkiang and Shanxi to 0.0364 between the populations from Hebei and Gansu. The six populations were clustered into three subgroups. The Gansu population was clustered into one subgroup, the same as the Inner Mongolia population. The four other populations were clustered into the third subgroup. The Nei's GST (0.2972) and gene flow among populations (Nm =1.1825) revealed large gene exchanges among populations.