Molecular Diversity of Seed-borne Fusarium Species Associated with Maize in India

Abstract

A total of 106 maize seed samples were collected from different agro-climatic regions of India. Sixty-two Fusarium isolates were recovered, 90% of which were identified as Fusarium verticillioides based on morphological and molecular characters. Use of the tef-1α gene corrected/refined the morphological species identifications of 11 isolates, and confirmed those of the remaining isolates. Genetic diversity among the Fusarium isolates involved multilocus fingerprinting profiles by Inter Simple Sequence Repeats (ISSR) UPGMA and tef-1α gene phenetic analyses; for which, we observed no significant differences among the isolates based on geographic origin or fumonisin production; most of the subdivision related to species. Genotyping was performed on the F. verticillioides isolates, using 12 primer sets from the fumonisin pathway, to elucidate the molec-ular basis of fumonisin production or non-production. One fumonisin-negative isolate, UOMMF-16, was unable to amplify nine of the 12 fumonisin cluster genes tested. We also used the CD-ELISA method to confirm fumonisin production for our 62 Fusarium isolates. Only 15 isolates were found to be fumonisin-negative. Interestingly, genotypic characterization re-vealed six isolates with various gene deletion patterns that also tested positive for the production of fumonisins via CD-ELISA. Our findings confirm the importance of molecular studies for species delimitation, and for observing genetic and phenotypic diversity, among the Fusaria.

Keywords: CD-ELISA.; Fumonisin gene cluster; Fusarium; Inter simple sequence repeats; Maize; tef-1α gene.

Fig. (1)

Phylogenetic tree inferred using tef-1α sequences from 62 Fusarium isolates sampled across different geographical locations in India. A sequence for an F. redolens strain (AY714109.1), downloaded from GenBank, was used as the out-group species.

Fig. (2)

An inferred UPGMA dendrogram based on DICE similarity estimates from the ISSR marker analysis of 62 Fusarium isolates. Species other than F. verticillioides are shown with thickened branches and noted to the right of the UOMMF number. Geographic origins for the sampled isolates are color-coded.