Urmila Dhua

Detection of seedborne Aspergillus flavus from rice cultivars using molecular markers

Aflatoxins are carcinogenic metabolites produced by Aspergillus flavus. Rice seeds may be contaminated by it at the time of harvesting or during storage. Detection of aflatoxigenic strains by TLC and analysis of genetic variability among 50 A. flavus cultures from seeds of various rice genotypes by PCR using 18 RAPD primers is reported here. About 58% isolates were aflatoxigenic whereas 42% were non-toxic. There were 246 bands and 48 haplotypes. Approximately 99% bands were polymorphic, and thus high degree of genetic variability was observed. All the primers were informative with PIC values of range 0.75–0.95. Seventeen RAPD markers were not found to be useful for the detection of aflatoxigenic A. flavus. However, one RAPD primer 3B could differentiate aflatoxigenic and non-toxigenic isolates to some extent. One allele of Primer 3B at approximately 480 bp was present in 85% aflatoxin non-producers and in 6% aflatoxigenic isolates. This information may be utilised for designing markers for differentiating toxic/non-toxic isolates of A. flavus.

Molecular phylogeny of endophytic Dendryphiella: In quest of finding out ancestor of important rice seed Micro-Flora

Thirteen endophytic non sporulating fungi present in healthy seeds of rice cultivars, popular in coastal India, were isolated by ‘host tissue transplant ’method. Those were identified by the molecular technique and phylogenetic analysis by Phylogeny fr software was done. The phylogeny tree of 32 taxa including 27 Dendryphiella species and five Cochliobolus miyabeanus spp. was rendered. There were two major groups. Five Cochliobolus miyabeanus spp. (out group) were together the smaller cluster whereas all the Dendryphiella species with same internal node. The Dendryphiella group was further subdivided in two sub groups where 10 marine Dendryphiella and 17 terrestrial endophytic Dendryphiella grouped in two different sister groups. The high bootstrap values for each subcluster justified their grouping in the proper bunch. This analysis indicated that marine and ‘terrestrial endophytic Dendryphiella ’had common ancestors.