Molecular and biochemical characterization of soil isolates of <em>Aspergillus niger</em> aggregate and an assessment of their antagonism against <em>Rhizoctonia solani</em>

Abstract

Sixteen Aspergillus niger aggregate isolates collected from different crop fi elds were subjected to RAPDPCR using 20 Operon primers and 8 synthetic primers. Twenty-two primers led to the amplifi cation of 727 fragments ranging from 3500 bp (OPA 11) to 200 bp (primer 06). Two bands were monomorphic, while the rest were polymorphic. Three amplicons produced by OPA 16 were recorded as isolate-specifi c as 2300 bp by AnC2 and AnR3, and as 2800 bp by AnC2 only. The highest genetic similarity (0.79) was measured between AnC2 and AnR3, and the lowest (0.17) between AnC2 and AnR2. Multivariate analysis of genetic similarity revealed three major clusters, named group I, group II and group III. All isolates were ochratoxin A negative (<1 ng g-1). Isolates AnC2 and AnR3, which produced HCN and solubilized the greatest amount of phosphorus, belonged to group I. These isolates also signifi cantly increased eggplant yield and caused the greatest inhibition of colonization by R. solani in dual culture. They also suppressed the root rot on eggplant and the soil population of R. solani in pot soil.