Integrated management of aflatoxin B₁ contamination of groundnut (Arachis hypogaea L.) with Burkholderia sp. and zimmu (Allium sativum L. × Allium cepa L.) intercropping

The efficacy of intercropping of the medicinal plant zimmu (Allium sativum L. × Allium cepa L.) and an antagonistic bacterium Burkholderia sp. strain TNAU-1 was evaluated separately and in combination for control of Aspergillus flavus infection and aflatoxin B₁ contamination in groundnut (Arachis hypogaea L.) under field conditions. The Burkholderia sp. strain TNAU-1 inhibited the growth of all the toxigenic and non-toxigenic isolates of A. flavus in vitro and the inhibition zone ranged from 3.1-11.3 mm. A talc-based powder formulation of the Burkholderia sp was developed for field application. When groundnut seeds were treated with the formulation of Burkholderia sp., significant increases in root length, shoot length and seedling vigor were observed. Zimmu intercropping (once in every three rows of groundnut) alone significantly reduced the A. flavus infection and aflatoxin contamination in groundnut. Seed treatment at 10 g/kg or soil application at 2.5 kg/ha on 30, 45, 60 days after sowing with the formulation of Burkholderia sp. also resulted in significant reduction in the infection by A. flavus and aflatoxin B₁ contamination in kernels. The maximum percentage reduction in aflatoxin B₁ content was achieved by the combination of zimmu intercropping, seed treatment and soil application of Burkholderia sp. Seed treatment followed by soil application with the formulation of Burkholderia sp. Recorded the highest pod yield in both the field trials. Zimmu intercropping or seed treatment or soil application with formulation of Burkholderia sp. significantly reduced the population of A. flavus in the soil. Application of Burkholderia sp. through seed or soil resulted in high colonization of Burkholderia sp. in rhizosphere soil, and the rhizosphere population increased with increase in the age of the crop. A colony PCR assay was developed using primers made to Burkholderia sp. specific sequence of the ribosomal DNA for accurate detection and confirmation of Burkholderia sp.