Metabolomic profiling and its association with the bio-efficacy of Aspergillus niger strain against Fusarium wilt of guava

Bio-control agents are the best alternative to chemicals for the successful management of plant diseases. The fungus Aspergillus niger is known to produce diverse metabolites with antifungal activity, attracting researchers to exploit it as a bio-control agent for plant disease control. In the present study, 11 A. niger strains were isolated and screened for their antagonism against the guava wilt pathogen under in vitro and in planta conditions. Strains were identified morphologically and molecularly by sequencing the internal transcribed spacer (ITS), β-tubulin, and calmodulin genes. The strains were evaluated through dual culture, volatile, and non-volatile methods under an in vitro study. AN-11, AN-6, and AN-2 inhibited the test pathogen Fusarium oxysporum f. sp. psidii (FOP) at 67.16%, 64.01%, and 60.48%, respectively. An in planta study was conducted under greenhouse conditions with 6 months old air-layered guava plants (var. Allahabad Safeda) by pre- and post-inoculation of FOP. The AN-11 strain was found to be effective under both pre- and post-inoculation trials. Furthermore, gas chromatography–mass spectrometry (GC–MS) analysis was carried out to characterize the volatile compounds of the most potential strain, A. niger. The hexane soluble fraction showed the appearance of characteristic peaks of hexadecenoic acid methyl ester (4.41%), 10-octadecanoic acid methyl ester (3.79%), dodecane (3.21%), undecane (3.19%), gibepyrone A (0.15%), 3-methylundecane (0.36%), and citroflex A (0.38%). The ethyl acetate fraction of the bio-control fungi revealed the occurrence of major antifungal compounds, such as acetic acid ethyl ester (17.32%), benzopyron-4-ol (12.17%), 1,2,6-hexanetriol (7.16%), 2-propenoic acid ethanediyl ester (2.95%), 1-(3-ethyloxiranyl)-ethenone (0.98%), 6-acetyl-8-methoxy dimethyl chromene (0.96%), 4-hexyl-2,5-dihydro dioxo furan acetic acid (0.19%), and octadecanoic acid (1.11%). Furthermore, bio-control abilities could be due to hyper-parasitism, the production of secondary metabolites, and competition for sites and nutrients. Indeed, the results will enrich the existing knowledge of metabolomic information and support perspectives on the bio-control mechanism of A. niger

A multigene phylogeny reveals the occurrence of fourteen dominant Penicillium species in India

168-181Penicillium contains 483 accepted species worldwide but the occurrence of predominant species in India is still unknown. Therefore, 35 isolates of 15 different states of India were procured from Indian Type Culture Collection (ITCC), New Delhi. All these isolates were made into eight species of Penicillium viz., “P. aethiopium”, “P. chrysogenum”, “P. crustosum”, “P. mononematosum”, “P. oxalicum”, “P. polonicum”, “P. singorense”, “P. spinulosum” and one species of “Talaromyces pinophilus” based on morphology and multigene analysis comprises ITS, cal, rpb2 and β–tub genes. Phylogenetic analyses using these sequences through maximum parsimonious method showed β-tub gene as a potential region for DNA barcoding to differentiate the species of Penicillium with maximum inter population diversity (2.15), coefficient of differentiation (8.54), barcode gap (1.93) and probability of correct identification (0.081) and it can be used as secondary barcode apart from ITS as universal primary barcode. The β-tub gene was also validated using six more species of Penicillium (P. canescens, P. daleae, P. janthinillum, P. ochrochloron, P. simplicissimum and P. vasconiae) isolated from soils of Delhi and Meghalaya states, where all the species showed clear differentiation from one another. In conclusion, fourteen predominant Penicillium species was established through morpho-molecular approach and three Penicillium species (P. mononematosum, P. singorense and P. vasconiae) were reported first time from India and β-tub sequence-based identification was the best to confirm the morphological based identification