A comprehensive mycofloral diversity of pedosphere, phyllosphere and aerosphere of Som. (Persea bombycina Kost.)

Abstract

Sericulture is an important cottage industry of Assam producing natural silk of both Mulberry and Non-Mulberry silk. The sericulture industry is closely associated with the Assamese traditions and rituals. In non-mulberry silk, Muga silkworm which is endemic to North-East India only produce exquisite silks of golden color. Rearing of Muga silkworm is one of the important aspects to producing silk of high quality. The quality of the primary host plant i.e. Som (Persea bombycina Kost.) greatly affects the quality of cocoon and silk produced by these industries. Therefore, planting and growing a disease-free plant has its own importance in sericulture. However, Som is very susceptible to different foliar diseases caused by fungi, which can reduce the yield of leaf from 13.8 - 41.6% annually. Therefore, a comprehensive mycofloral study of the host plant is important to forecast the future diseases and design different disease management procedures. This study has been done for a period of two years from 2014 - 2016 in Goalpara district of Assam and overall mycoflora of pedosphere (rhizosphere and non-rhizosphere), phyllosphere and aerosphere were identified and correlated with the seasonal variation. The rhizosphere, air, and phylloplane was dominated by Rhizopus stolonifer (22.13%; 15.08; 24.01) while Aspergillus niger (12.63%) was the dominant flora of non-rhizosphere. Seasonal variation was found to play an important role in shaping the mycofloral community structure in soil and phyllosphere. In summer, soil was majorly dominated by Aspergillus niger, Aspergillus fumigatus, and Curvularia lunata while Rhizopus stolonifer, Aspergillus clavatus, Penicillium chrysogenum dominated the winter soil. In phyllosphere, the Chatuwa and Jaruwa, the winter generations were mainly dominated by Rhizopus stolonifer. While as the environmental temperature gradually increased with relative humidity in Aheruwa, Bhodia, Kotia and Jethuwa generation there was a shift in diversity with a gradual increase in occurance of Alternaria alternata, Aspergillus niger, and Aspergillus flavus. Pestaloptiopsis disseminata one of the major pathogen of Som was found highest in aerosphere followed by phyllosphere and it was only dominated in Aheruwa generation. It was found that occurrence of P. disseminata were high when the temperature ranges between 25{degrees} - 28{degrees} with 70 -80% of relative humidity. This study provides a deep insight into the fungal diversity of host plant Som with respect to pedosphere, aerosphere, and phyllosphere and this knowledge can be used to better select the plantation area and design different disease management strategies to sustain and proliferate the industry for socio-economic development and to conserve its cultural essence.