Harnessing cyanobacterium-fungal interactions to develop potting mixes for disease-free tomato nursery

Cyanobacteria and their interactions with phytopathogenic fungi in soil-less potting mixes is a less explored aspect in the protected cultivation of crops, as fungal diseases often bring about serious losses. The nursery of tomato was raised with A. laxa amended /unamended soil-less substrate mixes [P:C, perlite: cocopeat (1:1); C:V, cocopeat: vermiculite (1:1); P:C:V, perlite: cocopeat: vermiculite: (1:1:1)]. Preliminary investigation of percent germination of tomato seeds in the different media with the treatments illustrated the differential influence of the media, and Anabaena laxa amended treatments showing highest values, including those challenged with F. solani . To further understand the nature of such interactions in the rhizosphere, transplantation of 30 d-old seedlings was undertaken in mesocosm experiments deploying soil-less substrate mixes (P:C, C:V, P:C:V) challenged with /without Fusarium solani or Rhizoctonia solani. Significant increases of 10–46% were recorded in the total soil polysaccharides and dehydrogenase activity with F. solani, and in IAA with R. solani , compared to control. Among the treatments, T4 ( A. laxa ± Fs) showed an almost 60% increase in terms of nitrogen and organic carbon content. This illustrated that A. laxa effectively interacted with both fungi and improved the nutrient availability in the media; interestingly, F . solani exhibited a growth stimulatory role. Cyanobacterium-fungal interactions led to better growth of tomato plants, illustrating that A. laxa amendment can be a promising option, particularly, in P:C:V, as media for developing robust and disease-free nurseries.