Secondary metabolite induced tolerance to Fusarium oxysporum f.sp. cubense TR4 in banana cv. Grand Naine through in vitro bio-immunization: a prospective research translation from induction to field tolerance

An innovative tissue culture mediated incorporation of metabolite-based biomolecule (Bio-immune) at in vitro stage itself in banana cv. Grand Naine was developed and validated for the production of Fusarium oxysporum f.sp. cubense TR4 tolerant plantlets. The novel bio-immune formulation developed by us, exhibited a significant antifungal potency against Foc TR4 with a high percent inhibition (100%) at a 2.5% concentration of bio-immune on the 5th, 7th, and 9th DAI. Bio-immune integrated during in vitro shoot proliferation stage in banana cv. Grand Naine recorded significant enhancement in the growth of roots and shoots. Bio-immune (0.5%) fortified media produced 12.67 shoots per clump whereas control registered only 9.67 shoots per clump. Similarly, maximum root numbers (7.67) were observed in bio-immune plants which were significantly higher over control (5.0). The bio-immunized banana transplants recorded a higher survival rate (97.57%) during acclimatization as compared to the control (94.53%). Furthermore, evaluation of the bio-immunized plants in pot experiments revealed that unimmunized plants treated with FocTR4 (TF) exhibited mortality between 60 and 90 days. On the 90th day after planting, a high mean disease severity index (DSI) of 3.45 was observed with unimmunized plantlets while the bio-immunized plants (TFBI) and ICAR-FUSICONT treated plants (TFTR) showed substantially reduced DSI (0.20 and 1.00) compared to FocTR4 treated control (TF). Significant increases in polyphenol oxidase (PPO), peroxidase (POD), β-1,3-glucanase, phenylalanine ammonia-lyase (PAL), chitinase activities, and enhanced phenol contents were recorded in bio-immunized plants compared to unimmunized plants. Field experiments at two different locations in Bihar, India revealed that bunch weight, no. of hands/bunch, and no. of fingers/hand of bio-immune treated plants were significantly higher compared to the control

Comparative Evaluation of In-vitro Bioefficacy of Microbial Bioagents and Novel Chemical Compounds against Fusarium oxysporum f.sp. Cubense

The Assam and North-eastern regions of India recognized as diverse repositories of wild and cultivated banana cultivars, confront a significant threat to banana varieties, Malbhog due to Fusarium wilt disease caused by Fusarium oxysporum f.sp. cubense (Foc). This study investigates the in-vitro bioefficacy of indigenous bioagents and new-generation chemical compounds against Foc to develop an integrated module subsequently, in line with the worldwide pursuit of environmentally conscientious and high-performance agricultural practices.In this study, four bioagents viz., Bacillus vallismortis, Bacillus amyloliquefaciens, Trichoderma harzianum, and Talaromyces pinophilus were screened in-vitro against Foc revealed the highest efficacy of B. vallismortis with 68.22 % mycelial growth inhibition of Foc followed by B. amyloliquifaciens with (60.05%) and the least inhibition was exhibited by T.pinophilus with (50.05%).To identify new generation chemical compounds, namely Propiconazole, Azoxystrobin, Tebuconazole + Trifloxystrobin were tested with a standard check Carbendazim wherein all the chemicals significantly inhibited the mycelial growth of the pathogen over control with Tebuconazole + Trifloxystrobin combination fungicide showing highest percent inhibition of 94% at 0.1% concentration followed by Carbendazim at 0.1%. Our study has identified potential microbial strains and chemical fungicides which can be further explored for the development and exploration of bio-fungicide and chemical fungicide-based biointensive integrated management of Fusarium wilt menace in malbhog banana in the region

Rhizospheric <i>Bacillus</i> spp. Exhibit Miticidal Efficacy against <i>Oligonychus coffeae</i> (Acari: Tetranychidae) of Tea

Oligonychus coffeae (Acari: Tetranychidae), popularly known as red spider mite (RSM) is one of the major pests of commercial tea (Camellia sinensis (L.) O. Kuntze) plantation world over. Many attempts have been made in the past to control this devastating pest using a variety of microbial bioagents, however, area-wise field success is very limited. We carried out an in vitro study to explore the potential of rhizospheric Bacillus spp. (B. amyloliquefaciens BAC1, B. subtilis LB22, and B. velezensis AB22) against O. coffeae through adulticidal and ovicidal activity. The 100% adult and egg mortality was observed with bacterial suspension (1 × 109 CFU/mL) by B. velezensis AB22, showing the lowest LC50 values for both adults and eggs of O. coffeae, i.e., 0.28 × 105 and 0.29 × 105, respectively. The study also throws some insights into the underlying mechanism through electron microscopy study and identification of some putative pesticidal metabolites from all the species. The three Bacillus species were observed to have four commonly secreted putative bioactive secondary metabolites, brevianamide A, heptadecanoic acid, thiolutin, and versimide responsible for their bio-efficacy against O. coffeae. The outcome of our study provides a strong possibility of introducing Bacillus spp. as a biological miticide and developing synthetic metabolites mimicking the mechanistic pathway involved in microbial bioefficacy