Biorational phomopsis blight management in eggplants using two bacteria isolated from the eggplant rhizosphere

Phomopsis blight, caused by Phomopsis vexans , is a major eggplant disease that significantly reduces output in Bangladesh. In order to produce a new fungicide, 210 bacterial strains were isolated from the rhizosphere of eggplants. Phylogenetic trees using 16S rRNA gene sequences of HSTUB 8 and HSTUB 16 revealed a close relationship with Serratia marcescens and Enterobacter ludwigii , respectively. Among the isolates, HSTUB 8 ( Serratia marcescens ) and HSTUB 16 ( Enterobacter ludwigii ) showed the maximum inhibition zones (1.6 cm and 0.9 cm, respectively) against P. vexans in vitro . In field conditions, basal application of pea bran-based formulated HSTUB 8 and HSTUB 16 followed by spraying of a suspension of both the bacteria exhibited a maximum reduction of disease incidence (64.70%) and severity (77.27%) over the control. The same bio-fungicide also resulted in enhanced growth and production, such as branches per plant (75.05%), plant height (32.28%), fruits/plant (404.54%), firmness of fruits (57.42%), and total soluble solids (66.67%) over the control. Basal application of pea bran-based HSTUB 8 followed by spraying of the suspension of the same bacterium yielded a higher total phenol content in the fruits (56.86 mg/100 g) as compared to the control (24.74 mg/100 g). All gathered data strongly indicate that the pea bran-based formulated bio-fungicides composed of S. marcescens HSTUB 8 and E. ludwigii HSTUB 16 can be used for both the production of high-quality fruits and the management of phomopsis blight disease of eggplants at field conditions in an effective and eco-friendly way.