Lemons (Citrus limon L.) are one of the most economically important and consumed fruit worldwide. The species is vulnerable to several postharvest decay pathogens, of which Penicillium italicum associated with blue mold disease is the most damaging. This study investigates the use of integrated management for blue mold of lemon using lipopeptides (LPs) extracted from endophytic Bacillus strains and resistance inducers. Two resistance inducers; salicylic acid (SA) and benzoic acid (BA) were tested at 2, 3, 4, and 5 mM concentrations against the development of blue mold on lemon fruit. The 5 mM SA treatment produced the lowest disease incidence (60%) and lesion diameter (1.4 cm) of blue mold on lemon fruit relative to the control. In an in vitro antagonism assay eighteen Bacillus strains were evaluated for their direct antifungal effect against P. italicum; CHGP13 and CHGP17 had the greatest inhibition zones of 2.30 and 2.14 cm. Lipopeptides (LPs) extracted from CHGP13 and CHGP17 also inhibited the colony growth of P. italicum. LPs extracted from CHGP13 and 5 mM SA were tested as single and combined treatments against disease incidence and lesion diameter of blue mold on lemon fruit. SA + CHGP13 + PI had the lowest disease incidence (30%) and lesion diameter (0.4 cm) of P. italicum on lemon fruit relative to the other treatments. Furthermore, the lemon fruit treated with SA + CHGP13 + PI had the highest PPO, POD, and PAL activities. The postharvest quality analysis of the lemon fruit including fruit firmness, total soluble solids, weight loss, titratable acidity, and ascorbic acid content revealed that the treatment SA + CHGP13 + PI had little effect on fruit quality compared to the healthy control. These findings indicate that Bacillus strains and resistance inducers can be used as components of integrated disease management for the blue mold of lemon.

The present study focuses on the reduction of significant postharvest blue mold disease of lemon (Citrus limon L) fruit through the use of Bacillus strains in vivo and in vitro conditions. Blue mold which is caused by Penicillium italicum is the most dangerous postharvest disease of lemon fruit and causes significant losses in citrus fruits. In this study, antagonistic compounds like Cyclic lipopeptides (CLPs) produced by Bacillus strains were used to control P. italicum. CLPs are considered best the antagonistic compound of Bacillus Strains that primarily play an important role in the reduction of plant diseases and have three important families such as iturin, fengycin, and surfactin. This study was carried out by using seven strains of the genus Bacillus that were used in vitro assay. Among these seven strains, two strains Bacillus licheniformis and Bacillus thuringiensis showed wonderful inhibition zone in vitro assay carried out in Petri plates. Further CLPs were extracted from the both best strains and used in vivo assay on lemon fruit and showed less disease incidence and lesion diameter of disease. Furthermore, lemon fruits treated with CLPs showed increasing defense mechanisms of enzymes P AL, PPO, and PO. This study indicates the strong antifungal effect of Bacillus strains and their metabolites CLPs against the blue mold of lemon.

The PGPR possesses antifungal activity against a broad range of pathogens. In this research study, the LPs of Bacillus strain B1 and B2 against Alternaria alternata were assessed. In vitro and in Planta assay on tomato fruit was made to check the post-harvest quality of fruits. The lipopeptides produced by both strains suppress the growth of the fungal pathogen Alternaria alternata and lessen the disease severity of the Alternaria rot on tomato fruits. The result revealed the quality of the Bacillus-treated fruits was also maintained and satisfactory. The lipopeptides of bacillus strain B1 and B2 represent a new innovative method to lessen the use of fungicides and chemical approaches to reduce the post-harvest loss caused by Alternaria alternata.