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In mulberry (Morus alba L.), various individual strains of plant growth-promoting rhizobacteria (PGPR) and synthetic analogs of naturally occurring plant activators have demonstrated their potential to elicit induced systemic resistance (ISR) against either brown leaf spot (Cercospora moricola) or leaf rust (Cerotelium fici ) diseases. However, these biological and chemical elicitors have not been evaluated so far against multiple infections of both these diseases which commonly occur during the post-rainy season. The present study was therefore aimed to assess the capability of PGPR strains and chemical plant activators, as individual and in integration, in elicitation of ISR against multiple infections. Three PGPR strains, Azotobacter chroococcum strain Azc-3, Bacillus megaterium strain Bm-1 and Pseudomonas fluorescens strain Psf-4, and plant activators, acetyl-salicylic acid (ASA), sodium salicylate (NaS) and 4-amino-n-butyric acid (ABA) were selected for the study. Under in vitro tests, all the plant activators up to 2000 ppm concentration exhibited their compatibility with the PGPR strains tested. Upon assaying of elicitors with plant-pathosystem, disease suppression was significantly (p ¼ 0.05) high with integrated application of PGPR strains and plant activators when compared to their individual applications. All the elicitors at individual application varied in their response to multiple infections with the plant age. However, integration of Azc-3 þ ASA provided greater suppression to multiple infections of brown leaf spot and leaf rust diseases during the entire growth period of mulberry plants. Thus, this combination of biological and chemical elicitors holds great promise to provide an effective ecofriendly alternative to the toxic chemical fungicides presently recommended for the control of brown leaf spot and leaf rust diseases in mulberry.

Various isolates of Macrophomina phaseolina were isolated from root rot disease affected mulberry gardens in south India. Pathogenicity trials exhibited that the different isolates (AP-01 to AP-09, KA-01 to KA-09 and TN-01 to TN-09) were found pathogenic to mulberry causing root rot disease. The results revealed that the sprouting percentage was significantly decreased (21.39 -44.28%), while root rot disease severity was found to be markedly increased (71.0 -100%). Thus the different isolates viz., AP-01 to AP-09, KA-01 to KA-09 and TN-01 to TN-09 fulfilled the Koch postulates. However, it was evident that the isolates (AP-01 to AP-09, KA-01 to KA-09 and TN-01 to TN-09) have exhibited variation in their virulency and the isolate AP-03 was found to be most virulent.