Antagonistic potential of certain soilborne fungal bioagents against Monosporascus root rot and vine decline of watermelon and promotion of its growth

Monosporascus cannonballus responsible for cucurbits Monosporascus root rot and vine decline, isworldwide spread notably in Tunisia. The most appropriate strategies to suppress disease development are thoseable to reduce the ascospores population using eco-friendly approach treatments. Seven soilborne fungal isolateswere tested in vitro (by dual confrontation technique) and in vivo in the greenhouse as potential bioagents againstthree virulent M. cannonballus isolates. In vivo experiments were divided into two assays, preventive and curativetreatments. Trichoderma viride and T. harzianum exhibited high inhibitory activities against M. cannonballusmycelial growth with values more than 90%, followed by Aspergillus niger (87.89%) and Paecilomyces victoriae(80.44%). Furthermore, these two Trichoderma spp. when applied preventively and curatively in in vivo trials,reduced significantly disease incidence (8.33% and 16.67-20.83%), root disease index (0.79-0.8 and 1.25-1.17),and reduced also ascospores index (1.5-1.54 asc/g of peat) and (2.54-2.42 asc/g of peat), respectively, incomparison with control treatments. Moreover, T. viride and T. harzianum enhanced the growth development ofwatermelon plants treated preventively and curatively in the greenhouse. They significantly improved differenthorticultural measurements with mean values of plant height (76.75-79.83 cm, and 81.83-80.92 cm), root volume(2.39-2.22 cm3, and 1.84-1.88 cm3), above grounds fresh weight (16.07-16.57 g, and 12.84-14.93 g) and dry wt.(2.49-2.6 g, and 2.66-2.70 g), underground fresh wt. (0.725-0.654 g, and 0.717-0.690 g) and dry wt. (0.147-0.214g, and 0.156-0.152 g). Based on current results, it appears that Trichoderma spp. could be employed in soiltreatments to promote watermelon plant growth and development.