Efficacy of Yeast in the Biocontrol of Bacterial Fruit Blotch in Melon Plants

Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, is the most important bacterial disease affecting melon plants in Brazil. The aim of the present study was to analyze the efficacy of yeasts for the biological control of BFB, applied by spraying to protect seedlings, foliage and fruits, and as a seed treatment. Additionally, the in vitro activity of the yeasts and plant growth promotion were evaluated. Among 60 strains, LMA1 (Rhodotorula aurantiaca), CC-2 (Pichia anomala) and LMS (Rhodotorula glutinis) were the most efficient for seedling protection. Among the three selected strains, only LMA1 and CC-2 maintained efficacy when tested on foliage and seeds, with reductions in the disease index and area under the disease progress curve of 58.6 and 47.2 %, respectively. Furthermore, LMA1 and LMS protected fruits. In vitro, neither of the strains inhibited bacterial growth, produced killer toxins, or showed competition for nutrients with the pathogen. None of the three yeasts promoted the growth of melon plants. Therefore, these yeasts have potential for BFB biocontrol in different disease stages and may be used in the integrated management of BFP.