Eficácia de leveduras no biocontrole da mancha aquosa em meloeiro

Abstract

The bacterial fruit blotch caused by Acidovorax citrulli is one of the most severe diseases of melon (Cucumis melo), and a major problem in the Northeast, the main melon producing region of Brazil. Strategies for control of bacterial blotch include chemical and physical treatments of seeds and chemical sprays of the plant canopy. Since these treatments are not efficient and resistant melon cultivars do not exist, other strategies have been studied, including biological control. Our objectives were to analyze the efficiency of yeasts in the biocontrol of this disease by protecting seedlings and plants, and by treating melon seeds; and to verify the in vitro activity against the pathogen and the growth promotion of melon plants. None of the 60 yeasts inhibited the growth of the pathogen, but the isolates LMA1 (Rhodotorula aurantiaca), LMS (R. glutinis) and CC-2 (Pichia anomala) stood out as the most effective in protecting seedlings. When tested in plants and seeds, LMA1 and CC-2 maintained effectiveness. In plants, the reductions in disease index (ID) and area under the disease progress curve (AUDPC) compared to the control reach 58.6 and 47.2%, respectively, while seed treatments reduced ID and AUDPC up to 34.3 and 45.5%. These isolates did not promote the growth of melon plants and did not produce killer toxins in vitro. R. aurantiaca (LMA1) and P. anomala (CC-2) were effective in protecting plants and seedlings and for seed treatment of melon. Therefore, the use of these yeasts jointly with other control methods, such as resistant varieties and copper compounds, is important in integrated management of bacterial fruit blotch.