Aureobasidium pullulans (De Bary) G. Arnaud, a Biological Control against Soft Rot Disease in Potato Caused by Pectobacterium carotovorum

In Morocco, Pectobacterium carotovorum is well known as causal agents of potato soft rot. Actually, there are no efficient bactericides used to protect potato against Pectobacterium spp. biological control using antagonistic could be an interesting approach to manage this disease. Thus, a collection of thirty antagonists isolated from compost, rhizospheres and endophytes of various crop plants in Morocco were evaluated for their ability to inhibit the phytopathogenic agent Pectobacterium carotovorum in vitro, in vivo and in greenhouse. The in vivo test showed that only ten antagonistic isolates have significantly inhibited the growth of P. carotovorum (P512C9), among them, eight isolates were completely efficient against the strain P512C9. In addition, seven isolates having the greatest pathogen inhibitory capabilities were subsequently tested for their ability to control soft rot potato in greenhouse. The results showed that the treatment by Ach inhibited the development of the soft rot with a reduction of an incidence of disease nearly 100 %. The treatments by the others isolates 2331-5, 1113-9, 2066-7, 2339-9, 2321-9 and 2015-1 have reduced up to 70.3 %, 64.5 %, 87 %, 85.9 %, 55.6 % and 89 % the disease of the pathogen (P512C9). The isolate Ach which had the strongest antagonistic activity against P. carotovorum, belongs to the yeast-like species Aureobasidium pullulans (De Bary) G. Arnaud. As well, the treatment with strain Ach has proved a high action on potato plant growth compared to others treatments. In conclusion, the results showed that the black yeast A. pullulans would be an interesting microorganism to be used as a bio-control agent against soft rot disease.