Pseudomonas of the rhizosphere of avocado (Persea americana Mill.) with biocontrol activity of Phytophthora cinnamomi Rands isolated in the central coast of Peru
In the rhizosphere, as the zone of biological activity, diversity of microorganisms can be found like bacteria of the genus Pseudomonas. They are characterized for controlling pathogens like Phytophthora cinnamomi, also to be promoters of growth. For this reason, in the present study, bacteria of the genus Pseudomonas were isolated from the avocado rhizosphere of the provinces of Casma, Huaral, and Lima. A total of six strains (R2, R5, R7, R10, S10 and S6) were selected for evaluating their biocontrol capacity against P. cinnamomi under in vitro and greenhouse conditions. In the in vitro test, strains S6 and S10 controlled 30.3 and 44 %, respectively. Under greenhouse conditions, Pseudomonas strains were inoculated on 4-month-old avocado cv. “Zutano” plants. Five months later, we evaluated the following variables: severity in roots, height increase, fresh root and leaf weight, and percentage of root and leaf dry matter. In greenhouse, the best strains in the control of P. cinnamomi were S6, R2, R7 and R10, controlling 55.2, 39.5, 33.7 and 31.0 %, respectively. In the increase of height, the strains S6, R2, R7 and R10 reached 11.4, 9.3, 7.6 and 5.1 cm, respectively. The percentage of dry matter of roots, strains S10, R10 and R7 obtained 29.6, 27.5 and 27.9 %, respectively. In this study, it was observed that although the application of Pseudomonas controls P. cinnamomi, it also induces the root and apical growth of avocado.