Root colonization and growth promotion of cover crops by Pochonia chlamydosporia

Several plants are used as cover crops in the no-tillage system in order to improve the physical, chemical and biological characteristics of the soil. The fungus Pochonia chlamydosporia (Goddard) Zare and Gams 2001, a biological control agent of plant parasitic nematodes (PPNs), is capable of promoting plant growth and adding it to the cover crop can increase the biomass of these plants and reduce the population level of nematodes in the soil. The objective of this work was to evaluate the ability of P. chlamydosporia to colonize soil and roots of the cover crops Pennisetum glaucum (L.) R. Br. (ADR 300, ADR 500 and ADRG 9050 cultivars), Urochloa ruziziensis (R. Germ. & Evrard) Crins, Crotalaria spectabilis Ro center dot th and Stylosanthes sp. and to promote the growth of these plants. P. chlamydosporia colonized the root systems of all the evaluated cover crops. Chlamydospores, conidia and hyphae were easily observed within the cells of plant roots. P. chlamydosporia increased the height of the shoots of all plants, except U. ruziziensis. The fungus also increased the total weight of the dry plant of cultivars ADR 300 and ADR 500 of P. glaucum, U. ruziziensis and C. spectabilis in 29, 17, 16 and 30%, respectively. The root volume of P. glaucum (ADR 300), U. ruziziensis and C. spectabilis were also increased in 66, 88 and 64%, respectively, in the presence of P. chlamydosporia. Higher numbers of colony forming units (CFU) of P. chlamydosporia g-1 of soil were detected in the presence of cultivars ADR 300 and ADR 500 of P. glaucum at the 12.5 cm soil depths (12.5, 25.0, 37.5 and 50.0 cm), highlighting the 12.5 cm depth with 10,684 CFU of P. chlamydosporia g-1 of soil. This is the first report of the colonization of cover crops roots by P. chlamydosporia and its resulting plant growth promotion effect, as well as the formation of chlamydospores of P. chlamydosporia inside their root cells. The application of P. chlamydosporia in the cover crop increases the biomass of crops that will be used as green manure and guarantee a greater establishment of the fungus in the area, consequently reducing even more the populations of PPNs in the soil.