Promoção de crescimento e colonização radicular por Trichoderma spp. Em pinhão manso (Jatropha curcas L.) e mamoneira (Ricinus communis L.)

Abstract

The search for renewable energy sources to replace petroleum has encouraged research activities for the development of technologies for this purpose. With the National Program of Biodiesel Production and Use (PNPB) launched by the Federal Government, oil crops have become the focus of these studies. Physic nut and castor bean have great potential for biodiesel production. Both are rustic and adapted to the climatic conditions of the Northeastern region of Brazil, constituting a viable alternative for family-based farming. Despite the positive perspectives for these crops, reliable information about cultivation systems, crop management, plant physiology and plant interactions with soil microorganisms is still necessary to increase productivity. This study aimed to evaluate the potential of 24 isolates of Trichoderma spp. on plant growth promotion and endophytic colonization of castor bean and physic nut. Trichoderma isolates were evaluated for their capacity to produce extracellular enzymes, indol acetic acid, and for phosphate solubilization. Additionally, plant nutritional status, plant growth promotion with seed inoculation and soil inoculation and incubation for different periods of time (0, 5, 10, 15, 20, 25 and 30 days) were evaluated. Isolates TCS4, TCS1, TC10, 312 and ES15 promoted an increase in physic nut height. Isolate TR7 promoted an increase in physic nut nitrogen content and root dry weight. Isolates TC40 and 312 promoted an increase in castor bean plant height, while isolates TCS12, TCS6, ES8, 312, TCS1, ES5, ES6, TC40 and ES6 increased stem diameter. Only isolate TR7 was able to increase shoot dry matter of castor bean plants. None of the isolates tested promoted an increase in the number of leaves and root dry matter. Isolates TR7, TR8 and TSO4 increased plant nitrogen content, but had no effect on phosphorus and potassium contents. Thirty-day incubation periods promoted the best results for plant shoot and root dry matter. Soil inoculation with isolates ES3, TCS30, TCS4, ES4, TC40, ES15, ES5, TC10 and TCS12 of Trichoderma spp. and incubation for 25 days promoted the best results for plant height. ES3 promoted an increase in shoot dry weight and TC40 in root dry weight. Isolates TCS24, ES15, TR7 and TR8 are producers of cellulase, while TC8 and TCS27 were able to solubilize phosphate. The other isolates were not able to produce chitinase, xylanase and indol acetic acid. All isolates were able to colonize the root system of both plant species, with the exception of TCS12 in castor bean. Linear and positive correlation was observed for root colonization and plant height for both physic nut and castor bean. Further research work is necessary in order to gain more knowledge regarding the interaction of the fungus Trichoderma and bioenergy crops.