Influência dos fungos dark septate sobre absorção de nutrientes e crescimento de plantas de arroz e tomate

Abstract

The dark septate endophytes (DSE) fungi can be used as plant growth promoter. However, how these fungi establish association with its host is still not fully understood. This study aimed to characterize dark septate endophytes fungi and evaluate nutrient uptake and growth of rice and tomato plants inoculated with these fungi. Using a randomized block design, DSE isolates obtained from Oryza glumaepatula were characterized for their ability to change pH of the potato-dextrose-agar (PDA) medium with bromothymol blue, as growth at different pHs (4, 5, 7 and 8), for ability to solubilize calcium phosphate and using organic and/or inorganic nutrient sources. Other assays were conducted in a growth chamber conditions and treatments consisted of rice (variety Piauí) and tomato (variety Santa Clara I- 5300) plants with and without inoculation with different DSE isolates (ERR 01, ERR 16, ERR 26 and ERR 42). In these trials were determined kinetic parameters, Vmax and KM , of NO3- uptake, NO3- - N , NH4+-N , free amino-N , soluble sugars and macronutrients contents. The results showed that the ERR 02 and ERR 04 isolates alkalized the middle and other acidified. In the test with different pHs was observed that only the growth of ERR 46 and ERR 02 fungi was not influenced by the pH ranges tested. None of the tested isolates was able to solubilize the calcium phosphate. It was also possible to observe that the ERR 04 fungi developed better in the presence of organic and/or inorganic nutrients sources, when compared to other isolates. The results of the experiment with rice showed that plants inoculated with the ERR 16 and ERR 01 fungi had a lower KM when compared to control. Moreover, in plants inoculated with the ERR 16 fungus, increases in amino-N, soluble sugars, N , P , K , Mg and S contents, fresh and dry weight of roots and shoots, height and number of tillers per plant, compared to the control. The results of the experiment with tomato showed that plants inoculated with the ERR 01 and ERR 42 fungi showed significant increases in soluble sugar, P , K , Mg and S content, dry weight of root, stem , leaf and shoot when compared to control. Furthermore, in the treatment inoculated with ERR 42 greater Vmax was observed. The study shows that the ERR 02 and ERR 46 fungi alone are not influenced by different pHs and ERR 04 fungus is promising for the tests of evaluation transfer of nutrients from the organic material to its host. Furthermore, the ERR 16 fungus shows potential to promote plant growth in rice and ERR 01 and ERR 42 fungi to tomato.