Influência do estresse hídrico e da compactação do solo na associação nematóide, rizobactérias e fungos micorrízicos arbusculares

Abstract

The thesis objective was evaluating effects of drought stress and soil compaction on plant × soil micro biota interaction (arbuscular mycorrhizal fungi, plant growth-promoting bacteria and root-knot nematode) in cowpea (Vigna unguiculata (L.) Walp.), meloeiro (Cucumis melo L.) e cana-de-açúcar (Saccharum L.). It was carried out five experiments under greenhouse. In the first experiment, it was evaluated the development and biochemical aspects of cowpea cultivar EPACE-10 submitted to drought stress (50 and 100% pot capacity) and Meloidogyne incognita parasitism. In the second experiment, it was evaluated the drought stress × Bacillus sp. ENM51 × M. incognita interaction on melon cultivar Gold Mine through plant growth variables, enzymes activity and phosphorus and nitrogen contents. In the third study, it was evaluated the effect of four soil compaction levels on the initial development of sugarcane variety RB 863129 under M. incognita parasitism. In the fourth one, the effect of soil drought stress and the arbuscular mycorrhizal fungi (FMA) Claroideoglomus etunicatum, Gigasporas rosea, Acaulospora longula and Fuscutata heterogama on sugarcane variety RB857515 initial vegetative development, fresh and dry biomass production, mycorrhizal colonization, enzymes activity and phosphorus, protein and amino acid contents were evaluated. And, in the fifth study, it was evaluated the effects of drought stress × M. incognita × FMA (C. etunicatum, G. rosea, A. longula and F. heterogama) interaction on vegetative initial development, biomass production, nematode and fungi multiplication, and physiological activity of sugarcane variety RB863129. The hydro stress level (50% pot capacity) decreased nematode reproduction on cowpea. The M. incognita parasitism potentiated the drought stress increasing soluble protein level. Oxidative enzyme responses to either hydro stress or M. incognita parasitism were variable. Peroxidase was not affected, catalase decreased with nematode parasitism, ascorbate peroxidase decreased with hydro stress and polyphenol oxidase decreased with hydro stress and/or M. incognita parasitism. In melon, nematode decreased haste length, haste fresh and dry biomasses, total plant fresh biomass, leaf and flower numbers; Bacillus sp. decreased nematode reproduction and gall number. In sugarcane, the increasing in soil compaction level from 1.65 g cm-3 to 1.82 g cm-3 decreased M. incognita reproduction and increased stalk length of the variety RB 863129, but it did not affect the other plant development variables. The 50% CP drought stress level decreased RB 857515 stalk diameter, fresh shoot and root biomass and FMA in soil and roots. The FMA and the 50% CP drought stress, isolated or in association, did not affect plant height, leaves number and dry plant biomass as well the phosphorus, total soluble proteins, catalase, ascarbate peroxidase, polyphenol oxidase, peroxidase, and proline contents in the variety RB857515. Either drought stress or M. incognita decreased initial vegetative development and fresh and dry biomass production of the variety RB 863129. The FMA increased fresh stalk and root biomass. Hydro stress increased FMA population in soil and roots. The FMA decreased gall and nematode numbers in roots. Either drought stress and M. incognita decreased ascorbate peroxidase contents in sugarcane, but the nematode increased polyphenol oxidase and total soluble protein in plant. Drought stress decreased P content in leaves but FMA increased P content in stalk, however, the increase in P promoted by the FMA did not occur under hydro stress. Catalase, peroxidase and proline levels were not affect by hydro stress, M. incognita and/or FMA, 45 days after nematode interaction.