Biotic Stress Caused by Meloidogyne Enterolobii in Physiology of Guava Tree Treated With Bacillus Methylotrophicus

Abstract

The interference of nematodes in the physiology of plants is little studied, as well as the ability of rhizobacteria to mitigate the physiological damage caused by nematodes. The objectives of this research were to monitor physiological changes in guava plants parasitized by Meloidogyne enterolobii and treated with bionematicide, active ingredient: Bacillus methylotrophicus (B.met) and to evaluate the efficiency of the bionematicide in controlling the nematode. The experiment was installed in a greenhouse and the treatments represented by: 1) 'Pedro Sato´ guava not inoculated and not treated with B. met (control); 2) 'Paluma' guava not inoculated and not treated with B. met (control); 3) `Pedro Sato´ not inoculated and treated with B. met; 4) `Paluma´ not inoculated and treated with B. met; 5) `Paluma´ inoculated and not treated with B. met; 6) `Pedro Sato´ inoculated and not treated with B. met; 7) `Pedro Sato´ inoculated and treated with B. met and 8) `Paluma´ inoculated and treated with B. met. Four applications of bionematicide were performed at a dosage of 3 mL/L of water per plant. Between the second and third application, the plants were inoculated with 5000 eggs and juveniles of M. enterolobii. Seven assessments of physiological parameters were performed. At 132 days after inoculation (DAI) the roots were weighed and the gall index, egg mass index and reproduction factor were determined. Meloidogyne enterolobii and B. met combined reduced the stomatal conductance and transpiration at 26 and 44 DAI, respectively. Photosynthesis was lower at 26 DAI in treatments that received the nematode and bacteria combined. Meloidogyne enterolobii and B. met isolated and combined reduced water use efficiency at 26 and 44 DAI. In root mass there was no difference between treatments. Gall index, egg mass index and reproduction factor were higher in treatments that received nematodes, regardless of the application with the bacteria.