Júlio Carlos Pereira da Silva

Volatile compounds produced by Fusarium spp. isolated from Meloidogyne paranaensis egg masses and corticous root tissues from coffee crops are toxic to Meloidogyne incognita

Meloidogyne species produce egg masses containing nutrients which may serve as feeding substrate for rhizospheric fungi. In the present work we isolated fungi form Meloidogyne paranaensis egg masses. Amongst the fungi isolated 67% belonged to the genus Fusarium and, within those, 52% of the isolates were of the species F. oxysporum. Isolates from F. oxysporum and F. solani significantly reduced M. incognita infectivity and reproduction in tomato when J2 were exposed to fungal volatiles, causing up to 100% immobility in in vitro tests. Water exposed to the volatile compounds produced by fungi and mixed to the J2 suspension caused toxicity in M. incognita J2 and reduced infectivity and reproduction of nematodes inoculated in tomato, when compared to the control. Using gas chromatography-mass spectrometry (GC-MS), the volatile compounds produced by F. oxysporum and F. solani were identified and gathered in six main categories: esters, alcohols, phenols, aldehydes, carboxylic acids and sesquiterpenes, making up a total of 23 molecules. For the first time, 12 molecules from various chemical groups were identified in the water exposed to the volatiles from F. oxysporum and F. solani. A lower number of molecules were detected in the toxic water when compared with the vapors produced by fungi. Within these molecules, various have been already reported as having high nematicidal activity. Thus, F. oxysporum and F. solani fungi from M. paranaensis egg masses produce volatile compounds with antagonistic activity to M. incognita.

Building soil suppressiveness against plant-parasitic nematodes

ABSTRACT Damage caused by plant-parasitic nematodes (PPNs) represents significant losses in agriculture worldwide. Sustainable and non-agrochemical practices have been sought out for the last few years aiming the reduction of PPN outbreaks, as such practices represent less interference in the soil health. In addition, certain soils naturally show high levels of suppressiveness against nematodes. Natural suppressive soils do not allow PPN increment by a balance in soil biotic and abiotic conditions. Such soils must be better understood by which components are responsible for their natural suppressiveness. Hence, keeping, stimulating or and even creating suppressive conditions in agricultural rhizosphere has been studied and applied to reduce PPN populations. There are many aspects that implicate in soil suppressiveness against PPN, such as microbiota activities, organic matter amount, chemical composition and physical constitution. However, any of those conditions is a single driver in suppressive soils against PPN. In this context, we intend to bring up an overview concerning the natural occurrence of suppressive soils against the most devastating PPNs worldwide and discuss the means used to induce suppressiveness in agricultural fields by sustainable management practices.