Peer review

The root-knot nematode (RKN) Meloidogyne javanica is one of the most economically important plant pathogens. Due to the high toxicity of chemical nematicides, the use of nematophagous fungi represents a promising alternative in nematode management. These biological agents offer a more sustainable and environmentally friendly approach to controlling plant parasitic nematodes (PPNs). The present study aimed to isolate and evaluate the nematicidal activity of three nematophagous fungi, viz., Paraconiothyrium cyclothyrioides, Aspergillus oryzae, and Lecanicillium psalliotae, against M. javanica under laboratory and greenhouse conditions. Three densities (1 x 10(6), 1 x 10(7), and 1 x 10(8) spores/ml) of each fungus were used. In vitro, the results revealed that all the tested isolates were effective at inhibiting egg hatching and mortality in second juveniles (J2s). However, the mortality of J2s and hatching inhibition of eggs were proportional to the fungal concentration and duration of the exposure period. Among the isolates, A. oryzae at a concentration of 1 x 10(8) spores/ml had the highest percentage of egg-hatching inhibition (95.5%) after 72 h of incubation. The highest juvenile mortality (100%) was recorded for P. cyclothyrioides at 1 x 10(8) spores/ml after 72 h. The in vivo results showed that all the tested isolates significantly reduced the number of galls, egg masses, and eggs in tomato roots and J2s in soil. In general, the greatest reductions in the galling index (40%) and number of egg masses per root (88.8%) were recorded for P. cyclothyrioides at 1 x 10(8) spores/ml, while the greatest reductions in the numbers of eggs (96.7) and J2s (98.1) were recorded for A. oryzae at 1 x 10(8) spores/ml. Moreover, the treatment of soil with P. cyclothyrioides, A. oryzae, L. psalliotae, and NemGuard granules resulted in significant increases in root and shoot length; in contrast, a decrease in root fresh weight was observed. Therefore, these data suggest that the three isolates, viz., P. cyclothyrioides, A. oryzae, and L. psalliotae, are essential elements for integrated M. javanica control in tomato crops.

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Salah-Eddine Laasli : No CIMMYT Affiliation