L Hidalgo-Díaz

Cultural and morphological characterization of Pochonia chlamydosporia and Lecanicillium psalliotae isolated from Meloidogyne mayaguensis eggs in Brazil

The root-knot nematode, Meloidogyne mayaguensis, causes serious economic loss to guava plantation in Brazil. Fungi associated with eggs of M. mayaguensis in Brazilian soil have not been studied yet, but this knowledge could form the basis for future field studies on biological control of this nematode. The egg parasitic fungi, Pochonia chlamydosporia var. chlamydosporia, P.chlamydosporia var. catenulata and Lecanicillium psalliotae, were isolated from M. mayaguensis eggs and analyzed based on their cultural and morphological characteristics. The optimum temperature for growth and spore production ranged between 24 and 28oC for P. chlamydosporia isolates. For the isolate of L. psalliotae, the best growth was at 30oC. In solid state fermentation, P. chlamydosporia isolates produced between 3.5 and 5.2 x 106 chlamydospores per g of colonized substrate, whereas L. psalliotae isolate produced 8.5 x 108 conidia per g of colonized substrate. Future studies are required to clarify the potential of these fungi as biological control agents of M. mayaguensis.

Effect of nematophagous fungi on reproduction of Meloidogyne enterolobii on guava (Psidium guajava) plants

The root-knot nematode, Meloidogyne enterolobii, is a major disease of guava, Psidium guajava, in Brazil and other countries. Egg-pathogenic fungi are considered potential biological control agents of root-knot nematodes and are associated with suppression of Meloidogyne spp. Glasshouse experiments were conducted in order to evaluate the effect of the fungi Paecilomyces lilacinus and Pochonia chlamydosporia on a population of M. enterolobii growing on guava plants. Guava seedlings of about 15-20 cm growing in plastic bags were inoculated with 10 000 eggs of M. enterolobii plant−1. Two months later, three isolates of P. lilacinus and one isolate of P. chlamydosporia were inoculated in the infested plants. The effect of the treatments was evaluated 6 months later. Although plant infection by nematodes was not attenuated, the number of eggs (g roots)−1 fell significantly. The number of egg masses infected with the fungi was inversely correlated with the number of eggs found in the roots. The most effective result (61.5% of control) was obtained with the isolate CG1003 of P. chlamydoporia, which was originally isolated from eggs of M. enterolobii in Brazil, followed by P. lilacinus (CG959 and CG1038) with about 40% of control. These fungi showed the ability to colonise healthy guava roots in glasshouse experiments. These results suggest that P. chlamydosporia can be selected as a potential biological control agent to be employed with other strategies in integrated management to control M. enterolobii on guava.

Efectos de plaguicidas y bioestimulantes vegetales sobre la germinación de clamidosporas y el desarrollo in vitro del hongo nematófago Pochonia chlamydosporia

BACKGROUND The effects of pesticides and plant bio-stimulants used in protected vegetable production systems on the fungus Pochonia chlamydosporia are unknown. AIMS The effectiveness of P. chlamydosporia against Meloidogyne spp. could be affected by products used in protected vegetable production systems. Two in vitro assays were carried out to evaluate any potential effect that pesticides and bio-stimulants often used in these systems could have on the fungus. METHODS The effect on chlamydospore germination was evaluated in a first assay, and mycelia growth and sporulation in a second. With these results, the compatibility of each product with the fungus was determined. RESULTS Chlamydospores germination was over 50% with the control, FitoMas E, Biobras-16 and Amidor. Lower results were observed with other products, with some of them even inhibiting germination completely. Fungal growth was potentiated by Biobras-16 to 106.23%, promoted up to 50-100% by the control, FitoMas E and Cuproflow, and was below 50% with the rest of the products.Cipermetrina, Benomilo, Zineb, Mitigan, Karate, FitoMas E and Amidor promoted fungal sporulation, which was below 50% with Cuproflow and completely inhibited by the other products. Fifty-four percent of the products evaluated were compatible with P. chlamydosporia, while 8% were toxic and 38%, very toxic. CONCLUSIONS Cipermetrina, Karate, Amidor, Benomilo, Zineb, Mitigan and FitoMas E were compatible with P. chlamydosporia. If it is necessary to use any of the other products for integrated pest management in protected vegetable production systems, it is recommended to avoid direct contact with P. chlamydosporia.