Meloidogyne mayaguensis has been reported in some states of Brazil causing severe damage on commercial guava (Psidium guajava L.). Accessions of Psidium spp. were selected from a collection maintained in Embrapa Clima Temperado (Pelotas, Rio Grande do Sul State). Plants of different accessions were grown from seed in plastic bags and, when they reached 15-20 cm in height, were inoculated with 10,000 eggs/plant of M. mayaguensis. Eight months after inoculation, the different accessions were evaluated for resistance to M. mayaguensis. Three accessions of P. guajava were highly susceptible (RF=59.2) to this nematode. Psidium friedrichsthalianium was considered to be moderately resistant (RF=1.9). Three accessions of P. cattleyanum were immune to M. mayaguensis (RF = 0). When used as rootstocks P. cattleyanum and P. friedrichsthalianium were compatible with P. guajava cv. Paluma. Considering these results, the use of resistant rootstocks provides a promising control method for M. mayaguensis in commercial guava crop.
An obligate parasite bacterium of the root-knot nematode, Pasteuria penetrans strain P10, isolated from Meloidogyne incognita females on banana roots in Imperatriz Maranhão State, Brazil, was evaluated in glasshouse conditions, using two doses of a dry root bionematicide (10 7 endospores (5.0 g/seedling) and 10 6 endospores (0.5 g/seedling)) on seedlings of cv. Mundo Novo coffee. The soil in which coffee seedlings were raised was inoculated previously with these two doses of P. penetrans and after 2 months the plants were transferred to soils of different textures: clay-sandy soil (38% clay, 2% silt and 60% sand) and sandy soil (17% clay, 0% silt and 83% sand). When the coffee plants were 30 cm high, they were inoculated with 20 000 eggs/plant of M. incognita race 1. The coffee plants were examined 8, 16 and 24 months after nematode plant infestation. The effectiveness of the biological control was determined by the reduction of nematode reproduction factor, which ranged from 62 to 67% in clay-sandy soil and 80 to 85% in sandy soil. The mechanism of suppression caused by the bacterium was evaluated by the percentage of infected second-stage juveniles (J2), number of endospores attached/J2 and number of infected females. The high levels of suppression were related to time, increasing from 8 to 24 months, and to the percentage of sand in the soil.
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