Levantamento, reprodução e patogenicidade de nematóides a fruteiras de clima subtropical e temperado. / Field survey, reproduction and pathogenicity of nematodes to subtropical and temperate fruits.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

In order to achieve a better knowledge on the nematodes found associated with subtropical and temperate fruits, a total amount of 149 soil and root samples were collected from within apple, blackberry, japanese apricot, loquat, macadamia, olive, peach, pear, persimmon, quince and raspberry orchards located in the states of São Paulo and Minas Gerais, Southeastern Brazil. From this survey, a number of species belonging to eleven genera were identified, namely Aorolaimus nigeriensis, Discocriconemella degrissei, Helicotylenchus dihystera, H. erythrinae, H. microcephalus, H. pseudorobustus, Helicotylenchus spp., Hemicycliophora poranga, Meloidogyne hapla, M. incognita, M. javanica, Mesocriconema onoense, M. ornata, M. sphaerocephalum, M. xenoplax, Mesocriconema spp., Pratylenchus brachyurus, P. zeae, Rotylenchulus reniformis, Scutellonema brachyurus, Tylenchulus semipenetrans, Xiphinema brevicollum, X. elongatum, X. krugi, X. setariae, X. surinamense and Xiphinema spp. The most frequent genera were Helicotylenchus, Mesocriconema and Xiphinema, which occurred in 60.4, 54.4 and 30.2 % of the samples, respectively; the two most common species found were Helicotylenchus dihystera and Mesocriconema xenoplax, detected in 49.0 and 38.8 % of the samples, respectively. However, only Meloidogyne incognita and M. javanica could be associated with peach trees that were stunted or showed general symptoms of decline; in these cases, the rootstocks did not have genetic resistance to root-knot nematodes. The host suitability of several genotypes of the mentioned fruit species, plus guava, were evaluated in relation to Meloidogyne incognita race 2 and M. javanica under greenhouse conditions. The plants were individually inoculated with 5,000 nematode eggs and kept to grow in plastic bags for four months. Nematode reproductive rate was determined with basis on gall index, egg mass index and numbers of nematodes per root system and per gram of roots. Only the cultivar GF-677 of Prunus persica x P. dulcis was susceptible to both nematode species. All other genotypes were poor/resistant hosts, even that some allowed the parasites to reproduce at low rates. The pathogenicity of Meloidogyne incognita race 2 to persimmon cv. Kyoto was also studied under greenhouse conditions. After six months of the inoculation with increasing nematode population levels – 0; 160; 800; 4,000; 20,000; and 100,000 eggs/plant – a negative correlation with plant height and top dry weight values was obtained. As an intense root galling was associated with low nematode reproductive rates and some depressive effects on the plant growth, the reaction was rated as being of intolerance.

ASSUNTO(S)

nematóides parasitos de planta plant diseases fruticultura fruit crops doenças de plantas plant-parasitic nematodes

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