Caractérisation du pouvoir pathogène et de la biodiversité de plusieurs populations de nématodes apparentés à Pratylenchus coffeae sur caféiers (Coffeae sp.) et bananiers (Musa sp.)

Abstract

The specific characterization of nematodes, like all other plant pests, is a major stake to develop efficient and durable control strategies. Recent studies showed that P. coffeae, causing important damages on banana and coffee plants in the neotropical region, in fact regrouped a specie complex very difficult to identify by classical taxonomy tools. Studies have been undertaken on some isolates of Pratylenchus spp. taken on these two crops, to precise their pathogenicity and try to define some characterization tools as acurrate as possible. A biochemical approach has been undertaken by the study of esterase diversity with the isoelectric focusing technique. This study has allowed to reveal an important diversity between isolates but still stay insufficient at this steps to clarify their taxonomic status. Studies in planta confirmed an important negative correlation between the nematode population development in roots (agressivity) and the amount damage (roots weight), on banana as well as coffee plant. Chlorophyll rate in banana leaves was also negatively correlated to the nematode number. On the other hand, this parameter was not considered on coffee plant, the plantlets, too young, presenting not sufficient chlorophyllian pigments. Isolates showed a large range of agressivity, and therefore, damage on studied plants. Moreover, the isolates taken on coffee plant were not able to develop on banana plant. In contrast, isolates taken on banana plant were able to develop on coffee plant. This result is not in agreement with the use of banana and coffee plant as intercrop on some countries. Isolates take on plantain were not able to develop neither on banana nor coffee plant. All results confirmed the important diversity between all Pratylenchus isolates. These data also showed the complexity of traditional populations regrouped under the name P. coffeae. They supported the necessity to find acurrate tools to clarify this specific complex and to adapt pest control. Among those, the varietal resistance could play a major part. Preliminary tests on Coffea canephora material screening, already know for these numerous resistances, outlet on the demonstration of a variety which were resistant to the complex “P. coffeae”, This variety belongs to the subgroup SG2 in the “Congolais” goup. However, following hardiness observations on this plant, this group is since a long time used like rootstock in many countries. Few studies have been carried out on the resistance of this plant material. It now appears necessary to encourage this way to find some efficient control strategie against this parasitic complex. (Résumé d’auteur