EFFECT OF LEGUMES ROTATION ON PINEAPPLE ROOT DISEASE IN HUIMANGUILLO, TABASCO, MEXICO

Quick decline in productivity is characteristic of agro-ecosystems established throughout tropical regions in the world. This is due to, amongst other causes, epidemic diseases. Frequently, attempts of management based on the use of external energy, normally of synthetic chemicals (mainly pesticides and fertilizers), sometimes result in major unbalances making agriculture, an unaffordable enterprise. Recent research results seem to indicate successful management strategies of root diseases by inducing deep changes in the agro-ecosystems structure, resulting in the recovery of the suppressive capacity of soils to locally important root diseases, based on the beneficial action of legume plants used in crop rotation systems. Pineapple production in the majority of the world’s productive regions is carried out as monocrop and its major diseases are: Mealybug wilt, heart and root rot (Phytophthora spp), nematodes root gall and root lesions such as Meloidogyne spp, Pratylenchus brachyurus and Rotylenchulus reniformis. The objectives of this work were to document the increased productivity of pineapple after legume rotations, as well as to define the beneficial effects of reducing root pathogen populations and/or incidences. In this study, the apparent stability resulting from the rotation with tropical legumes, evidenced by higher yields, could be partly explained by the lower incidence (isolation of root pathogens) and higher root weight of pineapple, particularly in Mucuna’s rotation. Pineapple plant height and root weight were significantly higher (P=0.0001) for M. deeringiana rotation 40.8cm and 23.67g respectively, whereas in Canavalia`s rotation plant height and root weight were 28.9cm and 7g respectively. In the control, plant height was 31.74cm and root weight was 8.14g.
Phytophthora was more frequently isolated than Pythium, and the species, based on its morphology more likely is P. citricola. Significant differences (P= 0.0068) were detected for frequency of isolation of Phytophthora sp. The higher incidence was detected on plants from the non-rotation treatment, followed by Canavalia with lowest incidence detected on M. deeringiana. This could explain the reduction in root weight of pineapple in the control and Canavalia plots. Significant differences (P= 0.046) were also observed for Pratylenchus populations among treatments, where the higher populations were detected for the control and Canavalia rotation, both in soil and roots.