Anatomical basis of cowpea resistance to the pod borer, Maruca testulalis (Geyer)

Abstract

The anatomy of damaged and undamaged young stem, peduncle and young pods were examined from transverse sections in three varieties of cowpea in order to evaluate the anatomical basis of resistance to the pod borer Maruca testulalis. While tissue development in the stem, peduncle and pods of the three varieties of cowpea were similar, the relative thickness of the various tissues were different in the order Vita-1>ICV-2>TVu 946. The smaller diameter and the relative abundance of strengthening tissues in the stem and peduncle of TVu 946, by limiting total ingestible biomass, might be restricting the damage to these organs by the pod borer. Pod damage, on the other hand, was concentrated on the parenchymatous tissue of the pod wall lining and inter-seed spaces and the sizes of this tissue were also different among the varieties in the order Vita-l>ICV-2>TVu 946, the same order of susceptibility to attack by M. testulalis. L’anatomie d’une jeune tige endommagee et non-endommagee, le pedoncule et des feunes cosses ont ete examines de la section transversale pour trois varieties d’haricot pour evaluer la base anatomique de la resistance au perceur de la cosse, Maruca testulalis. Tandis que le developpement du tissu dans la tige, le pedoncule et les cosses des trois varieties d’haricot etaient similaires, l’epaisseur relative des divers tissus etait differente dans l’ordre Vita-1>1CV-2>TVU 946. Le petit diametre et l’abondance relative des tissus de renforcement dans la tige et le pedoncule du TVU 946 en limitant la biomasse totale ingerable, auraient restreint le dommage a ces organes par le perceur de la cosse. L’abime de la cosse, de l’autre part, etait concentre sur le tissu parenchymateux de l’ecorse de la cosse et l’espace entre les grains et les grosseurs de ce tissu etaient aussi differentes parmi les varieties dans l’ordre Vita-1>1CV-2>TVU 946, susceptibilite a l’attaque par Maruca testulalis.