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Pod Wall Toughness Has No Effect on Cowpea Resistance to the Legume Pod Borer Maruca Testulalis Geyer (Lepidoptera: Pyralidae)

  • S. Oghiakhe
  • L. E. N. Jackai
  • W. A. Makanjuola
Research Article

Abstract

The possibility of the involvement of pod wall toughness in the resistance of cowpea, Vigna unguiculata (L.) Walp., to the legume pod borer, Maruca testulalis was studied. The toughness of non-intact and intact pod wall increased with age, but the rate varied at different growth stages of the pod as well as between cultivars. There was a positive and significant correlation (r = 0.82**) between pod age and pressure required to penetrate pod wall. No significant differences (P > 0.05) were observed in non-intact pod wall toughness between TVu 946 (resistant) and IT82D-716 (susceptible) at all the growth stages tested. However, significant differences (P < 0.05) were observed between these two cultivars for only 6-day-old intact pods where IT82D-716 recorded a higher value than TVu 946. Correlation between pod damage severity by M. testulalis and toughness of non-intact and intact pod wall of these cultivars at different growth stages were not significant.

While pod wall toughness would be a desirable trait, it is concluded from this study that pod walls of the cultivars studied did not play any appreciable role on cowpea resistance to the larvae of M. testulalis.

Key Words

Pod wall toughness cowpea (Vigna unguiculataMaruca testulalis resistance biophysical factors 

Résumé

Cette étude porte sur le role éventuel de la dureté de la paroi des gousses de niébé, Vigna unguiculata (L.) Walp., dans la résistance à Maruca testulalis. La duretée des gousses, intactes ou non, augmente avec l’âge et varie en fonction des cultivars. On a observé une corrélation positive et significative (r = 0.82**) entre l’âge de la gousse et la force requlse pour perforer la paroi de la gousse. Aucune différence significative de dureté n’a été notée chez les gousses non intactes de TVu 946 (résistant) et IT82D-716 (sensible) aux différents stades de maturation. Toutefois, des différences significatives (P < 0.05) sont apparues entre ces deux cultivars sur les gousses intactes de 6 jours, IT82D-716 affichant une dureté supérieure à celle de TVu 946. Les relations entre le degré de destructions de la paroi de M. testulalis et la résistance des murs de parois intacts et non-intactsdes différentes cultures à différents stades de développement étaient insignifiantes.

Bien que la dureté de la paroi de la gousse semble être une caractéristique désirable, cette étude nous permet de conclure qu’elle ne joue pas un role significatif a l’heure actuelle dans la résistance du niébé aux larves de M. testulalis.

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References

  1. Chiang H. S. and Jackai L. E. N. (1988) Tough pod wall: a factor involved in cowpea resistance to pod sucking bugs. Insect Sci. Applic. 9, 389–393.Google Scholar
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Copyright information

© ICIPE 1992

Authors and Affiliations

  • S. Oghiakhe
    • 1
  • L. E. N. Jackai
    • 1
  • W. A. Makanjuola
    • 2
  1. 1.International Institute of Tropical AgricultureIbadanNigeria
  2. 2.Department of Biological SciencesUniversity of LagosLagosNigeria

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