Studies on cowpea varietal resistance to the cowpea flower and pod borer, Maruca Testulalis (Geyer) (Lepidoptera: Pyralidae)
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Date
1985
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Publisher
Obafemi Awolowo University, Ile Ife, Nigeria
Abstract
Several varieties of cowpea, Vigna unguiculata s.sp. unguiculata (L,) Walp., were screened for
resistance to the cowpea flower and pod borer, Maruca testulalis (Geyer) using free-choice field
trials, cohort tests in large screened cages and no-choice tests in the screenhouse and the
laboratory. The dam-age potential of M. testulalis on Ife Brown cowpea was also studied using
controlled infestations in order to establish a base-line infestation level that could be used to
differentiate resistance effectively in no-choice tests.
The study on the damage potential showed that successful establishment of the first in star larvae
could only be obtained and sustained throughout the crop growth at the flower bud stage. At this
stage, infested plants showed significantly reduced numbers of flowers and pods as well as seed
yield. Two first in star larvae per plant was the lowest infestation that produced such significant
differences between infested plants and the control. Thus, it is suggested as an adequate level for
differentiating susceptible and resistant varieties in no-choice tests employing Ife Brown as a
standard.
The free-choice field trials showed significant differences in the degree of susceptibility of the
varieties screened. Using overall susceptibility indices that considered some parameters
associated with pest attack and which could affect flowering, podding and seed yield, TVu 1896
A/G, Sese, EW/1 and H64-3 were found to be moderately resistant to flower damage; while 2Ak
and TVu 1896 A/G were shown to be moderately resistant to pod and seed damage.
The field resistance was confirmed by the cohort and no-choice tests. TVu 1896 A/G and H51-1
were found to be resistant to pod and seed damage while TVu 946 and 2Ak were moderately
resistant. Non-preference for oviposition and larval feeding appeared responsible for the
resistance observed. Antibiosis manifested in form of reduced weight and size, and lengthened
pupal period was also observed
Description
129p
Keywords
Seed, Seedlings, Maize, Metabolism, Assimilation, Carotenes, Flavonoid, Oxidative, Growth, Glutamat, Dehydrogenase