Evaluation of okra genotypes for resistance to shoot and fruit borer earias vittella (Fabricius)
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Date
2008
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Publisher
CCSHAU
Abstract
Thirty genotypes of okra, Abelmoschus esculentus (L.) Moench were evaluated for
field resistance during 2007 to shoot and fruit borer, Earias vittella (Fabricius). On the
basis of observation recorded on infestation level of fruits on number basis seven
genotypes, two resistant (HB-03-29-7B and HBT-1-19-1-1-2), two moderately resistant
(HB-03-14-11 and HB-03-26-1), one highly susceptible (HBT-1-18-1-C-1) and two
popular varieties (Varsha Uphar and HBH-142) were selected for elaborate studies under
field and laboratory conditions. The resistant genotypes showed significantly (P<0.05)
less fruit infestation both on number and weight bases than the susceptible one. Number of eggs laid per fruit did not differ significantly among the genotypes, thereby,
conforming no oviposition antixenosis in resistant genotypes. The impact of trichome
density (r= 0.671) and length (r= 0.871) were positive and significant. Survival of larvae
was less on fruit blocks (67.00-82.66%) and on whole fruits (33.01-51.66%) of resistant
genotypes, viz. HBT-1-19-1-1-2 and HB-03-29-7B in comparison to that of highly
susceptible genotype HBT-1-18-1-C-1 (82.66% and 51.66%), respectively.. Longer larval
period (15.33 -14.66 days), pupal period (9.66 and 10.33 days), lowest pupal weight (0.07
and 0.08 mg) and lowest per cent adult emergence (93.00 - 93.33%) were observed on
fruit blocks of resistant genotypes than on highly susceptible (HBT-1-18-1-C-1) (10.33
days, 8.66days, 0.11mg and 96.33%), respectively. Longer developmental periods (larval
and pupal) and lower larval survival and adult emergence on resistant genotypes suggest
antibiosis mechanism of resistance. The influence of trichome density and length and
thickness of pericarp did not cause any significant impact on larval duration of shoot and
fruit borer. There was significant adverse effect of whole fruit pericarp on larval survival,
likewise, phenol (r= -0.493), phosphorous (r= -0.546) and tannin (r= -0.738) of fruits of
resistant genotypes manifested adverse effect on larval survival. These compounds
showed positive relationship with larval and pupal periods. Adult emergence also showed
significant (P < 0.05) negative relationship with tannin (r=-0.726). The adverse effects of
resistant genotypes were found on various food consumption and utilization indices of E.
vittella larvae.
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Keywords
regeneration, planting, biological phenomena, biological development, developmental stages, vegetative propagation, fruits, pigeonpeas, hybrids, genetic processes