Contents - Faperta

Evaluation of Transgenic Plants and Mapping Populations for Resistance to Insect Pests 55
DR
10
9
8
7
6
5
4
3
2
1
0
FIGURE 3.6 Reaction of three chickpea genotypes for resistance to Helicoverpa armigera under no-choice
cage screening in the greenhouse. DR, damage rating, 1 10% leaf area damaged, and 9 80% leaf area
damaged; DAI, days after infestation. *Number of larvae per plant.
and utilization of food by insects to gain a better understanding of the mechanisms of
resistance. Marfa et al. (2002) used whole plants or small pieces of leaves or stems of transgenic
plants to determine the degree of insect resistance in transgenic rice plants (transformed
with either the cry1B or maize proteinase inhibitor [mpi] genes) to rice stem borer,
Chilo suppressalis (Walker). The bioassay consisting of rice seeds germinated in vitro using
Murashige and Skoog medium in test tubes, and then infestation of each 3- to 4-cm long
seedling with one neonate larva obtained from surface-sterilized eggs of rice stem borer,
C. suppressalis has been found to be quite effective. On nontransformed plants, the larvae
developed normally, while those fed on plants transformed with cry1B died after a few
days of infestation. On transgenic plants with the mpi gene, the neonate larvae did not die,
but their growth was slower as compared to that on the nontransgenic control plants.
Detached Leaf Assay
The detached leaf assay has been used successfully in several crops in which a leaf with
a petiole, a small branch, or an infl orescence can be placed into water, 3% agar-agar, 1%
sugar solution, Arnon, or Hoagland solution in a plastic or a glass jar of appropriate
capacity to keep the leaves in a turgid condition for fi ve to seven days (Figure 3.8).
8 DAI
5 10 15 20 25
Infestation level*
ICC 506 ICCV 2 Annigeri ICCC 37
FIGURE 3.7 No-choice cage technique to screen chickpea for resistance to Helicoverpa armigera. ICCC 37,
Susceptible check and ICC 506, Resistant check.