Contents - Faperta

Evaluation of Transgenic Plants and Mapping Populations for Resistance to Insect Pests 47
pheromone, or kairomone traps in the fi eld. Light traps are effective in attracting brown
leaf hopper, N. lugens, green leaf hopper, Nephotettix virescens (Distant), and gall midge,
O. oryzae in rice (Prakasa Rao, 1975); stem borers of cereals (Sharma et al., 1992); and
H. armigera in cotton and food legumes (Sharma et al., 2005a). Kairomones present in the
leaves of susceptible pigeonpea varieties, which are attractive to egg-laying females of
H. armigera, can be used to increase insect abundance in the screening nursery. Moistened
fi shmeal is highly attractive to the sorghum shoot fl y, A. soccata, and is used in the interlard
fi shmeal technique to screen for resistance to this pest (Doggett, Starks, and Eberhart,
1970; Sharma et al., 1992).
Labelling the Plants or Inflorescences Flowering at the Same Time
The test material fl owering at the same time can be labelled with a ribbon or marked with
paint. Genotypes fl owering at different times can be marked with different colored labels.
This enables the comparison of the test material fl owering at the same time with the
resistant and susceptible controls of similar maturity. For comparisons to be meaningful,
the portion of the infl orescence (30 to 45 cm) can also be marked with twine or colored
labels. The data on insect damage should be recorded in the marked plants or portion of
infl orescence and comparisons made among the genotypes fl owering during the same
period. For this purpose, three to fi ve infl orescences may be tagged in each plot, depending
on the stage of screening of the material, and the resources available.
Techniques to Screen for Resistance to Insects under Artifi cial Infestation
Mass Rearing
Insects can be reared in large numbers on natural or artifi cial diets in the laboratory or
collected from the fi eld to screen the test material in the fi eld or in the greenhouse under
uniform insect infestation (Smith, 1989; Sharma et al., 1992; Smith, Khan, and Pathak, 1994).
Many insect species can be reared on natural diets. Greenbug, Schizaphis graminum
(Rondani) (Starks and Burton, 1977), brown planthopper, N. lugens (Heinrichs, Medrano,
and Rupasus, 1985), and many species of aphids and leafhoppers can be reared in the
greenhouse on their natural host plants. Protocols for mass production of insects on artifi -
cial diets for infestation of the test material under greenhouse or fi eld conditions have
been described for several insect species (P. Singh and Moore, 1985; Armes, Bond, and
Cooters, 1992; Sharma et al., 1992; Smith, Khan, and Pathak, 1994; N. Panda and Khush,
1995) (Figure 3.3).
Insect rearing should be planned such that the appropriate stage of the test insect is available
in adequate numbers for infesting the test material during the susceptible stage of the
crop. One of the major constraints to large-scale production of insects on artifi cial diets is
the high cost of infrastructure, particularly when special equipment and facilities with
appropriate control over temperature, relative humidity, and photoperiod are required.
Continuous production of insects on artifi cial diet also decreases their genetic diversity
(Berenbaum, 1986), which might lead to outcomes dissimilar to that of the natural populations
(Guthrie et al., 1974). This problem can be overcome by infusing insects from the fi eld
periodically or fresh culture can be initiated at the beginning of each season. This will also