Contents - Faperta

Host Plant Resistance to Insects: Potential and Limitations 87
FIGURE 4.3 Helicoverpa armigera damage at the vegetative (A) and reproductive (B) stages in resistant
(ICC 506EB) and susceptible (ICC 3137) genotypes of chickpea.
• Spotted pod borer, Maruca vitrata (Geyer), in pigeonpea and cowpea (Sharma,
Saxena, and Bhagwat, 1999; Sharma and Franzmann, 2000).
• Pea weevil, Bruchus pisorum L., in pea (Clement et al., 1994).
Moderate levels of resistance have been discovered (1) against the Colorado potato beetle,
Leptinotarsa decemlineata (Say), potato tuber moth, Phthorimaea opercullela Zeller, and
green peach potato aphid, Myzus persicae (Sulzer) in potato (Sams, Lauer, and Redcliffe,
1975; Sinden et al., 1986; Ortiz et al., 1990); (2) against the spotted alfalfa aphid, Therioaphis
maculata (Buckton) in alfalfa (Thomas, Sorensen, and Painter, 1966); (3) carrot fl y, Psila rosae
(Fab.) in carrot (Stadler and Buser, 1984); (4) fruit borers, H. zea and H. armigera in tomato
(Cosenza and Green, 1979; Kashyap and Verma, 1987); (5) cotton aphid, Aphis gossypii
Glover in muskmelon (Kennedy, Kishaba, and Bohn, 1975); and (6) cabbage maggot,
Hylemyia sp. in turnip (Varis, 1958). Insect-resistant cultivars with desirable agronomic
backgrounds have been developed in several crops, and cultivars with multiple resistance
to insect pests and diseases will be in greater demand in the future for sustainable crop
production. This requires a concerted effort from scientists involved in crop improvement
programs worldwide. At the moment, there is a great amount of variability in:
• Emphasis placed on plant resistance in crop improvement programs.
• Availability of cost-effective and reliable resistance screening techniques.
• Progress made in identifi cation and utilization of sources of resistance to insect
pests.
• Multilocational testing to understand genotype-environment interactions.
• Emphasis given to insect resistance in identifying and releasing new crop
cultivars.
• Efforts to spread and popularize insect-resistant cultivars.
Wild Relatives of Crops as Sources of Resistance to Insects
Wild species of crops are important sources of genes for resistance to biotic and abiotic
constraints (Stalker, 1980; Plucknett et al., 1987; Xiao et al., 1996). In cotton, resistance to
H. armigera has been reported in several wild species, such as Gossypium thurberi Todaro,