Contents - Faperta

Host Plant Resistance to Insects: Potential and Limitations 85
plant resistance to insects will play a major role in application of tools of biotechnology
for integrated pest management and sustainable crop production. Sources of resistance
with diverse mechanisms (genes) will be the key for marker assisted transfer of insect
resistance genes into high yielding cultivars. Conventional host plant resistance can
also be deployed along with the novel genes to make transgenic plants an effective
weapon for pest management. Host plant resistance to insects may be classifi ed into the
following categories.
Pseudo-resistance: Pseudo-resistance or false resistance through avoidance of insect
infestation.
Constitutive resistance: Constitutive resistance is independent of environmental
factors and is due to physico-chemical characteristics of the host plant that affect
the host selection and feeding behavior, survival, development, and fecundity of
insect pests, and thus, the extent of insect damage.
Inducible resistance: Inducible resistance is due to the infl uence of temperature,
photoperiod, plant-water potential, chemicals, and pathogen or insect damage on
the production and accumulation of secondary plant substances (phytoalexins) or
due to their effect on nutritional quality of the host plant.
Associate resistance: Associate resistance is due to the presence of resistant or nonhost
plants in the vicinity. Associate resistance also occurs in multilines or synthetics as
a result of diversion or delaying actions of mixture of plants resulting in slow development
of an insect biotype that is capable of damaging the resistant cultivars.
Identification and Utilization of Resistance
Extensive screening of germplasm has been carried out to identify sources of resistance
to insect pests in several crops (Painter, 1951; Panda and Khush, 1995; Clement and
Quisenberry, 1999; Sharma et al., 2003b; Smith, 2005). Sources of resistance have been
identifi ed against the following insect pests.
• Corn earworm, Helicoverpa zea (Boddie), corn borer, Ostrinia nubilalis (Hubner),
sugarcane borer, Diatraea grandiosella (Dyar), fall armyworm, Spodoptera frugiperda
( J.E. Smith), and spotted stem borer, Chilo partellus (Swinhoe), in maize (Mihm,
1982, 1985; Swarup, 1987).
• Brown planthopper, Nilaparvata lugens (Stal) (Figure 4.1), gall midge, Orseolea oryzae
Wood-Mason, and stem borers, Scirpophaga incertulas (Walker) and Chilo suppressalis
(Walker), in rice (Saxena, 1986; Kalode, Bentur, and Srinivasan, 1989; Smith,
Khan, and Pathak, 1994).
• Hessian fl y, Mayetiola destructor (Say), and greenbug, Schizaphis graminum (Rondani),
in wheat (Starks and Merkle, 1977; Roberts et al., 1979; Smith, 2005).
• Sorghum shoot fl y, Atherigona soccata (Rondani) (Figure 4.2), spotted stem borer, C.
partellus, sorghum midge, Stenodiplosis sorghicola (Coquillett), and head bug, Calocoris
angustatus (Lethiery) in sorghum (Sharma et al., 1992, 2003b; Sharma, Vidyasagar,
and Leuschner, 1988a, 1988b; Sharma, 1996; Padma Kumari, Sharma, and Reddy,
2000).