Contents - Faperta

Mechanisms and Inheritance of Resistance to Insect Pests 129
feeding by Spodoptera litura (F.), but result in slow growth of the larvae because of poor
nutritional quality of the food or the presence of secondary plant substances (Stevenson
et al., 1993). Larval mortality is the principal component of resistance to H. armigera in wild
tomato, Lycopersicon hirsutum f. sp. glabratum Mull. (Tingey and Sinden, 1982; Kashyap and
Verma, 1987). Antibiosis is also an important component of resistance to European corn
borer, Ostrinia nubilalis (Hubner) and corn earworm, H. zea in maize (Klun, Tipton, and
Brindley, 1967), and Colorado potato beetle, Leptinotarsa decemlineata (Say) (Sinden et al.,
1986) and potato tuber moth, Phthorimaea operculella (Zeller) in potato. The larvae of cabbage
looper, Trichoplusia ni (Hubner) are more effi cient in food utilization on the soybean
susceptible genotype, Davis, than on the resistant genotype, PI 227687 (H.C. Sharma and
Norris, 1993).
Antibiosis expressed in terms of larval mortality, slow growth, and delayed development
is one of the components of resistance to spotted stem borer, Chilo partellus (Swinhoe) (V.K.
Kumar, Sharma, and Reddy, 2005), and the sorghum midge, S. sorghicola (H.C. Sharma,
Vidyasagar, and Subramanian, 1993; H.C. Sharma, Franzmann, and Henzell, 2002) in sorghum.
Antibiosis is also expressed in terms of reduced fecundity in the sorghum head bug,
Calocoris angustatus (Lethiery) (H.C. Sharma, Lopez, and Nwanze, 1993).
Tolerance
Tolerance or recovery resistance enables a plant to withstand damage from an insect population
that is injurious to another cultivar without a tolerance mechanism of resistance.
Expression of tolerance is determined by the inherent capability of a genotype to overcome
an insect infestation or to recover from insect damage and/or add new plant growth after
insect damage. Plants with an ability to tolerate insect damage at times may produce more
yield than the plants of a nontolerant susceptible cultivar at the same level of insect infestation.
Tolerance often occurs in combination with antixenosis and antibiosis components
of resistance. Production of tillers in sorghum following damage to the main plant by sorghum
shoot fl y, A. soccata; and stem borer, C. partellu (H.C. Sharma and Nwanze, 1997),
serves as a component of recovery resistance (Figure 5.5). Fertility status and moisture
availability in the soil infl uence tiller production in plants damaged by shoot fl y and
stem borers in sorghum (H.C. Sharma, 1993). Increase in grain mass in panicles partially
damaged by sorghum midge, S. sorghicola (H.C. Sharma, 1997; H.C. Sharma, Abraham,
and Stenhouse, 2002), and less grain damage per unit number of head bugs, C. angustatus
(H.C. Sharma and Lopez, 1990, 1993; Padma Kumari, Sharma, and Reddy, 2000) serve as a
component of recovery resistance to insect feeding and damage in sorghum. Temperature
(Schweissing and Wilde, 1978) and nutrients (Schweissing and Wilde, 1979) affect the
tolerance of sorghum seedlings to damage by greenbug, Schizaphis graminum (Rondani).
Tolerance to insect damage has also been observed in alfalfa to weevil, Hypera postica
(Gyllen.) (Dogger and Hanson, 1963), in maize to corn earworm, H. zea (Wiseman,
McMillian, and Widstrom, 1972), in rice to brown planthopper, Nilaparvata lugens (Stal)
(Panda and Heinrichs, 1983; Heinrichs et al., 1984), in wheat to greenbug, S. graminum
(Starks and Merkle, 1977), in muskmelon to the aphid, Aphis gossypii Glover (Kennedy,
Kishaba, and Bohn, 1975), and in turnip to cabbage maggot, Hylemyia sp. (Varis, 1958).
Tolerance is an important component of resistance to H. armigera in cotton
(Balasubramanian, Gopalan, and Subramanian, 1977; Murthy et al., 1998). It is expressed in
terms of rejuvenation potential, healthy leaf growth, fl owering compensation potential,
and plant vigor. The cotton genotype JK 276-4, possessing quick rejuvenation and higher
fruiting effi ciency, suffers relatively less yield loss by H. armigera (Murthy et al., 1998).