Contents - Faperta

Physico-Chemical and Molecular Markers for Resistance to Insect Pests 159
to H. armigera (Nanda, Sasmal, and Mohanty, 1996). Several morphological traits such as
pod shape, pod wall thickness, and crop duration infl uence H. armigera damage in chickpea
(Ujagir and Khare, 1988). Main stem thickness, leafl et shape and length, leaf hairiness,
and peg length are associated with resistance or susceptibility to H. armigera, and tobacco
leaf caterpillar, Spodoptera litura (F.), in wild relatives of groundnut (Sharma et al., 2003).
The H. zea damage in tomato is associated with vine size and fruit number (Ferry and
Cuthbert, 1973). Calyx texture, fl owering, and fruit skin thickness are also associated with
resistance to H. zea (Cosenza and Green, 1979). Pubescence on the leaf tip is associated with
reduced defoliation by H. zea, Spodoptera exigua (Hubner), and soybean looper, Pseudoplusia
includens (Walker) in soybean (Hulburt, Boerma, and All, 2004).
Leaf Hairs
Leaf hairs (that do not produce glandular secretions) play an important role in host plant
resistance to insects. Hairy cotton varieties are preferred by the cotton leaf roller, Sylepta
derogata Fab. (Mahal, Dhawan, and Singh, 1980), cotton white fl y, B. tabaci (Ilyas, Puri, and
Rote, 1991), and tobacco budworm, H. virescens (Lukefahr, Haughtaling, and Graham, 1971;
Robinson, Wolfonbarger, and Doday, 1980). Glabrous cottons have 60% fewer eggs of
H. virescens than the hairy ones. Some of the eggs laid on glabrous surface are also dislodged.
Females of H. armigera also lay more eggs on hairy varieties of cotton compared to
the glabrous ones (Natarajan, 1990). However, leaf hairs in cotton confer resistance to leafhopper,
Amrasca biguttula biguttula Ishida (Sharma and Agarwal, 1983a) (Figure 6.2), and
western tarnished plant bug, Lygus hesperus Knight (Benedict, Leigh, and Hyer, 1983).
Similarly in soybean, H. armigera females laid three times more eggs on the pubescent lines
as compared to the nonpubescent ones (Panda and Daugherty, 1975), but pubescent varieties
are highly resistant to leafhopper, Empoasca fabae Harris (Kogan, 1982). Wild relatives of
pigeonpea such as Cajanus scarabaeoides (L.) F. Muell. and C. acutifolius (F. Muell. Ex Benth.)
Maesen with nonglandular trichomes are not preferred by H. armigera females for egg
laying (Sharma et al., 2001). Rice varieties with hairy upper leaf lamina are less susceptible
to the Asiatic rice stem borer, C. suppressalis (Patanakamjorn and Pathak, 1967), while wheat
varieties with pubescent leaves are resistant to the cereal leaf beetle, Oulema melanopus (L.)
(Wallace, McNeal, and Berg, 1974). Leaf hairs also confer resistance to the jassid, A. biguttula
biguttula in brinjal (Gaikwad, Darekar, and Chavan, 1991), and to the mustard aphid, Lipaphis
erysimi Kalten. in Brassica juncea L. (Lal, Singh, and Singh, 1999).
FIGURE 6.2 Leaf hairiness in cotton associated with resistance to leafhopper, Amrasca biguttula biguttula.