Contents - Faperta

166 Biotechnological Approaches for Pest Management and Ecological Sustainability
However, rice varieties resistant to gall midge, Orseolia oryzae Wood-Mason have higher
amounts of free amino acids and low amounts of sugars in the shoot tips, while stem borer,
Scirpophaga incertulas (Walker) resistant varieties have lower amounts of amino acids and
sugars than the susceptible ones (Vidyachandra, Roy, and Bhaskar, 1981). Chhabra et al.
(1990) suggested that high amounts of nonreducing sugars and low amounts of starch in
chickpea variety GL 645 might be responsible for its low susceptibility to H. armigera.
Mungbean varieties with high sugar and amino acid content in leaves are resistant to
whitefl y, B. tabaci and the jassid, Empoasca kerri (Prathi) (Chhabra et al., 1988). High amounts
of vitamin C in guava fruits are associated with resistance to the fruitfl y, Bactrocera correcta
Bezzi (Arora et al., 2000). Leafhopper, A. biguttula biguttula, injury in okra, Abelmoschus
esculentus (L.) Moench, is negatively associated with calcium, but positively correlated with
phosphorous content (Uthamasamy, 1985).
Enzymes
Amylase and protease inhibitors in pigeonpea have been shown to have an adverse effect
on growth and development of H. armigera (Giri and Kachole, 1998). There is considerable
variation in H. armigera gut protease inhibitory activity in developing seeds of chickpea
(Patankar et al., 1999), and proteinase inhibitors from the nonhost plants (groundnut,
winged bean, and potato) are more effi cient in inhibiting the gut proteinases of H. armigera
larvae than those from its favored host plants such as chickpea, pigeonpea, and cotton
(Harsulkar et al., 1999). Protease inhibitors and chlorogenic acid are associated with aphid
resistance in tomato (Felton, Broaduray, and Duffey, 1989). Common bean genotypes with
resistance to bean weevil, Zabrotes subfasciatus (Boh.) did not show a signifi cant inhibition
of amylase. These lines contained arcelin, a major compound in seed protein, which is not
digestible by Z. subfasciatus, and hence its amino acids were not available to this insect
(Minney et al., 1990).
Molecular Markers
Simultaneous occurrence of a trait in the same population of two or more discontinuous
variants or genotypes is called genetic polymorphism. A wide variety of techniques have
been developed in the past few years for detecting DNA sequence polymorphism (Paterson,
Tanksley, and Sorrells, 1991; Staub, Serquen, and Gupta, 1996). DNA fi ngerprinting or
profi ling is based on combined use of several single locus detection systems for understanding
various aspects of plant genomes. These include characterization of genetic
diversity, genome fi ngerprinting, genome mapping, gene localization, genome evolution,
population genetics, taxonomy, plant breeding, and diagnostics. A good marker for use
in genomic studies should (1) be polymorphic in nature, (2) be codominant in inheritance,
(3) occur frequently in the genome, (4) be selective neutral in behavior, (5) possess easy
access and fast assay, (6) be highly reproducible, and (7) provide ease of exchange of data
between laboratories.
Several types of molecular markers have been used to evaluate DNA polymorphism and
are generally classifi ed as hybridization-based markers and polymerase chain reaction
(PCR)-based markers. In the former, DNA profi les are visualized by hybridizing the
restriction enzyme-digested DNA to a labeled probe, which is a DNA fragment of known