Correlation of biochemical leaf traits and gall formation in six cultivars of mango, Mangifera indica L.

The factors determining the densities of herbivores include variation in genotype, the plant’s environment, differential host plant resistance and natural enemies that may act on herbivores (Stiling, 1994). Intra-population genotypic variations in resistance have been reported in several host plant species which exert selective pressures on the ability of insects for herbivory (Anderson et al., 1989). Several assumptions concerning the role of morphological and physio-chemical plant characters on the infestation of herbivores have been proposed in the past (Mattson and Haack, 1987; Price, 1991). The chemistry of leaf with respect to defensive compounds and nutritional values varies among clones of a single species and such variations are expected to influence the behavior of herbivores (Hemming and Lindroth, 1995). Ultimately, these variations in leaf quality could be a source to evolve genetically isolated groups within insect species with the adaptation of individual plants (Edmunds and Alstad, 1978). There are certain prerequisites to evolve such groups including variations in plant physiology and/or leaf traits exist among host individuals, and suitability of individual host plants for several generations of insects (Ruhnke et al., 2009). Of these, resource heterogeneity has been assumed an important factor, and explored in several tree species in the past (Marquis, 1988; Fortin and Mauffette, 2002; Roslin et al., 2006) and most of these studies were based on nutrient analyses. Mango (Mangifera indica L.) is one of the oldest cultivated and most economically significant tree for the people of the Indian subcontinent (Tharanathan et al., 2006). It is heavily attacked by different insect pests, including fruit flies, hoppers, mealy bug and gall formers. (Khan et al., 2013). Mango blister circular galls are now emerging threat to Asian mangoes and these are formed by still not described species of Cecidomyiidae (Diptera) in Pakistan ( Khan et al., 2013), but their taxonomic description is rare at Pakistan level. To date, there is a lack of basic knowledge, particularly in Pakistan, about the correlation of biochemical characteristics of leaves of different mango cultivars and gall formation. Therefore, the present study was carried out with major emphasis on to investigate the intra-specific variability in gall formation, and variation in leaf traits (nutrients) responsible for gall formation in six mango cultivars (Anwar ratole, Chaunsa, Dusehri, Fajri, Sindhri and Siroli) during 20092010. The findings of this research activity made it possible to explain the following research questions: a) Do leaf traits/nutrients of different mango cultivars vary among individual trees, and different zones within a tree? b) Is gall formation relate to leaf traits? c) Is variation in leaf traits/nutrients and gall abundance consistent across the study period? and d) Is gall abundance vary across different vertical strata (based on sunlight) of the mango canopy? Pak. J. Agri. Sci., Vol. 54(1), 91-96; 2017 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/17.3647 http://www.pakjas. com.pk