Alterations in The Photosynthetic Pigments of Cinnamomum Verum (Presl.) Due to Infestation by The Gall Mite, Aceria Doctersi (Nalepa, 1909) (Acari: Eriophyidae)

Aceria doctersi is a highly host specific eriophyid mite, infesting and inducing varying numbers of pouched galls on the leaves, leaf petioles, inflorescence and the young shoots of Cinnamomum verum, one of the most economically important spice and medicinal crop. In the present study, the feeding impact of a gall forming eriophyid mite viz. A.doctersi on the photosysthetic pigments of its host plant, C. verum was studied by analyzing chlorophyll a, chlorophyll b, total chlorophyll (a+b) and carotenoid contents of infested and uninfested leaves. The results of the study revealed a significant reduction in amounts of chlorophyll a, b, total chlorophyll and carotenoid pigments, thereby elucidating the potential of the mite in hindering the photosynthetic efficiency of the host plant. INTRODUCTION Eriophyid mites represent an exclusively phytophagous group exhibiting high host specificity (Keifer, 1982), (Weis, et al. 1992), inducing diverse types of abnormalities like galls , blisters, erinea, big buds, leaf rolling, stem and foliar deformation, russetting, silvering and bronzing of leaves etc. on their respective host plants (Castagnoli,1996). Neoplastic formations developed in the form of galls involve parasitism and are believed not to benefit the host plants (Armstromg 1995; Silva et al. 1996). The gall formers have been regarded as phloem parasites (Fay et al. 1996). The affected host plants respond to herbivore attack by altering photosynthetic rate which in turn would partly determine the resource base for defenses, changes in food quality, or compensatory growth (Larson, 1998). A. doctersi (Fig:1b) is an eriophyid species which feeds exclusively on C. verum, an important economic crop of multiple utility in medicine as astringent, antiseptic, carminative and stimulant and its use against Type 2 diabetes, (Lu, T et al. 2012) colds, diarrhea and various problems of the digestive system. In addition, Cinnamon essential oil has significant antioxidant and antimicrobial properties as well (Priyanga et al. 2013). A.doctersi while sucking the sap from the leaves, inflorescence and tender stem of C. verumm, stimulates the formation of innumerable number of pouched galls of varying dimensions. Quite often, individual galls become fused to form complex, irregular, massive structures, covering the entire leaf lamina including the midrib, veins and vein lets. This in several occasions results in severe distortion and subsequent drying up of leaves. (Fig:1c) Considering the medicinal and nutritional importance of C. verum, the present work was taken up to understand the severity of damage induced by A. doctersi on the photosynthetic rate of the plant, by assessing the alterations induced by the mite on the photosynthetic pigments like chlorophyll a, b total chlorophyll and carotenoids. MATERIAL AND METHODS Collection of plant samples: Leaf samples for pigment analysis such as the galled and uninfested leaves were collected from naturally growing plants of C. verum having a height of six feet in the Calicut university Campus area in Malappuram district, Kerala during AprilMay, 2013. For rating the degree of damage, four categories of fresh leaf samples were considered: (A) Uninfested control leaf; (B) Leaf tissue around gall; (C) Galled leaf tissue; (D) Mature gall tissue. Analysis of photosynthetic pigments: Chlorophyll a, chlorophyll b, total chlorophyll and carotenoids were extracted from one gram each of fresh normal healthy leaf tissue and mite infested leaf tissue in 80% acetone and measured spectrophotometricallyand calculated based on the formula by Arnon, 1949. The amount of the various pigments were expressed in μg/g of dry mass basis. Statistical analysis The data obtained on the quantitative analysis of photosynthetic pigments were analysed using ANOVA (SAS software, version 9.0.) Descriptive analysis was done by using SPSS, version 16.0. RESULTS Mite infested leaves and leaf galls collected from C. verum growing in various localities of Calicut University Campus appeared highly distorted, bearing pouch like galls, both on the abaxial and adaxial surfaces (Fig:1a). Results of quantitative analysis performed on the photosynthetic pigments revealed a drastic reduction in both a and b contents as well as carotenoid pigments (μg/g DW) when compared to the fresh uninfested, control leaves (Table:1). As shown in Table 1, mature galls showed significantly lower concentrations of chlorophyll a (405.4±4.1μg−1 DM) and chlorophyll b (336.3±3.5μg g−1 DM)), total chlorophyll (777.5±3.06 μg−1 DM) and carotenoid pigment (346.4±11.65μg g−1 DM) when compared to the control leaf tissue [chlorophyll a (2236.388±44μg−1 DM), chlorophyll b (1205.3±38μg g−1 DM)), total chlorophyll (3344±28μg−1 DM) and carotenoid pigment (4006.392± 34μg g−1 DM). Fig: 1a. Pouch like galls on the leaf of C. verum covering