MICROCLIMATE, FLOWER VOLATILE COMPOUNDS AND FLOWER-VISITING INSECTS RELATIONSHIP AND ITS IMPACT ON FRUIT PRODUCTION OF ARABICA COFFEE (COFFEA ARABICA)

• Main Author: Hafsah
• Format: Dissertations
• Language: Indonesia
• Subjects: Ilmu hayati ; Biologi
• Online Access: https://digilib.itb.ac.id/gdl/view/52251
• Institution: Institut Teknologi Bandung

Animals and plants respond to microclimate changes in their own ways. Their responses can indirectly affect the quantity and quality of the yield, including in coffee plant. The main objective of this study was to analyze the relationship of microclimate differences on the flower volatile compounds secretion and the diversity of visiting-flower insects, as well as their impact on the quantity, quality of the yields and the taste of coffee. The study was conducted in four central Arabica coffee plantation in Java, Indonesia, which showed differences in average annual rainfall. The profile of coffee’s flower volatile compound was analyzed using the SPME-GCMS method. Visiting insect on coffee flower were collected by direct sampling using sweeping net. The effect of visiting insects on crop yields was carried out through the mesh gauze experiments. During field observations, microclimate variables were measured, which consisted of physical, edaphic factors and shading tree canopy density. The quantity of coffee production were measured by counting the number of fruit set and fruit mass, while the quality parameters were done by calculating the percentage of peaberry formation and fruit defects. Metabolite analysis of coffee bean were done by analyzing the secondary metabolite composition of coffee bean by GC-MS profiling method, calculating the total of phenolic content (Folin Ciocalteu method) and the inhibitor concentration and antioxidant activity (IC and IC50) by DPPH method. Coffee flavor was analysed by measuring the caffeine and chlorogenic acid (CGA) content in coffee green beans using the HPLC method. A total of 114 volatile compounds were found in coffee flowers, in which 38 of them were known to have an association with insects. The secretion of flower volatile compounds was closely related to microclimate conditions. Water content and soil temperature are two edaphic factors that the most related with many coffee flowers volatile compounds. A lot of insects that were positively correlated with ?-Ocimene compound, indicated that this compound might be potential as general attractants to insect pollinators in coffee. The difference in microclimate has potentialy cause the differences in the diversity of insect flower visitors. Light intensity was the physical factor that most correlated with the presence of insect visitor. A total of 36 species were known visiting coffee flowers. Apis cerana, Lasioglossum sp, Episyrphus sp and Metallea setose were found in the observed flowers at all coffee plantations. Apis cerana, Lasioglossum sp, and Episyrphus sp have been widely reported as pollinator in coffee, but not with Metalea setose (Blowfly). This insect might be a potential new pollinator for coffee plants. Insect pollination was affect the increasing of fruit set formation (?=0.05). However, the presence of predatory insects during flowering period has potentialy reduce the fruit mass. In terms of quality, insect pollination can improve fruit quality by reducing pea berries production and fruit defects. The diversity of insect flower visitor was correlated with decreasing of pea berries production, whereas insect visiting intensity was correlated with decreasing of fruit defect production. As many as 40 metabolite compounds were found in green coffee beans, including hydrocarbons (13), fatty acids (12), phenolics (10), alkaloids (4) and sugars (1). Insect pollination did not show a significant effect on the composition of coffee beans secondary metabolite compounds. The metabolite composition of insect-pollinated bean did not show any differences with the metabolite composition of bean from other pollination treatment. Likewise, the total phenolic content and its ability to inhibit free radicals (IC). However, the total phenolic content of insect-pollinated bean was the lowest among all treatments and their ability to inhibit the free radicals was higher than the control. The insect visiting intensity was significantly affected the increasing of caffeine levels (? = 0.10) and decreasing of CGA levels (? = 0.05) in coffee beans. Insect-pollinated fruits were contain higher caffeine and a lower CGA than control that similiar with specialty coffee characteristics (cupping score > 80) that involved in this analysis. Insect pollination contributes to the improvement of the quality of the coffee taste by increasing the caffeine content and decreasing the phenol and chlorogenic acid (CGA) content. In the insect-pollinated coffee fruit, there is a tendency that the higher rainfall produced the lower of the percentage of pea berries, fruit defects, and inhibitor concentration (IC). On the other hand, the higher rainfall, the heavier of the fruit mass. Meanwhile, the percentage of fruit set and total phenolic compound tends to be constant. The presence of insects pollinator can overcome the decline in yields due to the increase of rainfall, by keeping in high fruit set production. In the insect-pollinated fruit, the higher rainfall triggered higher caffeine content and lower CGA content. The increase in rainfall in the future is predicted will produce coffee fruits with higher in caffeine and lower in CGA.