STUDY OF CHITOSAN EFFECT ON MORPHO-PHYSIOLOGICAL CHARACTERS AND CaRGA2 GENE EXPRESSION OF Phytophthora capsici INFECTED PEPPER (Capsicum annuum)

• Main Author: Mahani, Soraya
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/34615
• Institution: Institut Teknologi Bandung

Blight pepper disease by Phytopthora capsici is one of the most serious threat in pepper production in Indonesia, because it is attack at almost every phase of life and each part of pepper plant. To cope this problem, farmers usually use synthetic fungicides, but synthetic fungicides can cause various problems such as accumulation of residues, resistance of pathogens, disease epidemics, and environmental pollution. For that reason, an alternative fungicide need to be found. Nowadays, known chitosan could increase plant growth and has antifungal properties that can be used as an alternative to synthetic fungicide. Expression of CaRGA2 gene can be induced during Phytophthora capsici infection. The aim this research was to study the chitosan effect on morpho-physiological characters and resistance of Phytophthora capsici infected pepper using molecular study of CaRGA2 expression. This study contacted to four cultivars (CM334, Laba, Lado, and 15080). The pepper plants were treated chitosan by spraying in every week with a concentration range is 0; 0.2; 0.6; and 1 mg/ml. The inoculation of Phytophthora capsici by foliar spray at 33 days of age the plants. Phenotypic analysis was tested with observation of morpho-physiological characters (plant height, the number of leaves and chlorophyll content), Scanning Electron Microscopy (SEM), and resistance index of plants. Resistance index of plants tested at day 10 after inoculation using Disease Incidence Index and Disease Severity Index. Molecular analysis was done using RT-PCR and sequencing confirmation. The analysis of gene expression of CaRGA2 on leaf tissue of CM334 and 15080 cultivars after inoculated with Phytophthora capsici. The results showed that chitosan treatment on plants have height significantly different in all cultivars, in the number of leaves on CM334 and 15080 cultivars, and in the chlorophyll content on CM334, Lado and 15080 cultivars. The results of the resistance test with both methods showed that 1 mg/ml of chitosan was the best concentration in protecting plants from Phytophthora capsici on Laba, Lado and 15080 cultivars. Based on reverse transcriptase PCR, CaRGA2 did not express on the leaf tissue treated with 1 mg/ml chitosan while on the leaf tissue without chitosan, CaRGA2 was expressed. As a conclusion, chitosan 1000 ?g/ml can inhibit the infection of Phytophthora capsici in pepper, which cannot be characterized by CaRGA2 expression using reverse transcriptase PCR.