Caracterização de Pythium Cucurbitacearum, e controle alternativo da podridão do colo e das raízes do mamoeiro, grupo solo, cultivar Golden

Abstract

The damping-off of seedlings of papaya (Carica papaya L.) caused by species of Pythium has already been notified sometime in the world and recently in Brazil. The disease can lead to irreversible damage Culture, compromising its development. The implementation of an alternative control method with the use of natural products can arise as a viable solution for the production of the seedlings. This study aimed to characterize molecular and morphological species of Pythium cucurbitacearum and evaluate the effect of the products in the in vitro inhibition of the pathogen, and in control of root rot through the induction of resistance in papaya, seedlings, soil group, Golden cultivar. To this end, experiments were conducted in the Laboratories of Plant Pathology and Plant Pathology Molecular and and Plant Physiology of Center Agrarian Sciences, Federal University of Alagoas (CSA/UFAL). In the first experiment, we studied the species of Pythium, causal agent of stem rot and in roots of papaya, Soil group, cultivar Golden, from molecular and morphological characterization, pathogenicity, virulence in different hosts and establishment of culture media for mycelial growth of the pathogen. Later, in a second experiment, we evaluated the antifungal activity, incorporating the medium CA (Carrot and Agar), different concentrations of essential oils of peppermint (Mentha piperita L.), citronella (Cymbopogon nardus L.) and eucalyptus globules (Eucalyptus globulus L.), the inductor Ecolife®, aqueous extract of garlic (Allium sativum L.) and neem (Azadirachta indica A. Juss) emulsified, obtained from cold extraction of seeds (Natuneem®). The third experiment evaluated the potential of alternative products tested in vitro in selected doses to control in nursery conditions the papaya seedlings infected by Pythium cucurbitacearum. Based on the best results from the action of the products, it was performed a test in papaya seedlings with 60 days of age in order to evaluate the action of alternative products and LD β-amino-n-butyric acid (BABA), in activity of enzymes related to the induction of resistance in papaya leaves, by increasing activity enzyme Peroxidase (POX) and Phenylalanine Ammonia-Lyase (PAL), related with to plant defense responses. The results showed 100% genetic similarity of pathogen studied with the species Pythium cucurbitacearum, by phylogenetic analysis based on the Cox1 of DNA region constructed using the method of 'maximum likelihood tree' based on 1000 replicates the "bootstrap". The isolate was shown to be pathogenic to fruits and papaya plants showed virulence in different hosts. The means of culture PDA, CA, V8, CMA, CFMA and FMA provided good development of Pythium species studied. The essential oils tested, the inductor Ecolife®, the aqueous extract of garlic and the commercial product Natuneem®, Were effective in the in vitro control of Pythium cucurbitacearum. The essential oil of peppermint and inductor Ecolife® they had control of root rot in papaya. The essential oil of peppermint increased POX activity, with enzymatic peak in leaves collected 72 hours after the inoculation. The activity of PAL rose in the leaves collected at 24 hours after inoculation in the plants treated with the WDE and inductor Ecolife®. Increase of the enzyme was also observed PAL 96 hours after inoculation in the plants with the inductor BABA.