Doenças e pragas associadas à germoplasma de pinhão manso (Jatropha curcas L.)

Abstract

Jatropha (Jatropha curcas L.) is a potential crop for biodiesel production, with some initiatives cultivation in Brazil. The expansion of culture, the lack of parameters phytotechnical and their agro-climatic and edaphic zone as well as on the occurrence of diseases and pests, has resulted in investments in research. With regard to pests and diseases, though no statistics are available, a diversity of organisms is suspected of limiting productivity and reduce seed quality. Rust, for example, is a fungal disease that attacks the jatropha in some regions of Brazil. This pathogen causes defoliation early, causing damage to the plant. Therefore, this study aimed to: a) detect and identify major diseases and pests associated with plants of jatropha of Germplasm Collection of UFRRJ b) assess the damage caused by rust (Phakopsora arthuriana) of jatropha in conditions of Seropédica, RJ c) identify germplasm that present potential to manifest tolerance / resistance to rust, and d) develop and validate a diagrammatic scale to quantify the severity of rust on leaves of Jatropha curcas, this tool, very important in the process of monitoring the infectious agent. Samples were collected leaves and fruit of J. curcas, and insects capture. Then, screening was performed and the isolation of microorganisms on PDA medium was attempted. The rust severity was quantified in 220 accessions of the collection. A diagrammatic scale with levels of 1.7, 3.5, 5.0, 8.5, 10.5, and 13% of leaf area with lesions was constructed. Then, aiming at validation of scales, two evaluations in 35 photos of jatropha with rust symptoms, with different levels of severity was conducted by five inexperienced appraisers. The precision and accuracy of reviewers was assessed using simple linear regression and analysis of variance of errors. Among the pests, insects Retithrips syriacus and Empoasca sp., and mite Polyphagotarsonemus latus stood out as causing damage. Were reported as new records for Jatropha cultivation the presence of the following biting insects: - Liposcelis sp., Araecerus fasciculatus, Dachris sp., Omophoita albicollis, Lagria sp., Trigona spinipes and Melanchroia sp.; Sucking - Campylenchia hastata, Aphis gossypii, Pseudoparlatoria sp., Crinocerus sanctus, Leptoglossus gonagra, L. stigma and Sphictyrtus chryseis. Moreover, it could be proven that the environment where the culture was installed favored the development of Aspisoma hesperidium, predator of mollusc. With regard to assessments of plants with rust, the accesses 63 and 79, both from Jaíba not developed symptoms during the evaluation period. Among accessions, the number 28 (Lavras lot - 210), 62 (Lavras lot - 000), 116 (Petrolina), 129, 131 and 160 (Gold) were those with greater severity, whereas 08 (Janaúba ), 73 (Guapimirim), 106, 138 and 194 (Janaúba), 209 (Gold), and 219 (Petrolina) were classified with low severity of rust. The proposed diagrammatic showed good precision and accuracy for assessing the severity of rust on leaves of jatropha.