Estudos epidemiológicos e respostas fisiológicas à infecção da mancha-de-estenfílio em genótipos de tomateiro

Abstract

With the increase of gray leaf spot (Stemphylium solani) in tomato (Solanum lycopersicum) crops in Brazil is necessary to intensify the studies in order to develop appropriate evaluation methodologies; quantify the response of different genotypes to infection by the pathogen and the effect of environment on development of the disease. Therefore, was developed this work, which can be divided into four chapters: I) were evaluated the optimal conditions of temperature (10, 15, 20, 25, 28, 30 and 35 ° C), wetness period (2; 4; 6; 8; 12; 16; 20 and 24 hours) and photoperiod (0, 6, 12, 18 and 24 hours of darkness) for germination, emission and growth tubes; for mycelial growth of the pathogen in vitro and sporulation. Information for the production of conidia in vitro was obtained; II) the effect of temperature (15, 20, 25, 28 and 30°C), leaf wetness period (2; 6; 16; 24 and 48 hours) and the concentration of conidia (1x103, 1x104, 5x104 and 1x105 conidia mL-1) was determined in infection of S. solani on plants of 'Perinha Água Branca’ (susceptible) and 'Mascot' (resistant), as well as, the host response at different stages of development. The pathogen's ability to infect tomato fruit was tested and a protocol for disease evaluation under controlled conditions was obtained; III) the response of 55 tomato genotypes, in three developmental stages, was evaluated to S. solani infection; IV) the disease progress was evaluated in a pre-selected genotypes and the effect of disease on production was studied. The results obtained in four different chapters are described below. Chapter I) Maximum germination was obtained at 23 (SENA302) and 24.5ºC (SENA101); the higher emission of germ tube was obtained at 23.5 (SENA302) and 26.5ºC (SENA101); the higher growth tube at 23.5ºC; higher mycelial growth at 24.4 (SENA302) and 25.6ºC (SENA101) and higher sporulation at 15.6 (SENA302) and 18ºC (SENA101), both with 15.84 hours dark. The most favorable for germinative process was 16 hours of wetness period and six hours of wetting were enough to 50% of germination. The number and growth of germ tubes increased with exposure to dark. For conidia production is recommended the temperatures of 25 and 15ºC and conditions of alternated light. Chapter II) For the gray leaf spot evaluation under controlled conditions is recommended the use of alternating temperatures of 25 (day) and 15°C (night); 24 hours of wetness and suspension at 1x104 conidia mL-1. Disease severity was greater in older leaves, this effect is increased with the plant development. Chapter III) Adult plants were more susceptible to disease and according these evaluations were selected up accesses ENAS 1136 and ENAS 1143 as susceptible control and ENAS 1012; ENAS 1031; ENAS 1060; ENAS 1216; ENAS 1217 and ENAS 1223 for field trials. Chapter IV) it is indicated the ENAS 1217 for future breeding programs. It is recommended to evaluate the gray leaf spot severity between the fourth and the tenth leaf, close to 60 days after transplant.