Leaves morphological characters in sugarcane cultivars with different resistant grades to brown rust.

ACEVEDO, R.; LUQUE, A.C; ALFONSO, I.; DEBES M.A.; RODRÍGUEZ, E.; LA O, M.; ZARDÓN, M.A.; DÍAZ RICCI, J.C.; CASTAGNARO, A.P.; CAPOTE, M.; PIÑÓN, D.; ARIAS, M.E.

ACTA MICROSCOPICA

Instituto Venezolano de Investigaciones Científicas (IVIC)

Lugar: Caracas; Año: 2011 vol. 20 p. 1 - 2

0798-4545

Abstract The brown rust is a major disease of sugarcane caused by Puccinia melanocephala Sydow and P. Sydow (=Puccinia erianthi Padwick and Khan). In Cuba there is a wide program to obtain resistant cultivars to this disease, that have reduced significantly the infection levels of this pathogen in the fields (1), nevertheless a constant alertness is supported. In this paper, morphologic characters in sugarcane leaves and its relation with different resistant grades to this disease were analyzed in order to obtain knowledge about sugarcane resistant mechanism. Field grown sugarcane Saccharum officinarum, with different grades of rust resistance, cultivars B4362 (highly susceptible HS), My5514 (susceptible, S) and PR980 (resistant, R) were studied in three localities from the country: Havana, Matanzas and Santiago de Cuba. The central part of the leaves was analyzed in 3 samples obtained of 10 plants at the age of 3, 4, 6 and 9 months. The epidermis was obtained by the skill of Metckalfe (2); they were treated with blue of brilliant cresil and were observed on microscope slide with water-glycerin. Transversal leaves sections were cutted by hand, which were prepared of equal form. The remarks were done in optical microscope Leica DM 500. Also were prepared of traditional form for electronic microscope observations (Zeiss SUPRA 55VP). The morphologic characters analyzed were: cuticle thickness (CT), epidermis thickness (ET) and leaf plate thickness (LPT), number of stomata (NS) and quantity of prickles (QP) in the epidermis abaxial. The presence or absence of pustule was evaluated also, percentage of leaf area affected (LAA) and size of the biggest pustule (SBP). The information was processed using Variance Analysis, comparison of averages by Turkey?s method and Discriminating Analysis. In the epidermis were observed zones of brown coloration (necrotic), principally near to the stomata. In transversal leaves sections were found proper structures of the mushroom (pustule and uredospore) and rupture of the abaxial epidermis which was more notable in susceptible cultivars B4362 and My5514. Into the electronic microscope were observed specific details of the spores (Fig. 1). The Discriminating analysis showed that the presence of pustules (Pust) had a significant contribution (F=90,001) in the shape of the model of variables discrimination, allowing to corroborate the existing contrast between cultivars with different resistant grades to rust. Other variables that turned out to be highly significant were a cuticle thick (CT), epidermis thick (EP) and number of stomata (NS). The cuticle thick prevents the penetration of the fungi, since it constitutes a morphologic barrier (3) of equal way it happens with the epidermis thick. The thickest cuticle observed was always in the resistant cultivar PR980 (Fig. 2). All the obtained results indicate that morphologic characters as cuticle thick (CT), epidermis thick (ET) and number of stomata (NS) are in relation with rust resistance cultivars, so could be used as an indirect scoreboards in the early selection of resistant cultivars to this disease. Acta Microscópica 20 Supp. B .