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.M. ; LA O, M. ; ZARDÓN, MA.; DÍAZ RICCI; J.C.; CASTAGNARO, ,A.P. ; CAPOTE,M; PIÑÓN, D.; M. E. ARIAS2

Varadero

Jornada; XIV jornadas internacionales de las sociedades de MIcroscoko; 2017

Comite internacional de

IntroductionThe 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 obtainresistant cultivars to this disease, that have reduced significantly the infection levels of thispathogen 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 thisdisease were analyzed in order to obtain knowledge about sugarcane resistant mechanism.Materials and MethodsField grown sugarcane Saccharum officinarum, with different grades of rust resistance, cultivarsB4362 (highly susceptible HS), My5514 (susceptible, S) and PR980 (resistant, R) were studiedin three localities from the country: Havana, Matanzas and Santiago de Cuba. The central part ofthe 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 brilliantcresil and were observed on microscope slide with water-glycerin. Transversal leaves sectionswere cutted by hand, which were prepared of equal form. The remarks were done in opticalmicroscope Leica DM 500. Also were prepared of traditional form for electronic microscopeobservations (Zeiss SUPRA 55VP). The morphologic characters analyzed were: cuticle thickness(CT), epidermis thickness (ET) and leaf plate thickness (LPT), number of stomata (NS) andquantity of prickles (QP) in the epidermis abaxial. The presence or absence of pustule wasevaluated also, percentage of leaf area affected (LAA) and size of the biggest pustule (SBP). Theinformation was processed using Variance Analysis, comparison of averages by Turkey?smethod and Discriminating Analysis.Results and DiscussionIn the epidermis were observed zones of brown coloration (necrotic), principally near to thestomata. In transversal leaves sections were found proper structures of the mushroom (pustuleand uredospore) and rupture of the abaxial epidermis which was more notable in susceptiblecultivars B4362 and My5514. Into the electronic microscope were observed specific details ofthe spores (Fig. 1). The Discriminating analysis showed that the presence of pustules (Pust) had asignificant 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 anindirect scoreboards in the early selection of resistant cultivars to this disease.