Analysis of the effect of orange and brown rusts on the photosynthetic efficiency of susceptible and intermediate varieties of sugarcane

• Grant number: 13/06136-1
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): June 01, 2013
• Effective date (End): May 31, 2014
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal researcher: Lilian Amorim
• Grantee: André Bueno Gama
• Home Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Resistance to diseases is one of the main focuses of the genetic breeding programs of sugar cane in Brazil. The orange rust (Puccinia kuehnii) and the brown rust (Puccinia melanocephala) are important diseases considered in the plant selection of these programs. Although there are studies on the physiology of sugarcane that are affected by orange and brown rusts, there are no reports concerning the behavior of Brazilian varieties inoculated with different inoculum concentrations under controlled conditions. The interference of these diseases in the photosynthetic efficiency of susceptible and moderately resistant varieties has not been reported. The present study aims to evaluate the photosynthetic efficiency of Brazilian varieties of sugar cane susceptible or moderately resistant to orange and brown rusts under controlled conditions and different levels of disease severity. Susceptible and moderately resistant varieties for each of these diseases will be planted through one bud cutting in the substrate, and the originating plants will be inoculated after one month with urediniospores collected from leaves infected by P. Kuehne and P. melanocephala. Inoculum concentrations shall be 10³ and 105 spores/ml. the experiment will be carried out under controlled conditions (25 ºC and photoperiod of 12:00 h) and the experimental design will be completely randomized. The assessments will be made at 1, 8, 15, 22, and 29 days after inoculation, through evaluation of photosynthetic efficiency, stomatal conductance and transpiration rate. The severity of the diseases will also be measured by images processed on QUANT software. The variables corresponding to the gas exchanges will be related to each other and to the severity of the disease through the Pearson coefficient (r), and the statistical analyses will be performed by using non-linear regression processed on STATISTICA software. The results will allow inferring on production damage in varieties with different resistance responses under different inoculum pressures. (AU)