U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
3-2017
Citation
ANNUAL REPORT OF THE BEAN IMPROVEMENT COOPERATIVE, No. 60, March 2017. Published by USDA.
Abstract
INTRODUCTION: Ashy stem blight (ASB) caused by Macrophomina phaseolina (Tassi) Goidanich (Mp) is an important tropical disease that affects common bean in all growth stages. Resistance has been identified in common (Phaseolus vulgaris L.) and tepary (P. acutifolius A. Gray) bean gene pools (Miklas et al. 1998). Most of the ASB screening methods in the greenhouse have been conducted in seeds, seedlings, and plants at vegetative stages (Estévez et al., 2014; Pastor-Corrales and Abawi, 1988). However, a reliable screening technique that covers the entire cropping season needs to be assessed. Our objective was to evaluate the response of Phaseolus spp. genotypes to two M. phaseolina isolates throughout the crop season by the cutstem method.
MATERIALS AND METHODS: Phaseolus spp. genotypes were planted in a randomized complete block design with three replications at Isabela Research Substation. Plants were inoculated one and three times with the PRI16 and PRJD16 isolates in the 4th internode of the main stem and lateral branches according to the methodology described by Viteri et al. (2015). Inoculated plants were kept with mean day temperature of 36°C and night temperature of 28°C with 12 h light and humidity < 60% in the greenhouse, with watering as needed for plant growth. Ashy stem blight disease severity and the area under disease progress curve (AUDPC) were recorded on a single-plant basis from 7 to 42 days post inoculation using a 1 to 9 scale, where 1= no sign of infection in the inoculated internode and 9= Mp invasion beyond the third node with or without plant death. Plants with scores of 1 to 3 were considered resistant; 4 to 6 intermediate, and 7 to 9 susceptible (Singh et al., 2014). Also, resistant plants (scores ≤ 3) were verified at harvest.
Comments
U.S. government work.