Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

225
Development of a detached leaf assay for stripe [yellow]
rust resistance screening
A. Loladze, 1 K. Garland Campbell, 2 X.M. Chen 2 and K. Kidwell 1
1. Department of Crop and Soil Sciences, Washington State University, Pullman,
WA, USA; 2. Wheat Genetics, Quality, Physiology and Disease Research Unit,
USDA-ARS, WSU, Pullman, WA, USA
Stripe [yellow] rust caused by Puccinia striiformis Westend. f.sp. tritici Eriks. is a
major disease of wheat (Triticum aestivum L. em Thell.) worldwide, causing
significant yield and quality losses. Screening wheat germplasm for resistance
to stripe rust is conducted using greenhouse and field-based trials in the
seedling and adult stages of plant development, respectively. Because of their
efficiency, detached leaf assays have been developed for screening cereal crops
for resistance to several foliar pathogens; however, the long latent period of
stripe rust complicates detached leaf assay development for resistance to this
pathogen. The objective of this study was to develop an effective, efficient
detached leaf assay for screening wheat germplasm for resistance to stripe rust.
Detached seedling leaves of seven wheat differential cultivars were placed
on the artificial media, which consisted of 0.5% water-agar with the addition of
10 mg/L kinetin, a plant senescence retardant, and the pH of the media was
adjusted to 7. Leaf segments were inoculated with three races of stripe rust
using a fine paintbrush and placed in a dark growth chamber for 24 h at 10°C.
After the 24-h incubation period, the photoperiod conditions were set to 16/8
hours (day/night) at a temperature of 15–17/11–13°C (day/night).
Simultaneously, the same plant material was grown for 10–14 days and
inoculated in the greenhouse with a mixture of stripe rust spores and talcum
powder (1:20). The reactions of the wheat genotypes to stripe rust races were
recorded as infection types on a 0 (no infection) to 9 (completely susceptible)
scale. Infection types from the detached leaf assay matched those of the whole
seedling assay for all cultivars. The detached leaf assay provides a new method
for screening for stripe rust resistance that requires less space and time than
seedling evaluation methods and eliminates the need for greenhouse space
and dew chamber access.