Relative Ratio of Mature Pustules: A Simple Method to
Assess Partial Resistance of Barley to Puccinia hordei.
Guo-Liang Jiang, State Key Laboratory of Crop Genetics and Germplasm
Enhancement, Nanjing Agricultural University (NAU), Nanjing 210095, P.R.
China; Thierry C. Marcel, Laboratory of Plant Breeding, Graduate School of
Experimental Plant Sciences, Wageningen University, P.O. Box 386, NL-6700
AJ Wageningen, the Netherlands; Fernando Martínez, Instituto de
Agricultura Sostenible, C.S.I.C., Apdo. 4084, E-14080 Córdoba, Spain; and
Rients E. Niks, Laboratory of Plant Breeding, Graduate School of
Experimental Plant Sciences, Wageningen University (WUR), P.O. Box 386,
NL-6700 AJ Wageningen, the Netherlands. Plant Dis. DOI:
10.1094/PDIS-91-3-0301. Accepted for publication 3 October 2006.
In breeding plants for quantitative resistance to diseases, it is a
challenge to rapidly and accurately identify accessions with sufficient
levels of resistance from thousands of individual plants, families, and
lines. Most of the currently used assessment methods either are labor- or
time-consuming, such as measuring latent period (LP), or lack precision
and are subjective, such as a 1 to 9 scale or similar coding method to
estimate disease severity in the field. Taking barley leaf rust as an
example, we investigated a simple measure: the relative ratio of mature
pustules (RRMP). RRMP was computed as the ratio of mature pustules (which
are leaf spots caused by rust pathogens) to eventual total number of
pustules relative to this ratio in the susceptible control at a particular
time after a controlled inoculation and incubation. Results from a series
of experiments in seedlings and adult plants with different isolates of
the pathogen demonstrated that RRMP and relative LP were highly
correlated. This new measurement was as effective and powerful as LP for
evaluating quantitative resistance and identifying associated molecular
markers. Compared with LP, RRMP saved time and labor, and was much easier
and simpler to use on a large scale. Therefore, we conclude that RRMP
would be efficient in barley breeding programs, germplasm screening, and
fundamental studies, and probably also of great interest for research and
breeding in similar plant-pathogen systems.
