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Wheat Information Service
Number 84: 7-12 (1997)
Research article
The diversity of resources resistant to scab in
Triticeae (Poaceae)
Yong-Fang Wan, Chi Yen, Jun-Liang Yang and Deng-Cai Liu
Triticeae Research Institute, Sichuan Agricultural University,
Dujiangyan City 611830, Sichuan, China
Summary
Resistance to scab was evaluated using 1463 accessions from 85
species belonging to 17 genera in Triticeae. The results indicated
that 31 accessions from 5 species were highly resistant to initial
infection and spread. The accessions resistant both to initial
infection and spread were mainly found in perennial genera
Roegneria, Hystrix, Kengyilia, Agropyron and Elymus.
Roegneria was the best resistant genera. The differences of
resistance to scab in Triticeae are closely related to their
ecological conditions where they grow.
Introduction
Wheat blight or scab, caused by Gibberella zeae Petch
(=Fusarium graminearum Schwabe), has been one of the most
destructive disease in warm and humid wheat growing area of the
world. Up to now, no cultivars with immunity or resistance to both
initial infection and spread within spike tissue have been found in
Triticum and its relatives including Aegilops, Haynaldia
and Secale (Hanson et al. 1950; Liu 1985; Mesterhazy 1987;
Tomasovic 1989). In this situation, the diversity of resources
resistant to scab has to be evaluated in many other species in
Triticeae. In the present paper, results of the survey on the scab
resistance in Triticeae are reported.
Materials and methods
The conidia of Gibberella zeae Petch used for inoculation
of the test materials (Table 1) were
obtained according to Schroeder and Christensen (1963). The inoculum
was a mixed spore suspension of three isolates from scaby wheat
kernels, collected at Chengdu, Yaan and Dujiangyan cities, Sichuan
province, China. The concentration of spore suspension was, on the
average of 10 slides, about 50 spores per 10 x 10 microscope field.
Multifloret and single-floret injection were used for determining
resistance to initial infection and to the pathogen spread within
spike tissue, respectively.
Resistance to initial infection
The first florets of 12 spikelets per spike were injected with a drop
of 5 microliter conidial suspension with a microsyringe, and each
spike was covered with a cellulose bag. These injected spikelets were
daily investigated after inoculation to study the latent period of
infection. The assessment of resistance to initial infection was made
at maturity stage based on the percentage of infected spikelets as
follows: 0 = immune (I), 0.1-50% = highly resistant (HR), 50.1-70% =
resistant (R), 70.1-90% = moderately resistant (MR), 90.1-100% and
latent period of infection longer than 5 days = susceptible (S),
90.1-100% and latent period of infection shorter than 5 days = highly
susceptible (HS).
Resistance to spread
The first floret of one intermediate spikelet per spike was injected
with a drop of 5 microliter conidial suspension. The disease ratings
were recorded at wax maturity stage. The method of disease rating was
according to Xu and Fang (1982). The assessment of resistance to
spread was based on mean disease rating as follows: 0 = immune (I),
0.1- 1.99 = highly resistant (HR), 2.00-2.99= resistant (R),
3.00-3.60 = moderately resistant (MR), 3.61-4.20 = susceptible (S),
4.21-5.00 = highly susceptible (HS).
Results
Resistance to scab was evaluated using 1463 accessions of 85
species belonging to 17 genera of Triticeae. The results indicated
that there is no immune accession to scab in Triticeae (Table
2). However, 31 accessions from 5 species were highly resistant
to initial infection and to spread. Twenty-eight accessions from 13
species showed resistance to initial infection and high resistance to
spread. Thirty-five accessions from 15 species showed moderate
resistance to initial infection and high resistance to spread. One
accession was resistant both to initial infection and spread. Though
45 accessions were susceptible to initial infection, they were highly
resistant to spread. Out of the 45 accessions, 30 were hexaploid
common wheat.
The accessions that showed resistance to both initial infection and
spread were mainly found in the perennial genera Roegneria,
Hystrix, Kengyilia, Agropyron and Elymus. In particular,
67 out of 69 accessions of Roegneria were resistant to both
initial infection and spread, the response of which was the best
among Triticeae (Table 2).
The accessions which are listed in Table 1, but not included in the
Table 2 were sensitive to wheat scab.
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