Saskatchewan, Canada
Effect of storage of inoculated seed and dehulling on the
development of covered smut in barley
T.S. Grewal, B.G. Rossnagel & G.J. Scoles.
Plant Sciences Dept./ Crop Development Centre,
University of Saskatchewan, 51Campus Drive, Saskatoon,
SK S7N 5A8 CANADA
Introduction
Covered smut of barley (Hordeum vulgare L.) caused by Ustilago hordei (Pers.) Lagerh. occurs everywhere barley is grown resulting in yield reductions from 0.2 to 0.8 % in western Canada (Thomas and Menzies 1997). Preliminary results showed no difference in % infected heads from seed inoculated two months and that inoculated two weeks before planting (Ardiel 1999). Hulless barley is becoming a significant crop in western Canada (Rossnagel 2000). Compared to the use of disease resistant cultivars, seed treatment with systemic fungicides is less desirable for smut control. All available sources of covered smut resistance are hulled, thus resistance needs to be transferred from hulled to hulless types. This study was conducted to determine the length of time inoculated seeds could be stored without affecting infection level and if the hull of resistant hulled lines plays a role in resistance.
Materials and Methods
Seeds were inoculated with the spore suspension technique using a mixture of isolates of U. hordei (Ardiel et al. 2002). One hundred grams of seed of CDC Candle (susceptible hulless barley cultivar) were inoculated with U. hordei on the 15th of every month from April 2000 through May 2001. After drying, half the inoculated seeds were stored at 4°C and the remainder at RT. Planting was May 16, 2001 in the greenhouse and June 1, 2001 in the field at Saskatoon.
Four hulled cultivars, viz. Q21861, CDC Dolly, TR244 and RFLP Harrington, were hand dehulled to evaluate effects of dehulling on resistance. RFLP Harrington is susceptible and the others are resistant (Ardiel et al. 2002). There were three treatments: dehulled inoculated, dehulled non-inoculated and hulled inoculated. The experiment was conducted in the field and greenhouse in the summer of 2000 and 2001, with planting during the first week of June. Disease evaluations were as described in Ardiel et al. (2002).
Results and discussion
Higher infection levels were observed after late May to early June field planting vs. early May planting (unpublished data). Therefore, planting was at the end of May or first week of June for all experiments.
There was no disease on the non-inoculated check in the greenhouse, however, 6% infected heads were observed in the field (Table 1), likely due to slight cross contamination in the seeder used. In the field, linear and quadratic components were highly significant when the inoculated seeds were stored at RT indicating a significant reduction in disease incidence over time (Table 1). However, when inoculated seeds were stored at 4°C, disease incidence reduction was not drastic as only the linear component was significant. In the greenhouse, the linear component was significant only when the inoculated seeds had been stored at RT (Table 1). The field data show that inoculated seeds can be kept for up to six months at RT and a year at 4°C without a significant loss in infection frequency (Table 1). The implication is that when a population is screened in the greenhouse or field, reserve inoculated seed can be used several months later to confirm the reaction of putative resistant lines.
In the greenhouse, germination of the non-inoculated hulless check was 95% but germination of inoculated seed was drastically reduced (data not shown). Ardiel (1999) also observed poor emergence and/or emergence of short, thick, distorted seedlings that failed to flower from inoculated hulless barley.
In the field, all dehulled inoculated seed showed numerically higher levels of infection than hulled seed, however, this was statistically significant only for the susceptible cultivar RFLP Harrington (Table 2a). Unlike the field experiment, no infected plant was observed among resistant cultivars in the hulled inoculated treatment in the greenhouse(Table 2b). This may be due to the fact that only a few plants could be screened in the greenhouse. Following the removal of the hull from hulled barley, resistant cultivars gave the same level of resistance in the field and greenhouse. Therefore, the hull of barley, at least in these cultivars, does not play a significant role in imparting resistance to covered smut. Therefore resistance in these hulled lines should be transferable to hulless barley and we have been able to identify many hulless lines, in several populations from hulled x hulless crosses, with no or very low susceptibility.
References
Ardiel, G.S., Grewal, T.S., Deberdt, P., Rossnagel, B.G., and Scoles, G.J. 2002. Inheritance of resistance to covered smut in barley and development of a tightly linked SCAR marker. Theor. Appl. Genet. 104: 457-464.
Rossnagel, B.G. 2000. Hulless barley- western Canada's corn. In 'Proc 8th International Barley Genetic Symposium, Vol. 1'. Edited by S. Logue. Department of Plant Science, University of Adelaide: Adelaide, Australia. pp. 135-142.
Thomas, P.L., and Menzies, J.G. 1997. Cereal smuts in Manitoba and Saskatchewan, 1989-95. Can. J. Plant Pathol. 19: 161-165.
Table 1. Effect of storage of inoculated seed on the incidence of covered
smut in barley cv. CDC Candle in the field and greenhouse.
|
Field |
% infected heads |
Greenhouse |
% infected plants |
||||
|
Months after inoculation |
RT* |
4°C |
Months after Inoculations |
RT* |
4°C |
||
|
Noninoculated check |
6 k |
6 k |
Noninoculated check |
0 f |
0 f |
||
|
0.5 |
42 abcdef |
43 abcd |
0 |
69 abcd |
71 abc |
||
|
0.75 |
45 a |
44 ab |
0.25 |
98 a |
67 abcde |
||
|
1.0 |
44 abc |
40 abcdef |
0.5 |
70 abcd |
50 abcde |
||
|
1.5 |
41 abcdef |
40 abcdef |
1 |
90 a |
56 abcde |
||
|
2.5 |
40 abcdef |
44 abc |
2 |
75 abc |
33 bcdef |
||
|
3.5 |
45 a |
45 a |
3 |
71 abcd |
73 abc |
||
|
4.5 |
38 abcdefg |
43 abcd |
4 |
40 bcdef |
67 abcd |
||
|
5.5 |
39 abcdefg |
39 abcdefg |
5 |
66 abcd |
22 cdef |
||
|
6.5 |
40 abcdef |
42 abcde |
6 |
67 abcd |
51 abcde |
||
|
7.5 |
30 gh |
34 defgh |
7 |
56 abcde |
62 abcde |
||
|
8.5 |
32 fgh |
39 abcdefg |
8 |
52 abcde |
67 abcd |
||
|
9.5 |
20 ij |
29 hi |
9 |
44 abcdef |
18 ef |
||
|
10.5 |
14 jk |
41 abcdef |
10 |
27 cdef |
58 abcde |
||
|
11.5 |
|
35 cdefgh |
11 |
|
79 ab |
||
|
12.5 |
|
35 cdefgh |
12 |
|
46 abcdef |
||
|
13.5 |
|
33 efgh |
13 |
|
21 def |
||
|
|
|
|
|
|
|
||
|
Regression (change over time) |
|
|
|
||||
|
|
|
|
|
|
|
||
|
linear |
** |
** |
** |
|
ns |
||
|
|
|
|
|
|
|
||
|
quadratic |
*** |
ns |
ns |
|
ns |
||
* Seeds were stored at room temperature after inoculation.
Means followed by the same letter were not significantly different (P = 0.05).
**, *** Regression component significant at P £ 0.01, 0.001, respectively; ns = not significant.
a)
|
|
Cultivars |
|
|||
|
Treatment |
Q21861 |
TR244 |
CDC Dolly |
RFLP Harrington |
Mean |
|
|
|
|
|
|
|
|
Dehulled |
0.52 |
0.08 |
4.32 |
44.82 |
12.44 a |
|
Hulled |
0.06 |
0.00 |
2.61 |
17.14 |
4.95 b |
|
|
|
|
|
|
|
|
Mean |
0.28 b |
0.04 b |
3.46 b |
30.98 a |
8.69 |
b)
|
|
Cultivar |
|
|||
|
Treatment |
Q21861 |
TR244 |
CDC Dolly |
RFLP Harrington |
Mean |
|
|
|
|
|
|
|
|
Dehulled |
0.0 |
8.0 |
18.3 |
63.0 |
22.3 a |
|
Hulled |
0.0 |
0.0 |
0.0 |
52.7 |
13.2 a |
|
|
|
|
|
|
|
|
Mean |
0.0 b |
4.0 b |
9.2 b |
57.8 a |
17.7 |
* The values are presented as per cent infected heads (a) and per cent infected plants (b).
Means within a column or row followed by the same letter were not significantly different (P = 0.05).