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Interaction of net blotch and scald on barley a
a
b
c
d
K. Xi , C. Bos , T. K. Turkington , A. G. Xue , P. A. Burnett & P. E. Juskiw
a
a
Field Crop Development Centre, Alberta Agriculture and Food, c/o Lacombe Research Centre , Agriculture and Agri-Food Canada , Lacombe , AB , T4L 1W1 , Canada b
Lacombe Research Centre , Agriculture and Agri-Food Canada , Lacombe , AB , T4L 1W1 , Canada c
Eastern Cereal and Oilseed Research Centre , Agriculture and Agri-Food Canada , Ottawa , ON , K1A OC6 , Canada d
Canadian Grain Commission , 600-303 Main Street, Winnipeg , MB , R3C 3G8 , Canada Published online: 13 Aug 2012.
To cite this article: K. Xi , C. Bos , T. K. Turkington , A. G. Xue , P. A. Burnett & P. E. Juskiw (2008) Interaction of net blotch and scald on barley, Canadian Journal of Plant Pathology, 30:2, 329-334, DOI: 10.1080/07060661.2008.10540548 To link to this article: http://dx.doi.org/10.1080/07060661.2008.10540548
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NOTE Ep1dem1ology I Ep1denl10iog1e
Interaction of net blotch and scald on barley K. Xi, C. Bos, T.K. Turkington, A.G. Xue, P.A. Burnett, and P.E. Juskiw
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Abstract: Net blotch caused by Pyrenophora teres f. sp. teres and scald caused by Rhynchosporium secalis are major foliar diseases of barley (Hordeum vulgare) and often occur together in the same fields in central Alberta, Canada. The differential development of these two diseases in relation to seeding date was investigated in five field trials in 200 I and 2003 under natural infection conditions. Significantly higher scald severity on barley was observed in all trials with early seeding (from early to mid May) as compared with late seeding (from late May to early June). Scald severity tended to be higher than net blotch severity in the early seeding date trials, whereas net blotch severity was generally higher than scald severity with late seeding. The differential development of disease severity between net blotch and scald was likely affected by temperature, host resistance, and natural inoculum. The interaction of the development of P. teres and R. secalis on barley 'Harrington' was investigated in artificially inoculated field plots in 1993 and 1995. In 1995, a mixture of both inocula induced a greater area under the disease progress curve (AUDPC) and caused a greater grain yield reduction than either inoculum alone in both seasons. No difference in grain yield was observed among plots in which P. teres or R. secalis were inoculated separately for either season. The disease progression and yield reductions observed in the present study indicate an additive effect as a result of the interaction between the two pathogens attacking the same plant. Early seeding of scald susceptible barley cultivars should be avoided in scald-infested fields in central Alberta. Scald susceptible cultivars may be seeded late for swath grazing of barley to escape scald infection. Key words: net blotch of barley, scald of barley, barley seeding date.
Resume : Les rayures reticulees, causees par Pyrenophora teres f. sp. teres, et Ia rhynchosporiose, causee par Rhynchosporium secalis, sont des maladies foliaires de I'orge (Hordeum vulgare) et sont souvent presentes, simultanement, dans les memes champs en Alberta, au Canada. Le developpement differentiel de ces deux maladies a ete etudie en fonction de Ia date des semis au cours de cinq essais en champ respectant Ies conditions naturelles d'infection. Tous les essais bases sur le semis hatif (du debut a Ia mi-mai) ont affiche des taux de severite de Ia rhynchosporiose passablement superieurs a ceux bases sur Ie semis tardif (de Ia fin mai au debut juin). La severite de Ia rhynchosporiose tendait a etre plus importante que celle des rayures reticulees dans les essais bases sur Ie semis hatif. La severite des rayures reticulees etait habituellement plus importante que celle de Ia rhynchosporiose au cours des essais bases sur le semis tardif. Le developpement differentiel de Ia severite de Ia maladie entre les rayures reticulees et Ia rhynchosporiose etait de toute evidence influence par Ia temperature, Ia resistance de l'hote et l'inoculum naturel. L'interaction du developpement de P. teres et de R. secalis avec Ie cultivar d'orge 'Harrington' a ete etudiee en 1993 et 1995 sur des parcelles de terrain inoculees artificiellement. En 1995, l'utilisation d'un melange des deux inoculums a augmente Ia surface sous Ia courbe de progression de Ia maladie (SSCPM), ce qui a entraine une plus forte baisse des rendements que I'a fait chacun des inoculums pris individuellement, et ce, a chacune des deux saisons. Aucune difference de rendement n'a ete observee dans les parcelles ou P. teres et de R. secalis avaient ete inocules separement, peu importe Ia saison. La progression de Ia maladie et Ia baisse de rendement demontrees dans Ia presente etude indiquent un effet additif resultant de l'interaction de deux agents pathogenes qui s'attaquent a un meme plant. Le semis hatif de cultivars d'orge receptifs a I'egard de Ia rhynchosporiose devrait etre evite dans les champs du centre de I' Alberta qui en sont infestes. Afin d'eviter l'infection, ces cultivars d'orge receptifs peuvent etre semes tardivement a des fins de paturages d'andains. Mots-des : rayures reticulees de l'orge, rhynchosporiose de I'orge, date des semis de I'orge.
Accepted 20 March 2008. K. Xi, 1 C. Bos, and P.E. Juskiw. Field Crop Development Centre, Alberta Agriculture and Food, c/o Lacombe Research Centre, Agriculture and Agri-Food Canada, Lacombe, AB T4L IWI, Canada. T.K. Turkington. Lacombe Research Centre, Agriculture and Agri-Food Canada Lacombe, AB T4L IWI, Canada. A.G. Xue. Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, ON KIA OC6, Canada. P.A. Burnett. Canadian Grain Commission, 600-303 Main Street, Winnipeg, MB R3C 3G8, Canada. 1
Corresponding author: (e-mail:
[email protected]).
Can. J. Plant Pathol. 30: 329-334 (2008)
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Can. J. Plant Pathol. Vol. 30, 2008
Introduction
Materials and methods
Spring barley (Hordeum vulgare L.) is a major crop in Alberta and accounts for approximately 50% of the total barley production in western Canada (Anonymous 2005). The net form of net blotch, which is caused by Pyrenophora teres Drechs. f. sp. teres Smedeg. (P. teres), and scald, which is caused by Rhynchosporium secalis (Oudem.) J.J. Davis, are two major foliar diseases of barley (Tekauz 2003). Both diseases can be present in the same fields in central Alberta as a result of conducive environmental conditions (Xue et a!. 1994 ), with disease severity dependent on the availability of inoculum and the resistance of the cultivar being grown. Either disease may reduce grain yield (Martin 1985; Orr and Burnett 1993; Xi et a!. 2000) or dry silage yield of feed barley seeded in late May in central Alberta (Orr and Turkington 2001). Yield losses of winter barley as a result of the two foliar diseases have been reported in the United Kingdom (Shaw and Royle 1978) and United States (Mundt et a!. 1994 ). Net blotch and scald of barley can be managed by the use of resistant cultivars, fungicide foliar application, and seed treatment (Martin 1985) and cultural practices such as crop rotation and barley variety rotation using varieties with different genetic resistance (Tekauz 2003; Turkington et a!. 2005). Extensive knowledge has been obtained regarding the epidemiology of scald and net blotch (Shipton et a!. 1973, 1974 ). Both pathogens require adequate moisture for spore germination, infection, and subsequent disease development. Scald can rapidly develop under cool and wet growing conditions. Net blotch develops more rapidly in warm damp weather, but it can develop under cool conditions (Tekauz 2003 ). Rhynchosporium secalis had lower temperature ranges than P. teres for spore germination, infection, and lesion development when North American isolates of both pathogens were compared (Shipton eta!. 1973, 1974). Net blotch was more severe in early seeded crops in the high rainfall areas of western Australia, whereas early seeding allowed scald to become prevalent in south Australia (Wallwork 1995). Research in various locations and during different seasons demonstrated that late seeding tended to progressively reduce scald levels (Juskiw, unpublished data) or had little impact on scald severity (Juskiw and Helm 2003) in central Alberta. A greenhouse study showed that mixed inoculation of P. teres and R. secalis reduced disease severity compared with either inoculum alone (Xue and Burnett 1995). However, there is little information available on the interaction of scald and net blotch development on spring barley under field conditions (Cherif et a!. 2007) or on the yield response of spring barley resulting from the interaction of these two pathogens (Shaw and Royle 1978). Understanding the interaction between P. teres and R. secalis is necessary to develop integrated management strategies to control these pathogens in central Alberta. The first objective of the present study was to determine the impact of two seeding dates on spring barley genotypes in response to the interaction of the two pathogens under natural infection conditions. The second objective was to investigate the interaction of P. teres and R. secalis on disease development and grain yield components in inoculated plots of spring barley 'Harrington'.
The seeding date effect and the differential development of net blotch and scald were evaluated in five barley field trials (Tests 1-5) using the Lacombe and Stettler breeding nurseries of the Field Crop Development Centre, Alberta Agriculture and Food, Lacombe, Alberta, in 2001 and 2003. The genotypes studied consisted of commercial cultivars and breeding lines of spring barley with varying levels of resistance or susceptibility to net blotch and scald. Information on disease reaction for the commercial cultivars used as checks in the trials is described in Table I. To facilitate field operations, the early and late seeded plots were arranged from 50 m to I 00 m apart in the same field in each growing season. Each plot was 4.6 m trimmed to 2.5 m in length and 1.5 m in width consisting of eight rows with a 0.14 m row spacing. The seeding rate was 237 seeds·m- 2 for two-row and six-row hulled entries, and 323 seeds·m- 2 for hulless entries. Seeding dates for the various years and locations are listed in Table 2. The experiments were conducted using a three-replicate randomized complete block design (RCBD). Plots were naturally infected by P. teres and R. secalis. Disease assessments were made based on the entire plot at the soft-dough stage of development (GS 85) (Zadoks et a!. 1974) using a 0-9 scale described by Couture (1980) and Saari and Prescott (1975). The interaction of net blotch and scald on barley 'Harrington' was investigated in field plots with scald-infested barley stubble during the 1993 (Test 6) and 1995 (Test 7) growing seasons at the Lacombe Research Centre, Agriculture and Agri-Food Canada, Lacombe, Alberta. The experiments were conducted using a four-replicate RCBD and treatments consisted of inoculation with P. teres only, inoculation with R. secalis only, and inoculation with a mixture of the two pathogens. Plots were 3 m x 1.4 m and consisted of four rows with a 0.35 m row spacing. Seeding was done with a small-plot tractor-drawn seeder at a rate of 188 seeds·m-2 on 18 May for the 1993 season and 16 May for the 1995 season. Inoculum of P. teres was prepared by washing conidia from 1-week-old cultures grown on V8 medium in 9 em Petri dishes. The V8 medium consisted of I 00 mL V8 juice, 3 g CaC03, 15 g agar (Difco Laboratories, Sparks, Md.), and 900 mL of distilled water to make I Lin volume (Tekauz 1990). Inoculum of R. secalis was collected by washing conidia from 2-week-old cultures grown in 9 em Petri dishes on lima bean agar medium (LBA; Difco Laboratories) (Tekauz 1991 ). At growth stage (GS) 22-24 (main shoot and 2 to 4 tillers), the plots were sprayed with spore suspensions at approximately I x 10" conidia·mL- 1 for P. teres or at approximately I x 105 conidia·mL- 1 for R. secalis, whereas the concentration of the mixture of the two pathogens consisted of half the concentration of each inoculum as indicated above. Disease development with net blotch and scald was assessed in each plot based on percent leaf area diseased for the top three leaves of 10 randomly selected tillers in Test 6 and all leaves of I0 randomly selected tillers in Test 7. The first assessment was made at GS 31-37 (first node detectable to flag leaf just visible), two weeks after inoculation and subsequent assessments were done at 1-week intervals until the final assessment at GS 90 (ripening). Area under the disease progress curve (AUDPC)
Xi et al.: barley I net blotch I scald I disease interaction
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Table 1. Net blotch [Pyrenophora teres] and scald [Rhynchosporium secalis] reactions in barley check cultivars used in seeding date trials in 2001 and 2003 at Lacombe and Stettler, Alberta.
Check cultivar
Type
Hulled 2-row, Stettler, 2001 (Test I)
'AC Metcalfe' 'CDC Dolly' 'Harrington' 'Seebe'
2-row 2-row 2-row 2-row
hulled hulled hulled hulled
'Falcon' 'Phoenix'* 'Vivar' 'See be'
6-row 2-row 6-row 2-row
hulless hulless hulled hulled
'AC Lacombe' 'AC Metcalfe' 'CDC Dolly' 'Harrington' 'Falcon' 'Vivar'
6-row 2-row 2-row 2-row 6-row 6-row
hulled hulled hulled hulled hulless hulled
'AC Lacombe' 'CDC Dolly' 'CDC McGwire' 'Harrington' 'Falcon' 'Vivar'
6-row 2-row 2-row 2-row 6-row 6-row
hulled hulled hulless hulled hulless hulled
'AC Lacombe' 'AC Metcalfe' 'CDC Dolly' 'CDC McGwire' 'Falcon' 'Vivar'
6-row 2-row 2-row 2-row 6-row 6-row
hulled hulled hulled hulless hulless hulled
Hulless, Stettler, 2001 (Test 2)
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Hulled 2- and 6-row, Lacombe, 2001 (Test 3)
Hulled 2- and 6-row, Stettler, 2001 (Test 4)
Hulled 2- and 6-row, Stettler, 2003 (Test 5)
Scald reaction
Net blotch reaction
Test, location, year
s
I
s s s
I
s R I
s
s
I
s
R I
I
s
s s
I
s
I
s
I
I
R
s
s I
s
I
s
R
Note: R, resistant: I, intermediate: and S. susceptible. *Disease reaction was described in Anonymous (1997). Disease reactions for all other cultivars were described in Anonymous (2008).
Table 2. Net blotch [Pyrenophora teres] and scald [Rhynchosporium secalis] severity in barley seeding date trials in 2001 and 2003 at Lacombe and Stettler, Alberta.
No. of entries
Seeding date
Mean net blotch severity (min.-max.)
Mean scald severity (min.-max.)
Hulled 2-row, Stettler, 2001 (Test I)
20 20
Early (5 May) Late (31 May)
1.4 a (0-6) 1.2 a (0-6)
2.2 a (0-6) 0.5 b (0-3)
Hulless, Stettler, 2001 (Test 2)
20 20
Early (5 May) Late (31 May)
0.3 a (0-6) 1.2 a (0-6)
3.7 a (1-7) 0.9 b (0-3)
Hulled 2- and 6-row, Lacombe, 2001 (Test 3)
25 25
Early (10 May) Late (31 May)
4.0 a (0-7) 4.6 b (2-8)
1.2 a (0-6) 0.04 b (0-4)
Hulled 2- and 6-row, Stettler, 2001 (Test 4)
20 20
Early (5 May) Late (31 May)
1.2 a (0-6) 2.1 a (0-7)
2.7 a (1-6) 0.4 b (0-2)
Hulled 2- and 6-row, Stettler, 2003 (Test 5)
24 24
Early (15 May) Late (6 June)
0.1 a (0-5) 0.0 a (0)
2.3 a (0-5) 0.4 b (0-3)
Test, location, year
Note: Values for early and late seeding dates followed by different letters in the same column were significantly different at P < 0.05 or 0.01 according to an F test.
was obtained by integrating disease severity curves over time using the formula described by Shaner and Finney ( 1977). For grain yield and thousand-kernel mass (TKM), a small-plot combine was used to harvest the two central
rows for Test 6 and all four rows for Test 7 at plant maturity. The effect of seeding date was examined as a combined analysis for a series of experiments as described by Cochran
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Table 3. Temperature and precipitation for the 2001 growing seasons at Lacombe and Stettler and the 2003 season at Stettler, Alberta. 2001 Lacombe
Month
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May June July August September Average temperature Total precipitation
Mean daily air temperature ( 0 C) 11.4 12.8 16.3 16.8 11.4 13.7
200 I Stettler Monthly precipitation (mm) 7 83 6 42 12 150
and Cox (1957). Data from each trial of Tests l-5 were analyzed using the PROC MIXED procedure of SAS 9.1 (SAS Institute Inc., Cary, N.C., 2002-2003) with seeding date as a fixed effect and barley genotype as a random effect. For Tests 6 and 7, the data were analyzed using the PROC GLM procedure and linear orthogonal contrasts were used to determine the impact of both or individual pathogens on AUDPC and the yield components of 'Harrington'.
Results and discussion Higher scald severity was observed in Tests l-5 for early seeded barley than for late seeded barley (Table 2). In general, there were no differences in net blotch severity between seeding dates, except for significantly higher levels of net blotch in the late seeding date at Lacombe, 200 I (Table 2). As a result, scald severity tended to be higher compared with net blotch severity for the early seeded barley, and net blotch severity was generally higher compared with scald severity for the late seeded barley. The differential development of the two diseases under natural infection conditions may have been caused by cool weather in the early growing season that facilitated the onset and development of scald and retarded the infection and development of net blotch on the same plants. Air temperature and the amount of precipitation varied among locations and seasons in the present study (Table 3). However, a consistent increase in temperature from May to June suggests that the two pathogens have a different temperature requirement for infection and disease development, which supports the findings of Shipton et al. (1973, 1974) and Tekauz (2003). The development of either disease would also largely depend on the presence or absence of abundant pathogen inoculum and the relative resistance or susceptibility of individual cultivars. For example, 'AC Lacombe' and 'CDC Dolly' displayed low levels of scald with early seeding, but developed a relatively high level of net blotch in later seeding at the Lacombe breeding nursery (Fig. 1) where net blotch occurred more frequently than scald. The same cultivars showed a relatively high level of scald when seeded early, but developed a negligible level of net blotch at Stettler (Fig. 2) where scald was more severe than net blotch. Similarly, 'Vivar' developed a low level of scald when seeded early at Lacombe (Fig. l ), but showed a high level of scald at Stettler (Fig. 2). Competition between the two fungi for
Mean daily air temperature (0 C) 11.3 13.0 16.3 17.5 12.1 14.0
2003 Stettler Monthly precipitation (mm) 32 91 113 19 8 263
Mean daily air temperature (0 C) 8.1 14.0 18.9 19.7 12.7 14.7
Monthly precipitation (mm) 21 57 33 24 18 153
infection sites and during colonization of the plant leaf tissue may contribute to differential development of the two diseases. When disease pressure for both diseases was high, a negative correlation between disease severity of net blotch and scald was observed. This relationship was attributed to a competition between the two pathogens (Cherif et al. 2007). Induced resistance was considered to be the primary mechanism in impeding net blotch of barley previously infected by Septaria nodorum (Berk.) Berk. in Berk. & Broomel from wheat and Bipolaris maydis (Nisikado) Shoemaker from maize (J~rgensen et al. 1998). Contrasts indicated differences among the inoculation treatments for AUDPC in Test 6 (Table 4). Higher AUDPC values were found following inoculation with R. secalis than those following inoculation with P. teres (Table 5). The mixed inocula resulted in a lower AUDPC than for the R. secalis and lower yield compared with the average of either inoculum alone (Tables 4 and 5). For Test 7, inoculation with P. teres resulted in a higher AUDPC value than inoculation with R. secalis (Tables 4 and 5). The mixed inocula resulted in a higher AUDPC and greater yield reductions than either inoculum alone. There was no difference in yield between single inoculations of P. teres or R. secalis in Test 7, and inoculation treatments had no effect on TKW for either test (Tables 4 and 5). AUDPC from either inoculum alone consisted mainly of symptoms for the corresponding inoculum used, whereas AUDPC for the mixed inocula consisted mainly of symptoms caused by P. teres (data not shown). The predominance of symptoms caused by P. teres over R. secalis infection in the field trials agrees with previous observations from greenhouse tests (Xue and Burnett 1995). In the present study, it was observed that lesions caused by the mixture of inocula coalesced on the same leaves. Higher AUDPC levels from the mixed inocula than either inoculum alone in Test 7 (Tables 4 and 5) may have resulted from rapid development as a· result of the interaction between P. teres and R. secalis. The impact on yield losses in winter barley caused by the two pathogens is considered to be additive (Shaw and Royle 1978). The data suggest that early seeding of scald susceptible barley cultivars should be avoided in scald-infested fields in central Alberta. However, a relatively short growing season in central Alberta may not allow for delays in seeding for scald management when grain is produced. Alternatively,
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Fig. 1. Seeding date in relation to net blotch and scald severity using 6 barley cultivars in Test 3. Scald and net blotch severity between two seed dates based on 25 entries in the test were significantly different at P < 0.05, respectively, according to F tests (Table 2 ).
Fig. 2. Seeding date in relation to net blotch and scald severity using 6 barley cultivars from Test 5. Net blotch severity between two seeding dates based on 24 entries in the test was not significantly different at P > 0.05, whereas scald severity between two seed dates based on 24 entries in the test was significantly different at P < 0.05, according to F tests (Table 2).
Table 4. ANOVA and specific comparisons of area under the disease progress curve (AUDPC) and yield of 'Harrington' barley inoculated with Pyrenophora teres, Rhynchosporium secalis, or a mixture of both pathogens in field trials at Lacombe, Alberta, in 1993 and 1995.
Source Block Treatment Mean P. teres and R. secalis vs. mixture P. teres vs. R. secalis Error
Degrees of freedom
Test 6 (1993)
3 2
6
Test 7 (1995)
AUDPC
Yield (kg·ha- 1)
AUDPC
Yield (kg·ha- 1)
17.6 1025.7** 328.6**
115 093.8 478 616.8* 844 060.4*
31 884.6 48 841.4** 76 148.6**
94 451.5 128 157.6 202 642.4*
1722.8** 18.1
113 173.1 87 471.3
21 534.1 * 2 866.8
53 672.7 31 294.8
Note: *, significant at P < 0.05; **, significant at P < 0.01. Values are ANOVA mean squares.
Table 5. Mean area under the disease progress curve (AUDPC), yield, and thousand-kernel mass (TKM) of 'Harrington' barley inoculated with Pyrenophora teres, Rhynchosporium secalis, or a mixture of both pathogens in field trials at Lacombe, Alberta, in 1993 and 1995.
Test 6 (1993)
Test 7 (1995) (kg·ha- 1)
Treatment
AUDPC
Yield
P. teres R. secalis P. teres + R. secalis (mix)
50.9 80.3 54.5
4311.8 4073.9 3630.3
TKM (g)*
AUDPC
Yield (kg·ha- 1)
TKM (g)*
41.2 41.3 40.5
744.7 641.0 861.8
3943.4 4107.2 3749.6
45.1 44.4 44.8
*Inoculation treatments had no significant effect (P > 0.05) on TKM for either test.
barley used for swath grazing is typically seeded in mid-May to early June in western Canada (Hutton et al. 2004). This practice can limit scald development with late seeding of scald susceptible cultivars, while not compromising crop productivity in fields with abundant inoculum of R. secalis. The present study demonstrated that a mixture of P. teres and R. secalis inoculum caused more yield reduction in barley 'Harrington' than either pathogen inocu-
lated alone. This suggests that the net blotch and scald pathogens may interact at the onset of infection and subsequent leaf disease development under conducive conditions.
Acknowledgements The authors acknowledge financial support from the Natural Sciences and Engineering Research Council of Canada
334
through the Visiting Fellowships in Canadian Government Laboratories. Technical assistance from D. Orr, R. Lange, A. McCarty, N. Rauhala, and R. Werezuk was greatly appreciated. The authors thank Dr. Rong-Cai Yang for advice on statistical analysis.
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