1. health and fitness
2. disease

Research Pre-proposal for 2013
The Minnesota Wheat Research and Promotion Council
Small Grains Research & Communications Committee
Project Title: Performance of Best of the Best Wheat Cultivars and Elite Breeding Material to
Multiple Leaf Diseases Under In vitro and in Vivo Conditions
Research Group:
PI: Dr. Shaukat Ali, small grains pathologist, SDSU, Brookings, SD.
The PI of this proposal has a vast research experience on tan spot and SNB and is willing to
test every year one hundred wheat genotypes from each of the three regional breeding
programs under greenhouse conditions if funds are made available. The wheat genotypes that
exhibit resistance in the greenhouse will be further tested under field conditions in collaboration
with the tri-states breeders.
Co-PI: Dr. Karl Glover, spring wheat breeder, SDSU, Brookings, SD
This research will be primarily conducted in Dr. Ali’s laboratory and greenhouse. The lab is
equipped with all necessary tools for conducting the proposed research. Regional breeding
nurseries developed in SD by Dr. Glover will also be used for recording disease data to
accomplish the research objectives.
Collaborators: Dr. Anderson (U of M wheat breeder) Dr. Berzonsky (SDSU winter wheat
breeder), Dr. Mergoum (NDSU spring wheat breeder)
Importance:
Wheat is one of the most important sources of state revenue for Minnesota, North Dakota, and
South Dakota (Tri-states). In the year 2011, the Tri-states produced 438.7 millions bushels
(~$8/bushel) of wheat and contributed approximately $3.51billion dollars to the regional
economy. Every year, wheat produced in the region suffers yield losses to several pests and
diseases. Yield losses due to wheat diseases vary from year-to-year and location to location.
Severity of loss depends on the occurrence of favorable disease development conditions,
pathogen virulence, inoculum availability, and level of cultivar resistance; however, 5 to 7 %
yield losses ($175 to 245 millions) are common in each crop season. Tan spot, Stagonospora
leaf blotch, spot blotch, rusts, bacterial leaf streak/black chaff and Fusarium head blight (scab),
as well as common root rot are the most important diseases of wheat in the region. Each
impacts wheat production and ultimately affects the regional economy. Host resistance and
fungicides are the most effective disease management tools available for many fungal
diseases. However, because of the continual evolution of fungal pathogens virulence, the
development of resistant cultivars constantly requires identification of new sources of
resistance.
Wheat breeding teams at North Dakota State University (NDSU), South Dakota State
University (SDSU), and University of Minnesota (UM) are the major players in the development
of high quality and high yielding cultivars that are cultivated on most of the regional acreage.
Though, the breeding teams work mostly independently in developing wheat cultivars for their
respective states, wheat growers have the luxury to choose any of the regional wheat cultivar
for their crop production. The reason(s) for choosing a specific cultivar by an individual wheat
producer is not very clear. Protein content, disease resistance, straw strength, plant height, or a
combination of any and all characteristics in addition to yield potential are probably most highly
considered. . In 2012, 83.3%, 73.7%, and 60.6% of the spring wheat acreage planted in SD,
ND, and MN, respectively, were cultivars released by NDSU, UM, and SDSU wheat breeding
programs (USDA National Agri. Statistics Service) and contributed $2.54 billion dollars to tristates economy. In 2012, ‘Faller’, ‘RB07’, ‘Barlow’, ‘Samson’, ‘Vantage’, ‘Granite’, ‘Briggs’,
‘Brick’, ‘Howard’, and ‘Glenn’ were planted on vast acreages in tri-state region (USDA, NASS
2012; Anonymous 2012). All wheat cultivars developed by the NDSU, SDSU, and U of M
breeding programs go into regional nurseries for multiple years to measure their performance
(yield potential and other agronomic characteristics) under multiple environments prior to
registration. They are, however, generally not rigorously tested against important diseases,
especially leaf spotting diseases. The disease data available for any given wheat cultivar is
usually based from the regional breeding nurseries recorded by extension agents and/or
agronomists, using different disease rating scales. Furthermore, this disease data is not for a
particular leaf disease. This situation is not necessarily due to lack of pathologists interest in
screening material in greenhouse and developing disease nurseries under field conditions, but
perhaps lack of funds and other logistics. For example, disease nurseries for FHB are
developed in North Dakota, Minnesota, and South Dakota by the respective state plant
Pathologists and breeders through the National Wheat and Barley Scab Initiative and/or state
support. Recently, an increasing trend of foliar fungicide application has been observed to
benefit yield, without taking disease presence or absence into consideration; however, the
fungicide application treatments do not provide consistent results (Wiese and Mueller 2011).
This inconsistency could be due to 1) no disease pressure in the experimental field plots, or 2)
not all varieties respond to fungicides similarly. Anderson et al. (2012) also observed a yield
increase by fungicide application on cultivars that were rated susceptible to leaf disease. A
similar trend was observed in corn by Wiese and Mueller (2011) and reported that fungicide
use as a yield benefit could be possible only when the disease pressure is at or above the
threshold level, depending on the fungicide application cost and yield increase. Even assuming
that a fungicide application benefits yield, excessive use could exert selection pressure on the
pathogen populations and make them fungicide resistant, especially to fungicides with a single
mode of action. Additionally, the frequent use of fungicides may provide an opportunity for
weaker pathogens to thrive and cause major disease problems because the fungicide
eliminates beneficial competitive micro-flora. In recent years, corn and soybean production is
on the rise in the tri-state region and production of small grains has declined primarily because
of lower input costs and higher prices for corn and soybean. Additionally, researchers have
shown concern of slim chances of yield increase through currently available wheat germpasm,
as the rate of grain yield increase has been to the lowest level (<1 %/year) since 1980’s
(Graeybosch and Peterson, 2010; Reilly and Fuglie 1998; Fischer et al. 2009). However, the
increasing world population, low genetic potential for yield increase in current wheat
germplasm, and loss of agricultural land due to urbanization, will necessitate higher food
production with limited land and water resources. Minimizing the impact of pest and disease on
wheat production would help in filling the gap of food supply and demand worldwide.
As most wheat cultivars developed by any of the three public breeding programs can be
chosen and planted by producers anywhere in the tri-states region, it warrants that all best of
the best wheat cultivars currently grown in the region and advanced breeding lines that
potentially will be the future commercial cultivars, be tested for their reaction to tan spot, and
SNB. The information obtained from the objectives proposed will help to provide precise
information on cultivar reactions to important leaf diseases in the region and ultimately would
help in devising better IPM strategies. Also, it would help the regional wheat producers in
varietal selection for level of disease resistance in addition to agronomic and quality
characteristics.
Objectives
Determine the reaction of current best of the best wheat cultivars grown on large acreages and
elite breeding material to tan spot and stagnospora leaf blotch complex at seedling- and adultplant stage under greenhouse and field conditions
Assess the yield advantage of foliar fungicide application of leaf disease susceptible and
resistant wheat cultivars under field conditions
Evaluate tri-state regional breeding nurseries for multiple leaf and head diseases located at
multiple locations in South Dakota.
Methodology
Reaction of wheat genotypes to tan spots and stagnospora nodorum leaf blotch
Greenhouse experiment:
To meet the objective, seed of best of the best wheat cultivars and advanced breeding material
will be obtained from NDSU, SDSU, and U of M wheat breeders Drs. Anderson, Berzonsky,
Glover, and Mergoum, respectively. All wheat seed will be planted in conetainers containing
Sunshine potting soil mix. Three seeds will be planted in each conetainer and 18 seedlings of
each genotype will be maintained until tested for disease reaction. Nine seedlings of each
genotype at two-leaf stage will be inoculated individually with a spore suspension of P. triticirpentis race 1 and Stagnospora nodorum as described by Ali et al 2007. The inoculated
seedlings for tan spot and SNB will be rated for their disease reaction 8 days post inoculations
using 1-5 (1-2 are resistant and 3-5 are susceptible) and 0-5 (0 -2 are resistant and 3-5 are
susceptible) rating scales developed by Lamari and Bernier (1989) and Liu et al 2004,
respectively.
Field experiment:
Wheat genotypes that exhibit resistance to tan spot and SNB in greenhouse test will be planted
in hill plots (7-8 seed/hill) with three replications. The plants of all genotypes will be inoculated
individually with a spore suspension of P. tritici-repentis and S. nodorum at boot stage (Feeks
scale10). After inoculations, the plants will be misted for 30 seconds every 20 minutes for the
first 3 days of inoculation to induce disease development. The experiment will be conducted at
SDSU experiment research area located at Volga. The diseases data will be recorded after 810 days post-inoculation as mentioned for greenhouse experiment.
Effect of fungicide application on yield of wheat cultivars with different levels of resistance to
tan spot
Wheat plots of the two cultivars ‘Oxen’ (tan spot susceptible) and ‘Erik’ (tan spot resistant) will
be sown at the SDSU research stations located near Volga and NE Farm. Eighteen field plots
(9/cultivar) in total will be created at each location. The plot size will be 10 x 10 feet. There will
be three treatments in the experiment; these include 1) three plots of each cultivar will be
inoculated with P. tritici-repentis spore (3000 spores/ml) suspension at Feeks GS 10; 2) three
plots of each cultivar will be inoculated with spore suspension as in treatment 1 and then
sprayed with fungicide Folicure/Prosaro; and 3) three plots of each cultivar will be sprayed with
fungicide Folicure at seedlings and flag leaf stages. Treatments 1, 2, and 3 will provide us
information on effect of tan spot on yield in resistant and susceptible cultivars, effect of
fungicide application on the inoculated field plot, and effect of fungicide application on disease
free susceptible and resistant cultivars. All field plots will be rated for disease incidence and
severity 10 days post treatment 1. All field plots will be harvested individually and total yield,
thousand kernels weight, and test weight will be recorded and analyzed using the SAS
program. The experiment design will be a split randomized complete block design with three
replications. The cultivars will serve as the main plot and fungal inoculated and fungicide
sprayed plots will serve as sub-plot.
Evaluation of regional breeding nurseries for multiple diseases
The SDSU spring wheat breeder Dr. Glover establishes tri-state spring wheat breeding
nurseries at multiple locations throughout South Dakota every year. These nurseries will be
rated for leaf rust, stripe rust, leaf spot complex, and Fusarium head blight at appropriate
growth stages and disease data will be recorded and supplied to the respective breeder at the
end of the season.
Previous research
Tan spot (TS), caused by P. tritici-repentis (Died.) and Stagonospora nodorum blotch (SNB),
caused by S. nodorum are the most important fungal leaf spot diseases of wheat (Triticum
aestivum L.) worldwide (Hosford 1982; Lamari et al. 2003; Liu et al 2004). These leaf spot
diseases can cause 10 to 50% yield losses (Rees and Platz 1983; Shabeer and Bockus, 1988;
Bhathal et al. 2003; Eyal 1999). Host plant resistance is the most economical and
environmentally safe means of controlling these diseases. Although few resistance genes
effective against each race or pathogen causing leaf spot diseases have been identified (Ali et
al. 2007; Lamari and Bernier 1991; Singh and Hughes 2005; Xu et al. 2004), the majority of the
wheat cultivars grown in the northern Great Plains of the United States appeared to be
susceptible to the fungal leaf spot diseases (Ali et al. 2003; Singh et al. 2006). Eight races of P.
tritici-repentis (PTR) have been identified on the basis of their ability to induce necrosis and/or
chlorosis reaction on a set of differential cultivars (Lamari et al. 2003). Among them, races 1
through 5 have been observed in the US Great Plains and race 1 is the most prevalent race of
PTR in the United States (Ali et al. 2005; Ali and Francl 2002, 2003; Engle et al. 2006; Lamari
et al. 2003). Three host- selective Effectors/toxins (Ptr ToxA, Ptr ToxB, and Ptr ToxC) produced
by PTR have been isolated and characterized so far. Each one is responsible for inducing
typical chlorotic or necrotic symptom on susceptible or toxin sensitive wheat cultivars (Lamari et
al. 2003). Sensitivity to the Ptr ToxA was attributed to a single locus, Tsn1 that has been
mapped on the long arm of wheat chromosome 5B (Faris et al. 1996). The genotypes without
the Tsn1 gene are insensitive to the toxin (Anderson et al. 1999).
Stagonospora nodorum blotch is an important foliar disease of wheat worldwide (Eyal 1999).
Under severe epidemics, milling quality of the kernels is reduced (Eyal 1999). SNB has been
reported to cause yield losses up to 40% (Bhathal et al. 2003; Eyal 1999; Eyal et al. 1987; King
et al. 1983). Most genetic analyses have indicated that host resistance to SNB was under
polygenic control (Bostwick et al. 1993; Wilkinson et al. 1990). However, in some cases, it was
controlled by major genes (Kim et al. 2004; Ma and Hughes 1995; Wong and Hughes 1989).
Wilkin- son et al. (1990) found that the resistance to the leaf phase of SNB was inherited
polygenically in winter wheat cultivars. In contrast, monogenic control for resistance to the leaf
phase of SNB was reported in winter wheat (Kim et al. 2004; Wong and Hughes 1989). Several
major genes controlling a high level of resistance to SNB in the seedling stage in wheat and
wheat relatives have been reported (Ma and Hughes 1995; Murphy et al. 2000). A recessive
gene controlling resistance to SNB in a durum (T. durum) line was identified and named as
SnbTM (Ma and Hughes 1995). Two quantitative trait loci (QTL) for resistance to SNB have
been reported to be useful for marker assisted selection in wheat breeding programs (Liu et al.
2004). Multiple host selective effectors (toxins) have been isolated from S. nodorum and
observed to be associated with disease development. Recent studies indicate that major genes
are involved in resistance to SNB and follow the toxin model of the gene-for-gene interaction
(Friesen et al. 2006).
Fungicide use in plant disease management has a long history goes back to the 19th century
(Millardet 1885). However, fungicides used prior to the 1960’s were mostly protectant in nature
with multi-site inhibitors. These multi-site inhibitor characteristics, there were remote chances
for the pathogens to become fungicide resistance. In 1960’s systemic fungicides were
introduced that were very effective and provide more flexibility in use. Later in the 1970’s
systemic fungicide of DMI (strobilurins) were induced which were more specific and site
specific that increase the chances for pathogens to become fungicide resistance (Delph, 1980).
Fungicide resistance in P. tritici-repentis and S. nodorum populations has already been
reported in Europe (Peever et al. 1994; Reimann and Deising 2005).
Budget:
Total cost = $21,250/year
Budget requested in this proposal = $17,250
South Dakota Wheat Commission = $4,000
The budget is requested to cover the cost of; 1.5 month salary of technician; hourly time slip for
help in greenhouse, lab, field work, and data entry; lab, greenhouse, and field supplies and
space rent; and travel to monitor field experiments and data collection.
Timetable:
Project duration; Two years (2013 and 2014)
Year 1 (2013):
January through April– test 400 wheat genotypes for tan spot and SNB in Greenhouse
April through August- conduct field trials
September through November- data analysis and progress report preparation
Year 2 (2014)
January through April– test 400 wheat genotypes for tan spot and SNB in Greenhouse
April through August- conduct field trials
September through November- data analysis and final progress report preparation
References:
Ali S, Francl L. J. (2003) Plant Dis 87:418–42
Anderson et al. 2012. Varietal Trial Results. The Mineesota Agricultural Experiment Station
Report. PP 40-42.
Anderson et al. 1999. Phytopathology 89:293–297
Bhathal JS, Loughman R, Speijers J (2003). Eur J Plant Pathol 109:435–443
Engle et al. 2006. Plant Dis. 90:576-582
Lamari and Bernier (1989) Can J Plant Pathol 11:49–56
Lamari et al. (2003). Phytopathology 93:391-396
Liu et al. (2004). Phytopathology 94:1061-1067
Rees and Platz (1983). Aust. J. Agric. Res. 34, 39-46.
Shabeer and Bockus (1988). Plant Dis. 72:599-602
Millerdet (1885). J. Agric. Prat. 2:801-805
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Greybosch and Peterson (2010). Crop Science (September-October)
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Peever et al. (1994). Can. J. Plant Patholo. 16:109-117
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pp 332–344
Friesen et al (2006). Nature Genet. 38:953-956
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