INDIANA
PURDUE UNIVERSITY
Departments of Agronomy, Entomology, and Botany and Plant Pathology, and the USDA-ARS, Purdue University, West Lafayette, IN 47907, USA.
J.M. Anderson (USDAARS), H.W. Ohm, F.L. Patterson, and H.C. Sharma (Department of Agronomy); G. Buechley, S. Goodwin (USDAARS), D. Huber, K. Perry, and G. Shaner (Department of Botany and Plant Pathology); R.H. Ratcliffe, R. Shukle, C.E. Williams, S. Cambron, C. Collier (USDAARS), and J. Stuart (Department of Entomology).
Indiana farmers harvested 206,500 hectares (510,000 acres) of SRWW in Indiana in 2000, the same as in 1999. Average yield was 4,638 kg/ha (69 bu/acre) compared to 4437 kg/ha (66 bu/acre) in 1999. The state average yield for 2000 is the highest ever recorded for Indiana. Area seeded to wheat in Indiana for 2001 is 550,000 acres, similar to that of 1999 and 2000.
Diseases were not a serious problem in most Indiana wheat fields during 2000. Early in the spring, some varieties showed severe mottling from infection by WSSMV or SBMV. Most varieties grown in Indiana are at least moderately resistant to these viruses and outgrow symptoms. Although some rain fell during the spring vegetative period, there were no sustained periods of rainy weather and therefore leaf blotch was not severe. Rains that fell during flowering and early grain filling of wheat allowed some development of FHB, but generally the incidence of this disease was low. Wheat sown on land where corn residue was present was more likely to have Fusarium head blight than wheat sown on land without corn residue. Infection by the aphid-transmitted barley yellow dwarf virus was common. After wheat was mature, plants infected by this virus were often conspicuously moldy.
Control of wheat diseases with foliar
fungicides (Shaner and Buechley).
Trials were located in west-central (ARC) and southeast Indiana
(SEPAC). Several treatments reduced severity of powdery mildew
compared to the untreated control. In general, treatments applied
at Feekes 8 were more effective than those applied at Feekes 10.51.
Several treatments were inconsistent between locations in control
of leaf rust. For example, Folicur + Induce applied at Feekes
9 at SEPAC gave complete control, but was ineffective at ARC when
applied at Feekes 8. The timing of infection periods relative
to time of treatment could account for these differences. Septoria
and Stagonospora leaf blotches were not severe at either location.
Nonetheless, several treatments reduced severity compared to
the untreated control. Incidence of Fusarium head blight was
low at SEPAC and moderate at ARC. No treatment at SEPAC reduced
incidence compared to the untreated control. At ARC, Caramba,
Stratego, and Folicur + Induce, when applied at Feekes 10.51,
reduced head blight incidence significantly. Four treatments
at ARC reduced the percentage of scabby kernels compared to the
untreated control. Five treatments also reduced the level of
DON in grain, three of which were among those that reduced incidence
of scabby kernels. At SEPAC, DON levels were generally lower
than those at ARC, and no treatment had less DON than the untreated
control. Several treatments, however, had significantly greater
levels of DON than the untreated control. These were mostly treatments
that included a strobilurin fungicide. The correlation between
visibly scabby kernels and DON level, calculated on a plot basis
for the ARC experiment, was significant, but low (R = 0.41).
Scab Epidemiology (Shaner and Buechley). Airborne spores of Fusarium species were monitored
at two sites at the Purdue University Agronomy Research Center
(ARC) during the 2000 wheat season, using Burkard samplers. There
were no periods of sustained rainfall from the time of wheat anthesis
through grain filling, in contrast to what occurred during the
same wheat developmental period in 1996, when a major head blight
epidemic occurred. Nonetheless, spores of F. graminearum were
collected on many days during anthesis and early grain filling.
Spores were also recovered directly from head washings during
this period. The incidence of head blight was light to moderate,
as was the incidence of scabby kernels. This suggests that weather
conditions may have been limiting for infection rather than for
production of inoculum.
Biotype determination (Ratcliffe and Cambron). Hessian fly populations were collected in spring 2000 from Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Virginia. To our knowledge, these were the first collections of Hessian fly from Louisiana and southwestern Arkansas. The Hessian fly population from southern Alabama was predominantly biotype O, but also contained 23 % biotype L, indicating some loss of effectiveness of H7H8 resistance. In the northern two-thirds of Alabama, Hessian fly populations ranged from 55 % biotype L in the westcentral area to < 20 % biotype L in the eastcentral and northeastern area. H7H8 resistance is effective in much of the central and northeastern area, but resistance associated with H3, H5, and H6 is ineffective. Biotype composition of the fly population from southwestern Arkansas was quite varied. Based on data from this single collection, the effectiveness of available resistance genes would range from low for H5 and H6 to moderate for H3 and H7H8. Hessian fly populations tested from eastern North Carolina, South Carolina, and Virginia were predominantly biotype L, as were the populations collected from Louisiana and Mississippi. Based on this information, resistance associated with genes H3, H5, H6, and H7H8 would be ineffective throughout the mid-Atlantic state area and much of the mid-south. Fly populations in western Georgia and South Carolina are still predominantly biotype O and can be managed with wheat cultivars carrying H7H8 resistance. The high level of biotype L in Louisiana (77 %) and Mississippi (81 %) may indicate that flies giving rise to these populations were transported as flaxseed (pupae) in wheat straw from areas of high biotype L frequency, such as northern Alabama. Research was conducted in coöperation with personnel at the University of Georgia, Auburn, Clemson, and North Carolina State University, Lousiana State University, Virginia Polytechnic Institute and State University, AgriPro Seeds, Novartis Seeds, Inc., and Pioneer HiBred Intl., Inc.
Effectiveness of H13 resistance (Ratcliffe, Ohm, and Patterson). The Purdue cultivar INW9811 and/or germ plasm line Molly, which carry H13 resistance to biotype L, were tested against Hessian fly populations collected in autumn and winter of 1999-00 from central and eastern Maryland, eastern North Carolina and Virginia, central and west central South Carolina, and southwestern Arkansas. The frequency of biotype L in fly populations from Maryland, North Carolina, and Virginia ranged from 60 to 96 %. There was 16 % biotype L in the Arkansas population and none in the South Carolina population. INW9811 was not tested against fly populations from North Carolina and central South Carolina, but was highly resistant to populations from eastern and central Maryland, eastern Virginia, westcentral South Carolina, and southwestern Arkansas. Molly was highly resistant to all fly populations except that from central South Carolina, to which it demonstrated 70 % resistance. These results, and those reported in 1999 for tests with INW9811 against fly populations from Alabama and Georgia, demonstrate the broad range of effectiveness of H13 resistance against the Hessian fly in the eastern U.S. soft winter wheat region.
Hessian fly injury to wheat (Gamaelius and Ratcliffe). Feeding by Hessian fly larvae significantly altered leaf area, leaf, root, and total plant dry weight, and the amount of total chlorophyll, chlorophyll B, total nonstructural carbohydrates (TNC), and some long-chain sugars in susceptible, but not resistant wheat cultivars. Leaf area and dry weights were decreased significantly in susceptible cultivars following fly infestation, while total chlorophyll, chlorophyll B, TNC and some long-chain sugar concentrations were increased. Larval feeding did not significantly alter stem dry weight, tillering, or starch and short-chain sugar levels in either susceptible or resistant cultivars. A strong genetic component was expressed among susceptible cultivars which influenced the amount of injury caused by fly feeding and their relative susceptibility.
Hessian fly-induced mRNA in wheat leaves (Williams, Collier, Nemacheck, and Liang). Through gene-for-gene interactions, wheat plants respond to specific biotypes of Hessian fly upon the initiation of larval feeding. Plants containing the H9 resistance gene responded to avirulent biotype L larvae with a rapid increase in Hessian fly-induced mRNA in their leaves. A cDNA clone for one of these genes was isolated and characterized. The expression of this gene increased in leaves for two days before returning to pre-infestation levels by day five. This increased expression correlated with the onset of resistance and indicated the involvement of a systemic component in this gene-for-gene interaction. The derived amino acid sequence of the gene was similar to several others that are induced by BTH (benzothiadiazol) and jasmonic acid, both systemic inducers of defense-response genes. In addition, the sequence was similar to other pathogenesis-related proteins, such as jacalins and beta-glucosidase aggregating factor, that are capable of binding macromolecules during disease and insect-resistance responses.
Resistance from wheatgrass. (Sharma, Anderson, and Ohm). Two BYDV-resistant addition lines, provided by Professor Zhiyong Xin at the Beijing Academy of Agricultural Science, with either a Th. intermedium group-1 or group-2 chromosome pair were previously crossed to cultivar Patterson and the seed irradiated with gamma rays. Approximately 1,300 M4 plants and 700 M5 plants from selected M4 families have been tested (ELISA) for resistance to BYDV P-PAV. A small subset of the M5 plants have been analyzed by microsatellite markers to identify polymorphisms that will be useful in identifying chromosome groups 1 and 2 translocation lines. Field trials of lines containing group-7 Th. intermedium translocations have shown that this resistance is quite good but is not sufficient to completely protect against PAV infection. Consequently, identification of lines containing group 1 and 2 translocations will facilitate pyramiding Th. intermedium-derived BYDV resistance genes. We also have initiated matings of some of the putative translocation lines with elite wheat lines and with chromosome group-7 translocations to boost the resistance to PAV.
In order to determine if there is enhanced
resistance to the PAV isolate of the virus with any two of the
groups 7, 2, and 1 chromosomes from Thinopyrum in the wheat genome,
hybrids between disomic addition lines of these chromosomes were
produced in all possible combinations and tested by ELISA. In
general, ELISA values were lower in double-monosomic addition
lines. Thus, resistance could be additive. Resistance was enhanced
more in chromosome 'group 1/group 2' hybrids compared to 'group
7/group 1' or 'group 7/group 2' hybrids, possibly because groups
1 and 2 each have smaller contributions to resistance compared
to group 7. We are evaluating the desirable translocations with
BYDV resistance from the group-7 chromosomes for germ plasm release.
Pathogen genetics (Goodwin, Cavaletto, Roberts, and Abbasi). Work on the genetics of the S. tritici leaf blotch pathogen, M. graminicola, identified a transposable element as the cause of polymorphisms revealed by a DNA fingerprint probe. This transposon has 29- and 79-bp direct repeats and codes for a reverse transcriptase enzyme. The enzyme appears to be active at a high frequency during both sexual and asexual reproduction and is not present in closely related fungi. Therefore, it might have been recently acquired by M. graminicola.
Phylogenetic analyses showed that the closest relative of M. graminicola is the barley pathogen, S. passerinii. This species has no known sexual stage and is thought to reproduce exclusively asexually. However, we have cloned and sequenced the genes for two mating type idiomorphs from S. passerinii, and showed that both mating types occur in the same fields in Minnesota and North Dakota. Therefore, this pathogen most likely has a sexual stage that might complicate efforts to manage speckled leaf blotch on barley. A simple PCR test was designed to detect the two mating types in infected barley leaves.
Phylogenetic analyses of the ITS region of rust fungi in the genus Puccinia revealed that P. graminis in Iran is highly variable and might be composed of a number of cryptic, sibling species, each adapted to specific grass hosts. Isolates from wheat had the most common ITS haplotypes; most of the genetic variation for this fungus remains in Iran, which strengthens the conclusion that the Middle East is the center of origin for this pathosystem. Using the ITS database for Puccinia, it was possible to identify rust specimens from aecial hosts that were difficult to identify by morphological characters.
Work with a possibly new gene for resistance
to S. tritici blotch in the synthetic wheat W7984 revealed
that the gene probably is located on the long arm of chromosome
7B. Experiments to confirm this location are in progress. If
confirmed, this will be the first major gene for resistance to
S. tritici blotch to be mapped in wheat.
Nature of virulence (Huber and Ian Thompson, Botany & Plant Pathology Department; and Darrell Schulze, Agronomy Department). Research on take-all has continued to focus on the nature of virulence of G. graminis var. tritici (Ggt). In a screen of virulent isolates of Ggt collected from the major wheat-producing areas of the world, all virulent isolates were able to oxidize Mn from the readily available Mn+2 form to the nonavailable Mn+4 oxidized form. Avirulent isolates are not able to oxidize Mn+2. Many isolates were temperature insensitive (15-25°C), however, some isolates oxidized Mn and were virulent only at the lower or higher temperatures. Using high-energy x-ray fluorescent techniques (microXANES and XRF) we demonstrated that 'free-living' Ggt in soil oxidized Mn along hyphae and precipitated it in soil much the same as observed during pathogenesis in the infection court. The oxidative virulence factor of Ggt is an extracellular enzyme, whereas there also appears to be a membrane-bound Mn oxidative factor in both Ggt and Ggg. We currently are characterizing the enzyme and studying its molecular-genetic basis. Biological and cultural control of take-all appears to function through suppression of oxidative action rather than through inhibition of Ggt growth. This research permits specific targeting of mechanisms to understand and enhance disease control.
Field plots established at four locations
in Indiana differing in soil type, micronutrient availability,
and weather pattern are used to evaluate various approaches to
providing a full nutrient sufficiency and its relationship to
disease suppression. Copper and Zn may be supplied by soil or
seed applications, whereas Mn is only temporarily available if
broadcast-applied because of rapid oxidation by soil microorganisms
in most soils. We are continuing our research with various formulations
and sources of the micronutrients and their abiotic and biotic
interactions in soil to further enhance availability and uptake
efficiency leading to greater disease resistance.
Brett Roberts joined the Goodwin lab as
a biological science research technician during May, 2000. Previously,
he worked for the USDA-ARS at Stoneville, MS. Yang Tian began
a Ph.D. program in S. Goodwin's lab during August, 2000. Mehrdad
Abbasi received a grant from the Iranian government to spend several
months in S. Goodwin's lab studying the phylogenetics of rust
fungi from wild grasses and other hosts in Iran. He began his
work during October, 2000. Lubaki Zantoko completed the requirements
for the Ph.D. degree in entomology under the guidance of R. Shukle.
Lingrang Kong began a postdoctoral research position in H. Ohm's
lab in October 2000, managing DNA marker research and collaborating
with other wheat lab groups at Purdue in a genomics initiative
to identify resistance genes. Ted Kisha accepted a USDA-ARS Research
Geneticist position at Pullman, WA in August 2000. Ahmed Abo-Doma,
Ain Shams University, Cairo, Egypt, studied as a Visiting Scholar
from June-December 2000 with H. Ohm and J. Anderson to identify
markers for BYDV resistance from chromosome groups 1 and 2 from
wheatgrass. Boovaraghan Balaji joined the Anderson lab as a post-doctoral
associate in May 2000 to identify and characterize wheat proteins
that specifically interact with BYDV proteins in both resistant
and susceptible lines. Ligia Ayala-Navarrete also began a post-doctoral
position in J. Anderson's lab in December 2000, to develop microsatellite
markers for characterizing translocation lines and to determine
mechanisms of BYDV replication and movement in oats. Hathaithip
Wiangjun began a Ph.D. program in the Anderson lab in January,
2001, to examine the mechanisms of wheatgrass-derived BYDV resistance.