PURDUE UNIVERSITY
Departments of Agronomy, Entomology, and Botany and Plant Pathology,
and the USDA-ARS, Purdue
University, West Lafayette, IN 47907, USA.
J. Anderson (USDA-ARS),
W. Berzonsky, I. Dweikat, D. McFatridge, H. Ohm, F. Patterson,
and H. Sharma (Department of Agronomy); G. Buechley, S. Goodwin
(USDA-ARS),
D. Huber, K. Perry, and G. Shaner (Department of Botany and Plant
Pathology); R. Ratcliffe, C. Williams, S. Cambron, F. Maas, M.
Jones, C. Collier, and C. Liang (USDA-ARS,
Crop Production and Pest Control Research Unit (Department of
Entomology)).
Production.
Farmers in Indiana seeded 850,000 acres (344,000
ha) of wheat in the fall of 1995 and harvested 720,000 acres (291,000
ha) the following spring. Average yield was 38 bu/acre (2,553
kg/ha) for a total production of 27.36 million bushels (745 million
kg). The harvested area was 9 % greater than in 1995, but total
production was only 69 % and yield per acre was only 37 % that
of 1995. The state average yield of 38 bu/acre was the lowest
since 1976. Private brands comprised 56.4 % of the acreage, compared
to 64.5 % of the acreage in 1995. Among publically developed
cultivars, Clark was most popular, occupying 15.9 % of the state
wheat area (Data source: Indiana Agricultural Statistics Service,
Purdue University).
The 1996 Indiana wheat crop was beset by several
calamities. The winter was stressful, and damage to the crop
was extensive. Some fields that would normally have been abandoned
and planted to a spring crop were retained, because wet spring
weather interfered with planting of corn and soybeans. Rainfall
was frequent during the spring, which favored Stagonospora and
Septoria leaf blotches and S. nodorum glume blotch.
Rains continued during the flowering period throughout most of
the state. Consequently, scab was widespread and severe. Stem
rust was moderately severe, but developed late and was not too
damaging.
Drs. Peggy Sellers and Karen Rane of the Plant and
Pest Diagnostic Clinic conducted a survey for Karnal bunt by examining
grain samples from virtually every county elevator in Indiana
handling wheat. Results were negative. Once the Karnal bunt
assays were performed, we examined these samples for scab. For
the nine crop reporting districts, the average percentages of
visibly scabby kernels were as follows:
Northwest 16.8 % West central 13.0 % Southwest 5.6 %
North central 25.5 % Central 8.7 % South central 6.9 %
Northeast 13.0 % East central 13.6 % Southwest 11.4
%
An informal survey of mycotoxin in wheat samples
by Dr. Charles Woloshuk revealed levels of DON from 0 to 50 ppm.
The FDA discourages use of wheat grain with greater than 2 ppm
DON.
Natural epidemics of leaf and glume blotch and of
scab were uniform in the breeding nurseries and cultivar trials.
We were able to obtain excellent notes on reactions of lines
to these diseases. Scab reaction was less influenced by flowering
date than has been the case in previous years, so notes from this
year are probably a good indication of true resistance. Incidence
(percent of heads showing any symptom of scab) and severity (percent
of spikelets scabbed on infected heads) were correlated (R = 0.64).
However, some lines had a low incidence and high severity; whereas
others had high incidence and low severity. Cultivars that show
these different reactions possibly have different genes that affect
scab development. We found some range in resistance to leaf blotch
among cultivars available for production in Indiana, but it is
not large. A few cultivars retain a green flag leaf longer than
others, which should contribute to better yield and test weight.
Partial resistance to leaf rust:
Studies of a population derived from the cross of slow-rusting
wheat CI 13227 with susceptible wheat Suwon 92 indicate that four
genes with unequal effect control the partial resistance of CI
13227. A gene at one of the loci exerts a major effect on latent
period. In breeding for slow-rusting resistance, slow-rusting
plants may be selected from bulk populations that were carried
for several generations.
We also evaluated the F7 progeny of the
cross between CI 13227 and Clark. Although Clark appears to be
susceptible, it displays a mixture of susceptible-type pustules
and very small, resistant flecks. CI 13227 has susceptible-type
pustules, but they are smaller and take longer to develop than
on a fully susceptible cultivar, which accounts for its partial
resistance. Many progeny of `Clark
x CI 13227'
cross had a greater and different kind of resistance than seen
in either parent, a necrotic-fleck reaction. This resistance is
evidently the result of interaction of genes from both parents,
and if combined into an adapted cultivar, could give durable protection
against leaf rust.
Naturally occurring strains of P. recondita
were evaluated for variation in latent period on susceptible and
partially resistant wheat cultivars. `Isolate
x cultivar'
interactions were significant. All strains had the same latent
period on a susceptible cultivar, but differed in their adaptation
to partially resistant cultivars. No strain completely overcame
the partial resistance of any cultivar. (Shaner, Buechley, and
Valezquez)
Scab: Three Midwestern
and three Chinese isolates of F. graminearum were compared
for virulence to wheat cultivars with different degrees of resistance.
The Chinese isolates were slightly more virulent, but resistance
was not cultivar-specific. Four wheat cultivars from China
were consistently resistant to spread of infection within the
spike, regardless of the isolate. A severe natural epidemic of
scab revealed that many lines from the scab resistance breeding
program had milder symptoms in the field and produced better quality
grain than susceptible checks.
We have found that the cultivar Chokwang, which we
originally studied as a source of partial resistance to leaf rust,
has some resistance to scab. Chokwang is not as resistant as
Ning 7840 or Sumai 3, but it is more resistant than any of our
SRWW cultivars. The cultivar may have genes for resistance different
from those in the Chinese sources, which might augment the Ning
7840 resistance.
We compared different methods of inoculation with
the scab fungus on several cultivars with different degrees of
resistance. Covering each inoculated head with a plastic bag
resulted in greater severity than covering the head with a glassine
bag. Inoculation by placing into a central floret a piece of
cotton that had been dipped in a spore suspension, was as effective
as injecting a spore suspension with a syringe. Injection by
syringe was quicker. Regardless of inoculation method, there
were significant differences among cultivars in susceptibility.
Patterson was most susceptible, followed by Clark and Frontana.
Sumai 3 and Ning 7840 were the most resistant. If post-inoculation
high humidity was provided by only a glassine bag, there was almost
no scab development on these two cultivars; if it was provided
by a plastic bag (higher humidity), there was some spread of scab
in the head. Soft red wheat cultivar Freedom had significantly
less scab than Clark and Patterson, but more than Sumai 3 and
Ning 7840.
Scab will probably need to be brought down to manageable
levels through a combination of resistant cultivars and cultural
practices that reduce the amount of inoculum. As part of a multistate
study, we monitored the presence of spores of G. zeae on
wheat heads from head emergence through flowering. The wheat
heads assayed for spores were within about 60 feet of a field
with abundant corn residue from 1995 on the soil surface. Spores
could be detected on heads throughout this period, and subsequent
scab development was severe. We do not know how far spores from
corn residue can be carried by wind, and we plan to investigate
this in the spring of 1997. (Bai, Shaner, and Buechley)
Foliar fungicides: Averaged
over several years and locations, Tilt fungicide applied at flag
leaf emergence has protected the flag leaf of wheat and increased
yield an average of 5 bu/acre (336 kg/ha) and test weight an average
of 1 lb/bu (13 kg/m3). A combination of Bayleton and
Mancozeb applied at head emergence gave similar results. On Patterson
wheat in 1996 when diseases were severe, Tilt provided more striking
protection and increased yield from 67 bu/acre (4,502 kg/ha) in
untreated plots to 78 bu/acre (5,241 kg/ha). (Buechley
and Shaner)
Insect surveys. Surveys
were conducted to monitor Hessian fly infestations in commercial
wheat fields and Purdue University or USDA wheat trials located
throughout Indiana in the autumn of 1996. The incidence of Hessian
fly was low in all areas where wheat was planted after the fly-free
date. However, fly infestation was high in an insecticide trial
established in Posey County on 25 September, 1996, approximately
2 weeks before the fly-free date for southwestern Indiana. There
was an average of 37 % infested plants, and an infestation rate
of two flaxseed per plant in untreated Clark control plots in
this study. Adjacent wheat fields seeded approximately 2 weeks
later (at or near the fly-free date) had very low incidence
of Hessian fly infestation and injury. Information obtained from
this trial demonstrated the susceptibility of wheat cultivars
with the currently deployed Hessian fly-resistance genes to fly
populations in Indiana (biotype L), and the value of delayed fall
seeding as a cultural control method for the Hessian fly.
(Cambron and Ratcliffe)
Biotype composition of Hessian fly populations
from the mid-south and southeastern U.S. and effectiveness
of resistance genes H9 to H19 to Arkansas
populations. Fourteen Hessian fly
populations from Arkansas, Georgia, Illinois, North Carolina,
and Virginia were evaluated for biotype composition, and two Arkansas
populations were tested for response to Hessian fly-resistance
genes H9 to H19 in Purdue wheat lines. Hessian
fly populations from Arkansas, Illinois, North Carolina, and Virginia
were predominantly biotype L and virulent to all resistance genes
currently deployed in soft winter wheat cultivars. Biotypes G,
J, L, M, and O were identified from Hessian fly populations collected
from west central Georgia, although only biotypes M and O were
identified from populations sampled from southwestern Georgia.
The presence of biotypes J and L in Hessian fly populations from
central Georgia will reduce the effectiveness of wheat cultivars
carrying the resistance gene combination H7H8 in this area.
Wheat lines with single resistance gene pairs H9, H10,
H13, H14, and H16 to H19 were resistant
to both Arkansas Hessian fly populations, although lines with
single resistance genes H11, H12, or H15
were susceptible to one or both populations. (Ratcliffe and Cambron,
in cooperation with Ohm and Patterson)
Analysis of five unnamed Hessian fly-resistance
genes in wheat. Triticum aestivum
and T. turgidum mapping populations were constructed to
localize five unnamed loci for Hessian fly resistance. Each parental
line was shown to contain only a single locus for Hessian fly
resistance. The five genes were rated for relative strength of
resistance in heterozygotes. (Williams, Collier, Liang, and Jones,
in cooperation with Ohm, Maas, and Patterson)
Gene H9.
With the screening of 1,500 10-mer primers, we have identified
six markers in association with gene H6 and four with gene
H9. Linkage analyses were made using F2 populations
of 400 progeny for H6, 1,000 progeny for H9 and
248 progeny segregating for both H6 and H9 in an
effort to integrate all of the markers within the region (2 m.u.)
that encompass the H6 -H9 genes. The majority
of the markers (7 of the 10) were clustered within 3 cM of the
two genes. Sequence analysis of these markers reveals a high
degree of homology (> 90 %) between one of the markers for
gene H9 and the rDNA that is located near the telomere
on the long arm of chromosome 5A, suggesting that H9 is
located on the long arm. (Dweikat and Ohm)
Barley yellow dwarf virus resistance research.
Strain survey. BYDV was
prevalent on wheat in Tippecanoe County, Indiana, during the 1995-96
season. In plots of the cultivar Patterson, structured unbiased
sampling and ELISA testing of 42 plants revealed 16 (38 %) to
be infected, although symptoms were not evident. Fourteen of
these plants were infected with the PAV serotype. The remaining
two infected plants harbored the RPV serotype. No mixed infections
were observed. The MAV, SGV, and RMV serotypes were not observed.
Samplings of symptomatic wheat (n = 19) revealed 15 plants infected
with either the PAV or RPV serotype; the remaining four plants
were infected with both serotypes. These results contrast with
observations in the 1994-95
season when both the RMV serotype and mixed infections with multiple
BYDV serotypes were common. Although most of the wheat was asymptomatic,
older cultivars of oats planted in adjacent fields were significantly
damaged by high BYDV infection. (Perry)
BYDV-resistant germplasm.
The germplasm line P29 was released. Germplasm P29 is
an alien substitution line from Th. intermedium and
is resistant to BYDV. The Thinopyrum chromosome that imparts
BYDV resistance substitutes for chromosome 7D of wheat. The presence
of the Thinopyrum chromosome was confirmed by FISH , using
Th. intermedium genomic DNA as a probe. The chromosome
composition of the potential translocations that were developed
from Th. intermedium substitution, and addition
lines studied in M4 generation, was found to be stable
(2n = 42). M5 progeny testing for BYDV resistance
by ELISA showed the expected results and established homozygosity
for BYDV resistance. The translocations are being characterized
for BYDV resistance and amount of wheatgrass DNA (J. Anderson's
lab). This source of resistance is being incorporated into the
breeding program. A BC1F2 population was
developed from germplasm line P29 from crosses with ph
mutant to induce recombinations between wheatgrass and wheat chromosomes
to transfer the BYDV resistance. (Sharma and Ohm)
Molecular analysis of wheatgrass derived BYDV
resistance. We have determined that an
introgressed wheat line (P29), where a group 7, Th. intermedium
chromosome was substituted for 7D, is moderately resistant to
subgroup I BYDV strains (PAV) and completely resistant to subgroup
II BYDV strains (RPV and RMV). To localize this BYDV resistance,
a detailed molecular genetic analysis was made on the alien group
7 Th. intermedium chromosome contained in line P29
to determine its structural organization. Triticeae group
7 RFLP markers and rye-specific repetitive sequences used
in the analysis showed that the alien chromosome in the P29 substitution
line has distinguishing features. The 350-480
bp rye telomeric sequence family was present on the long arm as
determined by Southern and fluorescence in situ hybridizations.
However, further analysis using rye dispersed repetitive sequences
indicated that this alien chromosome does not contain introgressed
segments from the rye genome. The alien chromosome is homoeologous
to wheat 7A and 7D as determined by RFLP analysis. The apparent
colinearity with wheat group 7 chromosomes and rice chromosome
6 has allowed us to use these RFLP markers and in situ hybridization
to identify translocation lines developed from g-irradiated
alien substitution lines and addition lines. From this analysis,
we have identified resistant translocation lines containing less
than a full long arm translocation, which are being incorporated
into the breeding program. The BYDV resistance locus also has
been localized to the distal portion of the long arm of the group
7 Th. intermedium chromosome. (Bucholtz,
Crasta, Greene, Francki, Zhu, Anderson)
Anther culture. Anthers
from `wheat
x wheatgrass'
hybrids and backcrosses were cultured to investigate the possibility
of isolating alien addition lines. Callus induction in F1
hybrids was only 0-2
% with some improvement in backcrosses. Limited data show that
the chromosome numbers in the pollen-derived plants/organs of
wide hybrids can be reduced to produce alien addition lines.
In an effort to improve the efficiency of anther culture, co-culture
of intact anthers with ovules on solid media was tried in wheat
and backcrosses of the wide hybrids. Wheat genotypes differed
significantly for callus induction and plantlet regeneration.
Co-culture did not improve anther development in wheat,
but had some beneficial effect on the ability to culture anthers
of wide hybrids. (Sharma)
Septoria pathogens.
We have been investigating the population biology of the Septoria
pathogens to determine whether there is gene flow among populations
of the pathogens infecting the major market classes of wheat in
the central United States. Isolates of Mycosphaerella graminicola
(S. tritici blotch), Phaeosphaeria nodorum (S.
nodorum), and of the barley pathogen S. passerinii
were collected in the midwestern and north central states. Twenty-nine
isozyme systems were screened for polymorphisms, and eight useful
systems were identified, although the level of polymorphism was
low. There was very little genetic differentiation between populations
of M. graminicola and P. nodorum in
Indiana/Ohio and Minnesota/North Dakota, indicating either a high
level of gene flow or strong selection for the isozymes identified.
All three species (M. graminicola, P. nodorum,
and S. passerinii) were easily distinguished by
isozyme analysis alone. Analyses with RAPD primers revealed much
more polymorphism. Some RAPD primers appeared to identify multiallelic
loci. Bands from these loci are being cloned and sequenced for
developing markers for characterizing genetic diversity in populations
of these pathogens. (Goodwin)
Glume blotch. DNA from
two uniformly resistant and two uniformly susceptible F7
families from a recombinant inbred population (Purdue 831800 x
Purdue 871327) has been bulked and is being screened by amplifying
products from RAPDs for molecular markers associated with glume
blotch resistance. Bulked DNA is being screened. To date, approximately
200 primers have been screened. Putative markers will be screened
again and retested for cosegregation. We are in the process of
producing recombinant inbred populations for three other sources
of resistance to glume blotch. F2 populations were
produced by intercrossing highly susceptible and highly resistant
plants originating from the same advanced Purdue lines in a field
nursery evaluated in 1995. These populations will be grown and
evaluated in 1997 field nurseries. (Berzonsky and Ohm)
Heterozygous translocations.
Frondoso, a parent of Atlas 66 wheat, and other wheat lines originating
from Brazil were examined for the presence of quadrivalents at
meiosis. Six of nine lines originating from Frondoso had quadrivalents,
which are indicative of a heterozygous reciprocal chromosome translocation.
Frondoso, Fronteira, Atlas 50, Wakeland, and Coastal were crossed
with Chinese Spring double-ditelosomic 2A and 2D lines.
Meiotic analyses of the hybrids indicate they likely carry a 2A/2D
translocation. Because Frondoso is a parent of Atlas 66, it is
the probable source of the Atlas 66 translocation, and the detection
of a 2A/2D translocation in Fronteira traces it back to an earlier
Brazilian origin. Aneuploid progeny can be produced from non-cooriented
segregations from these quadrivalent-forming cultivars.
Genetic studies and breeding may be impacted when these cultivars
are used. (Berzonsky)
Rye translocations. Four
SRWW cultivars (GR 876, Freedom, Pioneer7
cultivar 2510, and Grant) having the T1RS-1BL
translocation were probed for the loss of rye chromatin using
rye-specific telomeric, dispersed, and centromeric sequences.
In situ hybridizations and Southern hybridizations of the probes
to each cultivar indicate that each maintains a complete 1RS chromosome
arm despite arising from three separate breeding programs. Therefore,
SRWW breeders will likely be required to deliberately manipulate
the loss of 1RS chromatin to eliminate undesirable quality loci
but still maintain higher yield and pest resistance loci. (Berzonsky,
Francki, Anderson, and Ohm)
Personnel.
Dr. Ouafae Benlhabib from Institute of Agronomy and
Veterinary, Morocco, and a collaborator on a PSTC/AID project
spent 1 month at Purdue University working with H. Sharma. Dr.
X. Hu joined S. Goodwin's
research group in a postdoctoral position and is focusing on identifying
molecular markers linked to Septoria resistance genes.
Maria Manetti from Argentina began studies toward the M.S. degree
with H. Ohm, developing DNA markers associated with scab resistance
genes. Brad Nelson began studies toward the Ph.D. degree with
H. Ohm, developing DNA markers associated with plant maturity
and plant height.
Publications.
Anderson JM, Crasta O, Francki M, Bucholtz D, Sharma
H, and Ohm HW. 1997. Molecular and cytogenetic analysis of barley
yellow dwarf virus resistant translocation lines containing Thinopyrum
intermedium chromosomal segments. Proc Plant and Animal
Genome V, San Diego, CA., Jan. 12-17. p. 90.
Bai G and Shaner G. 1996. Variation in Fusarium
graminearum and cultivar resistance to wheat scab. Plant
Dis 80:975-979.
Benlhabib O, Hmoud R, and Sharma H. 1996. Analyse
cytogenetique et androgenetique de descendants intergeneriques
entre Triticum aestivum et Agropyron species. Actes
IAV, Maroc 16:27-32.
Berzonsky WA. 1996. Brazilian origin and inheritance
of a heterozygous reciprocal chromosome translocation in wheat
(Triticum aestivum L.). Cytologia 61:253-258.
Berzonsky WA, Francki MG, Anderson JM, and Ohm HW.
1996. A cytological and molecular comparison of soft red winter
wheat varieties with 1RS.1BL. Agron Abstr 88:73.
Berzonsky WA and Ohm HW. 1997. Breeding cereal
small grains for value-added uses. ASA monograph chapter.
In press.
Buechley G and Shaner G. 1996. Control of bunt
and loose smut of wheat with fungicidal seed treatments, 1995.
Fungicide and Nematicide Tests 51:307.
Cambron SE, Ohm HW, Ratcliffe RH, and Patterson FL.
1996. A second gene for resistance to Hessian fly in Iumillo
Wheat. Crop Sci 36:1099-1101.
Cebert E, Ohm H, Patterson F, Ratcliffe R, and Cambron
S. 1996. Genetic analysis of Hessian fly resistance in durum
wheat. Agron Abstr 88:88.
Crasta O, Francki M, Greene A, Bucholtz D, Sharma H, Ohm H, and Anderson J. 1996. Molecular characterization of Thinopyrum chromatin in wheat toward targeted mapping of BYDV resistance. 2nd Inter Crop Sci Cong, New Delhi, 17-24 November, 1996.
Desjardins AE, Proctor RH, Bai G, McCormick SP, Shaner
G, Buechley G, and Hohn T. 1996. Reduced virulence of trichothecene-nonproducing
mutants of Gibberella zeae in wheat field tests. Mol Plant-Microbe
Inter 9:775-781.
Drake DR and Ohm HW. 1996. Inheritance of head scab resistance in wheat. Agron Abstr.
Dweikat I, Ohm H, Patterson F, and Cambron S. 1997.
Identification of RAPD markers for 11 Hessian fly resistance
genes in wheat. Theor Appl Genet (in press).
Dweikat I, Zhang W, Ohm H, Cambron S, and Ratcliffe
R. 1996. Construction of a high resolution map for Hessian fly
resistance genes H6 and H9 in wheat. Proc Plant
Genome IV, 15-19
January, San Diego, CA. (Abstract).
Gyulai G, Dweikat I, Janovsky J, Ohm H, Kiss E, Sharma
H, and Heszky L. 1996. Analysis of Agropyron, Bromus
and Agropyron x Bromus by ISSR-PCR. EUCARPIA
Cong. Poland, 6-11
October, 1996.
Hodges TK, Aldemita R, Kononowicz-Hodges H,
Macdonald B and Anderson JM. 1996. Agrobacterium-mediated
transformation of japonica and indica rice varieties.
Workshop on In Vitro Manipulation of Wheat and Small Grains,
World Cong In Vitro Biol, San Francisco, 22-27
June, 1996.
Hu XY, Bostwick D, Sharma H, Ohm H, and Shaner G.
1996. Chromosome and chromosomal arm locations of genes for
resistance to Septoria glume blotch in wheat cultivar Cotipora.
Euphytica 91:251-257.
Hu XY, Ohm HW, and Dweikat I. 1997. Identification
of RAPD markers linked to PM1 for resistance to powdery
mildew in wheat. Theor Appl Genet (in press).
Lehman JS and Shaner G. 1996. Genetic variation
in latent period among isolates of Puccinia recondita
f. sp. tritici on partially resistant wheat cultivars.
Phytopathology 86:633-641.
Ohm HW and Berzonsky WA. 1996. Screening a recombinant
inbred population for resistance to glume blotch. Agron Abstr
88:73.
Ohm HW, Ratcliffe RH, Patterson FL, and Cambron SE.
1997. Resistance to Hessian fly conditioned by genes H19
and proposed gene H27 of durum wheat line PI422297. Crop
Sci 37:113-115.
Patterson FL, Ohm HW, Johnson JW, and Wickersham
DS. 1996. Registration of five wheat pollen fertility restorer
germplasm lines: PR143, PR189, PR267, PR270, and PR302. Crop
Sci 36:1424.
Ratcliffe RH, Ohm HW, Patterson FL, Cambron SE, and
Safranski GG. 1996. Response of resistance genes H9-H19
in wheat to Hessian fly (Diptera: Cecidomyiidae)
laboratory biotypes and field populations from the eastern United
States. J Econ Entomol 89:1309-1317.
Ratcliffe RH and Hatchett JH. 1997. Biology and
genetics of the Hessian fly and resistance in wheat. In:
New Developments in Entomology (Bondari K ed). Research Signpost,
Scientific Information Guild, Trivandrum, India. In press.
Ratcliffe RH, Ohm HW, Patterson FL, and Cambron SE.
1997. Biotype composition of Hessian fly (Diptera: Cecidomiidae)
populations from Arkansas, Georgia, Illinois, North Carolina and
Virginia. J Entomol Sci 32:in press.
Shaner G and Buechley G. 1996. Effect of foliar fungicides on control of wheat diseases, 1995. Fungicide and Nematicide Tests 51:231.
Sharma H. 1996. Maintenance of haploid genome of
Agropyron junceum in wheat. Wheat Info Serv 83:21-24.
Sharma H, Ohm H, and Perry K. 1997. Registration
of wheat germplasm line P29 with BYDV resistance. Crop Sci 37:In
press.
Sharma H, Jekkel Z, Benlhabib O, and Ohm H. 1996.
Effect of concomitant ovule culture on anther culturability in
wheat and wheatgrasses. World Cong In Vitro Biol, San Francisco,
22-27
June, 1996. p. 84A.
Sharma H, Benlhabib O, Jekkel Z, and Ohm H. 1996.
Anther culture and concomitant ovule culture of wheat x wheatgrass
hybrids and wheat. Agron Abstr 88:160.
Yang X, Ohm H, and Dweikat I. 1996. Identification
of RAPD markers linked to a gene for resistance to Septoria
tritici in wheat. Agron Abstr 88:169.
Zhang G and Goodwin SB. 1996. Enzyme polymorphism
among isolates of Mycosphaerella graminicola (anamorph
Septoria tritici) and Septoria passerinii.
Phytopathology 86:S90.
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