Annual Progress Report on Malting Barley Research March, 2007

5. Collect isolates of barley pathogens and determine their virulence phenotype.
In 2006 we had difficulty in making isolations from leaf lesions probably due to the fact that
there were few well developed infections on the material collected.
A survey of fields was undertaken in July 2006 for common root rot (CRR) caused by
Bipolaris sorokiniana which finds dry soil conditions favorable for development.
Cochliobolus sativus was isolated from approximately 80% of the more than 200 sub-crown
internodes showing symptoms. After identification we subcultured the isolates using a
single conidium in order to ensure that we did not have a mixed culture. The single
conidium isolates were dried down and are in stage at -80 C. We were able to add these
collections to the large collection we amassed in 2002-2006 and they will be used by the
grad student Sanjay Gyawali to study diversity of the pathogen.
6. Molecular Markers and Resistance Genes to Septoria in Barley. Dr Seonghee Lee a
PhD student (August 2002-July 2006) completed his research on identifying molecular
markers for resistance genes to Septoria leaf blotch in barley. Septoria speckled leaf
blotch (SSLB) caused by the pathogen Septoria passerinii is a common leaf disease in
cultivated barley in North Dakota. The disease causes economic losses in yield and malting
quality, and genetic resistance is the preferred method of control. Identification of molecular
markers for SSLB resistance genes will allow marker-assisted selection (MAS) in breeding.
To develop molecular markers for resistance, susceptible cultivars were crossed with three
resistant lines, each containing one the three genes. The F2 generation and F2.3 families
were evaluated for resistance in the green house and F2.3 families in the field. Sequence
tagged site (STS) markers SUBC285, SOPC2, SOPAH5, and SOPBA12 each closely
linked to one of the three genes, were produced from RAPD markers. Another STS marker,
MWG938 linked to Rsp2, was also identified. The STS markers were screened on breeding
material with know phenotype as well as diverse genetic material. The STS markers linked
to Rsp genes will be very be useful for maker-assisted selection and for gene pyramiding
with other genes in barley breeding programs trying to incorporate SSLB resistance in their
cultivars.
In order to utilize the three single dominant genes it is important to know the diversity in the
pathogen and its capacity to develop virulence to the resistance genes. The genetic
structure of Septoria passerinii from nine field populations was examined at several scales;
within lesions, among lesions in a leaf, among leaves in a field, and among fields in ND and
western MN, using amplified fragment length polymorphism (AFLP) markers. A total of 390
isolates were sampled from seven barley fields located in ND and MN. AFLP DNA
fingerprints identified 176 different genotypes among 390 (non-clone corrected) isolates in
the nine different fields. In two intensively sampled sites, ND16 (Williston ND) and ND17
(Langdon ND), one to four different genotypes only were found within a lesion. A higher
level of genetic and genotypic diversity was found within a leaf where six to nine different
genotypes were found on each leaf. The genetic diversity within a leaf was similar to the
genetic diversity within a field. The pattern of genetic variation within and among lesions on
a leaf was similar to that observed in the closely related Mycosphaerella graminicola which
is known to have regular cycles of sexual reproduction in the field. A lack of correlation
between geographical distance and genetic distance was found, and this suggests the
potential for a high level of gene flow between different geographical regions. The
population genetic structure described in this study for S. passerinii in North Dakota and
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