Title:

Impact of Ergot in Kentucky Bluegrass and Nematodes in Perennial Ryegrass on Seed Production in Sustainable Nonthermal Grass Cropping Systems

Investigators:

Steve Alderman, USDA-ARS Research Plant Pathologist
Reed Barker, USDA-ARS Research Plant Geneticist

Progress:

Objective 1:

Evaluation of resistance of Kentucky bluegrass cultivars to ergot.

One hundred and four cultivars of Kentucky bluegrass were established in a randomized replicated trial of Hyslop Field Station during 1993. During the spring and summer of 1994 data collected included day of flower initiation, mid anthesis, flower ending, and seed maturity for each plant. Ergot ascospore populations were monitored with a Burchard 7-day recording volumetric spore trap. At harvest, 20 seed heads were removed from each plant and evaluated for ergot incidence. Each set of heads were hand threshed, cleaned, and ergot removed and counted. Remaining seed was weighed. One thousand seeds were removed using a seed counter and weighed to determine 1000 seed weight.

Data (mean percent ergotized seed) were subject to analysis of variance and means separated by Duncan multiple range test. Mean value of percent ergotized seed ranged from 0 to 0.47. Several cultivars had significantly greater ergot and others had significantly less ergot than the majority of cultivars, which rated intermediate in susceptibility. Additional analyses will be made to determine if susceptibility or resistance is related to duration of flowering or to a combination of flowering duration and cumulative ascospore numbers during the period of flowering.

Data from the 1995 production year were not collected because of severe confounding effects of rust. A vigorous rust control program is planned and data acquisition will continue during the spring of 1996.

Publications:

Publications from this work have not been possible to date.

Investigators:

Steve Alderman, USDA-ARS Research Plant Pathologist
Marvin Butler, OSU extension agent

Objective 2.

Evaluation of impact of ergot in Kentucky bluegrass seed production.

During 1991-1994 combine-run samples of Kentucky bluegrass were obtained from seed companies in eastern and central Oregon. Samples were cleaned with a combination of handscreens and air column-to remove debris and lightweight material but retain ergot. A 10 g subsample from each seed lot was examined for ergot under 5X magnification. Sclerotia were counted and weighed. Percent ergot, based on weight and number of seed were determined. Percent seed lost during recleaning was estimated from records at the OSU seed lab for 19 fields from eastern Oregon. Cultivar name, field acreage, and yield data were obtained for seed from eastern Oregon. Similar data will be collected from central Oregon.

Ergot severity (percent sclerotia by weight) in Kentucky bluegrass seed in 1991-1994 was 0.20, 0.04, 0.07, and 1.15%, respectively. Percent seed replaced by sclerotia in 1991-1994 was 0.05, 0.01, 0.03, and 0.44%, respectively. High levels of ergot occurred in only two of the six cultivars examined. In susceptible cultivars as many as 504 sclerotia/g seed were detected. This equated to 47% ergot by weight, or 25% infected seed. A significant relationship between ergot severity and yield was not detected. However, a 9% reduction in marketable seed weight occurred when seed lots contaminated with ergot were recleaned to meet purity standards.

Publications:

Alderman, S.C. and D.D. Coats. 1995. Impact of ergot in Kentucky bluegrass grown for seed in eastern and central Oregon. Phytopathology 85:1207 (abstract).

Alderman, S.C., D.D. Coats, and F. Crowe. 1996. Impact of ergot in Kentucky bluegrass grown for seed in eastern Oregon. Plant Disease (under review).

Investigators:

Steve Alderman, USDA-ARS, Research Plant Pathologist
Russell Ingham, OSU, Plant Nematologist

Objective 3.

Plant pathogenic nematode species and populations in perennial ryegrass seed production fields.

During February 24-March 30, 1995, soil cores were taken from 51 perennial ryegrass seed production fields within the Willamette Valley. Fields were selected at random from a list of fields registered with OSU Office of Seed Certification. Nematodes were identified at the OSU plant nematology lab.

Root lesion nematodes (Pratylenchus sp. ) were found in nearly all fields sampled and high numbers of nematodes were recovered from most fields. Nematodes were not identified to species but this should be done prior to establishment of rotational crops. At least two species of Praylenchus occur in the Willamette Valley. The impact of Pratylenchus on production of clover or wheat are not clearly established although wheat may be more tolerant than clover.

Root-knot nematodes (Meloidogyne sp.) were found in about half of the fields sampled. Three species of Meloidogyne occur in the Willamette Valley, although M. nassi is the most common species found in grass and cereal crops. If M. nassi is present, cereal crops should be avoided, although clover would be an acceptable rotational crop.

The risk from pin nematodes (Paratylenchus sp.) is not clearly established. There appears to be little concern about dagger (Xiphinema sp.), stubby root (Paratrichodorus sp.) or ring (Criconemella sp.) nematodes unless vegetable or fruit crops are considered for rotation. In a rotational schedule, clean summer fallow may reduce nematode populations. However, it is important to maintain such a field free of weeds, which can serve to significantly increase nematodes, depending on the host-nematode combination. In some fields, low pH may be an important factor in exasperating the impact of nematodes.

The host range for species of nematodes identified in the study will be determined and risk to susceptible rotational crops estimated. The survey was repeated during November, 1995 based on a separate random selection of ryegrass fields. In addition, five fields which had high levels of root-lesion or root-knot during the February survey were resampled in November to determine if populations changed. Assessment of these samples is in progress.