|Mcgrath, J Mitchell - Mitch|
Submitted to: Annual Beet Sugar Development Foundation Research Report
Publication Type: Experiment Station
Publication Acceptance Date: 5/1/2004
Publication Date: 6/30/2004
Citation: McGrath, J.M., Duckert, T.M., Koppin, T.K. 2004. Aphanomyces disease nursery and selection. 2003 Annual Beet Sugar Development Foundation Research Report. p. D10-D11.
Technical Abstract: Sixty-six entries, predominantly from crosses between C869, a monogerm self-fertile Western US breeding line with no Aphanomyces selection history; SP6822, a multigerm self-sterile Eastern US breeding line with resistance to Aphanomyces and the pollinator parent of USH20; and two Plant Introductions (PI540409 and PI540625) that showed excellent Aphanomyces resistance in a germplasm screen in Texas, were field evaluated under severe seedling and chronic Aphanomyces disease pressure. Stand counts at 10, 20, and 30 days were used to assess seedling disease pressure, and harvest stand was used as a gauge of chronic symptoms. At harvest, most germplasm with a Plant Introduction in their pedigree showed highly branched roots (sprangles) indicative of wild germplasm. Most lines showed brown surface lesions, sometime deep, indicative of chronic Aphanomyces symptoms, however genetic segregation for Aphanomyces reaction was evident. Selections for further breeding were made from 35 of the 198 total plots, representing 27 entries in the test. Selections were based on lack of extensive visual disease, typical sugarbeet root shape and lesser degree of sprangles, and yield potential based on relative size and weight of roots. One entry (SP6822-4 x PI540625) showed negligible disease symptoms, no sprangles, and a nicely shaped taproot. Forty-one of these showed lesions <1 to 5 mm restricted to the lenticel regions, and may represent a source of near-immunity to Aphanomyces disease. A new source of Aphanomyces resistance may be present in these materials, and after further evaluation and selection, improved germplasm will be released to industry.