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Title: Screening Rhizoctonia crown and root rot resistance of Beta PIs from the USDA-ARS, National Plant Germplasm System, 2011

Author
item Panella, Leonard
item Vagher, Travis
item FENWICK, ANN - Beet Sugar Development Foundation

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2012
Publication Date: 8/10/2012
Citation: Panella, L.W., Vagher, T.O., Fenwick, A.L. 2012. Screening Rhizoctonia crown and root rot resistance of Beta PIs from the USDA-ARS, National Plant Germplasm System, 2011. Plant Disease Management Reports:FC083. Online publication doi:10.1094/PDMR06.

Interpretive Summary: Thirty sugar beet and sea beet (crop wild relative) lines from the Beta collection of the USDA-ARS were screened for resistance to Rhizoctonia root and crown rot, at the USDA-ARS Fort Collins, CO Research Farm. The rhizoctonia screening nursery in 2011 had five replications in one-row plots 4 m long. Seed was planted on May 17 to moisture and furrow irrigated as needed. Because of adverse weather the field crusted and had to be replanted on July 7. The field was hand weeded on 30 Jul and thinned on 6 Aug. Inoculation was with dry, ground, barley grain inoculum of Rhizoctonia solani on August 17. Beets were harvested September 28 and each root was rated for rot on a scale of 0 (no damage) to 7 (dead plant with root completely rotted). Temperatures remained high throughout September and there was mild to moderate, uniform disease pressure in the replanted experiments. This experiment had mild disease pressure and the sugar beet susceptible control had a DI of only 3.1 (3.0 = is usually considered the point when the line is considered susceptible). Nonetheless two-thirds of the lines (most of which were wild accessions of sea beet) showed less resistance than the susceptible check. The following lines, PI 552534, PI 232888, PI 552533 and PI 612768, were not significantly different from the best performing highly resistant check (FC709-2, DI 1.3). These plant introductions were all sugar beet germplasm, although none have been selected for resistance to Rhizoctonia root rot. Three sea beet lines from Northern Europe, PI 504234, PI 540675, and PI 546411, were not significantly different from the resistant check (FC703, DI 1.9). These accessions will be retested and, if the resistance is confirmed, entered into the USDA-ARS Rhizoctonia root rot-resistance breeding program at Fort Collins, CO. These data will be entered into the USDA-ARS, NPGS GRIN database (http://www.ars-grin.gov/npgs/index.html).

Technical Abstract: Thirty beet (Beta vulgaris subsp. maritima (L.) Arcang and Beta vulgaris subsp. vulgaris L.) plant introduction (PI) accessions from the Beta collection of the USDA-ARS National Plant Germplasm System were screened for resistance to Rhizoctonia root and crown rot, at the USDA-ARS Fort Collins, CO Research Farm. The rhizoctonia screening nursery in 2011 was a randomized complete-block design with five replications in one-row plots (76 cm row spacing) 4 m long. The field had been planted to sugarbeet in 2007 and summer fallowed since then. The soil (Garrett loam, 0 to 1 % slope, pH 7.8) was fumigated with Telone® II in late Oct 2008, for control of soil borne diseases (esp. rhizomania) and pests. Manure was applied 4 days later and the field was roller harrowed in Nov 2008. Field was land leveled Mar 2011, and bedded a month before planting. Seed was planted on May 17 to moisture and furrow irrigated as needed. No herbicides were used this year. Because of adverse weather the field crusted and had to be replanted on July 7. The field was hand weeded on July 30 and thinned on August 6. Inoculation with dry, ground, barley grain inoculum of Rhizoctonia solani isolate R-9 (AG-2-2) was applied to the crown of the plants on August 17 at a rate of 5.3 g m-1 row. A Gandy® electrically driven applicator was used to apply the inoculum and the field was cultivated afterwards to place soil onto the plant crowns. Beets were harvested September 28 with a single row lifter (pulled and cleaned by hand), and each root was rated for rot on a scale of 0 (no damage) to 7 (dead plant with root completely rotted). Dunnett’s one-tailed t-test was used to compare entries to the resistant check (FC703) and the highly resistant check (FC709-2). Temperatures remained high throughout September and there was mild to moderate, uniform disease pressure in the replanted experiments. This experiment had mild disease pressure and the sugar beet susceptible control had a DI of only 3.1 (3.0 = is usually considered the point when the line is considered susceptible). Nonetheless two-thirds of the Plant Introductions (most of which were wild accessions of sea beet, i.e., B. v. subspecies maritima) showed less resistance than the susceptible check. The following accessions, PI 552534, PI 232888, PI 552533 and PI 612768, were not significantly different from the best performing highly resistant check (FC709-2, DI 1.3) based on Dunnett’s one-tailed t-test. These plant introductions were all sugar beet germplasm (Beta vulgaris ssp. vulgaris), although none have been selected for resistance to Rhizoctonia root rot. Three sea beet accessions from Northern Europe, PI 504234, PI 540675, and PI 546411, were not significantly different from the resistant check (FC703, DI 1.9). These accessions will be retested and, if the resistance is confirmed, entered into the USDA-ARS Rhizoctonia root rot-resistance breeding program at Fort Collins, CO. These data will be entered into the USDA-ARS, NPGS GRIN database (http://www.ars-grin.gov/npgs/index.html).