Fargo sugar beet germplasm evaluated for Rhizoctonia crown and root rot resistance in Idaho, 2022

Rhizoctonia crown and root rot (RCRR) is a serious fungal root disease problem for sugar beets worldwide that is caused by Rhizoctonia solani. In-furrow chemical treatments and host resistance are the primary control measures for RCRR. However, resistance is controlled by a number of genes (quantitative trait) which makes it challenging and time consuming to introgress resistance into commercial hybrids. In order to identify additional sources of resistance, 40 lines from the USDA-ARS Fargo sugar beet program were evaluated along with two check cultivars for resistance to RCRR. The lines were arranged in a randomized complete block design with 6 replicates. The trial was inoculated at the ten-leaf growth stage with 0.02 oz of dried barley inoculum per plant on the 30 June. The roots were evaluated for root rot on 2 August. The rhizoctonia susceptible check had 76% of its root area covered in rot and 5% of its roots were harvestable. On the other hand, the resistant check had only 30% rot and 64% of its roots were harvestable. Lines 17N0043-12 and 17N0043-16 had a level of rhizoctonia resistance similar to the resistant check based on the root rot, disease index, and harvestable roots. These lines will be retested and investigated further for potential release to the general public so they can be utilized to improve RCRR resistance in commercial sugar beet cultivars