Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 12, 2012
Publication Date: August 10, 2012
Citation: Eujayl, I.A., Strausbaugh, C.A. 2012. Sugar beet germplasm evaluated for resistance to rhizomania and fungal growth in storage in Idaho, 2011. Plant Disease Management Reports. 6:FC087. Interpretive Summary: Twenty-one advanced sugarbeet germplasm accessions were evaluated for response to rhizomania in the rhizomania nursery in the North Farm, NWISRL during 2011 season as well as for storage period (Oct. 2011 to Feb. 2012). The objectives of this study were to identify germplasm that carry resistance to the disease and utilize these lines in the breeding program. The entries were evaluated for rhizomania foliar symptoms, including leaf narrowing, yellowing, and upright growth. Additionally, mature roots from the experimental plots were scored for rhizomania root symptoms and evaluated for storability performance in an indoor commercial storage facility set to hold at 35°F for 18 weeks days. It is established by previous research results, if roots are compromised by rhizomania or lack good storability, root will rot in storage as indicated by fungal growth on the root surface. In this study susceptible and resistant checks performed as expected in the rhizomania. In the storage all resistant checks developed high level of root surface rots (67 to 91%). We identified three germplasm entries that performed similar to the rhizomania resistant checks in addition to out-perform the resistant checks in storability. This germplasm will be used in the breeding program to identify additional sources of resistance to both rhizomania and storage fungal rot.
Technical Abstract: Resistance to rhizomania is a basic requirement for cultivars’ approval for commercialization. The objectives of this research were to identify germplasm accessions that carry resistance genes to rhizomania and storage root rots. Twenty-one sugar beet (Beta vulgaris L.) germplasm from the USDA-ARS Kimberly sugar beet program and four check cultivars were screened for resistance to Beet necrotic yellow vein virus (BNYVV) during the 2011 growing season and during the 2011/2012 storage period for fungal growth in an indoor storage. The rhizomania evaluation was conducted at the rhizomania nursery in the USDA-ARS North Farm in Kimberly, ID. The crop was managed according to standard cultural practices and pest control. The plots were rated twice (4 weeks apart) for foliar symptom for percentage of plants with yellow, stunted, and upright leaves. At maturity the plants were mechanically topped and hand harvested with the aid of a single-row lifter at maturity. Ten roots per plot were rated for symptom development using a scale of 0-9 (0 = healthy and 9 = dead). Rhizomania symptom development was uniform and other disease problems were not evident in the nursery. The susceptible check was rated at 98 to 99% foliar symptoms and a high root rating. The three resistant checks entries had limited to no foliar symptoms (0 to 5%) and a low root rating (DSI=14 to 20). To evaluate storability, eight roots per plot were placed in a mesh onion bag and placed in an indoor commercial storage facility. After 18 weeks of storage, the roots were evaluated for the percentage of root surface area covered by fungal growth. The resistant checks had a high percentage of fungal growth in storage (67 to 91%) indicating resistance to BNYVV does not preclude roots from storage rot. The BNYVV susceptible check also had considerable fungal growth in storage as expected. Based on previous research, roots show rots and surface fungal growth when are compromised by BNYVV or lack storability. A single entry (K944-62) had BNYVV resistance similar to the resistant checks and additionally had low rot in storage (18%). Other two entries (K944-191 and K39-16) also showed good level of resistance to both BNYVV and storage rots (16 and 17%). This germplasm will be used in the breeding program to identify additional sources of resistance to both BNYVV and storage fungal rot.