Location: Soil Management and Sugarbeet ResearchTitle: Beet curly top resistance in USDA-ARS Fort Collins sugar beet pre-breeding germplasm, 2022
Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2023
Publication Date: N/A
Interpretive Summary: Fungal and viral pathogens continue to threaten sugar beet yields and crop quality throughout much of the U.S. beet sugar producing regions. One such viral pathogen, the Beet Curly Top Virus, is transmitted to sugar beet planted by the Beet Leafhopper insect vector. While insecticides can be used to control the Beet Leafhopper populations to limit the spread of this virus, planting sugar beet lines with enhanced resistance to Beet Curly Top Virus is also an important tool for growers. USDA-ARS scientists in Fort Collins, CO and Kimberly, ID screened a panel of sugar beet germplasm for resistance to the Beet Curly Top Virus. The research team identified four highly resistant lines derived from USDA-ARS pre-breeding programs with resistance equivalent to the commercial resistant check. An additional 5 germplasm lines had higher resistance than the susceptible check lines. These lines represent potentially useful genetic resources for developing hybrid lines for sugar beet growers with enhanced resistance to the Beet Curly Top Virus.
Technical Abstract: Thirty sugar beet (Beta vulgaris L.) germplasm lines by the USDA-ARS sugar beet pre-breeding programs and three commercial check cultivars were screened for resistance to Beet curly top virus (BCTV). The curly top evaluation was conducted at the USDA-ARS North Farm in Kimberly, ID. The germplasm was planted on 3 May in two-row, 10-ft long plots with 22-in. row spacing. Treatments were arranged in a randomized complete block design with six replications. Plants were inoculated at the four- to six-leaf growth stage on 15 Jun with approximately six beet leafhoppers infected with BCTV per plant. The beet leafhoppers were redistributed two times a day during the first seven days by dragging a tarp through the field. The plants were sprayed with Admire Pro on 27 Jun to kill the beet leafhoppers. Plots were rated for foliar symptom development on 6 Jul using a scale of 0 to 9 (0 = healthy and 9 = dead). Data were rank transformed prior to analysis in SAS (Ver. 9.4) with mixed linear models (Proc MIXED). Mean separation was based on a PDIFF comparison with a probability cutoff of 0.05. Curly top symptom development was uniform and no other disease problems were evident in the plot area. The resistant (mean rating of 4.2) and susceptible (mean ratings of 6.6 and 7.6) checks performed as expected for the visual ratings. Statistically, nine of the entries contain at least some minor resistance since their visual ratings were significantly lower than those for both susceptible checks. However, only four entries (EL44, C842, FC220xF1024, and FC721) were not significantly different from the commercial resistant check. These four entries represent prior USDA-ARS pre-breeding germplasm releases that all have exhibited resistance in prior evaluations. In the 2021 Curly Top nursery, FC220xF1024, C842, and EL44 all exhibited statistically similar resistance compared to the resistant check. The unreleased pre-breeding germplasm 20161028PF had an average rating of 6.1, which statistically more resistant than both susceptible checks. 20161028PF is a half-sib seed lot of FC301, which as previously shown to have moderate levels of resistance to Curly Top. Resistant entries identified here, along with entries with similar levels of resistance from prior years, will be retested. If resistance is confirmed, these lines will be considered for incorporation into the USDA-ARS germplasm improvement program as a source of resistance to BCTV.