Location: Sunflower and Plant Biology Research
Project Number: 3060-21220-028-28-S
Project Type: Specific Cooperative Agreement
Start Date: Jun 1, 2014
End Date: Sep 30, 2017
The proposed project seeks to improve Sclerotinia management and the accuracy of crop loss assessments in dry beans, soybeans, and sunflowers by quantifying the impact of infection timing on seed yield, seed quality, and Sclerotinia severity (in sunflowers, targeting head rot) and by optimizing dry bean and soybean fungicide application strategies relative to the timing of disease onset. The project also seeks to develop and validate disease assessment methods for Sclerotinia head rot of sunflowers that more effectively capture differences in disease tolerance. Finally, the project seeks to advance the development of commercial sunflower hybrids with reduced susceptibility to head rot by screening commercial breeding lines and hybrids for resistance in multi-location nurseries. Specific objectives are, as follows: (1) Quantify the impact of infection timing on seed yield, seed quality, and Sclerotinia severity in dry beans, soybeans, and sunflowers (in sunflowers, targeting head rot). (2) Optimize fungicide application strategies in dry beans and soybeans relative to infection timing and the occurrence of environmental conditions favorable to Sclerotinia. (3) Evaluate whether differences in tolerance to Sclerotinia head rot of sunflowers can be effectively quantified with assessments of disease progression and the incidence and severity of shattering in diseased sunflower heads. (4) Establish multi-location nurseries to screen commercial sunflower breeding lines and hybrids for susceptibility to Sclerotinia head rot. (5) Assess whether head rot resistance screening results significantly change when disease assessments are modified to more fully quantify differences in disease tolerance.
The impact of Sclerotinia infection timing on seed yield, seed quality, and Sclerotinia severity in dry beans and soybeans and the associated implications for fungicide usage will be evaluated in field trials conducted in Carrington, ND. Field trials will be conducted on a site with a previous history of Sclerotinia epidemics, with supplemental overwintered sclerotia added at seeding to ensure consistent disease pressure. Sclerotinia infection at early, mid- and late bloom will be facilitated by excluding rainfall or supplying supplemental irrigation through microsprinklers, as necessary. At each targeted infection timing, a non-treated check and two fungicide treatments will be evaluated. Infection timing, apothecia production, and Sclerotinia incidence and severity will be assessed weekly during bloom in non-fungicide-treated buffer plots, with infection timing assessed by plating senesced flowers onto Sclerotinia semi-selective media. Air temperature and relative humidity within and above the canopy, leaf wetness, and soil moisture 2 cm below the surface will be monitored from late vegetative growth to maturity. Field trials will be established in Carrington and Langdon, ND under microsprinkler irrigation to (1) identify disease assessment methods for Sclerotinia head rot of sunflowers that more effectively describe differences in disease tolerance and to (2) evaluate the impact of the timing of Sclerotinia infection on seed yield, seed quality and Sclerotinia head rot severity in sunflowers. A pair of oilseed hybrids (Carrington and Langdon) and a pair of confectionary hybrids (Carrington only) differing in susceptibility to Sclerotinia head rot will be tested. Sclerotinia infection at early, mid-, and late bloom will be facilitated by inoculating heads with laboratory produced ascospores of Sclerotinia sclerotiorum at the target growth stage. A noninoculated control will be included. Sclerotinia incidence and severity will be assessed a minimum of three times, including once at maturity, and incidence and severity of shattering in diseased heads will be assessed prior to harvest. Sclerotinia head rot resistance screening nurseries will be established under microsprinkler irrigation in Carrington, Langdon, and Oakes, ND to facilitate the development of commercial hybrids with reduced susceptibility to head rot and to evaluate how screening results are affected when parameters that more accurately quantify tolerance to head rot are assessed. Commercial hybrids and experimental lines will be solicited; fees will be assessed for each line submitted for testing, but partial grant support is requested to keep the service affordable. Three types of screening nurseries will be established: a nursery for screening up to 50 entries in a single environment, two nurseries to provide multi-location testing of 26 of these entries, and an inbred screening nursery. Each head will be inoculated with ascospores of S. sclerotiorum at mid-bloom and again at late bloom. Sclerotinia incidence and severity will be assessed a minimum of three times, including once at maturity, and shattering in diseased heads will be assessed at maturity.