Key Deliverable 1: Discover genetic resources to CLB and integrate into elite germplasm
The University of Missouri released S18-6013C in 2023 as a high yielding and high oil cultivar. It is a semi-determinate early group V [relative maturity (RM) 5.2] soybean cultivar. It was tested across eight states in 42 environments, it yielded 117.5% of the non-Xtend check mean and 103.2% of the Xtend check mean. It averaged 19.6% oil, 35.1% protein, and 47.4% meal protein at 13% moisture. Seeds of S18-6013C have been submitted to the Missouri foundation seed program for production.
In 2023, The University of Missouri also released S19-19923HOLL, a high yielding, high oleic acid, low linolenic acid soybean cultivar derived from CLB resistant parent. It is an early group V maturity (relative maturity 5.2), determinate soybean cultivar. It yielded 99.7% of the non-Xtend check mean, 90.6% of the Xtend check mean across 33 environments. It averaged 79.6% oleic acid and 2.2% linolenic acid. It was in the Uniform Group V early test.
Key Deliverable 2: Determine fungicide efficacy at diverse field locations and develop an internet-based fungicide resistance distribution map.
The LSU AgCenter has optimized Loop-mediated isothermal amplification (LAMP) assay to identify QoI resistance in CLB pathogens. In 2023, The LSU AgCenter has collected CLB isolates from multiple counties/parishes from Arkansas, Mississippi, and Louisiana. Some lab work is currently in progress, but the approximate number of isolates per state are:
Louisiana - 184 Isolates - Collected from Four Parishes
Arkansas - 53 Isolates - Collected from Two Counties
Mississippi - 50 Isolates - Collected from Two Counties
The University of Arkansas identified a total of 50 Cercospora isolates, out of which 62% are C. flagellaris, 32% C. kikuchii and 6% are C. sojina. Identified Cercospora spp. were isolated from mainly soybean seed collected from Arkansas, Indiana, Ohio and Michigan. An additional 30 to 50 isolates, that are currently being cultured or stored, will be sequenced and added to the current collection. Furthermore, an in vitro assay will be conducted to evaluate sensitivity of the 50 identified Cercospora isolates to a QoI (Azoxystrobin) and DMI (Tetraconazole) fungicides at different concentrations.
A website to display CLB research information has been set up and approved by the United Soybean Board. This website will include a CLB distribution map.
Key Deliverable 3: Evaluate the efficacy and profitability of fungicides to CLB and develop application protocols.
Rachael Wolf, a MS student from the University of Arkansas, has completed her thesis on the development of a detached leaf assay for cultivar resistance to target spot, caused by Corynespora cassiicola. She used her method to evaluate soybean lines from the 2019 and 2020 Cercospora Leaf Blight region study for target spot resistance. A paper on her results will be submitted in the near future.
The University of Arkansas related seed infection by Diaporthe longicolla, Cercospora species, and total seed infection, as well as visible seed damage to 46 seed constituents measured by NIR of seed from five Cercospora Leaf Blight cultivar tests conducted in 2019, 2020 and 2021 in Arkansas. Stepwise regression was used develop multiple regression equations with combinations of seed factors that significantly related seed composition to each of the seed infection parameters. The University of Arkansas is currently exploring methods for presenting thier results and then will write a paper on the results.
The LSU AgCenter presented information regarding fungicide efficacy against CLB at parish production meetings in 2023.