b"Fighting Back AgainstAsian Soybean RustWith new Asian Soybean Rust resistant soybean varieties on the way, theres hope for South American farmers.Ashley RobinsonSOUTH AMERICA ISknown for its fields of soybeans, butTo manage ASR, farmers have used a wide range of strategies for the past few decades those fields have been threatenedfrom fungicide control to widening crop rotations. One strategy by one deadly diseaseAsian Soybean Rust (ASR). While farm- that has shown success is switching to planting early season soy-ers have fought back with resistant soybean varieties and man- bean varieties, which allows the crop to mature before the ideal agement strategies, the disease has always come roaring back.ASR weather conditions develop, she adds. However, fungicide There is hope on the horizon though with new soybean varietiesresistance has become a growing problem in the ASR fight.on the way. There are two different kinds of fungicides used to control Asian Soybean Rust is in fact the biggest disease issue affect- ASRsingle site and multi-site. Single site fungicides target the ing tropical soybean production, particularly in South Americaspecific metabolic process of the pathogen which if the pathogen where soybean used to be grown year-round. With no break inmutates it can overcome, Sergio Brommonschenkel, a profes-the growing season, the pathogen really built up, Diana Horvath,sor at Universidade Federal de Viosa, explains. The multi-site president of 2Blades, explains. fungicide doesnt have specific targets which makes it harder to The ASR pathogen is found in both North and South America,develop resistance too, he adds. but the hot weather of the southern hemisphere continent makesIt's not just fungicides that ASR is becoming resistant to, but it a huger threat to farmers there. According to Loren Giesler,also soybeans bred with ASR resistance in them. P. pachyrhizi an extension plant pathologist with the University of Nebraska- can quickly overcome single resistance genes making ASR-Lincoln, ASR is caused by Phakopsora pachyrhizi which is anresistant soybean varieties no longer a protection method, aggressive pathogen. It can cause yield losses ranging from 10Brommonschenkel says.- 80%.There is more help on the way though. In 2019, a full sequenc-Its most common symptoms can be found on the leaves start- ing of the ASR pathogen genome was decoded and released ing in the lower canopy, Giesler writes. Lesions can also developby researchers paving the way for transgenic ASR-resistant on petioles, pods, and stems. Once the plant starts floweringsoybean varieties. One of the groups involved in the decoding of development of ASR symptoms happens fast causing significantP. pachyrhizi, 2Blades, is breeding ASR-resistant soybeans using levels of defoliation under the right environmental conditions. Tantransgenics. The researchers investigated soybean relatives and to reddish brown lesions grow as the disease advances. Plantsfound ASR resistance in them.will prematurely lose their leaves as it progresses. Through a process called map-based cloning, we screened With the right conditions, as soon as the spores of the fungusa collection of different legumes and tracked resistance to a spe-get into the soybean field, the crop is destroyed in as little ascific location in these legume genomes. We were able to identify three weeks, Horvath says. effective resistant genes, and they look promising for delivering For South American nations, theyre the perfect hosts foreffective and durable resistance in soybean, Horvath explains.ASR. The pathogen thrives in tropical hot conditions, she adds.In 2013, 2Blades entered in a partnership with Pioneer, now The pathogen is a bio tropical fungus that can live on a wideCorteva, to add the ASR resistance genes into Cortevas soy-range of host plants, not just soybeans.bean hybrid varieties. In 2022, Corteva released a news release In South American nations, such as Brazil, farmers have twostating the company had conducted field trials in Latin America growing seasons during the year and in the past have doubleof the new soybean varieties with results showing strong ASR cropped soybeans in fields thus increasing the incidence of ASR.resistance. The soybean varieties are in Cortevas hands now and To try and stop ASR, there have been policies put in place tohavent been released publicly yet.stretch the rest period for fields between the growing seasons,2Blades is currently working with Bayer CropScience to provide Horvath says. novel ASR resistance genes for Bayers soybean varieties.SW20/ SEEDWORLD.COMLATAM"