b"Brazil, farmers have two growing sea-sons during the year and in the past have double cropped soybeans in fields thus increasing the incidence of ASR. To try and stop ASR, there have been policiesWith the right conditions, as soon as the spores of the fungus get into the put in place to stretch the rest periodsoybean field, the crop is destroyed in as little as three weeks. for fields between the growing seasons, Horvath says. Diana HorvathTo manage ASR, farmers have used a wide range of strategies from fungicide control to widening crop rotations. One strategy that has shown success is switch-ing to planting early season soybean varieties, which allows the crop to mature before the ideal ASR weather conditions develop, she adds. However, fungicide resistance has become a growing prob-lem in the ASR fight.There are two different kinds of fungicides used to control ASRsingle site and multi-site. Single site fungicides target the specific metabolic process of the pathogen which if the patho-gen mutates it can overcome, Sergio Brommonschenkel, a professor at Universidade Federal de Viosa, explains. The multi-site fungicide doesnt have specific targets which makes it harder to develop resistance too, he adds. It's not just fungicides that ASR is becoming resistant to, but also soybeans bred with ASR resistance in them. P. pachyrhizi can quickly overcome single resistance genes making ASR-resistant soybean varieties no longer a protection method, Brommonschenkel says.There is more help on the way though. In 2019, a full sequencing of the ASR pathogen genome was decoded and released by researchers paving the way for transgenic ASR-resistant soybean varieties. One of the groups involved in the decoding of P. pachyrhizi, 2Blades, is breeding ASR-resistant soybeans using transgenics. The researchers investigatedDefoliated soybean plants in a field infected with Asian Soybean Rust.PHOTO: SERGIO BROMMONSCHENKELsoybean relatives and found ASR resist-ance in them. resistance in soybean, Horvath explains. varieties with results showing strong ASR Through a process called map-basedIn 2013, 2Blades entered in a partner- resistance. The soybean varieties are in cloning, we screened a collection of dif- ship with Pioneer, now Corteva, to addCortevas hands now and havent been ferent legumes and tracked resistancethe ASR resistance genes into Cortevasreleased publicly yet.to a specific location in these legumesoybean hybrid varieties. In 2022,2Blades is currently working with genomes. We were able to identify effec- Corteva released a news release statingBayer CropScience to provide novel ASR tive resistant genes, and they look prom- the company had conducted field trialsresistance genes for Bayers soybean ising for delivering effective and durablein Latin America of the new soybeanvarieties.SWOCTOBER 2023SEEDWORLD.COM /61"