Plant diseases cost farmers across the globe untold millions of dollars annually from lost yields. Growers in Louisiana know all too well the importance of being prepared for diseases after Asian soybean rust moved into their state in 2004.
Speaking at the recent Conservation Systems Cotton & Rice Conference, Morganza, La., producer George LaCour Jr. hammered home the point of being proactive and prepared for future plant diseases. “We knew the problem was coming, but we just didn’t know when,” says LaCour. “A group of scientists from the LSU Ag Center traveled to Brazil to look at it. They returned, set up protocols for handling it once it showed up in our state, and because of that, we’re still growing soybeans today.”
After the disease arrived, Homeland Security Presidential Directive Number 9 was issued calling for the establishment of a National Plant Disease Recovery System (NPDRS) task force coordinated by the USDA. “The purpose of the effort is to ensure that tools, infrastructure, communication networks, and the needed capacities are in place to allow the mitigation of high-impact consequences from future plant disease outbreaks,” explains Dr. Jodi Scheffler, research geneticist, USDA-ARS. “A list of potential diseases that could threaten U.S. agriculture was established, and for each disease on that list, a recovery plan (which is revised regularly) was created.”
These plans were established to help the USDA and other stakeholders prepare for and recover from any new plant diseases identified domestically. One disease has already reared its head in the Western region of the U.S. – Fusarium wilt Race 4. “Cotton Incorporated has invested research money to learn more about this disease, and hopefully figure out a way to control it,” adds LaCour. “Some Pima varieties have survived the disease, but it kills upland varieties dead.”
Fusarium wilt Race 4 will remain in fields for generations, but researchers are looking into the possibility of developing a resistant variety to help mitigate plant damage. In 2016, Scheffler saw cotton blue mold disease (CBMD) in Brazil. “I never dreamed it would make it to the U.S., but last year a virus much like CBMD appeared in the Southeast. We don’t have a fix for it currently,” says Scheffler. “It appears to be transmitted by aphids, so we need good communication between our growers and researchers to keep in front of it.”
In 2018, a sweet potato nematode was identified in North Carolina. Now it is in Louisiana. “The Louisiana grower knew something didn’t look right, so he called someone who came out and investigated it,” says LaCour. “Now we have that disease quarantined in a 1-acre area. Had that grower not been proactive, it would have spread.”
Technology and Genetics
Scheffler’s role in the task force has been breeding resistant cultivars before the invasive diseases arrive. Twenty years ago, when she started working for USDA, Scheffler never envisioned working internationally on U.S.-based problems. However, through international partnerships, she has been able to create much needed safeguards against cotton disease threats for U.S. growers.
Establishing a monitoring and tracking system was a priority. One problem encountered early was figuring out the best way to create management methods to accompany the resistant cultivars. “You don’t want to bring the disease into the U.S., so USDA developed partnerships with Paraguay, Brazil, and Argentina,” adds Scheffler. “Soybean rust was one of our first diseases sampled. We knew the disease was present in Paraguay, so USDA soybean geneticists worked with scientists in Paraguay who had previously screened for the disease.”
DNA markers are now being used which prevent the need for soybean rust resistance screening in an infected field each year. Scheffler sent sample accessions and potential host plant resistant lines to her partners in the collaborating countries. “Between 2011 and 2015, our partners in Pakistan screened over 5,000 cotton lines,” says Scheffler. “This lets me know if a marker shows resistance and allows me to discard those that do not.”
In 2009, the governments of Pakistan and the U.S. focused on Cotton Leaf Curl disease. Scientists agree that a field or plant infected with the disease amounts to a “zero yield” outcome. Cotton production in Pakistan was nearly terminated because of the virus. “It’s one of their top threats to cotton,” says Scheffler. “It’s transferred by whiteflies and those pests do not recognize border crossings, so they’re all over the place. They’ve been identified in India, China, the Philippines and of late, some islands north of Australia.”
Pakistan has a rather large germplasm collection. It screened every accession and found no resistance, so 5,000 seeds from USDA’s germplasm collection and 300 lines containing host plant resistance were given to the researchers in Pakistan. “Between 2011 and 2015, our partners in Pakistan screened over 5,000 cotton lines,” says Scheffler. “Multiple sources were found from those screenings and based on that work, we’ve been able to develop diagnostic tests and DNA markers. We also have some resistant germplasm releases ready to deploy if needed.”
Other projects, like creating heat-tolerant lines, are currently being pursued in a province of Pakistan where temperatures soar to 113 degrees some days.
Importance of Communication
A few crop consultants in Georgia reported seeing an unfamiliar virus-like disease in 2017. Those sightings spread into Mississippi and Alabama last year. After lab diagnostic tests were conducted on samples, it was determined not to be cotton leaf curl disease. “It may have been something similar to cotton blue mold disease,” adds Scheffler.
Based on previous NPDRS work, models, and past team efforts, substantive work has been done. Cotton Incorporated funded a great deal of the initial research work through U.S.-based universities and USDA, whose plant specialists have all contributed to this ongoing work.
Dr. Kater Hake, vice president, Agricultural and Environmental Research, Cotton Incorporated, understands the long-range implications of these projects. “Maintaining U.S. cotton’s viability and profitability has to be protected through both short-term and long-term research projects with specific goals. We can’t wait until a disease from another part of the world makes it way to the U.S. before we start looking for solutions,” says Hake.
During their presentations, LaCour and Scheffler continuously stressed the importance of across-the-board communication among producers, Extension and all scientists to stay ahead of plant diseases of the future. “If all growers become more proactive as we watch over our crops each year, we can play an important role to stave off future threats to our livelihood,” concludes LaCour.