Fresh from the Field-July 20, 2017

Oh the gall!

Crown gall disease is an incurable malady that affects many woody and herbaceous plant species, such fruit and nut trees, grapevines, and roses. The disease is caused by a soil-borne bacterium, Agrobacterium tumefaciens that modifies the plant’s genome and causes large, cancer-like tumors (galls) to grow at its base. 

Given the economic impact of this disease on growers, researchers at Oregon State University have taken a major step toward developing an on-site detection tool for crown gall disease.

With NIFA support from the Specialty Research Crop Initiative and Agriculture and Food Research Initiative grant programs, the researchers developed molecular tools to work with commercially available kits that allow the user to quickly and effectively test plants for the disease, using a dipstick that reveals the presence of the pathogen in minutes. Early and rapid detection of Agrobacterium is key to the management of crown gall because there is no cure for the disease, noted Jeff Chang, associate professor, and Elizabeth Savory, postdoctoral researcher, in OSU’s College of Agricultural Sciences and coauthors of the study.

Read about crown gall. Image provided by Lynn Ketchum at Oregon State University.

Mosquitoes without boundaries 

The Asian tiger mosquito (Aedes albopictus) thrives in temperate climates and is widely distributed in the eastern and central United States as well as parts of the Southwest. The species is adept at taking advantage of human-altered environments, and humans are its preferred targets. The Asian tiger mosquito may be a vector for viruses including dengue, chikungunya, Zika, and West Nile.

A team of scientists led by Eliza Little, Ph.D., of Columbia University and Dr. Leisnham of the University of Maryland, are looking at how socioeconomic, ecological, and climatic factors interact to drive populations of the Asian tiger mosquito in an urban environment.

Scientists know where to find mosquitoes on larger spatial scales, such as counties or towns. But habitat suitability for the Asian tiger mosquito varies at a much finer scale than that, and control efforts need to happen at this same scale. Little and colleagues looked at field-collected data on containers (potential mosquito breeding sites), infrastructure, vegetation, precipitation, and abundance of larval and adult Asian tiger mosquito across five neighborhoods of varying socio-economic status in West Baltimore, Maryland. Their aim was to determine which factors are present in city blocks with large mosquito populations. The researchers found that the three most important variables for mosquito hotspots were precipitation, number of abandoned buildings, and vegetation.

This research was supported by the Hatch Multistate Research Fund.

Read more about mosquito habitat in Entomology Today. Image provided by Susan Ellis, Bugwood.org

No need for seeds in watermelon

Consumers love the convenience and taste of seedless watermelons, and Florida growers are responding to the demand by producing seedless cultivars. Yet, seedless watermelon might be more susceptible to fusarium wilt, a major soil-borne disease in Florida watermelon production, noted Xin Zhao, a University of Florida professor of horticultural sciences and lead author of a new study examining rootstocks, flavor and texture of watermelons.

University of Florida scientists have found a way to stave off potential diseases while retaining that flavor. 

Grafting is a useful tool to manage soil-borne diseases, but in this study, researchers were concerned that if they grafted watermelon onto squash rootstocks, they might reduce its fruit quality and taste. Overall, study results showed no loss in taste and major fruit quality attributes like total soluble solids and lycopene content.

This research project was supported by NIFA's Specialty Crop Research Initiative (SCRI).

Read more about watermelons at Laboratory Equipment. Image provided by Xin Zhao at University of Florida.

Risk management for new farmers

Farmers face a number of pressures, such as price, production, regulations, and financial risks. These demands may inform their decisions on production and risk management.

The Extension Risk Management Education (ERME) program, funded by USDA’s National Institute of Food and Agriculture provides training to help producers learn new strategies to manage complex and growing agricultural risks.

The ERME extension team developed a pilot program on safe and appropriate pesticide use for Hmong produce growers in Wisconsin. They modified the curriculum to present information in a culturally appropriate manner, using native language, visuals and hands-on activities when practical.

The program seeks to help producers reduce crop losses and save money through reduced spraying. By knowing and understanding the crop families, they will manage their pests more effectively and protect themselves, their crops, and the environment.

As a result of this outreach, 43 Hmong produce growers were reached. Seventy-seven percent of the participants have applied new information and skills to their farming operation. Twenty-three percent of the participants took the private pesticide applicator test, and 67 percent of those passed the exam.

The research was supported by the North Central Extension Risk Management Education Center in Lincoln, Nebraska.

Read risk management newsletter.  

The summer of plant defenders

While the human immune system is adaptive, plants don’t have immune cells that can fight off pathogens. In this video, YouTube vlogger The Simple Biologist, Katie Bredbenner, explains plant defense. She discusses a Duke University project led by Dr. Xinnian Dong that uses gene editing to create disease-resistant plants. Researchers identified the Natriuretic Peptide Receptor (NPR1) as beneficial to achieve broad-spectrum disease resistance without affecting plant growth and development. The researchers applied NPR1 gene to different gene codes and discovered that plants go into defense mode without altering the number of protein gene copies used to fight off the disease. Stronger plants may result in reduction of pesticide usage. 

This project was supported through the NIFA Agriculture and Food Research Initiative (AFRI)

Watch the video.