UC Davis plant pathologist Shahid Masood Siddique

It's somewhat like that when plant-parasitic nematodes (microscopic round worms) play “chemical hide and seek” with their plant host, says plant pathologist  Shahid Masood Siddique, an assistant professor in the UC Davis Department of Entomology and Nematology.

“The success of plant-parasitic nematodes depends on their ability to locate a suitable host in the soil,” says Siddique, corresponding author of the newly published Spotlight article, “Chemical Hide and Seek: Nematode's Journey to Its Plant Host,” in the journal Molecular Plant.

Nematodes can be deadly to plants, not only because of the direct damage they cause (they extract water and nutrients from their hosts such as wheat, soybeans, sugar beets, citrus, coconut, corn, peanuts, potato, rice, cotton and bananas) but the role of some species as virus vectors.

“Plant-parasitic nematodes are among the most destructive agricultural pests, causing more than $100 billion in losses per year in the United States,” Siddique said, noting that nematodes are especially damaging to potato, soybean and wheat crops.

Although the success of nematodes depends on their ability to locate a suitable host in the soil, what attracts them to their host “has largely remained unknown,” wrote the four-member UC Davis team of Siddique, Natalie Hamada, Henok Zemene Yimer and Valerie Williams. “Recent studies have revealed that host-seeking by nematodes is a complex process that involves multiple stages in the interaction.”

“Most damage is caused by a small group of root-infecting sedentary endoparasitic nematodes including cyst nematodes and root-knot nematodes (RKNs),” the team of UC Davis researchers wrote in their abstract. “Second stage juveniles (J2s) of plant-parasitic nematodes hatch from eggs into the soil and localize to the roots of host plants. The success of these non-feeding J2s depends on their ability to locate and infect a suitable host.”

For eight decades, scientists have researched the attraction of plant-parasitic nematodes to the host root, ever since the pioneering Maurice Blood Linford (1901-1960) of the University of Illinois, Urbana, Ill., observed in 1939 that the larvae of root-knot nematodes congregate in the cell elongation region behind the root cap.

“Both volatile and soluble components in the rhizosphere have been shown to influence nematode movement,” the UC Davis researchers wrote. “Methyl salicylate, a volatile chemical root signal, has been demonstrated to be a strong root attractant for RKN towards several Solanaceous plants (nightshade family). The non-volatile tomato root exudate quercetin was shown to elicit concentration dependent attraction or repulsion effect against Meloidogyne incognita to host root. Three recent studies have revealed that the recognition of and response to hosts by infective juveniles is a complex process that involves multiple stages in the interaction.”

Siddique focuses his research on basic as well as applied aspects of interaction between parasitic nematodes and their host plants. “The long-term object of our research is not only to enhance our understanding of molecular aspects of plant–nematode interaction but also to use this knowledge to provide new resources for reducing the impact of nematodes on crop plants in California.”  

Bruce Hammock in 1980

Bruce Hammock today

Entomologist Marlin Rice, a past president of the Entomological Society of America (ESA), penned the piece, titled "Bruce D. Hammock: Science Should Be Fun!"

Wrote Rice: "Bruce D. Hammock is widely known for his groundbreaking research in insect physiology, toxicology, pharmacology, and experimental therapeutics. Early contributions were in fundamental regulatory biology, development of both small molecules and recombinant viruses as environmentally friendly pesticides, and the application of accelerator mass spectrometry to biological science. His laboratory pioneered the use of immunoassay for the analysis of human and environmental exposure to pesticides and other contaminants.His laboratory provides graduate training that is diverse in disciplines and research areas. He recently formed a company, EicOsis, to develop an orally active non-addictive drug for inflammatory and neuropathic pain for humans and companion animals."

Hammock, who joined the UC Davis faculty in 1980 from UC Riverside, has directed the UC Davis Superfund Research Program (funded by the National Institutes of Health's National Institute of Environmental Health Sciences) for nearly four decades. He is a member of the National Academy of Sciences, and a fellow of the National Academy of Inventors and ESA.

A native of Little Rock, Ark., Bruce received his bachelor's degree in entomology (with minors in zoology and chemistry) magna cum laude from Louisiana State University, Baton Rouge, in 1969. He received his doctorate in entomology-toxicology from UC Berkeley in 1973 with John Casida at UC Berkeley. Hammock served as a public health medical officer with the U.S. Army Academy of Health Science, San Antonio, and as a postdoctoral fellow at the Rockefeller Foundation, Department of Biology, Northwestern University, Evanston, Ill.

Read the feature story here.

Some Related Links:

• Bruce Hammock and EicOsis, Innovator of the Year
• Bruce Hammock Receives $6 Million Grant
• Bruce Hammock Water Balloon Battle: 15 Minutes of Aim
• Research Could Lead to Drug to Prevent or Reduce Autism, Schizophrenia 
• Hammock Lab Union Draws 100 Scientists from 10 Countries
• Bruce Hammock: Scientist Extraordinaire

(Editor's Note: Thanks to Lisa Junker, ESA's director of publications, communications and marketing, who reached out to "our publishers at Oxford" to grant free community access to this feature story in American Entomologist)

Michael Hoffmann, recipient of Leigh Distinguished Alumni Award

Hoffmann, who received his doctorate in entomology in 1990 from UC Davis, studying with Professor Ted Wilson and later Professor Frank Zalom, will present the Leigh Distinguished Alumni Seminar on “Our Changing Menu--What Climate Change Means to the Foods We Love and Need,” the title of his upcoming book. The seminar was initially set for April 15 at the International House, UC Davis, but due to the global coronavirus outbreak, it has been postponed.

Prior to his retirement, Hoffmann served as executive director of the Cornell Institute for Climate Smart Solutions for several years. He continues to provides visionary leadership, communicates to a wide range of audiences the challenges and opportunities that come with a changing climate, and builds partnerships among public and private organizations.

Hoffmann co-chairs the President's Sustainable Campus Committee and helps lead a climate change literacy initiative for students, staff, and faculty. He dedicates his time toward what he calls “the grand challenge of climate change and (to) help people understand and appreciate what is happening through food.” Effectively communicating about climate change, Hoffmann presented a TEDX talk in 2014 on “Climate Change: It's Time to Raise Our Voices” that drew widespread attention.

A native of Wisconsin, Hoffmann holds a bachelor of science degree (1975) from the University of Wisconsin, and his master's degree from the University of Arizona (1978). He served with the U.S. Marines in Vietnam from 1967 to 1971, attaining the rank of sergeant.

Hoffmann remembers well his experiences at UC Davis. “I was privileged to work with many dedicated faculty in entomology and several other departments.”

After receiving his doctorate at UC Davis, Hoffmann joined the faculty of Cornell in 1990 as an assistant professor, with 60 percent Extension and 40 percent research duties, and advanced to associate professor in 1996, and professor in 2003. His academic career focused on administrative endeavors (80 percent) beginning in 1999.

Hoffmann's career at Cornell included serving as associate dean of the College of Agriculture and Life Sciences, associate director of Cornell Cooperative Extension, director of the Cornell University Agricultural Experiment Station, and director of the New York State Integrated Pest Management Program. He helped initiate a leadership and professional development week-long program that benefited more than 400 faculty at Cornell and beyond.

Prior to his administrative duties, he worked to develop and implement cost-effective and environmentally sensitive tactics for management of insect pests.  He emphasized biological control, development and application of insect behavior modifying chemicals, and novel control tactics, all in an integrated pest management (IPM) context. Much of his research and Extension programming was multi-state and multidisciplinary in nature. 

Among his entomological achievements, he

• Developed unique, cost-effective and environmentally benign biological control tactics for insect pest of sweet corn, peppers and potatoes, and presented wide scale demonstrations on conventional and organic farms in New York, Virginia, Massachusetts and Canada.
• Published the first popular guide to beneficial insects (64 pages, with more than 5,000 copies distributed)
• Developed patented unique fiber barrier technology for pest control

Highly honored for his expertise, Hoffmann was selected the recipient of the Experiment Station Section Award for Excellence in Leadership in 2015. He won an Entomological Foundational Professional award for Excellence in Integrated Pest management, Entomological Society of America, Eastern Branch, in 2006. He created a one-of-a-kind culture of sustainability at the Cornell University Agricultural Experiment Station focused on reducing the carbon footprints and costs, and ensuring staff well-being. He helped initiate a leadership and professional development week-long program that has benefited more than 400 faculty at Cornell and beyond.

Hoffmann authored more than 100 refereed publications, mostly related to entomology.

The Leigh seminar memorializes cotton entomologist Thomas Frances Leigh (1923-1993), an international authority on the biology, ecology and management of arthropod pests affecting cotton production. During his 37-year UC Davis career, Leigh was based at the Shafter Research and Extension Center, also known as the U.S. Cotton Research Station. He researched pest and beneficial arthropod management in cotton fields, and host plant resistance in cotton to insects, mites, nematodes and diseases. In his memory, his family and associates set up the Leigh Distinguished Alumni Seminar Entomology Fund at the UC Davis Department of Entomology. When his wife, Nina, passed in 2002, the alumni seminar became known as the Thomas and Nina Distinguished Alumni Seminar.

Leigh joined the UC Davis Department of Entomology in 1958, retiring in 1991 as an emeritus professor, but he continued to remain active in his research and collaboration until his death on Oct. 26, 1993.  The Pacific Branch of the Entomological Society of America awarded him the C. F. Woodworth Award for outstanding service to entomology in 1991.

Michael Hoffmann has been selected to deliver the Thomas and Nina Leigh Distinguished Alumni Seminar

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The seminars, coordinated by community ecologist Rachel Vannette, assistant professor, UC Davis Department of Entomology and Nematology, are held on Wednesdays from 4:10 to 5 p.m.

The schedule:

Wednesday, April 1
Javier Ceja-Navarro, research scientist, Biological Systems and Engineering, Biosciences, Berkeley
Topic: (He researches multitrophic interactions in ecosystems such as digestive tracts of insects and soil)
Host: Rachel Vannette, assistant professor, UC Davis Department of Entomology and Nematology

Wednesday, April 8
Reginald “Rex” Cocroft, professor of biology, University of Missouri
Topic: (He researches plants as receivers of insect sound and vibration)
Host: Rick Karban, professor, UC Davis Department of Entomology and Nematology

Thomas and Nina Leigh Distinguished Alumni Seminar (to be determined)
Michael Hoffmann, emeritus professor, Cornell University
Topic: “Our Changing Menu: What Climate Change Means to the Foods We Love and Need”
Host: Steve Nadler, professor and chair, UC Davis Department of Entomology and Nematology

Wednesday, April 22
(To be announced)

Wednesday, April 29
Dhruba Naug, professor, Department of Ecology and Evolutionary Biology,  Colorado State University
Topic: (He combines his interests in behavioral and cognitive ecology to understand the functioning of individuals and social groups. His research involves experimental work in behavior and physiology complemented by approaches based on individual based modeling.)
Host: Rachel Vannette, assistant professor, UC Davis Department of Entomology and Nematology

Wednesday, May 6
Xianhui "Nitrol" Liu, Joanna Chiu lab, UC Davis Department of Entomology and Nematology
Topic: Exit seminar (title pending)
Host: Joanna Chiu, associate professor and vice chair, UC Davis Department of Entomology and Nematology

Wednesday, May 13
Andre Kessler, chemical ecologist and professor Cornell University
Topic: (He is chemical ecologist whose research focuses on the mechanisms, ecological consequences and the evolution of plant induced responses to herbivore damage)
Host: Rick Karban, professor, UC Davis Department of Entomology and Nematology

Wednesday, May 20
Shalene Jha, University of Texas, Austin
Topic:  "Plant-Insect Interactions in the Face of Global Change"
Host: Charlie Nicholson, Neal Williams lab, UC Davis Department of Entomology and Nematology

Wednesday, May 27
Rebecca Godwin, doctoral candidate, Jason Bond lab, UC Davis Department of Entomology and Nematology
Topic: Exit seminar (title pending)
Host: Jason Bond, Schlinger Chair in Insect Systematics, UC Davis Department of Entomology and Nematology

Wednesday, June 3
Esther Ngumbi, assistant professor of entomology and African-American studies, University of Illinois
Topic: (Pending)
Host: Elvira DeLange, Christian Nansen Lab, UC Davis Department of Entomology and Nematology

For more information, contact Rachel Vannette at rlvannette@ucdavis.edu. The winter seminars just concluded.