New Parasite Could Wreak Havoc in Chinese Vineyards

Researchers hope identifying a new species of parasitic round worm will help protect China’s vineyards.

(CN) — Researchers in China announced the discovery of a new species of root-knot nematode found attacking the vineyards of Yunnan province. Named after the grapevines it lives in and destroys, Meloidogyne vitis is the most recently identified species in a genus of roundworms infamous for devastating crops worldwide. 

“M. vitis found in Yunnan Province poses a serious threat to grape production and seriously damage grapes thereby causing severe root knots, leaf yellowing and shedding, roots were atrophied and distorted, dwarfed plants and reduced fruit size,” lead author Yang Hu, of Yunnan Agricultural University, said in an email.

“We consider M. vitis to be of equal threat as other root-knot nematodes. Whether there are certain characteristics make it particularly vicious, we don’t know yet, and further research will also be necessary to explore,” Hu added.

Other parasitic nematodes infect coffee, olives, and kiwis and have been identified in vineyards from Australia to South Africa, France and the United States.

Known for its grape production, Yunnan province in central China produced 7 billion yuan ($1 billion) worth of the fruit in 2014. Grapes from the region are produced to be eaten fresh and dried, as well as squeezed into juice and fermented into wine.

Researchers at the Yunnan Agricultural University found the nematodes in samples of grape roots and soil from Luliang County vineyards in the Yunnan province. The parasites infected 90% of the roots collected, allowing researchers to extract and study females and eggs.

Once the eggs hatched, researchers observed second-stage juveniles, raising them on cucumber roots alongside males. When compared to M. mali, another common root-knot nematode, researchers noticed distinct physiological features. Genetic analysis further supported naming the organism as a novel species.

Pear-shaped and white, the newly named M. vitis is not only genetically distinct from its Meloidogyne cousins but also features several physiological distinctions, including a perineal pattern that researchers described as shaped like a monkey face or dumbbell.

Root-knot nematodes not only live in roots, they also pierce through cell walls to take in nutrients. In response to the infestation plant roots form galls, taking nutrients away from healthy growth and stunting the development of fruit.

“The destroyed fibrous roots and root hairs initially show slight swelling,” the researchers wrote in their paper, published Wednesday in the journal PLOS ONE. “In later stages, the diseased roots become rotten, which directly affects the absorption of water and nutrients by the root system and results in great reductions in grape yield and fruit quality.”

Another species of root-knot nematode, M. icognita, has been found to reduce yield by 80% among vulnerable grapes, as by as much as 40% in grapes considered to have some resistance to the parasites. Additionally, researchers warned “root-knot nematodes can also interact with bacteria, fungi and other pathogens to further increase damage to grapes.”

The loss of production caused by these parasites leads to “significant economic losses,” making them of concern to both researchers and farmers alike.

Hu said grape growers are currently screening crops for resistant varieties, but also use chemical pesticides like metam sodium and methy bromide to address infestations. Many growers also use broth from certain fungi and marigolds as biocides.

“We need to identify root-knot nematode species so that we can carry out targeted control programs to better protect vineyards,” Hu said.

The specimens collected will remain with the nematode collection at the Yunnan Agricultural University in China.

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