Research on San Joaquin Valley rootstock is aimed at finding new root-knot nematode resistant rootstocks that are superior to some Valley standbys that include Freedom and Harmony.

Last year, USDA released three improved nematode resistant rootstocks: Matador, Minotaur and Kingfisher. The releases came after vineyard performance evaluation at Kearney and virus testing by Foundation Plant Services, said Peter Cousins, a grape rootstock breeder and geneticist with USDA’s Agricultural Research Service at Cornell University.

All three of the new releases showed improved efficiency compared to Freedom with higher fruit to pruning ratios. Cuttings of the rootstocks are available from Foundation Plant Services.

Cousins said there are 60 species of grapes worldwide and some have a natural resistance to nematodes.

A presentation on understanding water use of grapevines and what goes on inside the vines bore something of a resemblance to the 1987 science fiction comedy in which humans take a fantastic journey through a rabbit.

Andrew McElrone, with USDA-ARS in Davis, showed 3-D and motion film images of the xylem tissue in vines that maintain a continuous supply of water to the leaf surface.

He explained that during a drought plants face xylem tensions great enough to trigger what is known as cavitation and formation of air bubbles that can block the conduit that carries water. The damage is akin to an embolism in the human body, and some of the devices used to track what is happening in the xylem are also used for humans.

They include High Resolution Computed Topography and Nuclear Magnetic Resonance imaging similar to medical diagnostic CAT scans and MRIs.

Researchers have also developed a custom software packaged called PHAST (Physiologically-based High-speed Automated Software Technique) that automatically extracts vessel dimensions and distribution of intervessel connections.

The research takes on added importance due to water limitation issues in some years. In some instances, McElrone said, plants can repair themselves after an embolism.