Project Number: 2032-21000-020-11
Start Date: Aug 20, 2013
End Date: Aug 20, 2014
A set of diverse Juglans genotypes representing accessions from Mexico, Central America, and South America (see Table 1) will be introduced into tissue culture by nodal cuttings taken from semi-soft current-year’s growth. The seedlings used initially will be selected to maximize diversity and the total number introduced will depend on ease of introduction and rate of successful multiplication of the initial choices. We will attempt a minimum of 20 individuals representing all listed species and add additional genotypes as results and resources allow. In addition, methods been developed for clonally propagating walnuts by rooted cuttings, forcing shoots from branches, hardwood cuttings, and a modified air-layering procedure. The later, in particular, would be suitable to this work. These methods generally produce fewer plants than micropropagation but can be employed relatively quickly, can produce a few plants for initial work, and will be used to supplement the in vitro approach, particularly if any genotypes prove difficult to culture. The appropriate size and condition of micropropagated or cutting-produced Juglans plants for use in the screening procedures for resistance to each pathogen have been previously established. As plants are generated by either method and reach appropriate size, they will be distributed to the participating plant pathologists. Testing and evaluation procedures for each of these pathogens have been established through previous work on other Juglans species and these procedures will be employed for this work or adapted if necessary.