In Vitro Collection for the Safe Storage of Grapevine Hybrids and Identification of the Presence of Plasmopara viticola Resistance Genes.

This paper focuses on the creation of an in vitro collection of grapevine hybrids from the breeding program of the Kazakh Scientific Research Institute of Fruit Growing and Viticulture and investigates the presence of Plasmopara viticola resistance mediated by Rpv3 and Rpv12 loci. We looked at the optimization of in vitro establishment using either shoots taken directly from field-grown plants or from budwood cuttings forced indoors. We further screened for the presence of endophyte contamination in the initiated explants and optimized the multiplication stage. Finally, the presence of the resistance loci against P. viticola was studied. The shoots initiated from the field-sourced explants were the more effective method of providing plant sources for in vitro initiation once all plant accessions met the goal of in vitro establishment. The concentration of phytohormones and the acidity of the culture medium have a great effect on the multiplication rate and the quality of in vitro stock cultures. Out of 17 grapevine accessions, 16 showed the presence of single or combined resistance loci against P. viticola. The grapevine accessions identified as carrying Rpv3 and Rpv12 alleles represent important genetic resources for disease resistance breeding programs. These accessions may further contribute to the creation of new elite cultivars of economic interest.

Virus Elimination from Naturally Infected Field Cultivars of Potato (Solanum tuberosum) by Transgenic RNA Interference.

Tissue culture methods enable virus elimination from vegetatively propagated crop plants but cannot prevent new infections. Here we used a tissue culture transgenic approach for curing field cultivars of Solanum tuberosum through the stimulation of RNA interference (RNAi)-based antiviral defenses. Expression cassettes carrying inverted repeats of potato virus S (PVS, genus Carlavirus) movement or coat protein sequences were used for the transformation of potato cultivars naturally infected with PVS and/or a related carlavirus potato virus M (PVM), without or with potato virus Y (PVY, genus Potyvirus). A high proportion of transformants PCR-positive for transgenes were cured from both carlaviruses and PVY. After 3-year field trials, 22 transgenic lines representing seven cultivars remained free of any virus or became infected only with PVY. Vegetative progenies of the transgenic lines of cultivar Zeren (initially coinfected with PVS, PVM, and PVY), sampled after in vitro propagation or field trials, and other field cultivars accumulated transgene-derived 21, 22, and 24 nt small interfering (si)RNAs almost exclusively from the PVS inverted repeats. Additionally, some field progenies accumulated 21-22 nt siRNAs from the entire PVY genome, confirming PVY infection. Taken together, transgenic RNAi is effective for virus elimination from naturally infected potato cultivars and their sequence-specific immunization against new infections.