Analysis of Thermal Characteristics of Potato and Hop Pollen for Their Cryopreservation and Cross-Breeding.

This study investigated the thermal properties of potato and hop pollen for cryopreservation and subsequent cross-breeding. Phase transitions and frozen water content in selected pollen samples were measured using a differential scanning calorimeter (DSC). Unlike hop pollen, potato pollen showed high variability in thermal properties and water content. Three specific types of pollen samples based on their thermal characteristics and water content were distinguished by DSC in potato: (1) 'glassy', with a water content lower than 0.21 g water per g dry matter; (2) 'transient', with a water content between 0.27 and 0.34 g of water per g of dry matter; (3) 'frozen', with a water content higher than 0.34 g of water per g of dry matter. Only the 'glassy' pollen samples with a low water content showed suitable properties for its long-term storage using cryopreservation in potato and hops. Cryopreservation of pollen did not significantly reduce its viability, and cryopreserved pollen was successfully used to produce both potato and hop hybrids. The results indicate that cryopreservation is a feasible technique for the preservation and utilization of pollen of these crops in the breeding process.

Evaluation of genetic variability of wild hops (Humulus lupulus L.) in Canada and the Caucasus region by chemical and molecular methods.

Wild hops (Humulus lupulus L.) are potential new germplasms to expand the variability of genetic resources for hop breeding. We evaluated Canadian (62 plants) and Caucasian (58 plants) wild hops by their chemical characteristics and with molecular genetic analyses using sequence-tagged site and simple sequence repeat markers, in comparison with European (104 plants) and North American (27 plants) wild hops. The contents of alpha and beta acids varied from 0.36% to 5.11% and from 0.43% to 6.66% in Canadian wild hops, and from 0.85% to 3.65% and from 1.22% to 4.81% in Caucasian wild hops, respectively. The contents of cohumulone and colupulone distinctly differed between European and North American wild hops: the cohumulone level in alpha acids was in the range 46.1%-68.4% among North American wild hops and in the range 13.6%-30.6% among European wild hops. The high content of myrcene and the low contents of humulene, farnesene, and selinenes were typical for wild hops from Canada, in contrast to wild hops from the Caucasus region. We compared the chemical characteristics with molecular genetic data. Chemical characteristics differentiated wild hops into North American and Eurasian groups. Molecular genetic analysis was able to separate Caucasian wild hops from European wild hops. We proved a hop phylogeny by means of wide molecular analysis.