The types and methods of natural pollination of flax Linum usitatissimum L

Common flax is referred to self-pollinators with the probability of entomophilic and anemophilic cross-pollination up to 1-5%, that creates some problems in maintaining varietal purity. The formation conditions and the frequency of cross-pollination in flax have not been studied sufficiently. The possibility of aerial cross-pollination of this crop has a polemical character. Studies were conducted at the All-Russian Research Institute of Oil Crops (VNIIMK), Krasnodar in 2015-2017. The probability and frequency of cross-pollination were studied on oil varieties of flax VNIIMK 620, Danik, VNIIMK 630 and Surprise with brown and yellow seed coloring. During the budding and flowering phase, the dynamics of anther opening, the pollen transfer to the stigmas of pistils and the wind transfer of pollen were studied. It was revealed that the share of cross-pollination in flax varied within the limits of 0.15-0.87%, in some cases increasing up to 1.33-1.75%. The transfer of pollen was noted at a distance of up to 9 m. However, it was not possible to separate the contributions of entomophilic and anemophilic cross-pollination into genetic impurities of flax varieties. The main insects-pollinators of flax in the Krasnodar region are honey bee and alfalfa leaf-cutting bee. The types of position of stamens and stigmas of pestles that promote self-pollination and cross-pollination in flax are revealed. The dimensions of individual pollen grains in the studied flax varieties are 56-65 μm, which ensures their free transfer by wind. The more massive agglomerates with the size of 110-370 μm, consisting of several cytosolized pollen grains, can also be subjected to the wind transfer. The beginning and intensity of the wind transfer of the flax pollen is determined by a rate of its stickiness loss and shedding from the surface of the anther, the size of the pollen agglomerates and the wind speed. Therefore, in order to avoid the risks of possible entomophilic and anemophilic cross-pollination, seed growing fields of different flax varieties should be placed on separate, non-adjacent fields.