Viktoras Pranckietis

Cold acclimation efficiency of different Prunus and Fragaria species and cultivars in vitro@@@Įvairių Prunus ir Fragaria rūšių bei veislių augalų užsigrūdinimo in vitro efektyvumas

Winter hardiness is one of the main traits affecting survival, productivity and cultivar choice for important horticultural plants in a temperate climatic zone. Given the complexity of the trait and the often fluctuating winter weather, extensive field testing over many years would be required to gain reliable results. Testing for cold tolerance under controlled conditions to grade genotypes has been used in several plant breeding programs to identify superior genotypes of different species. The aim of the present study was to investigate cold tolerance of microshoots of different genotypes of the genera Prunus and Fragaria after 7, 14, 28 and 56 days of cold acclimation, by measuring ion leakage and evaluating the critical temperature (CT50) after freezing in vitro. Genotypes of Rosacea family demonstrated distinct patterns of CT50 change during cold acclimation. Cold acclimation for 56 days decreased the CT50 value by 1.3–2.0°C for Prunus microshots and by 0.8–2.1°C for Fragaria microshoots in comparison to nonacclimated plants. The results of cold acclimation and freezing treatments of Rosacea family plants in vitro show that for maximal cold hardiness, acclimation for 56 days or longer is required. Sour cherry (Prunus cerasus) cv. ‘Orkolija’, garden strawberry (Fragaria × ananassa) cv. ‘Melody’, Virginia strawberry (F. virginiana) and musk strawberry (F. moschata) were the most winterhardy after 56 days’ cold acclimation. The data obtained in the study can be used to improve breeding and cryopreservation technologies of Rosacea plants, and lay the foundation for identification of genes responsible for efficient cold acclimation and low temperature tolerance.

THE EFFECT OF AGRONOMIC AND CLIMATIC FACTORS ON WINTER OILSEED RAPE (BRASSICA NAPUS L.) ROOT NECK GROWTH IN AUTUMN

The aim of this study was to investigate the growth habit of winter oilseed rape root neck during the vegetative period in autumn. Such information is important for better understanding of winter oilseed rape growth pattern at early stages of development with the purpose to improve over winter survival. Field trials were conducted on Endocalcari – Epihypogleyic Cambisols . For the determination of changes of winter oilseed rape root neck thickness during autumnal development the effect of planting date, seedbed nitrogen application, stand population density, number of calendar days after emergence, accumulated by plants growing degree days and interaction among these factors was tested. For the description of the root neck growth pattern Boltzmann’s growth function performing a nonlinear fitting of estimating parameters was used. Results collected in the experiments indicate that the effect of sowing date including accumulated by plants growing degree days and the number of calendar days after emergence showed much greater effect on winter oilseed rape root diameter than seeding rate or pre-plant nitrogen application. On the basis of collected data winter oilseed rape root neck growth model was developed. These studies that relate mentioned factors to fall growth of winter oilseed rape root neck are presented in the paper. Keywords: growing degree days, number of calendar days, nitrogen application, stand population density. Article DOI: http://doi.org/10.15544/RD.2015.025