An efficient utilization of genetic resources from the genebanks is partly limited by insufficient phenotypic data, including information on the stress tolerance. Therefore, we focus on assessment of the methods and tools for rapid evaluation of the traits associated with drought tolerance. In our previous program, we have created a collection of 35 diverse winter wheat genotypes selected from hundreds of accessions of Slovak Genebank at NAFC-RIPP Piestany, Slovakia, which greatly covers a diversity of leaf traits, especially chlorophyll content, leaf thickness, leaf area and some other. To examine the links between leaf traits and drought stress responses, we have realized phenotyping experiment using a whole collection of 35 wheat genotypes. Plants were grown in pots outdoors and in a growth phase of stem elongation, a half of the plants were exposed to long-term (permanent) moderate water deficit by limiting water supply. The growth responses to drought were assessed by the automated phenotyping platform (PLANTSCREEN) with RGB imaging, as well as VNIR and SWIR hyperspectral image analyses. Moreover, the manually operated measurements of chlorophyll content (SPAD), chlorophyll fluorescence, leaf temperature (IR thermal imaging) and VNIR hyperspectral records were performed in 3-4 days interval to assess the effect of drought stress on photosynthetic apparatus. The measurements were followed by the analyses of aboveground biomass and grain yield. Our results indicated variations in responses to prolonged drought, such as decrease of plant height, increase of canopy temperature and the decrease of leaf area index (LAI) due to the senescence of nonproducing tillers. We observed a high diversity in the level of reduction of the flag leaf area, leaf chlorophyll content, spectral reflectance and parameters derived from fast chlorophyll fluorescence records indicating unequal effects of drought on the photosynthetic apparatus of diverse wheat genotypes. Moreover, we identified a close relationship between the changes of leaf traits and leaf optical properties measured by the hyperspectral reflectance records. Our results indicated that some of the parameters based on spectral reflectance and chlorophyll fluorescence techniques can be useful to assess the drought tolerance of the genotypes.

Acknowledgement. The study was supported by the national grants APVV-15-0562 and VEGA-1-0831-17.