This study was conducted to assess drought tolerance and regional-based patterns of diversity of bread wheat accessions and to identify new sources of diversity that could accelerate the development of improved wheat varieties better suited to meeting the challenges posed by changing climate in Southern and Eastern Europe. For this, genetic diversity assessed by simple sequence repeats (SSR) markers was compared with diversity evaluated using 19 phenotypic traits averaged over irrigated and drought-stress field conditions. Thirty-six SSR were used to profile 96 wheat genotypes from the collection of genetic resources at the Institute of Field and Vegetable Crops, Novi Sad, Serbia. A total of 46 loci and 366 alleles were detected, with a range of 3–21 alleles per locus. The polymorphic information content was estimated to be 0.61. The genetic distance for all possible 4560 pairs of genotypes ranged from 0.06 to 0.91 with an average of 0.65. Genotypes were grouped according to their drought tolerance (high, medium, low) and region of origin. Analysis of molecular variance showed that over 96% of the total variation could be explained by the variance within the drought tolerance and geographical groups. As a whole, genetic diversity among the high drought tolerance genotypes was considerably higher than that among low drought tolerance genotypes. Comparative analysis of SSR diversity among six regional groups revealed that the genotypes from North America exhibited more genetic diversity than those from other regions. Two dendrograms were constructed based on phenotypic and molecular analyses using the Unweighted Pair Group Method with Arithmetic Mean method and were found to be topologically different. Genotypes characterised as highly drought tolerant were distributed among all SSR-based cluster groups. This implied that the genetic basis of drought tolerance in these genotypes was different, thereby enabling wheat breeders to combine these diverse sources of genetic variability to improve drought tolerance in their breeding programs.

Changes in climate are likely to have a negative impact on water availability and soil fertility in many maize-growing agricultural areas. The development of high-throughput phenotyping platforms provides a new prospect for dissecting the dynamic complex plant traits such as abiotic stress tolerance into simple components. The growth phenotypes of 20 maize (Zea mays L.) inbred lines were monitored in a non-invasive way under control, nitrogen, and water limitation as well as under combined nitrogen and water stress using an automated phenotyping system in greenhouse conditions. Thirteen biomass-related and morphophysiological traits were extracted from RGB images acquired at 33 time points covering developmental stages from leaf count 5 at the first imaging date to leaf count 10–13 at the final harvest. For these traits, genetic differences were identified and dynamic developmental trends during different maize growth stages were analyzed. The difference between control and water stress was detectable 3–10 days after the beginning of stress depending on the genotype, while the effect of limited nitrogen supply only induced subtle phenotypic effects. Phenotypic traits showed different response dynamics as well as multiple and changing interaction patterns with stress progression. The estimated biovolume, leaf area index, and color ratios were found to be stress-responsive at different stages of drought stress progression and thereby represent valuable reference indicators in the selection of drought-adaptive genotypes. Furthermore, genotypes could be grouped according to two typical growth dynamic patterns in water stress treatments by c-means clustering analysis. Inbred lines with high drought adaptability across time and development were identified and could serve as a basis for designing novel genotypes with desired, stage-specific growth phenotypes under water stress through pyramiding. Drought recovery potential may play an equal role as drought tolerance in plant drought adaptation.

Phenotypic measurements under controlled cultivation conditions are essential to gain a mechanistic understanding of plant responses to environmental impacts and thus for knowledge-based improvement of their performance under natural field conditions. Twenty maize inbred lines (ILs) were phenotyped in response to two levels of water and nitrogen supply (control and stress) and combined nitrogen and water deficit. Over a course of 5 weeks (from about 4-leaf stage to the beginning of the reproductive stage), maize phenology and growth were monitored by using a high-throughput phenotyping platform for daily acquisition of images in different spectral ranges. The focus of the present study is on the measurements taken at the time of maximum water stress (for traits that reflect plant physiological properties) and at the end of the experiment (for traits that reflect plant architectural and biomass-related traits). Twenty-five phenotypic traits extracted from the digital image data that support biological interpretation of plant growth were selected for their predictive value for mid-season shoot biomass accumulation. Measured fresh and dry weights after harvest were used to calculate various indices (water-use efficiency, physiological nitrogen-use efficiency, specific plant weight) and to establish correlations with image-derived phenotypic features. Also, score indices based on dry weight were used to identify contrasting ILs in terms of productivity and tolerance to stress, and their means for image-derived and manually measured traits were compared. Color-related traits appear to be indicative of plant performance and photosystem II operating efficiency might be an importance physiological parameter of biomass accumulation, particularly under severe stress conditions. Also, genotypes showing greater leaf area may be better adapted to abiotic stress conditions.

Barley (Hordeum vulgare L.) is often grown in sites with low rainfall and high temperature during grain filling. Because spike architecture is one of basic footprints of barley domestication, the importance of spikes in adaptation to different environments or abiotic stresses can be hypothesised. In order to compare different barley spike types in terms of kernel growth and yield components, we tested 15 two-row and 10 six-row winter genotypes in eight environments where terminal drought was simulated by defoliation at 7 days after heading (7 DAH). Control plants were grown intact. On average, two-row genotypes outyielded six-row genotypes by 17% under control conditions and 33% under simulated late drought. Observations of kernel dry weights from 7 DAH through to harvest maturity at 5-day intervals were regressed onto a measure of thermal time. After preliminary evaluation of four nonlinear (S-shaped) models for kernel dry-weight accumulation, the ordinary logistic model was deemed the most appropriate in most cases and was finally applied to all plant-growth curves. Four parameters were estimated from the logistic model. Whereas two earliness estimators (inflection point and thermal time needed to reach maximum kernel weight) were similar for the two barley types, maximum kernel weight (Ymax) and mean rate of kernel growth (RG) were higher (P < 0.05) in two-row than in six-row barleys. Differences in Ymax and RG among six-row barley genotypes were greater between control and defoliation treatments than between years, whereas among two-row barley genotypes, differences between years were greater, suggesting better stability of six-row types and better drought tolerance of two-row types in the tested barley set.

The tissue culture response (TCR) of immature embryos, evaluated according to callus formation, percentage of regenerative green-spotted calli and the number of plants per embryo, was investigated in 96 wheat genotypes of worldwide origins. Immature embryos were collected 12-15 DAP from field-grown plants during three successive years 2003, 2004 and 2005. Year 2003 was with high air temperatures and tropical days during a period of vegetation, while the environmental conditions were more favorable for plant growth in the next two years, 2004 and 2005. Embryos were cultured on standard MS medium containing 2 mg l-1 2, 4-D. In all genotypes calli were efficiently induced, ranging from 36.7 to 100% (2003), 68.4 to 100% (2004), and 94.3 to 100% (2005). The calli occasionally formed green spots, but frequencies markedly differed among genotypes that varied from 0 to 72.5% (2003), 0 to 97.9% (2004), and 0 to 94.0% (2005). Coefficient of variation was highest in term of percent of regenerative calli (66.7%) following by a number of plants per embryo (35.6%) and callus formation (5.1%). Components of phenotypic variance showed that factor year (71.4%) had the highest impact on expression of callus formation, genetic factor (47,1%) on percentage of regenerative green-spotted calli and interaction year/genotype (30.3%) on number of plants per embryo. The results indicated factor genotype as the most important for determining regeneration potential in wheat.