Chlorophyll a fluorescence gives information about the plant physiological status due to its coupling to the photosynthetic electron transfer chain and to the further biochemical processes. Environmental stresses, which acts synergistically, disturbs the photosynthesis. The OJIP test, elaborated by Strasser and co-workers, enables comparison of the physiological status of plants grown on polluted vs. control areas. The paper shows that the Chl a measurements are very useful tool in evaluating of heavy metal ions influence on perennial grasses, tested as potential phytoremediators. Among 5 cultivars tested, the highest concentration of Cd and Zn ions, not associated with the yield reduction, was detected in the biomass of tall fescue cv. Rahela. Chl a fluorescence interpreted as double normalized curves pointed out Rahela as the outstanding cultivar under the HM ions stress.

The indica-derived rice blast resistance genes Pi-ta² and Pi-ta, introgressed into a japonica background, were mapped on the middle of chromosome 12 with restriction fragment length polymorphism (RFLP)/random amplified polymorphic DNA (RAPD) markers and several nearly isogenic lines (NILs). Pi-ta² cosegregated with XNpb 289 and 196, and was flanked by closely linked markers at 0.3 (ta²-1) and 0.7 cM (XNpb 088, 319/079) on the left (up) side, and at 0.3 (RUBss) and 0.7 cM (XNpb316) on the right (down) side of the map, in F₂ analyses of Pi No. 4 × japonica crosses, with 160 recessive homozygotic individuals corresponding to 320 chromosomes. CHEF (contour-clamped hexagonal electric field) Southern blotting suggested that XNpb088 and XNpb239-1, both very close to Pi-ta², were spanned by a 170-kb band, suggesting about 500 to 750 kb/cM as the physical/genetic distances ratio in the crosses of Pi No. 4 × japonica, which was rather low in recombination ratio, in this region. Pi-ta was mapped to the position overlapping Pi-ta² by graphical genotype analysis of an NIL with a very narrow introgressed region, Shimokita. This result suggested that these functionally related genes are allelic or at least very closely located, and that they may be derived from a common ancestral gene. However, RFLP analyses of the NILs of these two genes indicated that they are derived from rather different genomes, refuting the report that NILs of Pi-ta share a common donor with those of Pi-ta². This indicates that the two genes differentiated at a rather ancient time. Two other pedigrees, describing spontaneous recent origins of Pi-ta in japonica, were also refuted and a single indica origin of the gene was indicated.

Wide hybrids have been used in generating genetic maps of many plant species. In this study, genetic and physical mapping was performed on ph1b-induced recombinants of rye chromosome 2R in wheat (Triticum aestivum L.). All recombinants were single breakpoint translocations. Recombination 2RS–2BS was absent from the terminal and the pericentric regions and was distributed randomly along an intercalary segment covering approximately 65% of the arm's length. Such a distribution probably resulted from structural differences at the telomeres of 2RS and wheat 2BS arm that disrupted telomeric initiation of pairing. Recombination 2RL–2BL was confined to the terminal 25% of the arm's length. A genetic map of homoeologous recombination 2R–2B was generated using relative recombination frequencies and aligned with maps of chromosomes 2B and 2R based on homologous recombination. The alignment of the short arms showed a shift of homoeologous recombination toward the centromere. On the long arms, the distribution of homoeologous recombination was the same as that of homologous recombination in the distal halves of the maps, but the absence of multiple crossovers in homoeologous recombination eliminated the proximal half of the map. The results confirm that homoeologous recombination in wheat is based on single exchanges per arm, indicate that the distribution of these single homoeologous exchanges is similar to the distribution of the first (distal) crossovers in homologues, and suggest that successive crossovers in an arm generate specific portions of genetic maps. A difference in the distribution of recombination between the short and long arms indicates that the distal crossover localization in wheat is not dictated by a restricted distribution of DNA sequences capable of recombination but by the pattern of pairing initiation, and that can be affected by structural differences. Restriction of homoeologous recombination to single crossovers in the distal part of the genetic map complicates chromosome engineering efforts targeting genes in the proximal map regions.Key words: homoeologous recombination, genetic mapping, RFLP, RAPD, wheat, rye.

In situ hybridization with total genomic DNA (GISH) has become a powerful tool in characterization of alien introgressions in wheat. With recent simplification it can now be used in large scale screening for new chromosome constructs. Its level of resolution in routine applications was tested on sets of recombined wheat-rye chromosomes with genetically determined positions of the translocation breakpoints. The resolution level of GISH visualized by an enzymatic color reaction was much lower than that of GISH with fluorescent probes but both techniques failed to reveal the presence of some distally located breakpoints. The limits of resolution for the two methods were at least 9.8 and 3.5 cM of the relative genetic lengths of chromosome arms, respectively, in configurations with proximal rye and terminal wheat segments when rye DNA was used as a probe. When wheat DNA was used as a probe, a terminal wheat segment estimated to be ca. 1.6 cM in length could not be visualized. An example of induced recombination between a chromosome of Agropyron elongatum and wheat illustrates that these resolution limits of GISH may hamper isolation of critical translocation breakpoints in a chromosome engineering effort.

The impact of drought on wheat (Triticum aestivum L.) production is shown, using an example data set of almost 60 yr from six climate‐specific regions in Poland. Drought was measured using the standardized precipitation index (SPI) and the hydro‐thermal coefficient of Selyaninov (HTC). Yield trends were estimated by Bayesian linear regression over two periods, 1961–1991 and 1992–2019, identified by a changepoint detection method. Bayesian inference is used as it allows the estimation of a credible interval of regression coefficients instead of point estimates and asymptotic confidence intervals, thus comparisons between regression coefficients are more meaningful. We detected an increase in yield in both time periods and in all regions. The average winter wheat yield increased by 97% in the first period and by 35% in the second (19.8–39.1 dt ha⁻¹ and 32.9–44.5 dt ha⁻¹, respectively). Spring wheat yield increased by 96% in the first period and by 42% in the second (16.8–37.9 and 22.9–32.5 dt ha⁻¹, respectively). Yield losses in drought years were estimated using the paired t test to compare mean difference between real yields and yields estimated from regression lines for nondrought years. The highest yield losses due to drought were in regions I (–19.3% spring wheats, –6.3% winter ones) and III (–16.1% spring and –8.3% winter wheats) over the 1992–2019 period.