It is generally believed that plant polyploids exhibit greater tolerance to abiotic stress conditions than their diploid counterparts. The aim of the present research was to investigate the mechanisms underlying enhanced drought tolerance in the autotetraploid apple ‘Redchief’ as compared to its diploid counterpart. The study was conducted on potted plants over two growing seasons, and simulated drought conditions were induced by limiting or withholding irrigation. Under drought stress, the responses of the clone ‘Redchief’ 4x-25 and its diploid counterpart were compared at physiological, biochemical, and molecular levels. In addition, changes in leaf anatomical structure, stomatal characteristics, and parameters related to growth dynamics were examined in drought-challenged plants. The results indicate that apple tetraploids have a greater ability to adapt to water-deficit conditions than diploids. Under drought stress, apple tetraploids exhibited better physiological and biochemical parameters and maintained a greater capacity for continued growth than diploids. We propose that the primary mechanism underlying the increased drought tolerance in apple tetraploids is a faster and more efficient activation of antioxidant defenses and proline accumulation compared to diploids. The high plasticity of anatomical traits in apple tetraploids in response to adverse environmental conditions was also demonstrated.

This study aimed to assess the phenotypic changes in tetraploids of two gooseberry genotypes (‘White Triumph’ and AGR9, 2n = 4x = 32) in relation to their diploid counterparts (2n = 2x = 16). Tetraploid plants of the ‘White Triumph’ cultivar were characterized by lower growth dynamics than the diploid (control) plants, with the exception of clone A7/2-4x, whose height was increased. Tetraploid plants from three AGR9 gooseberry clones exhibited enhanced growth dynamics compared to control plants. The stomatal length of tetraploid gooseberry genotypes was greater than that of the control, but the stomatal density was lower in tetraploids. The leaf blades and petiole lengths of the tetraploid, ‘White Triumph’, and AGR9 plants were significantly larger than those of their diploid counterparts. Almost all nine evaluated anatomical traits (upper and lower epidermis thickness, palisade and sponge tissue thickness, amount of intercellular spaces, midrib diameter, phloem and xylem thickness, and surface of midrib cells) of the leaves in tetraploids were significantly greater than those of their diploid counterparts. Principal component analysis (PCA) distinguished genotypes according to the ploidy level. The first two principal components explained 74.8% of the total variance, with PC1 (49.99%) representing the primary axis separating diploid (2x) and tetraploid (4x) genotypes. To the best of our knowledge, there have been no published reports on the phenotypic assessment of gooseberry tetraploids. The vigorous gooseberry tetraploids characterized in this study are likely the first of their kind to be reported.

Chromosome counts and DNA content analyses are of tools used in studies of organismal variability that contribute to the breeding progress of ornamentals. The aim of this study was to determine the ploidy level and genome size of 20 Hippeastrum genotypes using Feulgen staining, DAPI staining, and flow cytometry. Different ploidy levels were identified. Within the population, there was one diploid and three triploids, and the remaining were tetraploids. The DNA content increased with the ploidy level: 32.63 pg in the diploid 43.68–47.08 pg in triploids, and 58.57–62.23 pg in tetraploids. The presence of a possible triploid–tetraploid chimera was detected but not confirmed by chromosome counts. The information gained may be useful in planning breeding efforts in the genus.