Drought-tolerant Plainsman V and drought-sensitive Cappelle Desprez winter wheat genotypes were subjected to heat stress at 34/24°C combined with water withholding during early seed development in order to identify the joint effect of the stressors on embryo and endosperm development. During and after five days of treatment histological observations were made on the developing kernels and compared to yield data. Combined stress shortened the duration of the grain fill. With regard to kernel abortion, thousand-kernel weight and yield per spike, Plainsman V tolerated simultaneous elevated temperature and water withdrawal better than Cappelle Desprez. As a consequence of the stress the accumulation of B-type starch granules was almost completely absent in the endosperms of the sensitive genotype. The results indicate that compared to the drought-sensitive genotype, the tolerant genotype also showed increased tolerance of simultaneous drought and heat stress.
In the present work the effect of microalgal and cyanobacterial biomass on anther cultures of wheat (Triticum aestivum L.) was studied. Investigations were made on the influence of media supplemented with a biomass of four terrestrial and fresh-water microalgal and cyanobacterial strains (1-2 g l-1) on the androgenic response, frequency of microspore-derived embryo-like structures, and their regeneration capacity in anther cultures of wheat. The addition of 1 g L-1 of cyanobacterium biomass MACC 643 to the induction and regeneration media significantly improved the androgenic response by 50% in the genotype Mv Pálma, and reduced the requirement for the synthetic auxin 2,4-D.
Drought stress frequently occurs in the reproductive stage of wheat, causing significant yield loss. To study the developmental stage dependency of the effect of drought stress on photosynthesis, plants of the drought-tolerant Plainsman V and sensitive Cappelle Desprez winter wheat varieties were grown in phytotron chambers and subjected to water withholding during three phenophases of reproductive development: meiosis, anthesis and early seed development (ESD).Stomatal conductance (gs) and net photosynthesis (Anet) showed similar characteristics. Meiotic-stage drought only decreased the values of Cappelle Desprez significantly. Stressed Plainsman V showed a significantly smaller reduction and better regeneration for these parameters at anthesis. The decreases in gs and Anet were similar in both varieties when drought was applied during ESD. Studies on the intercellular CO2 concentration (Ci) inflexion point implied that metabolic impairment was less typical of stressed Plainsman V than of Cappelle Desprez at meiosis and anthesis. The quantum efficiency of PSII (ΦPSII) did not decline in either genotype during meiotic-stage drought. Stressed Plainsman V showed significantly higher ΦPSII values compared to Cappelle Desprez at anthesis. During ESD, the values for stressed plants of both genotypes decreased to a similar extent.The results indicate that the effect of drought stress on photosynthesis shows developmental stage dependency during the reproductive life cycle of wheat.
In the present study the applicability of a self-constructed doubled haploid line (DH 105) in the in vitro breeding of maize was evaluated. This line, which contained only 50% exotic (Chinese) germplasm, could be used to transmit in vitro androgenic ability into non-responsive breeding materials. F1 hybrids resulting from single crosses between the moderately responsive line DH 105 and recalcitrant genotypes with high breeding value showed a considerable heterosis effect in their androgenic responses. Most of the hybrids had favourable morphological and agronomic characters on the basis of “per se” evaluation. The data of the experiments showed that these F1 hybrid plants could be successfully used as anther donors, since numerous fertile DH plants were developed from their anther cultures. By the use of this in vitro breeding strategy the genetic variability can be widened and the effectiveness of inbred line production might be improved.