Disinfection Efficiency Among Black Alder and Hybrid Alder Genotypes and Their Influence on Alder Seed Germination In Vitro

ABSTRACT The presented study aimed to test a set of Alnus genotypes, including hybrids of black and grey alders ( A. glutinosa  ×  A. incana ) and A. glutinosa , based on their spring phenology, using in vitro screening assays. We evaluated the disinfection efficiency and the susceptibility of the surviving fungi in different Alnus genotypes, comprising five with early spring phenology, four with late spring phenology and four hybrids. Then, the best‐performing explants of four Alnus genotypes, including at least one of early and late spring phenology, as well as one hybrid, were selected to evaluate the explant influence on other Alnus seed germination under stress from the fungus Cladosporium cladosporioides inoculum. The explants of Alnus hybrids 047 and 026 were characterised by stronger leaf development than the A. glutinosa genotype 19–43–8 K, which, however, displayed the highest success of explant sterilisation. The explants of A. glutinosa genotype 19–43–8 K and of Alnus hybrid 026 were shown to increase germination of neighbouring (planted in the same test tube) Alnus seeds and seedling development, especially root system expansion under the stress from C. cladosporioides . These results point to the potential of the selected Alnus genotypes to relieve biotic stress in other Alnus seeds.