Effect of plant growth promoting rhizobacteria (PGPRs) and stratification on germination traits of Crataegus pseudoheterophylla Pojark. seeds

• Seed germination of Crataegus seudohetrophylla for the first time.
• Up to 18.33% germination was obtained for seeds co-inoculated by a combination of PGPRs using alternate temperature stratification.
• Introducing combinations of PGPRs as an efficient alternative to promote C. pseudoheterophylla seed germination.

This study investigated seed germination of Crataegus pseudoheterophylla Pojark using different combinations of growth promoting rhizobacteria and stratification regimes. The PGPR treatments were Azotobacter chroococcum 12, Azospirillum lipoferum OF, Pseudomonas fluorescens 169, Bacillus subtilis FzB24 and combinations (co-inoculation) using two or all PGPR inoculants. The control was no inoculation followed by stratification. Temperature regulation in the stratification regime was 1 month at the constant temperature of 23 °C, then 3 months at 4 °C. The alternate temperature regime was 1 month at 4 °C, then 2 weeks at 23 °C followed by 1 month at 4 °C, then 2 weeks at 23 °C, then 1 month at 4 °C. The effects of these treatments were evaluated and results showed that treatments of PGPR inoculation stimulated germination in terms of percentage of seed germination, speed of germination and mean germination time, and effect was significant at (p < 0.05). Higher percentages of seed germination (18.33%) and speed of germination (4.82 number/day) were recorded for co-inoculated seeds by the combination of all bacterial inoculants and the alternate temperature stratification regime. Results showed a higher percentage of seed germination using alternate temperature stratification than for the constant temperature stratification regime. These results suggest that PGPRs in combination were effective in terms of promoting germination of C. pseudoheterophylla seeds.