Effects of in vivo mycorrhization on micropropagated fruit tree rootstocks

In order to establish an endomycorrhizal symbiosis on micropropagated plant s and to evaluate its effect on plant growth and survival, three rootstocks belonging to the Prunus genus were used: M51 (P. dulcis), GF677 (P. persic a x P. dulcis) and cv Citation (P. domestica x P. persica). The plants were micropropagated and in vitro rooted. Spores of Glomus mosseae (LMSS) and S cutellospora calospora (SCLS) and root fragments of clover or corn mycorrhi zed by them were used as inocula. Plants were inoculated in: (1) the early acclimatization phase; (2) the transplant phase; (3) in both phases. Two si milar experiments were conducted for each plant genotype, differing only in the type of inoculum. One month after transplanting, plant survival indexe s, mycorrhization percentages and growth parameters for each plant were rec orded. No significant effects were observed on survival. In M51 no mycorrhi zae were found and no significant growth effects were recorded in either ex periments. LMSS infected GF677 in the second experiment, but not in the fir st, when inoculated in the transplant phase, with a better establishment wh en a second inoculation was done. Citation was not colonized by LMSS in eit her experiment. SCLS was able to establish mycorrhizal infection of Citatio n and GF677 only in the first experiment, and only when inoculated in the a cclimatization phase. There were significant positive effects of the inocul ation phase, the inoculum strain and the plant genotype on growth parameter s, regardless of whether symbiosis was established or not. In conclusion, M 51 did not seem to be dependent on the establishment of an endomycorrhizal symbiosis, at least with the fungal strains used in our experiments. On the contrary, Citation and GF677 seemed positively influenced by inoculation, even when there was no infection by the mycorrhizas. This fact is probably due to growth promoter components of the inocula - possibly microflora. (C) 2000 Elsevier Science B.V. All rights reserved.