In vitro fruit trees rooting by Agrobacterium rhizogenes wild type infection

Abstract

Agrobacterium rhizogenes infection at the base of microcuttings in vitro can improve the rooting of some fruit species. A study was carried out comparing rooting of almond, apple, plum, Pyrus pyraster and two hybrid rootstocks, when infected with A. rhizogenes strain 1855, with and without the addition of hormones. Three responses occurred: genotypes rooted without auxins; genotypes rooted only with auxins; genotypes rooted only after infection. All genotypes rooted after bacterial infection. In the first group the auxins increased rooting percentages. No substantial differences were found with and without infection in hormone free media, while the rooting percentages tended to decrease with the combination auxin/infection. In the second group, infection on hormone free media increased rooting; in addition there was a synergistic effect between auxins and infection in pears. In the third group only infection induced rooting. A random sample of roots obtained from infection was molecularly analysed. Amplification of the sequences of rolB and vir genes was done using PCR. Roots non-transgenic and confirmed as transgenic were, respectively, 67 % and 6.8 % respectively. In the remaining 26.2% both genes appeared, thus it was not possible to confirm their transgenic nature. Some microcuttings showed both transformed and non-transformed roots.