The effects of exogenous auxin and rol genes on root formation in Rosa hybrida L. ‘Moneyway’

Abstract

The effect of indole-3-butyric acid (IBA) on the formation of non-transformed and rol gene transformed roots on stem slices of in vitro cultured shoots of Rosa hybridu L. 'Moneyway' was examined. Formation of adventitious roots on this rootstock was dependent on the IBA dose; it was not affected by the presence of other root primordia on the same explant. Application of 0.32 to 1 PM IBA during 5 days, followed by transfer to medium without hormones resulted in maximum root formation (90%) after three weeks. The formation of such untransformed roots was completely inhibited by transfer to medium with 5 mg 1-l kanamycin two days after excision. Ri roots were formed upon inoculation with A. rhizogenes LBA9402 harbouring two plasmids: pRil855, comprising the rol genes and the binary plasmid p 35Sgusintron with the nptll gene for kanamycin resistance and the CaMV 35Sgusintron gene. The formation of these Ri roots on kanamycin-containing medium was independent of the presence of IBA. Stem slices inoculated with a disarmed A. tumefuciens GV3 101, harbouring only the nptll gene, formed callus and subsequently roots in the presence of kanamycin exclusively on medium with high IBA concentrations (10 or 100 pw. Root formation at 100 PM IBA was considerably improved by transformation with the rolB gene under the influence of the strong CaMV 35s promoter. In addition, low IBA (0.1 and 1 ,uM) stimulated the formation of roots only on stem slices transformed with A. tumefuciens harbouring the rolA+rolB+rolC genes; the rooting response at 10 PM IBA was much improved. It was concluded that the 35SrolB gene and especially a combination of rolA, B and C genes promote the rooting response.Abbreviations: BAP = 6-benzylaminopurine; FeEDDHA = ferric ethylenediamine di(o-hydroxyphenylacetate); IBA = indole-3-butyric acid; LSD = least significant difference; RIM = root induction medium; SE = standard error; X-glut = 5-bromo-4-chloro-3-indolyl glucuronide

Genes and signalling in root development

“…In woody species, a role for auxin is also evident in promoting the formation of de novo root meristems. This is seen in species as diverse as rose ( Rosa hybrida ; Vandersalm et al ., 1996), yew ( Taxus baccata ; Nandi et al ., 1996), poplar ( Populus spp. ; Dolezelova et al ., 1996), eucalyptus (Gupta & Mascarenhas, 1987; McComb, 1995), pine ( Pinus sylvestris ; Flygh et al ., 1993), Mussaenda erythrophylla (StHilaire et al ., 1996) and apple ( Malus sp.…”

“…; Noiton et al ., 1992; Vanderkrieken et al ., 1992; DeKlerk et al ., 1995; DeKlerk et al ., 1997; Jasik & DeKlerk, 1997), for example, where exogenous auxin induces new roots. Infection of both woody and herbaceous species by Agrobacterium rhizogenes leads to adventitious rooting, due to elevated auxin production or sensitivity in the affected cells (Vandersalm et al ., 1996; Jasik et al ., 1997). Therefore, the effects of exogenous auxin on de novo root formation are broadly similar in numerous dictyledonous species, both herbaceous and woody.…”

Ocimum kilimandscharicum 4CL11 negatively regulates root formation by inhibiting polar auxin transport via flavonoids accumulation

“…Few woody plant species are also known to produce de novo ARs from stem cuttings. Common examples are rose (Rosa hybrida) 48 , poplar (Populus spp.) 49 , eucalyptus 50 , pine (Pinus sylvestris) 51 , and apple (Malus sp.)…”