MOLECULAR BREEDING OF PETUNIA HYBRID 'FAMOUS LILAC DARK VEIN' FOR COMPACT GROWTH INDUCTION BY MKS1 AND GA2OX CONSTITUTIVE OVEREXPRESSION

One of the top targets of recent breeding programs in ornamental plants is focused on developing an alternative way to the chemical growth retardants application in production of plants with compact growth habit. We describe work on Petunia hybrid ‘Famous Lilac Dark Vein’ plants with overexpressed MAP kinase 4 nuclear substrate 1 (MKS1) and gibberellin 2-oxidase (GA2ox) genes. Petunia plants were transformed with pCAMBIA modified vectors in separate experiments, containing constructs either with the MKS1 or the GA2ox gene under the control of Ca35S promoter. The transformation was performed with the use of Agrobacterium tumefaciens strain GV3101. The integration and expression of the transgene was investigated using Southern blot and RT-PCR analysis. The mean internode lengths of the MKS1-transgenic lines were 2.5-fold shorter than those of the wild-type plants. The flowering delay in MKS1-transgenic lines was observed with a range of 6 to 11 days in comparison to the wild-type plants. The mean internode lengths of the GA2ox-transgenic lines were 6.5-fold shorter than those of the wild-type plants. The flowering delay in GA2ox-transgenic lines was observed with a range of 7 to 12 days in comparison to the wild-type plants. The flower morphology either in MKS1- or GA2ox-transgenic lines did not differ from wild-type plants. Constitutive overexpression of both MKS1 and GA2ox genes results in compact phenotype but also lead to delayed flowering.