The Gibberellic-Acid Insensitive gene Vvgai1 impacts both vegetative growth and organogenesis rate in Vitis labruscana

Abstract

Context and purpose of the study. As other perennial crops grapevine is facing the challenges of climate changes. One of the major issues is global warming and variations of the water budget. Vitis labrusca, originated from the east coast of north america was largely used in breeding varieties adapted to warm and humid summers in USA, Brazil and Japan for instance. In order to develop innovative material to explore the mechanisms of adaptation to climate changes, we introduced the Vvgai1 mutation in V. vinifera x V. labrusca hybrids.

Material and methods. According to Chaib et al. (2010) and Chatbangyong and Torregrosa (2015), 24 plants were recovered from crossing V. labruscana cv. Isabelle x V. vinifera microvine V3. The V3 genotype displays female flowers and carries the Vvgai1 mutation at heterozygous status, allowing the obtention of both macro (MaV) and microvines (MiV) when crossed with a non dwarf genotype. Plants were acclimatized in 3 l pots and established in a greenhouse in semi-controlled climatic conditions. The progeny was phenotyped by assessing various parameters, including: phyllotaxis, leaf and shoot sizes, phytomer initiation rate, shoot lignification, level of tendrils and inflorescence initiation and distribution and sex ratio.

Results. The phenotyping confirmed that the dwarf trait of V. vinifera and the semi-discontinuous tendril production of V. labrusca could be introgressed into V. vinifera x labrusca background through crossbreeding. Vvgail1 mutation induced a strong miniaturisation of leaf and internodes size in half of the progeny as observed in crosses involving V. vinifera genotypes. Microlabruscana lines exhibited a significant reduction of shoot growth, due to the reduction of both internode length and phyllochron. The lignification process was two fold quicker in MaV than MiV. The shift from the alternate spiral (juvenil) to distichous (adult) phyllotaxis and the appearance of the first tendril occurred at lower node rank in MaV when compared to MiV. While MaV did not produce any reproductive organs during the first vegetative cycle, MiV displayed the first flowers around the internode 18, a few months after embryo rescue. As the sex ratio observed was 50% female and 50% hermaphroditic MiV, confirming V. labrusca progenitor to be heterozygous for the sex locus. These experiments provide a new set of microvine genotypes and morphology data for studying the response of V. labruscana to abiotic and biotic factors.