S04 - Session O2 - Somaclonal variation and induced mutagenesis in several grapevine cultivars - -

Authors: Luca Capriotti *, Silvia Sabbadini, Cecilia Limera, Oriano Navacchi, Bruno Mezzetti

Biotic stresses, especially those caused by fungal, and oomycete causal agents represent serious agronomic problems throughout the grapevine crop cycle. In the course of evolution, several new species have emerged as a result of heritable changes that appeared in genetic pre-existing material throughout a process attributable to the terms of genetic mutations. This evolutionary process can be exploited in plant breeding programs for functional gene studies and to provide new opportunities in the constitution of a new cultivar. Intending to create a large genetic variability in grapevine cultivars ( Vitis vinifera ), large populations of plants were regenerated in vitro through shoot organogenesis and somatic embryogenesis. Meristematic bulk regeneration system has been applied in combination with chemical mutagens (EMS and Sodium azide), finding the doses and times of application that halved shoot regeneration (LD50) in Ancellotta, Chardonnay, Lambrusco Salamino, Merlot, Pinot Grigio cultivars, whereas whole flowers, anthers, and pistils of Ancellotta and Lambrusco Salamino cultivars have been used as starting explants for the in vitro regeneration of somatic embryos. From both regeneration morphogenic systems (organogenesis and somatic embryogenesis) incoming populations containing new putative mutagenized plants have been obtained. A preliminary selection for identifying mutants with increased tolerance/resistance to major grape diseases (powdery mildew and downy mildew) has been performed in the first year of plant development in the greenhouse. Among the plants that have undergone mutagenic treatments, some of the plants had a different phenotype compared to that of the reference variety, and in almost all the different populations, plants expressing reduced symptoms have been identified. All plants have been transferred to the field to be assessed at reduced severe disease infection to identify clones with stable increased tolerance/resistance to the diseases, while still maintaining the standard characteristics of the cultivar of origin. suggested corrections Biotic stress, caused mainly by fungal and oomycete pathogens, is a serious agronomic problem throughout the grape growing cycle. Just as mutations are the engine of evolution, this may also be the case in breeding programmes and for functional gene studies. Large populations of grape plants of the cultivars 'Ancellotta', 'Chardonnay', 'Lambrusco Salamino', 'Merlot' and 'Pinot Grigio' were regenerated in vitro by means of shoot organogenesis. Also, whole flowers, anthers and pistils of the cultivars 'Ancellotta' and 'Lambrusco Salamino' were used as starting plants for somatic embryo regeneration. Both were done in combination with chemical mutagens (EMS and sodium azide), of which doses and times of application were chosen that halved shoot regeneration (LD50). This resulted in mutated plants. A first selection to identify mutants with increased tolerance/resistance to major grape diseases (powdery mildew and downy mildew) was carried out in the first year of plant development in the greenhouse. Among the plants that underwent mutagenic treatments, some showed a different phenotype from the reference variety, and plants with reduced symptoms were identified in almost all different populations. All plants were transferred to the field to evaluate whether they combined a stable increased disease resistance with the maintenance of the standard characteristics of the cultivar.