Composite plants for a composite plant: an efficient protocol for root studies in the sunflower using composite plants approach.

Sunflower (Helianthus annuus L.) is an important oilseed crop in the world and the sunflower oil is prized for its exceptional quality and flavor. The recent availability of the sunflower genome can allow genome-wide characterization of genes and gene families. With plant transformation usually being the rate-limiting step for gene functional studies of sunflower, composite plants can alleviate this bottleneck. Composite plants, produced using Agrobacterium rhizogenes, are plants with transgenic roots and wild type shoots. Composite plants offer benefits over creating fully transgenic plants, namely time and cost. Here we outlined the critical steps and parameters for a protocol for the production of sunflower composite plants. We tested more than a dozen genotypes and three constitutive promoters to validate the utility and efficiency of this protocol. Moreover, functional gene characterization by overexpression and RNAi silencing of a root-related transcription factor, HaLBD16, further emphasize the value of the system in the sunflower studies. With the protocol developed here an experiment can be carried efficiently and in only 2 months. This procedure adds to the arsenal of approaches for the functional genetics/genomics in sunflower for characterization candidate genes involved in root development and stress adaptation. Key message: Composite plants technique described here is fast and efficient approach for roots functional studies in sunflower. [ABSTRACT FROM AUTHOR]