Anther Culture and Chromosome Doubling in Mediterranean Japonica Rice.

Anther culture is the most used technique to produce doubled haploid lines in rice. This technique is well developed in a wide range of indica rice genotypes. However, in japonica type, and more specifically, the Mediterranean japonica, the protocols are yet to be optimized. Japonica and indica have different androgenic response, as well as different induction and regeneration rates, albinism ratios and chromosome doubling competence. The step-by-step anther culture protocol presented in this chapter allows to regenerate doubled haploid rice plantlets from anther microspores in 8 months. We also include an in vitro chromosome doubling protocol to induce doubled haploids from haploid plantlets by immersion in a colchicine solution. This chromosome doubling protocol complements the anther culture by taking advantage of the regenerated haploid plantlets.

Colchicine and osmotic stress for improving anther culture efficiency on long grain temperate and tropical japonica rice genotypes.

Anther culture is a fast tool to obtain double haploid plant lines for breeding purposes. In rice, this procedure is commonly performed in two steps: i) induction of calli from anthers and ii) regeneration of plantlets from calli. It has been stated that genotype highly influences the anther culture efficiency, so the media used in each step should be optimized for each variety. In this study, we tested different media modifications of an efficient protocol optimized for a medium sized grain temperate japonica NRVC980385, used as a control, in a long grain temperate japonica rice variety (NRVC20120346), and two long grain tropical japonica varieties (303012 and 303013). We found that the addition of 150 mg l-1 colchicine to the induction medium worked best for all genotypes except for NRVC20120346, whose best induction was obtained with the colchicine-free medium. Referring to regeneration, increased gelling agent in the medium provided the best rates in NRVC980385, improving our former NRVC980385-optimized anther culture protocol. Sorbitol fortified regeneration medium worked the best in the case of the long grain varieties. The presence of colchicine in the induction medium was also related to a higher obtention of double haploid plantlets. This study highlights that genotype is a key factor in the performance of rice anther culture. It has set a first anther culture study on long grain japonica varieties and optimizes the anther culture protocol for temperate japonica medium grain NRVC980385 with the use of colchicine and other additives that increase osmotic stress.