RNA-Seq analysis of Orobanche resistance in tobacco: development of molecular markers for breeding recessive resistance from Wika tobacco variety
Orobanche spp. (broomrape) is an obligate root parasite that can attack a wide spectrum of plants, including tobacco. It is responsible for economic losses in Europe since 2002 and its incidence in many tobacco growing countries is increasing. Preventive and curative methods exist, including the use of agrochemicals, however dissemination is important due to the high multiplication rate of the parasite and very small seeds.
The tobacco variety Wika shows lower or later germination of broomrape seeds. This seems to be conditioned by a single recessive gene. Artificial testing in Petri dishes was developed to evaluate the ability of tobacco plantlets to stimulate seed germination. Different lines derived from Wika, with susceptible control lines, were tested and studied by RNA-Seq. Candidate markers including SNPs or genes differentially expressed between susceptible and resistant lines were identified. A F2 population segregating for Wika recessive tolerance was then used for validation and mapping. All the candidates mapped on chromosome 14 of the tobacco genetic map. The Nicotiana collection of varieties from Imperial Tobacco was also tested with these markers, highlighting or confirming other potential donors.
KASP™ genotyping or markers for conventional gel electrophoresis are now available to pilot the transfer of Wika recessive tolerance into elite lines.
RNA-Seq technology combined with good experimental testing has proven again its high efficiency to identify useful markers for tobacco breeding.