Accelerate the breeding of Armillaria resistant rootstocks for peach and cherry through the use of DNA information.
The most economical and durable solution to combat Armillaria is the use of resistant rootstocks. A recently funded project has developed genome sequences and transcriptomic data for sources of ARR resistance including P. maackii, P. cerasifera and P. munsoniana (wild plums), and the peach x plum hybrid rootstock MP-29 (Wells Fargo, http://www.eurekalert.org/pub_releases/2015-12/cu-cr120315.php). These data have yielded a short list of candidate genes and biochemical pathways that may contribute to resistance.
Newly detected resistant sources were used in breeding with standard peach and cherry rootstocks. Hybrid seeds were included in the resistance pipeline screening.
We have identified genomic regions controlling peach tree short life (PTSL) tolerance in resistant rootstock Guardian®. Comaprion of genomic regions controlling PTSL response between Lovell (PTSL susceptible) and Guardian® (PTSL tolerant) shows exponential increase of number genes involved in plant tolerance to diseases in tolerant rootstock.
The DNA test for pre-screening hybrid seedlings for PTSL tolerance are in the validation stage.
Transcriptome analyses in ‘MP-29’ (ARR resistant) and ‘GF305’ (ARR susceptible) after co-cultivation with Armillaria spp, have detected differentially expressed genes and revealed key genes NOT encoded in peach, that appear to be critical to resistance.
One of the detected genes present in MP-29 but not GF305 was Oxalate oxidase (+chitinase). This gene naturally exists in wheat, banana, and other plant species. It neutralizes/degrades oxalic acid that is required by fungus for wood infection. Fungus is allowed to live as a saprophyte, reducing chance for evolution of resistance.
