Allele mining of eukaryotic translation initiation factor genes in Prunus for the identification of new sources of resistance to sharka.

Members of the eukaryotic translation initiation complex are co-opted in viral infection, leading to susceptibility in many crop species, including stone fruit trees (Prunus spp.). Therefore, modification of one of those eukaryotic translation initiation factors or changes in their gene expression may result in resistance. We searched the crop and wild Prunus germplasm from the Armeniaca and Amygdalus taxonomic sections for allelic variants in the eIF4E and eIFiso4E genes, to identify alleles potentially linked to resistance to Plum pox virus (PPV). Over one thousand stone fruit accessions (1397) were screened for variation in eIF4E and eIFiso4E transcript sequences which are in single copy within the diploid Prunus genome. We identified new alleles for both genes differing from haplotypes associated with PPV susceptible accessions. Overall, analyses showed that eIFiso4E is genetically more constrained since it displayed less polymorphism than eIF4E. We also demonstrated more variations at both loci in the related wild species than in crop species. As the eIFiso4E translation initiation factor was identified as indispensable for PPV infection, a selection of ten different eIFiso4E haplotypes along 13 accessions were tested by infection with PPV and eight of them displayed a range of reduced susceptibility to resistance, indicating new potential sources of resistance to sharka.

Cryopreservation of native Kazakhstan apricot (Prunus armeniaca l) seeds and embryonic axes.

BACKGROUND: Preserving the genetic diversity of Central Asia includes conserving wild apricots found in the foothills of several mountain ranges. These include primitive and genetically diverse populations with important characteristics for crop improvement. Apricot seeds have a short storage life, so cryopreservation of the seeds of wild populations is important for conserving the genetic diversity. OBJECTIVE: This study was to determine a suitable protocol for long-term storage. METHODS: This study tested a range of protocols using embryos and embryonic axes for storage of an important population of wild apricots and to determine if seed size and the distribution of moisture in the seed play a role in successful cryopreservation. RESULTS: Germination of scarified whole seed from trees in the Jungar population of Prunus armeniaca varied from 63 to 90 percent after 1 h in liquid nitrogen (LN) and was generally better at 7 % moisture content (MC) than at the original 14 percent MC. Embryos (4 percent MC) from stratified seed had only 33 % germination after LN exposure. Isolated embryonic axes from non-stratified seed germinated at 86 to 100 % following drying to 4 % or 7 % MC. Examination of three seed sizes determined that the MC of whole seed, embryos and isolated axes varied with the seed size and shape. MC of whole seeds and embryos decreased as size decreased, however, the axis MC did not. MC of medium-size seed was more evenly distributed between the axis and endosperm than in the larger or smaller samples. Cryopreservation of axes from medium-sized seed was good at any moisture content and a 1-h drying time was significantly better than 90 min. for axes of all seed sizes. Cryopreservation of axes using vitrification protocols initially designed for shoot tips produced germination similar to or lower than seed and axis drying techniques. CONCLUSION: We recommend storing apricot germplasm as unstratified seed dried to 7 % MC or as isolated embryonic axes.