Construction of an almond linkage map in an Australian population Nonpareil × Lauranne

Background: Despite a high genetic similarity to peach, almonds (Prunus dulcis) have a fleshless fruit and edible kernel, produced as a crop for human consumption. While the release of peach genome v1.0 provides an excellent opportunity for almond genetic and genomic studies, well-assessed segregating populations and the respective saturated genetic linkage maps lay the foundation for such studies to be completed in almond. Results: Using an almond intraspecific cross between ‘Nonpareil’ and ‘Lauranne’ (N × L), we constructed a moderately saturated map with SSRs, SNPs, ISSRs and RAPDs. The N × L map covered 591.4 cM of the genome with 157 loci. The average marker distance of the map was 4.0 cM. The map displayed high synteny and colinearity with the Prunus T × E reference map in all eight linkage groups (G1-G8). The positions of 14 mapped gene-anchored SNPs corresponded approximately with the positions of homologous sequences in the peach genome v1.0. Analysis of Mendelian segregation ratios showed that 17.9% of markers had significantly skewed genotype ratios at the level of P < 0.05. Due to the large number of skewed markers in the linkage group 7, the potential existence of deleterious gene(s) was assessed in the group. Integrated maps produced by two different mapping methods using JoinMap® 3 were compared, and their high degree of similarity was evident despite the positional inconsistency of a few markers. Conclusions: We presented a moderately saturated Australian almond map, which is highly syntenic and collinear with the Prunus reference map and peach genome V1.0. Therefore, the well-assessed almond population reported here can be used to investigate the traits of interest under Australian growing conditions, and provides more information on the almond genome for the international community.Iraj Tavassolian, Gholmereza Rabiei, Davina Gregory, Mourad Mnejja, Michelle G Wirthensohn, Peter W Hunt, John P Gibson, Christopher M Ford, Margaret Sedgley, and Shu-Biao W

Cryopreservation of in vitro almond shoot tips by vitrification

Shoot tips of two almond scion cultivars, 'Ne Plus Ultra' and 'Nonpareil 15-1', and one almond/peach hybrid rootstock were successfully cryopreserved using a one-step vitrification technique. Three week old in vitro cultures were cold-hardened at 4°C on the multiplication medium (Murashige and Skoog for 'Ne Plus Ultra' and the hybrid rootstock; Almehdi and Parfitt for 'Nonpareil 15-1') for three weeks. Shoot tips, 2-2.5 mm long, were excised and precultured for 1 d at 4°C on the same basal medium, without plant growth regulators, supplemented with 0.7 M sucrose. After the preculture, the shoot tips were incubated in vitrification solution at 25°C for 45 min for the almond scion cultivars and 160 min for the hybrid rootstock, and then stored under liquid nitrogen (LN) for at least 3 d. After rapid thawing at 30°C, the shoot tips were washed with the appropriate liquid basal medium containing 1.0 M sucrose and then cultured on the same basal medium, solidified with agar, but excluding NH4NO3 or (NH4)2SO4. Shoot regeneration was usually observed within 2-3 weeks. Survival after LN, recorded as the percentage of shoot tips that produced at least one new shoot four weeks after thawing, was 87.5, 60.0 and 72.5% for 'Ne Plus Ultra', 'Nonpareil 15-1' and the hybrid rootstock respectively. The one-step vitrification method is a promising simple technique for cryopreserving almond scion and rootstock shoot tips from in vitro cultures.http://www.jhortscib.org/Vol75/75_2/17.ht

Update on long-term cryopreservation of almond germplasm

In 1999, we presented our work at XI GREMPA on conservation of almond (Prunus dulcis) germplasm by cryopreservation of almond shoot tips. “Nonpareil”, “Ne Plus Ultra” and an almond-peach hybrid rootstock, Prunus dulcis “Titan” x P. persica “Nemaguard” were successfully cryopreserved for 6 months using a one-step vitrification technique. That work has since been extended to test for plant viability and genetic integrity after storage under liquid nitrogen for up to 2 years. Mean survival of shoot tips was 80% for “Ne Plus Ultra”, 54% for “Nonpareil”, and 78% for the hybrid rootstock, and there were no significant differences in survival between 3 days and 2 years. Genetic stability was tested by comparing DNA from the original trees, with leaves regrown from tissue culture, and from leaves regrown from cryopreserved shoot tips. Some changes in the structure and methylation of the DNA were found that were probably related to the in vitro culture process. These changes may have affected agronomic performance. Fruit and kernel characteristics have been monitored and compared to authentic non-preserved cultivars.http://www.actahort.org/books/726/726_19.ht

Update on long-term cryopreservation of almond germplasm

In 1999, we presented our work at XI GREMPA on conservation of almond (Prunus dulcis) germplasm by cryopreservation of almond shoot tips. "Nonpareil", "Ne Plus Ultra" and an almond-peach hybrid rootstock, Prunus dulcis "Titan" x P. persica "Nemaguard" were successfully cryopreserved for 6 months using a one-step vitrification technique. That work has since been extended to test for plant viability and genetic integrity after storage under liquid nitrogen for up to 2 years. Mean survival of shoot tips was 80% for "Ne Plus Ultra", 54% for "Nonpareil", and 78% for the hybrid rootstock, and there were no significant differences in survival between 3 days and 2 years. Genetic stability was tested by comparing DNA from the original trees, with leaves regrown from tissue culture, and from leaves regrown from cryopreserved shoot tips. Some changes in the structure and methylation of the DNA were found that were probably related to the in vitro culture process. These changes may have affected agronomic performance. Fruit and kernel characteristics have been monitored and compared to authentic non-preserved cultivars

Determination of almond S-alleles using PCR primers designed from their introns

M.G. Wirthensohn, C. Channuntapitat, S.A. Ramesh, G. Collins, M. Sedgleyhttp://www.iamz.ciheam.org/en/pages/novedades_docs/OM%20A63%20-%20GREMPA%20.pd

Long-term cryopreservation of almond germplasm: an update

NUCIS Newsletter : information bulletin of the FAO Research Network on Nut

Identification of incompatibility genotypes in almond (Prunus dulcis Mill.) using specific primers based on the introns of the S-alleles

Identification of the incompatibility genotypes of almond cultivars is important in breeding programmes for designing crosses and for selecting progeny. This paper describes a novel molecular technique for the identification of S-alleles in almond based on the use of PCR primers designed from the sequences of the introns without the need for restriction enzyme digestion. Nine specific pairs of primers have been designed for the S1, S2, S5, S7, S8, S9, S10 (putative), S23 and Sf alleles, and these confirmed the S-allele specificities for 22 of the 23 accessions for which published information is available. This technique provides a precise method for identifying S-alleles from the genomic DNAs of almond cultivars, and will be useful for confirming the segregation of alleles in breeding progeny.C. Channuntapipat, M. Wirthensohn, S.A. Ramesh, I. Batlle, P. Arús, M. Sedgley, G. Collin