The Australian almond breeding programme

The Australian almond breeding programme commenced in 1997 and aims to produce superior scion and rootstock cultivars adapted to local conditions. A broad approach is employed, with the project divided into the four major categories of hybridisation, molecular breeding, tissue culture and pathology. Classical hybridisation involving controlled hand pollination is aimed at utilising the best of the available gene pool. Parents include the Californian cultivars that form the backbone of the Australian industry, local Australian selections, and European cultivars with useful characters. Seedlings are evaluated in the field for characters of interest, including self-fertility, kernel size and tree form. Molecular breeding includes research into genetic fingerprinting, genome mapping and transformation. We aim to develop markers for important characters, so that selection can proceed on young seedlings prior to flowering and fruiting, with savings in time and field space. A novel technique for identifying S-alleles has been developed, and a new S-allele has been identified in some Australian selections which we have called Sx pending positive identification. Tissue culture includes a number of important areas. Cryopreservation research is important for low temperature genebank storage, micropropagation for multiplication of new rootstocks, and transformation for introducing single characters into otherwise satisfactory varieties. Pathology work includes both viral and fungal pathogens. Material is screened for Prunus necrotic ringspot (PNRSV) and prune dwarf (PDV) viruses, using grafting, ELISA and PCR methods. In addition, work has commenced into the anthracnose disease of almonds, which is caused by the pathogen Colletotrichum acutatum, and causes major losses in the Australian industry. Many important milestones have been achieved. Virus tested breeding progeny have been planted for first evaluation in 2000. PNRSV has been determined to be the more significant virus in almonds so far. PDV has not been detected using ELISA, but initial work with a DNA-based technique has produced a positive response. Micropropagation methods for both rootstocks and scions have been developed, and rootstocks have been generated for use in test blocks to assess the performance of imported material. Shoot tips have been successfully recovered after cryopreservation in liquid nitrogen and grown into potted plants, and regeneration methods for transformation have been developed. Genetic fingerprints are available for the almond cultivars grown in Australia, and development of molecular markers for the hard shell character is underway. The work is conducted in collaboration with overseas research groups, to take advantage of the long experience of these programs, and to contribute to the international effort in Prunus improvement.