Occurrence and mechanistic basis of diplogamete formation in apple (Malus x domestica Borkh.)

ISHS Secretariat
Occurrence and mechanistic basis of diplogamete formation in apple (Malus x domestica Borkh.)

Han Palmers is a PhD student in the laboratory for Plant Genetics and Crop Improvement (PGCI) at the Catholic University of Leuven (KU Leuven), Belgium. His research concerns the occurrence and genetic control of meiotic plasticity in apple, and its application to apple breeding. Meiosis, the reductional division, is a key process in plant reproduction that usually serves to halve the somatic chromosome number to generate haploid gametes. In several plant species, meiotic aberrations can result in the formation of diploid (2n) gametes. These 2n gametes form a direct route to polyploid progeny, and are therefore thought to play an important role in plant genome evolution. Usually, 2n gamete formation is under genetic control, though it can be strongly influenced by environmental stimuli, such as temperature stress. In apple, the existence of triploid cultivars in the diversity collection suggests that diploid gametes were involved. However, little is known about the rate and mechanistic basis of 2n gamete formation in apple. This limits the use of meiotic plasticity as a tool in apple breeding. To investigate the occurrence and genetic variation in 2n gamete production in apple, Han is surveying the apple reference collection (REFPOP), a genetically diverse collection of 269 accessions used for apple breeding replicated in six countries throughout Europe. Natural variation in diplogamete formation is quantified via the characterization of pollen size, male meiotic stability, and seed ploidy. Accessions showing a significant production of 2n gametes will be subjected to extensive cytological analysis to elucidate the underlying cellular mechanism. Han will integrate the natural variation in diplogamete formation in genome-wide association studies (GWAS). His goals will be to identify and characterize genetic elements that contribute to diplogamete formation. The knowledge gained from this research will improve the understanding of meiotic plasticity in apple and will provide tools to increase the production of diploid gametes, thereby facilitating apple breeding.

Han Palmers won the ISHS Young Minds Award for the best poster presentation at the I International Symposium on Reproductive Biology of Fruit Tree Species, which was held virtually in France in November 2021.

Han Palmers, Laboratory for Plant Genetics and Crop Improvement, KU Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium, e-mail: han.palmers@kuleuven.be

The article is available in Chronica Horticulturae

diplogamete formation
Young Minds Award Winners