Conventional and molecular breeding systems in fig (Ficus carica L.)
Breeding program for fig cultivars for fresh and dry consumption was initiated 12 years ago in Israel targeting fruit quality and shelf life extension as the major objectives. Diverse genetic resources were used for the breeding efforts including 300 genotypes and hybrids of fig and other Ficus species. Yearly assessment of about 8000 hybrid seedlings revealed the best parents and cross combinations and selection of about 60 promising hybrids. As a result, 20 Israeli fig cultivars were achieved. One early and one late ripening cultivars are commensally in use, while the others are currently being evaluated in experimental orchards in Israel and worldwide. In another strategy, interspecific hybrids between F. carica × F. pumila, F. carica × F. palmata and F. carica × F. auriculata were obtained. Leaves, shoots and fruits of the hybrids were characterized. While some of the interspecific hybrid fruits showed fig characteristics, others exhibited new kind of fruit species. Fruit-tree breeding is a long-term process with many limitations, thus alternative methods should be used in order to accelerate the selection. Genome editing is a new powerful tool for precise gene manipulation. However, efficient and widely applied methods for targeted modification of fruit tree genomes are not yet available. Targeted mutagenesis using ZFN system was developed to induce mutagenesis in fig. This knockout gene system can be used to eliminate fig genes that negatively affect fruit quality, to confer susceptibility to pathogens or to divert metabolic flux away from valuable end-products. In order to isolate targeted genes controlling fruit quality and shelf life extension, differential expression of ethylene production and of potential ripening-regulators, ethylene-synthesis and signal-transduction genes were characterized in fig ripening on the tree and following pre-harvest 1-MCP application. Several ethylene-related-genes and cell wall modifying genes suitable for knockout were isolated. The advent of genomics to identify and isolated genes controlling traits and genome editing will allow us to speed up the breeding process. Implementation of conventional and molecular breeding strategies will provide valuable information and will allow to develop new fig cultivars for the use of fresh and dry fig industries.
Flaishman, M.A., Peer, R., Freiman, Z.E., Izhaki, Y. and Yablovitz, Z. 2017. Conventional and molecular breeding systems in fig (Ficus carica L.). Acta Hort. (ISHS) 1173:1-10
fig breeding, selection, fruit quality, fruit ripening, new cultivars, genome editing