Tropical fruit genomes and postharvest technologies
The number of fruits that have had their genomes sequenced stands at least at 12, with the Durian genome being published in 2017. The cost of sequencing has decreased dramatically in the last ten years though the quality of the genome assemblies in absence of linkage maps is a limitation. Following from the gene predictions made from these assembled genomes has been gene expression profiles (transcriptomes) from some fruit development stages and ripening. Network analysis can be done on the expression profiles to determine control points in regulations of various ripening processes. This focus has been on gene expression with more data suggesting that small RNAs also play a role in the regulation of these developmental processes. An underlying assumption is that fruit ripening processes are similar across species. However, fruit ripening seemly evolved independently in different plant groups opening up the possibility that the gene controls, plant growth regulator involvement and gene modules used to arrive at the fully ripe fruit might be different between different species. The difference in ripening patterns between the two broad categories of climacteric and non-climacteric fruit might reflect differences within these categories. We have known for many years that ethylene responses and fruit ripening varies with the stage of different fruit development and ethylene concentration. Hence, we cannot assume that because a specific gene or small RNA play a significant role in a particular species A that in species B the same gene or allele is as critical to the process. Expression studies then allow the correlation of some predicted genes expression pattern to biochemical or physiological functions. The most difficult step is to test and confirm that the gene function hypothesis about cause-and-effect does directly connect the gene to phenotype. Knowledge of the genes involved in various aspects of fruit development and ripening opens various possibilities for modification. For postharvest technology and its focus on offering the consumer high quality safe product that meets their needs and wants, via traditional breeding with marker selection to genetic modification. Examples of application would be new cultivars with more controlled flowering giving more concentrated harvesting thus reducing costs, different more convenient shapes and sizes giving less wastage, improved flavor and aroma, and added vitamin and mineral availability, improved storage life with less chilling susceptibility and reduced water loss, less discoloration following cutting and minimal processing and greater disease resistance. In some of these areas, success has already been achieved examples include pineapple flowering control and chilling related internal browning, and virus resistance in papaya.
Paull, R.E. and Chen, N.J. (2020). Tropical fruit genomes and postharvest technologies. Acta Hortic. 1299, 113-122
sequencing, fleshy fruit, gene expression, evolution, regulation