Developing fruits of a banana. Image credit: Josch13.
Banana cultivars are among the most consumed fruits worldwide: over 100 million tons of banana are produced yearly.
Besides, banana cultivars are also the fifth most produced food crop in the least-developed countries; as a result, they play an important role in maintaining food security in these regions.
The demand for cultivated bananas continues to grow; however, their production is greatly affected by a complex of biotic and abiotic stresses.
“In banana, the most efficient ploidy level for agronomic performance is triploid, which has given rise to more vigorous plants, higher sterility, and larger fruits without seeds,” said co-senior author Dr. Xue-Jun Ge from the South China Botanical Garden and colleagues.
“Cavendish-type bananas, which have a monospecific M. acuminata origin, account for around half of the global banana production.”
“Nearly all of the global banana export trade relies on the clones derived from a unique triploid cultivar of Cavendish banana, leading to a narrow genetic basis in this type of banana.”
In the new study, the authors developed a telomere-to-telomere reference genome of a banana cultivar ‘Baxijiao’ consisting of three haploid assemblies.
“This reference genome consists of three haploid assemblies, the sizes of which were estimated to be 477.16 Mb, 477.18 Mb, and 469.57 Mb, respectively,” they said.
“Genome quality assessments confirmed the contiguity (LAI: 19.84, 20.65 and 20.22) and completeness (BUSCOs: 97.40%, 97.80% and 93.80%) of the genome.”
“Within the three haploid assemblies, 19, 17 and 17 telomeres were identified, respectively.”
“In terms of repetitive regions, 256.48 Mb (53.76%), 258.29 Mb (54.14%), and 258.84 Mb (55.13%) were identified.”
“In addition, a total of 37,185, 37,241, and 37,178 high-confidence protein-coding genes were predicted from each assembly.”
“Although with monospecific origins, the three haploid assemblies showed great differences with low levels of sequence collinearity.”
“Several large reciprocal translocations were identified among chromosomes 1, 4 and 7.”
The researchers detected an expansion of gene families that might affect fruit quality and aroma, such as those belonging to sucrose/disaccharide/oligosaccharide catabolic processes, sucrose metabolic process, starch metabolic process, and aromatic compound biosynthetic process.
They also observed an expansion of gene families related to anther and pollen development, which could be associated with parthenocarpy and sterility of the Cavendish cultivar.
“This telomere-to-telomere and haplotype-resolved reference genome will thus be a valuable genetic resource for biological studies, molecular breeding and genetic improvement of banana,” the scientists concluded.
Source: Sci News