A telomere-to-telomere gap-free reference genome assembly of avocado provides useful resources for identifying genes related to fatty acid biosynthesis and disease resistance

Avocado (Persea americanaMill.) is an economically valuable plant because of the high fatty acid content and unique flavor of its fruits. Its fatty acid content, especially the relatively high unsaturated fatty acid content, provides significant health benefits. We herein present a telomere-to-telomere gapless genome assembly (841.6 Mb) of West Indian avocado. The genome contains 40 629 predicted protein-coding genes. Repeat sequences account for 57.9% of the genome. Notably, all telomeres, centromeres, and a nucleolar organizing region are included in this genome. Fragments from these three regions were observed via fluorescence in situhybridization. We identified 376 potential disease resistance-related nucleotide-binding leucine-rich repeat genes. These genes, which are typically clustered on chromosomes, may be derived from gene duplication events. Five NLRgenes (Pa11g0262, Pa02g4855, Pa07g3139, Pa07g0383, and Pa02g3196) were highly expressed in leaves, stems, and fruits, indicating they may be involved in avocado disease responses in multiple tissues. We also identified 128 genes associated with fatty acid biosynthesis and analyzed their expression patterns in leaves, stems, and fruits. Pa02g0113, which encodes one of 11 stearoyl-acyl carrier protein desaturases mediating C18 unsaturated fatty acid synthesis, was more highly expressed in the leaves than in the stems and fruits. These findings provide valuable insights that enhance our understanding of fatty acid biosynthesis in avocado.