A Chromosome-level Reference Genome of African Oil Palm Provides Insights into Its Divergence and Stress Adaptation

The palm family(Arecaceae),consisting of2600 species,is the third most economically important family of plants.The African oil palm(Elaeis guineensis)is one of the most important palms.However,the genome sequences of palms that are currently available are still limited and fragmented.Here,we report a high-quality chromosome-level reference genome of an oil palm,Dura,assembled by integrating long reads with150 genome coverage.The assembled genome was 1.7 Gb in size,covering 94.5%of the estimated genome,of which 91.6%was assigned into 16 pseudochromosomes and 73.7%was repetitive sequences.Relying on the conserved synteny with oil palm,the existing draft genome sequences of both date palm and coconut were further assembled into chromosomal level.Transposon burst,particularly long terminal repeat retrotransposons,following the last whole-genome duplication,likely explains the genome size variation across palms.Sequence analysis of the VIRESCENS gene in palms suggests that DNA variations in this gene are related to fruit colors.Recent duplications of highly tandemly repeated pathogenesis-related proteins from the same tandem arrays play an important role in defense responses to Ganoderma.Whole-genome resequencing of both ancestral African and introduced oil palms in Southeast Asia reveals that genes under putative selection are notably associated with stress responses,suggesting adaptation to stresses in the new habitat.The genomic resources and insights gained in this study could be exploited for accelerating genetic improvement and understanding the evolution of palms.

Insects as a feed ingredient for fish culture: Status and trends

Fish culture plays an important role in supplying high-quality proteins and omega-3(n-3)long-chain polyunsaturated fatty acids.Aquaculture has been the fastest growing sector in agriculture.Fishmeal is an important component of commercial fish feeds,but ensuring a sustainable supply of fishmeal is in question.A good source of proteins in aquafeeds is insects.For the past 20 years,investigations have been carried out on insect meals as alternative sources for fishmeal.Thus far,the results on replacing fishmeal in feeding aquaculture species have been promising.However,some challenging issues including costs and scaling up of insect production remains.In this review,we aim to summarize the status of applying meals of eight insect species in formulated aquafeeds.We also discussed issues in replacing fishmeal in fish feeds with insect meals and listed some future research directions to make insect meals an important source of proteins for green,profitable and sustainable(GPS)aquaculture.It is certain that in the near future,large-scale insect farming and processing to produce insect meals as an ingredient of fish feeds will have positive impact on the sustainability and profitability of aquaculture.