The pest is yet to come
The bluegreen aphid, or blue alfalfa aphid (Acyrthosiphon kondoi), is a species of aphid found in many regions of the world, including all states of Australia. The aphid are most noticeable in the springtime, but they can also be active during winter and autumn. It is mainly a pest of plants in the family Leguminosae, affecting crops such as pea, lupin, medics, lentil and cowpea. Heavy infestation of aphids can cause significant plant damage through their feeding on upper leaves, stems and terminal buds of host plants. This subsequently causes the deformation of leaves and removes critical nutrients from the plant, making it become yellow and wilt as a result.
Bluegreen aphids are very similar in appearance to the closely related pea aphids (Acyrthosiphon pisum) but can be distinguished from other aphids by their long legs, antennae and cornicles and are often found to be more grey-green to blue-green in colour.
Aphids can reproduce both asexually and sexually, however in Australia, the sexual phase is often lost. Bluegreen aphid reproduces asexually whereby females give birth to live young, which are often referred to as clones. Once aphids gain wings, they fly into crops from broad leaf weeds or other crop legumes and medics, and colonies of aphids start to build up.
A study published in 2012 by Humphries et al., found a new biotype of bluegreen aphid in south-eastern Australia (Acyrthosiphon kondoi Shinji) that was able to overcome resistance in a broad range of pasture legumes, causing severe damage and mortality in seedlings in previously resistant pasture legume cultivars. This biotype hasn’t been observed since. The CSIRO estimates that the annual economic impact of invertebrate pests, including bluegreen aphids, ranges between $500 million for loss of production in Australia and upwards of $2 billion dollars in New Zealand.
Here we report the first chromosome-length reference genome assembly for bluegreen aphids, which was assembled using a DNA-Seq data from a single aphid biotype (an asexual clone) of A. kondoi Shinji, collected from narrow-leafed lupin (Lupinus angustifolius L.) near Kelleberrin, Western Australia. Draft genome assembly from a combination of Illumina short reads, Eurofins Long Distance Jumping libraries and PacBio long sequence reads was led by Prof Karam Singh, CSIRO & Dr Lars Kamphuis, Curtin University. Subsequently, in situ Hi-C data was generated by DNA Zoo Australia which was used to generate a chromosome length reference genome for bluegreen aphid.
See the 5 chromosomes of the new genome assembly in the interactive contact map below:
This data provides a much-needed genetic resource to help combat bluegreen aphid infestations, supporting functional and molecular research into the species and efforts toward critical legume crop survival.