Invasion of sorghum in the Americas by a new sugarcane aphid (Melanaphis sacchari) superclone

Abstract

In the United States (US), the sugarcane aphid (SCA) Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae) was introduced in the 1970s, however at that time it was only considered a pest of sugarcane. In 2013, a massive outbreak of M. sacchari occured on sorghum, resulting in significant economic damage to sorghum grown in North America including the US, Mexico, and Puerto Rico. The aim of the present study was to determine if the SCA pest emergence in American sorghum resulted from the introduction of new genotypes. To this end we used microsatellite markers and COI sequencing to compare the genetic diversity of SCA populations collected in the Americas after the 2013 SCA outbreak on sorghum (during 2013–2017) to older samples collected before the pest outbreak (during 2007–2009). Our results show that the SCA outbreak in the Americas and the Caribbean observed since 2013 belong to populations exhibiting low genetic diversity and consisting of a dominant clonal lineage, MLL-F, which colonizes Sorghum spp. and sugarcane. The comparison of MLL-F specimens collected post-2013 with specimens collected in Louisiana in 2007 revealed that both populations are genetically distinct, according to COI sequencing and microsatellite data analyses. Our result suggest that MLL-F is a new invasive genotype introduced into the Americas that has spread rapidly across sorghum growing regions in the US, Mexico, Honduras and the Caribbean. The origin of this introduction is either Africa or Asia, with Asia being the most probable source.

Influence of Sorghum Cultivar, Phenological Stage, and Fertilization on Development and Reproduction of Melanaphis sacchari (Hemiptera: Aphididae)

“…Aphid population growth was numerically greater in our cultivar study (DKS 38-88) than our phenology study (SP 7868), suggesting these cultivars differ in their levels of susceptibility. Continued investigation of resistant germplasm is required, because genetic variation exists among US populations of M. sacchari that could lead to the development of new biotypes able to overcome cultivar resistance (Medina et al 2017;Nibouche et al 2018).…”

Lack of transmission of Sugarcane yellow leaf virus in Florida from Columbus grass and sugarcane to sugarcane with aphids or mites

“…These observations could explain the high incidence of SCYLV in commercial fields and germplasm collections in Florida [3]. Additionally, three genetically distinct haplotypes of the sugarcane aphid were recently reported in the USA: Haplotype H1 that mainly infests Sorghum species but also found on sugarcane, haplotype H3 that mainly colonizes sugarcane but also found on sorghum and Johnsongrass (S. halepense), and haplotype H6 that infests Johnsongrass and sugarcane [25].…”

“…Not more than two aphids were collected from the same plant and DNA was extracted from each single aphid using the Qiagen DNeasy Blood & Tissue kit according to the manufacturer's protocol. The Cytochrome C oxidase subunit I (COI) gene used for genotyping was amplified by PCR as described by Nibouche et al [25]. Amplification products (658 bp) were purified using the QIAquick Purification kit and sent to Eton Bioscience (North Carolina Branch) for bidirectional sequencing.…”

“…Furthermore, in 2013, massive outbreaks of M. sacchari occurred on sorghum in the USA [43]. These outbreaks were attributed to the invasion of sorghum in the Americas by a new superclone of this aphid [25]. This dominant superclone was identified as a specific clonal lineage (MLL-F) belonging to haplotype H1 of M. sacchari [25].…”

“…These outbreaks were attributed to the invasion of sorghum in the Americas by a new superclone of this aphid [25]. This dominant superclone was identified as a specific clonal lineage (MLL-F) belonging to haplotype H1 of M. sacchari [25]. Invasion of sorghum by a new clone of the sugarcane…”