Morphometric and molecular discrimination of the sugarcane aphid, Melanaphis sacchari, (Zehntner, 1897) and the sorghum aphid Melanaphis sorghi (Theobald, 1904)

Abstract

Melanaphis sacchari (Zehntner, 1897) and Melanaphis sorghi (Theobald, 1904) are major worldwide crop pests causing direct feeding damage on sorghum and transmitting viruses to sugarcane. It is common in the scientific literature to consider these two species as synonyms, referred to as the ‘sugarcane aphid’, although no formal study has validated this synonymy. In this study, based on the comparison of samples collected from their whole distribution area, we use both morphometric and molecular data to better characterize the discrimination between M. sacchari and M. sorghi. An unsupervised multivariate analysis of morphometric data clearly confirmed the separation of the two species. The best discriminating characters separating these species were length of the antenna processus terminalis relative to length of hind tibia, siphunculus or cauda. However, those criteria sometimes do not allow an unambiguous identification. Bayesian clustering based on microsatellite data delimited two clusters, which corresponded to the morphological species separation. The DNA sequencing of three nuclear and three mitochondrial regions revealed slight divergence between species. In particular, the COI barcode region proved to be uninformative for species separation because one haplotype is shared by both species. In contrast, one SNP located on the nuclear EF1-α gene was diagnostic for species separation. Based on morphological and molecular evidence, the invasive genotype damaging to sorghum in the US, Mexico and the Caribbean since 2013 is found to be M. sorghi.

Host plant resistance, foliar insecticide application and natural enemies play a role in the management of Melanaphis sorghi (Hemiptera: Aphididae) in grain sorghum

“…Melanaphis sorghi (Theobald) which was until recently known as Melanaphis sacchari Zehntner in previous literature ( Nibouche et al, 2021 ), is an invasive multivoltine piercing and sucking pest of sugarcane, Saccharum officinarum (L.), and sorghum, Sorghum bicolor (L.) in Asia, Africa, Oceania, Central, South and North America ( Sharma and Nwanze, 1997 ; Singh et al, 2004 ). Melanaphis sorgi was first detected on the Florida peninsula on the southeastern coast of the United States in 1977 and consequently only achieved a minor pest status in sugarcane production ( Denmark, 1988 ; Mondor et al, 2006 ).…”

Melanaphis sorghi (Hemiptera: Aphididae) Clonal Diversity in the United States and Brazil

“…In the U.S. since 2013, the MLL-F “superclone” ( M. sorghi ) has been found feeding on sorghum, sugarcane, Johnsongrass, giant miscanthus, and Columbus grass whereas aphids classified as MLL-D have been found feeding only on sugarcane [ 13 , 14 ]. Recently, MLL-C, and D aphids have been classified as M. sacchari , MLL-A and F aphids have been reclassified as M. sorghi, and MLL B and E aphids have not been assigned a species designation although SSR and EF1-α sequence data suggest both belongs to M. sorghi [ 15 ]. Although the Entomological Society of America has not adopted this change, the common names have also been altered and aphids that are classified as M. sacchari have a common name as sugarcane aphids and aphids classified as M. sorghi are now called sorghum aphids [ 15 ].…”

“…samples were collected from Peru on sugarcane and were also found to be MLL-C [ 13 ]. In a personal communication, three samples collected from Brazil in 2020 were reported to be M. sorghi but the host plant (sorghum or sugarcane) from which it was collected or the MLL it was assigned was not reported [ 15 ]. Diversity of Melanaphis spp.…”

Parasitoids and Predators of the Invasive Aphid Melanaphis sorghi Found in Sorghum and Non-Crop Vegetation of the Sorghum Agroecosystem

“…Supported by morphometric and molecular research, the aphid on sorghum and Johnson grass is considered a superclone, distinct from that found on sugarcane [ 2 ]. It was reclassified as Melanaphis sorghi (Theobald) (Hemiptera: Aphididae) with its likely origin in Africa or Asia [ 3 ]. Since 2013, M. sorghi outbreaks on sorghum have caused economic loss resulting from direct plant damage that reduces seed yield and from indirect seed yield loss due to aphid honeydew disrupting mechanical harvest [ 1 ].…”