''Rhopalosiphum maidis'', common names corn leaf aphid and corn aphid, is an

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

, and a pest of

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

and other

crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydroponics ...

. It has a nearly worldwide distribution and is typically found in agricultural fields, grasslands, and forest-grassland zones. Among aphids that feed on maize, it is the most commonly encountered and most economically damaging, particularly in tropical and warmer temperate areas. In addition to maize, ''R. maidis'' damages

rice Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...

sorghum ''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many othe ...

, and other cultivated and wild

monocots Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of t ...

Description

The bodies of wingless

parthenogenetic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

females are green or whitish-green. The head, antennae, legs,

cornicle The cornicle (or siphuncule) is one of a pair of small upright backward-pointing tubes found on the dorsal side of the 5th or 6th abdominal segments of aphids. They are sometimes mistaken for cerci. They are no more than pores in some species. ...

s, tail, and transverse bands on the abdomen are black-brown. The body has sparse short hairs. The length of the antennae is less than half the length of the body.

Cornicle The cornicle (or siphuncule) is one of a pair of small upright backward-pointing tubes found on the dorsal side of the 5th or 6th abdominal segments of aphids. They are sometimes mistaken for cerci. They are no more than pores in some species. ...

s are not longer than the finger-like tail. In winged females, the head and thoracic section are black-brown and the

s are shorter than in the wingless females. Most ''R. maidis'' populations are anholocyclic, ''i.e.'' reproduction occurs entirely by

parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

. However, sexual reproduction has been reported in

Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

and

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...

, with ''

Prunus ''Prunus'' is a genus of trees and shrubs, which includes (among many others) the fruits plums, cherries, peaches, nectarines, apricots, and almonds. Native to the North American temperate regions, the neotropics of South America, and the p ...

'' ssp. as the primary host. In populations in

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

and

Kenya ) , national_anthem = "Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi , ...

, males but not sexually reproducing females have been found.

Agricultural interactions

In winter, winged

females and larvae survive on wild-growing

, from which they move to agricultural fields in the spring. Fields populate gradually, starting from the edges to the center. Reproduction is rapid, with up to twelve generations per year. The aphid population reaches a maximum late in the summer. Dense populations of ''R. maidis'' on maize (''

Zea mays Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

'') can cause direct damage through the removal of photosynthates. Large amounts of honeydew that is deposited by aphid feeding on maize tassels can prevent pollen shed and decrease yield by up to 90%. Several damaging maize viruses, including ''Maize yellow dwarf virus'', ''

Barley yellow dwarf virus Barley yellow dwarf (BYD) is a plant disease caused by the ''barley yellow dwarf virus'' (BYDV), and is the most widely distributed viral disease of cereals. It affects the economically important crop species barley, oats, wheat, maize, tritical ...

'', ''

Sugarcane mosaic virus ''Sugarcane mosaic virus'' (SCMV) is a plant pathogenic virus of the family ''Potyviridae''. The virus was first noticed in Puerto Rico in 1916 and spread rapidly throughout the southern United States in the early 1920s. SCMV is of great concern ...

'', and ''

Cucumber mosaic virus ''Cucumber mosaic virus'' (CMV) is a plant pathogenic virus in the family ''Bromoviridae''. This virus has a worldwide distribution and a very wide host range, having the reputation of the widest host range of any known plant virus. It can be tra ...

'', are transmitted by ''R. maidis''. In addition to feeding on maize, ''R. maidis'' infests a variety of cultivated grasses, including

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...

oat The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and pseudocereals). While oats are suitable for human con ...

rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to both wheat (''Triticum'') and barley (genus ''Hordeum''). Rye grain is u ...

sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with ...

, and

. Barley is a particularly suitable host for ''R. maidis'', though there also is considerable within-species variation in resistance.

Chemical ecology

Under enhanced CO₂ conditions, the growth rate and reproduction of ''R. maidis'' on barley were significantly decreased. Volatiles of barley grown under enhanced CO₂ were also less attractive than those from plants grown under atmospheric CO₂. Temperature and crowding have differential effects on wing formation in

parthenogenetically Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

reproducing ''R. maidis'' on barley. Maize inbred lines vary in their resistance to ''R. maidis'' and other insect pests. Relative to other maize-feeding aphids (''

Rhopalosiphum padi Bird cherry-oat aphid (''Rhopalosiphum padi'') is an aphid in the superfamily Aphidoidea in the order Hemiptera. It is a true bug and sucks sap from plants. It is considered a major pest in cereal crops, especially in temperate regions, as well ...

'', ''

Schizaphis graminum The greenbug, or wheat aphid (''Schizaphis graminum''), is an aphid in the superfamily Aphidoidea in the order Hemiptera. It is a true bug and feeds on the leaves of Gramineae (grass) family members. Its original distribution is the Palaearct ...

'', ''

Sitobion avenae The English grain aphid (''Sitobion avenae'') is an aphid in the superfamily Aphidoidea in the order Hemiptera. It is a true bug and sucks sap from plants. It lives on grasses, sedge and rushes and can be a significant pest of cereals. This s ...

'', and ''

Metopolophium dirhodum ''Metopolophium dirhodum'', the rose-grain aphid or rose-grass aphid, is a species of sap-sucking insect in the family Aphididae found worldwide. Its primary host is rose, and its secondary host is a grass, including cereals such as wheat, barley ...

''), ''R. maidis'' exhibits a greater tolerance of benzoxazinoids, the most abundant class of maize defensive metabolites. Nevertheless, lineage-specific variation in maize resistance to ''R. maidis'' was associated with differences in the abundance of 2,4-dihydroxy-7-methoxy-l,4-benzoxazin-3-one glucoside (

DIMBOA DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) is a naturally occurring hydroxamic acid, a benzoxazinoid. DIMBOA is a powerful antibiotic present in maize, wheat, rye, and related grasses, DIMBOA was first identified in maize in 1962 as ...

-Glc), an abundant maize benzoxazinoid. Both increased DIMBOA-Glc synthesis and reduced conversion to 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA -Glc) can enhance maize seedling resistance to ''R. maidis''. Maize mutations that knock out benzoxazinoid biosynthesis increase ''R. maidis'' reproduction. In some instances, caterpillar feeding can enhance the conversion of DIMBOA-Glc to HDMBOA-Glc, thereby increasing maize resistance against ''R. maidis''. The defense signaling molecules 2-oxo-phytodienoic acid (OPDA) and ethylene are involved in regulating maize resistance to ''R. maidis''. In olfactometer experiments, ''R. maidis'' were repelled by volatiles from damaged maize plants. One of the major volatiles emitted by damaged maize is the terpene (''E'')‐β‐farnesene, which also functions as an alarm pheromone for

aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

s and thus may be repellent. Mutations of a maize terpene synthase, ''TPS2'', made the plants more attractive for ''R. maidis.''

Genome sequencing

There is within-species variation in the chromosome numbers of ''R. maidis'', with karyotypes of 2n = 8, 9, and 10 having been reported. Whereas ''R. maidis'' strains on maize tend to have 2n = 8, those on barley generally have 2n = 10. To better enable research related to ecological interactions, virus transmission, pesticide resistance, and other aspects of the species biology, a high-quality genome was assembled from a

''R. maidis'' lineage collected from maize. CC-BY_icon

Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License. The assembled genome is 321 Mb in size and features a total of 17,629 protein-coding genes. Assembly of the genome was facilitated by the extremely low level of heterozygosity in the sequenced ''R. maidis'' isolate.

Hosts

Barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...

Millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets al ...

s *

Rice Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...

* Several

Gramineae Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns and ...

species *

Sorghum ''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many othe ...

s *

Sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with ...

Wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

References

{{Taxonbar, from=Q3703370 Aphidini Agricultural pest insects Insects described in 1856 Taxa named by Asa Fitch Hemiptera of Asia Insect pests of millets