The response of resistant kiwifruit (Actinidia chinensis) to armoured scale insect (Diaspididae) feeding

Abstract

The responses of five experimental genotypes and one commercial variety of kiwifruit (Actinidia chinensis) to attack by two polyphagous, congeneric armoured scale insect pests (Hemiberlesia rapax and H. lataniae) are described. H. lataniae feeding elicits a response in the bark and fruit of all but one of the experimental genotypes, leading to the development of wound periderm over a 4-5 week period, and death of the insect. The response, which differs slightly between tissue types and genotypes, consists of wound periderm formation in a bowl shape beneath and around the insect, preventing its stylet from reaching normal unmodified parenchyma tissue. Wound periderm cell walls become suberised and cells beneath the insect become filled with phenolic compounds. In some cases, cells beneath the insect become hypertrophic or undergo lysis, exhibiting characteristics of a hypersensitive-like response. The remaining genotype showed no physical change in tissue structure in response to H. lataniae feeding, and the insects survived but were substantially reduced in size. These results suggest that both physical and chemical plant resistance responses are involved. In contrast, H. rapax elicited no observable histological response from any of the genotypes and the insects developed normally on bark and fruit. Both insect species developed normally on leaf petioles and these exhibit only slight cell wall thickening in response to their feeding. This unusual plant defensive response to a sucking insect has similarities to simple types of gall formation in response to insect and pathogen attack and has characteristics of resistance gene-mediated models of plant defence.

Histología del daño en fruto y rama de aguacate ‘Hass’ por escamas armadas (Hemiptera: Diaspididae)

“…The low deposition of phenolic compounds observed in branch sections with brown scales and two species of scale per branch section is possibly due to the branch already showing secondary growth. Hill et al (2011) observed that mature branches of kiwi (Actinidia chinensis) infested with H. lataniae showed a slower and less pronounced response to the colonization by this scale compared to that observed in young branches.…”

“…No structural changes were observed in tissues of avocado branches in response to the colonization by armored scales (Figures 2A and 2B). Hill et al (2011) found that only some kiwi genotypes (Actinidia chinensis) infested with H. lataniae induced the formation of a wound at the point of contact between the periderm of the branch and the scales; the collenchyma cells showed accumulation of phenolic material, hypertrophy and cellular collapse. Fruto.…”

“…No se observaron alteraciones estructurales en los tejidos de rama de aguacate en respuesta al establecimiento de las escamas armadas (Figuras 2A, y 2B). Hill et al (2011) observaron que solo algunos genotipos de kiwi (Actinidia chinensis) infestados con H. lataniae, indujeron la formación de una herida en el punto de contacto entre la peridermis de la rama y la presencia de esta escama y las células del colénquima mostraron acumulación de material fenólico, hipertrofia y colapso celular.…”

“…La escasa deposición de compuestos fenólicos observada en secciones de rama con escama café y con dos especies de escama por sección de rama, posiblemente se deba a que la rama ya presentaba crecimiento secundario. Hill et al (2011), observaron que ramas maduras de kiwi (Actinidia chinensis) infestadas con H. lataniae mostraron una respuesta más lenta y menos pronunciada al establecimiento de esta escama comparada con la observada en ramas jóvenes.…”

“…los estiletes en la cutícula ni en las células epidérmicas de los frutos y ramas de aguacate (Figuras 4A y 4B). De acuerdo con el nivel de resolución microscópico, el estilete penetró intracelularmente las células parenquimatosas del exocarpio, la epidermis y corteza de rama (Figuras 4C y 4D), lo cual coincide con lo reportado en ramas de mora (Yasuda, 1979), en hojas y ramas de cítricos (Washington y Walker, 1990), y en ramas y frutos de kiwi (Hill et al, 2011) infestados con escamas armadas.…”