PROBING BEHAVIOR OF BIOTYPES OF THE SPOTTED ALFALFA APHID ON RESISTANT AND SUSCEPTIBLE ALFALFA CLONES¹

Abstract

The probing behavior of four biotypes of the spotted alfalfa aphid, Therioaphis maculata (Buckton), feeding on resistant and susceptible alfalfa clones (genotypes) was investigated. Salivation, X‐pattern, and ingestion waveforms, and probing sequences were similar among four biotypes probing the substrate of a susceptible clone. On one resistant clone (‘Moapa’ C‐905) probing sequences produced by biotypes A and C were similar but abnormal; stylet penetration of the phloem sieve element and ingestion were lacking or greatly suppressed. On another resistant clone (Moapa C‐908) probing sequences produced by biotype A were normal whereas those produced by biotype C were abnormal; stylet penetration of phloem sieve elements and ingestion were completely lacking. The salivation probe was successfully completed by both biotypes on the resistant clones; salivation time was significantly longer on the resistant clone than on the susceptible clone. The data suggest that the mechanism of resistance is based on a chemical interaction between the plant and aphid, and that the system is related to the phytoalexin theory of host‐plant resistance and to the phenol‐phenolase reactions of plants and sap‐sucking insects. Zusammenfassung PROBEVERHALTEN VON BIOTYPEN DER LUZERNEZIERLAUS AN RESISTENTEN UND ANFÄLLIGEN LUZERNEKLONEN Untersucht wurde das Probeverhalten von vier Biotypen der Luzernezierlaus (Therioaphis maculata (Buckton)) an resistenten und anfälligen Luzerneklonen (Genotypen) mit Hilfe der McLean‐schen elektronischen Messung. Dabei wurden die drei Wellenformen (1) für Speichelfluss, (2) für das Eindringen in ein Siebelement (= X‐pattern) und (3) für die Nahrungsaufnahme graphoanalytisch aufgenommen und analysiert. Auf anfälligen Klonen war das Probeverhalten, gemessen an Form und Abfolge von (1)–(3) bei allen Biotypen gleichartig. Dagegen waren auf einem resistenten Klon („Moapa” C‐905) die Probestiche der A‐ und C‐Biotypen zwar ähnlich aber anormal: Stechborstenpenetration in das Siebelement und Nahrungsaufnahme daraus waren stark gehemmt bzw. fehlten. Bei einem anderen resistenten Klon („Moapa” C‐908) waren die Probestiche des A‐Biotypus normal, während die des C‐Biotypus anormal waren; beim letzteren unterblieben Stechborstenpenetration in das Siebelement und Nahrungsaufnahme vollständig. Bei beiden Biotypen lief die Speichelflussphase auf resistenten Klonen erfolgreich ab; die Dauer des Speichelflusses war dabei auf resistenten Klonen bedeutend länger als auf anfälligen. Die Daten weisen darauf hin, dass der Resistenzmechanismus auf einer chemischen Interaktion zwischen Wirtspflanze und Blattlaus beruht und dass dieser Mechanismus in Zusammenhang gebracht werden kann mit der Phytoalexintheorie über die Resistenz der Wirtspflanze und mit den Phenol‐Phenolasereaktionen zwischen Pflanzen und saftsaugenden Insekten.

PROBING BEHAVIOR OF THE GREENBUG (SCHIZAPHIS GRAMINUM, BIOTYPE C) ON RESISTANT AND SUSCEPTIBLE VARIETIES OF SORGHUM

“…Similar responses by other species of aphids feeding on resistant host plants have been reported: Myzus persicae (Sulzer) on resistant varieties of sugar beets (Haniotakis & Lange, 1974); Therioaphis maculata (Buckton) on resistant lines of alfalfa (Nielson & Don, 1974); Aphis gossypii Glover on resistant varieties of muskmelon (Kennedy et al, 1978). An increase in the number of separate probes and duration of nonprobing was also associated with greenbugs feeding on resistant lines of sorghum.…”

Responses of a compatible lucerne variety to attack by spotted alfalfa aphid: changes in the redox balance in affected tissues

“…Phenolics have similarly been shown to increase in lucerne tissues attacked by the aphids in the present study, increasing by at least 60~o in attacked leaves and 79.9~o in attacked stems, both estimates being subject to underestimate because of interference from the higher reducing content of healthy leaves. As in the interaction between rose and rose aphid, dynamic changes in phenolics occurred in lucerne both during and after infestation in a manner similar to the production of phytoalexins (Nielson & Don, 1974). As in the interaction between rose and rose aphid, dynamic changes in phenolics occurred in lucerne both during and after infestation in a manner similar to the production of phytoalexins (Nielson & Don, 1974).…”

Mi-Mediated Resistance Against the Potato AphidMacrosiphum euphorbiae(Hemiptera: Aphididae) Limits Sieve Element Ingestion

“…When conÞned on plants with Mi, the aphid responds to the lack of a suitable feeding site with increased motivation to search and hence to probe. Increased numbers of separate probes have been associated with resistance to aphids in a variety of plants, including the spotted alfalfa aphid, Therioaphis maculata (Buckton), feeding on alfalfa cultivars (Nielson and Don 1974) and A. gossypii on muskmelon (Kennedy et al 1978). The tendency to produce many short and separate probes on resistant tomato is potentially very important with regard to nonpersistent virus transmission, which is favored by very short and frequent probes by the vector (Raccah 1986).…”