Sieve element occlusion provides resistance against Aphis gossypii in TGR‐1551 melons

Abstract

Feeding behavior and plant response to feeding were studied for the aphid Aphis gossypii Glover on susceptible and resistant melons (cv. Iroquois and TGR-1551, respectively). Average phloem phase bout duration on TGR-1551 was <7% of the duration on Iroquois. Sixty-seven percent of aphids on TGR-1551 never produced a phloem phase that attained ingestion (EPG waveform E2) in contrast to only 7% of aphids on Iroquois. Average bout duration of waveform E2 (scored as zero if phloem phase did not attain E2) on TGR-1551 was <3% of the duration on Iroquois. Conversely, average bout duration of EPG waveform E1 (sieve element salivation) was 2.8 times greater on TGR-1551 than on Iroquois. In a second experiment, liquid nitrogen was used to rapidly cryofix leaves and aphids within a few minutes after the aphids penetrated a sieve element. Phloem near the penetration site was then examined by confocal laser scanning microscopy. Ninety-six percent of penetrated sieve elements were occluded by protein in TGR-1551 in contrast to only 28% in Iroquois. Usually in TGR-1551, occlusion was also observed in nearby nonpenetrated sieve elements. Next, a calcium channel blocker, trivalent lanthanum, was used to prevent phloem occlusion in TGR-1551, and A. gossypii feeding behavior and the plant's phloem response were compared between lanthanum-treated and control TGR-1551. Lanthanum treatment eliminated the sieve element protein occlusion response and the aphids readily ingested phloem sap from treated plants. This study provides strong evidence that phloem occlusion is a mechanism for resistance against A. gossypii in TGR-1551.

Greenbug (Schizaphis graminum) herbivory significantly impacts protein and phosphorylation abundance in switchgrass (Panicum virgatum)

“…In response to plant herbivores, reactive oxygen species (ROS) are generated in plant tissues 49 . Plant defense responses against aphids include calcium influxes 50 , accumulation of ROS 51 , phloem occlusion 52,53 , and callose deposition 54 . High and low accumulation or reduction of ROS make plants resistant or susceptible to aphids, respectively.…”

Priming Melon Defenses with Acibenzolar-S-methyl Attenuates Infections by Phylogenetically Distinct Viruses and Diminishes Vector Preferences for Infected Hosts

“…The Aphis gossypii colony used for this study originated from aphids collected from squash near Reedley, CA about a decade ago and reared on melon since then [39]. All aphids used here were reared on melon in the laboratory under climate-controlled conditions of 24 ± 2 • C and supplemental LED lighting providing a 16 h light/8 h dark photoperiod.…”

Pectin Methylesterases Modulate Plant Homogalacturonan Status in Defenses against the Aphid Myzus persicae

“…It has been described that differences in the duration of phloem ingestions (waveform E2) can be caused by the presence of deterrent compounds or a clogging mechanism in the phloem (Harrewijn and Kayser, 1997;Klingler et al, 1998;Tjallingii, 2006;Zhang et al, 2011). In these cases, the duration of phloem salivation (waveform E1), which always precedes phloem ingestion (waveform E2), is significantly longer, since this feeding activity corresponds to an aphid mechanism to overcome the defensive elements of the host (Tjallingii, 2006;Peng and Walker, 2018). However, the EPG analysis showed no differences in phloem salivation (waveform E1) between pmei13 and wild-type plants, and hence the existence of a phloem trait different from clogging systems or deterrent compound presence may be involved.…”