Location of resistance factors in the leaves of potato and wild tuber‐bearing Solanum species to the aphid Myzus persicae

Abstract

Analysis of electrically recorded feeding behaviour of aphids was combined with colony‐development tests to search for sources of resistance to Myzus persicae (Sulzer) (Homoptera: Aphididae) in tuber‐bearing Solanum species (Solanaceae), aiming at a reduction of potato leaf roll virus (PLRV) transmission. Twenty genotypes, originating from 14 gene bank accessions, representing 13 wild tuber‐bearing Solanum spp., three Solanum tuberosum L. (potato) cultivars, and one S. tuberosum breeding line, were selected. Colony‐development tests were carried out in no‐choice experiments by placing adult aphids on plants of each genotype and counting numbers of nymphs and adults on young plants after 8 and 15 days, and on flowering plants after 14 and 30 days. Large differences were observed among genotypes: some developed small colonies and others developed large ones. Also, in a few genotypes, resistance in mature plants was different for leaves of different ages; young leaves were resistant to aphids whereas old senescent leaves were susceptible. The electrical penetration graph (DC‐EPG system) technique was used to study aphid feeding behaviour on each Solanum genotype for 6 h. Electrical penetration graph (EPG) results also showed large differences among the genotypes, indicating resistance at the leaf surface and at three different levels of plant tissue (epidermis, mesophyll, and phloem). Therefore, it was concluded that different mechanisms of resistance to M. persicae exist among the genotypes analysed. EPGs recorded from aphids on Solanum berthaultii Hawkes and Solanum tarijense Hawkes with and without glandular trichomes showed that strong surface resistance can bias EPG parameters associated with resistance located in deeper tissues. Experimental evidence is presented that the resistance to aphids in the genotypes with glandular trichomes strongly depends on these morphological structures.

Electrical Penetration Graph monitored feeding behavior of cowpea aphid, Aphis craccivora Koch. (Hemiptera:Aphididae), on faba bean, Vicia faba L. (Fabaceae), cultivars

“…This fact was confirmed by leaf surface observation through scanning electron microscope (Figure 2), which showed that there was no trichome or wax layer structures that might disturb aphid stylet penetration (Powell et al, 1999, Perdikis et al, 2008, Vallejo et al, 1994. A large number of test probes and a long time until the first phloem phase activity, commonly indicate the resistance factor in peripheral layers of plant tissue (i.e., epidermis and mesophyll) (Alvarez et al, 2006). However, they were not present in the studied resistant cultivar Gazira2.…”

Detached Leaf Assay to Screen for Host Plant Resistance to <I>Helicoverpa armigera</I>

“…All the parameters in colony development assay indicated that the order of cultivar resistance from the highest to the lowest was Gazira2 > Misr > Giza3 Improved > Goff1 > Misr1. Results obtained from the colony development assays probably reflect a similar phenomenon in the field because aphids were allowed to move freely and to feed in any part of the plant (Alvarez et al 2006). Factors such as plant height, leaf surface, leaf size, or leaf color supposedly affect the results of colony development assays (Bernays and Chapman 1994).…”

In Vitro Culture as a Stressful Factor Triggers Changes in Polyphenols, Flavonoids and Antioxidant Activity in Somatic Hybrids between Solanum tuberosum and S. bulbocastanum and their Respective Parents

“…This wild species has effective resistance mechanisms to different abiotic stress factors, but also to some biotic agents, like aphids (Alvarez et al, 2006), nematodes (Austin et al, 1993) or fungi (Lokossou et al, 2010). In this context, higher TPC, TFC and AA were actually expected for the wild species, all three physiological traits taken into consideration being actively involved in the resistance mechanisms (Lattanzio et al, 2006;Mierziak et al, 2014).…”