Factors involved in enhancing host susceptibility towards aphid clonal propagation on leaf foliage of Arabidopsis

The present study identified factors that enhanced host susceptibility towards Myzus persicae’s clonal proliferation in the model plant, Arabidopsis thaliana. A particular aphid inoculum, i.e. five aphids release per plant among three inoculums (1, 5 and 10 aphids per plant) showed enhanced susceptibility towards aphid clonal propagation in 21-day-old Arabidopsis leaf foliage. Five aphid number was common among the 28, 35, 42, 49-day-old Arabidopsis leaf foliage except 42-day-old Arabidopsis. Prior aphid herbivory enhan­ced host susceptibility in Arabidopsis. The aphid ino­culum at 6 am showed enhanced host susceptibility in comparison to 12 noon and 6 pm. The enhanced susceptibility on leaf foliage was realized in the presence of flower stalk. Aphid preferred to proliferate significantly on the flower stalk as compared to leaf foliage. Within leaf, aphid colonized more in mid-rib region as compared to minor vein area in the mature leaf. ProPAD4 :: GUS and ProADF3 :: GUS showed poor expression in mid-rib region in aphid-challenged leaf foliage. The aphid feeding based primed vascular sap showed degraded peptide bond, a possible reason for favouring enhanced aphid clonal proliferation in the primed Arabidopsis leaf foliage. Results showed that the enhancing of host susceptibility in Arabidopsis to Myzus persicae is influenced by quorum number of aphid’s inoculum, prior aphid feeding and circadian rhythms. Differential spatial resistance within whole plant and within leaf was also recorded. The enhanced host susceptibility was also correlated with microbiota enrichment in aphid-herbivore leaf vasculature sap as well as aphid body including aphid apical part containing salivary gland