Game of 'Mones: Comprehending Bemisia tabaci MEAM1 Nymph-Based Resistance and Defense Phytohormone Signaling in Alfalfa

• Main Author: Thomas, Patrick
• Other Authors: Walling, Linda
• Format: Thesis
• Language: English
• Published: eScholarship, University of California 2022
• Subjects: Genetics; Bioinformatics; Molecular biology; Antarc*; Antarctica
• Online Access: https://escholarship.org/uc/item/839596bs; https://escholarship.org/content/qt839596bs/qt839596bs.pdf

Hemipteran insects are a significant threat to food security in California and worldwide; their piercing-sucking mouthparts make them difficult for host plants to perceive. Of these insect pests, the whitefly (Bemisia tabaci) is a cosmopolitan pest which stunts plant growth and development, vectors viruses, and also secretes honeydew which can result in sooty mold growth on host plants. Whiteflies are extant on all continents except Antarctica and climate change increases the propensity superabundant whitefly populations will be more common worldwide over time. Whiteflies are difficult to control as the release of natural enemies in crops has limited effectiveness and whiteflies circumvent the pesticides by rapidly adapting by developing insecticide resistance. For this reason, integrated pest management (IPM) programs centered around host plant resistance (HPR) may be the most effective means of controlling whiteflies. An effective, nymph-based whitefly-resistance mechanism was identified in alfalfa. While this mechanism may greatly inhibit whitefly population over generations, the polyploid nature and limited genomic resources in alfalfa make elucidating this resistance a challenge. Here, we describe whitefly-resistance found among three alfalfa populations. Upon screening 84 individual lines from the three populations (two resistant and one susceptible), we concluded whitefly resistance was multigenic as a continuous spectrum of phenotypes from highly resistance to highly susceptible in each population. We identified several highly resistant (R1, R2 and R3) and susceptible lines of alfalfa (S1) for further studies. Through a series of experiments exploring B. tabaci MEAM1, MED1 and NW1 behaviors, we determined the whitefly-resistance displayed in R1, R2 and R3 lines were distinct and both antibiosis and antixenosis were detected for all three whitefly species. MEAM1 nymph mortality was displayed in all R lines, while the nymph mortality mechanisms did not impact MED whitefly. In addition, differences in ...