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Abstracts - Bruno H.S. Souza

COMMON BEAN INDUCED DEFENSE RESPONSES UNDER DOUBLE ATTACK BY WHITEFLY AND FALL ARMYWORM

Amanda M. Nascimento1, Camila S.F. Souza1, Allison F. Chiorato2, Moacir R. Forim3 and Bruno H.S. Souza1*

1 The University of Lavras - UFLA; brunosouza@den.ufla.br

1 The University of Lavras - UFLA; amandanascimentoagro@yahoo.com.br

1 The University of Lavras - UFLA; camilasfs1068@gmail.com

2 Agronomic Institute of Campinas - IAC; afchiorato@iac.sp.gov.br

3 São Carlos Federal University - UFSCar; mrforim@ufscar.br

* Correspondence: brunosouza@den.ufla.br

Plants are constantly attacked by multiple herbivorous insect species, and often at the same time. Plant induced defense responses are differentially triggered depending on herbivore feeding habit, e.g. if the insect is a leaf chewer or sapsucker. This study investigated if a chewing lepidopterous larvae (fall armyworm, FAW, Spodoptera frugiperda) and a piercing-sucking insect (silverleaf whitefly, SLW, Bemisia tabaci biotype B) pests would trigger different defense responses in common beans (Phaseolus vulgaris cv. IAC-Una) when the plants were individually or simultaneously infested. Three-week-old plants (V2) in the greenhouse were artificially infested on the primary leaves with either 50 SLW adults, 2 third-instar FAW larvae, 50 SLW adults + 2 third-instar FAW larvae or were kept uninfested, constituting four treatments. The primary leaves were enclosed with voile-fabric cages where the insects were allowed to injure the plants for 48h. Approximately 10 days after insect and cage removal from the plants, a set of plants (V3) of all treatments were assigned for SLW oviposition preference assessment in acrylic cages in the laboratory. Another group of plants was used for collection of the trifoliate for trichome quantification. A second assay were conducted in Petri dishes to evaluate neonate FAW larvae preference for the primary leaves or the trifoliate in each induced treatment. SLW deposited similar numbers of eggs among treatments when given a choice for oviposition in cages. Trichome density on the adaxial leaf surface was significantly higher in FAW-infested plants, intermediate in the control and double-infested plants, and lower in SLW-infested plants. FAW consumed less of the leaf directly injured by SLW when plants were SLW-infested, but consumed more of the same leaf when plants were additionally infested by FAW. This study reveals that common beans differentially respond to injury when individually or simultaneously infested by SLW and FAW. We will conduct a follow-up study with single and mixed application of MeSa and MeJA to investigate if they respectively mimic SLW and FAW infestation, as well as plants contents of phenolics, lignin, peroxidase, and catalase as possible induced resistance mechanisms. In addition, analysis of volatile and non-volatile chemical profile of induced plants will certainly advance our understanding on this plant-insect interaction system. Knowledge on the duration of plant induced responses is also important for improvement of strategies to be deployed in Integrated Pest Management.