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Title: SCREENING BETA VULGARIS L. FOR SUGARBEET ROOT MAGGOT (TETANOPS MYOPAEFORMIS RODER) RESISTANCE USING AN IN VITRO BIOASSAY

Author
item Smigocki, Anna
item IVIC-HAYMES, S - TOWSON UNIV TOWSON MD
item Campbell, Larry
item BOETEL, M - NORTH DAKOTA STATE UNIV

Submitted to: Journal of Sugarbeet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2006
Publication Date: 1/20/2006
Citation: Smigocki, A.C., Ivic-Haymes, S.D., Campbell, L.G., Boetel, M.A. 2006. Screening beta vulgaris l. for sugarbeet root maggot (tetanops myopaeformis roder) resistance using an in vitro bioassay. Journal of Sugarbeet Research. 43:1-13.

Interpretive Summary: Since the sugarbeet root maggot is considered the most serious pest of sugarbeet in the United States and Canada and has spread to over two-thirds of the more than l.5 million U.S. beet-producing acres, effective approaches for control of this insect are needed. We devised a novel laboratory technique for studying the interaction of the sugarbeet root maggot with roots of susceptible and moderately resistant sugarbeet plants. We demonstrated that the root maggot insects moved away from the resistant roots but aggregated and fed on the susceptible roots. We showed that more than half of the insects were killed on susceptible roots that were first dipped in compounds that kill other insects. We conclude that laboratory cultivation of sugarbeet roots facilitates rapid screening of sugarbeet plants for resistance and for screening of compounds that may be useful for management of the root maggot. This information will be used by scientists for evaluating pesticides and newly developed plant varieties and should lead to the discovery of new methods for insect control.

Technical Abstract: An in vitro system was used to study the interactions between sugarbeet (Beta vulgaris L.) roots and the most devastating insect pest of sugarbeet, the sugarbeet root maggot (SBRM, Tetanops myopaeformis Röder). Sources of root material included sugarbeet seedlings and hairy root cultures of susceptible (F1010) and moderately resistant (F1016) germplasm. First- and second-instar SBRM were obtained from eggs of laboratory-reared flies or from soil samples collected from infested sugarbeet fields, respectively, and used to infest root tissues in vitro. Second-instars aggregated and fed on F1010 roots but moved away from the F1016 tissues. Damage to F1010 roots included rasping and tunneling marks as well as severed roots. On in vitro propagated hairy roots that were stained in 0.01% saffranin or crystal blue, evidence of SBRM feeding included severed roots and saffranin or crystal violet in the frass and intestinal tracts of insects. Approximately 50% of first-instar SBRM died within 24 h after they were placed on F1010 hairy roots dipped in leaf extracts prepared from insect resistant transgenic Nicotiana plants. In comparison, only 0 to 7% of the control larvae died. This development of an in vitro SBRM bioassay using sugarbeet seedlings and hairy root cultures provides a tool for rapid analysis of resistance genes and mechanisms and will facilitate studies of root-SBRM interactions under controlled conditions.