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ARS Home » Research » Publications at this Location » Publication #72633
Title: EFFECT OF SOIL MOISTURE AND SOYBEAN GROWTH STATE ON RESISTANCE TO MEXICAN BEETLE (COLEOPTERA: COCCINELLIDAE

Author
item JENKINS, ERICA - HORT-CR SCI-OSU, COLUMBUS
item HAMMOND, RONALD - ENTOMT-OSU/OARDC, WOOSTER
item ST. MARTIN, STEVEN - HORT-CR SCI-OSU, COLUMBUS
item Cooper, Richard

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plant breeders have been breeding for insect resistance in soybeans for the past 20 years, but only 4 resistant varieties have been released. Concern has been raised about the level of resistance and the effect of environmental conditions and age of the plant on this resistance. This research demonstrated that under good moisture conditions the level of resistance was lower and that as plants reach the seed filling stage, the resistance level also decreased. These results raise questions as to whether the resistance lasts long enough to prevent yield losses from insect feeding and suggest higher level of genetic resistance should be sought.

Technical Abstract: Although plant breeders and entomologists have been working on the development of insect-resistant soybean, Glycine max (Merrill), lines and cultivars over the past 20 years, only 4 cultivars have been released. This has led to questions about the potential for insect resistance in soybeans. One concern is whether the resistance in soybeans can persist at the desired level under differing environmental conditions and growth stages. Four soybean genotypes which differed in their insect resistance levels were grown at 3 soil moistures in the greenhouse. Insect bioassays were conducted by rearing Mexican bean beetle, Epilachna varivestis Mulsant, on excised leaves and comparing larval mortality, developmental periods, and pupal and adult weights. Bioassays were conducted during soybean V4 to R2 growth stages and the R3 to R5 growth stages. Total mortality and larval development periods increased on all soybean genotypes as soil moisture decreased. Decreased expression in resistance in soybeans was observed in plants grown in high soil moisture during the R3 to R5 bioassays compared with the V4 to R2 growth periods. Resistance was lost for the moderately resistant line, HC83-193, and decreased for the highly resistant line, HC83-123-9 during the R3 to R5 bioassays. Ramifications of less resistance with increased soil moisture for growers and problems related to breeding programs, especially when differences are obtained with greenhouse and field grown plants, are discussed.