Resistant potato, selections contain leptine and inhibit development of the Colorado Potato beetle (Coleoptera : Chrysomelidae)

We recently described a new source of host-plant resistance to the Colorado potato beetle, Leptinotarsa decemlineata (Say), in a tetraploid potato (So lanum tuberosum L.) selection, NM2858-1. This genotype, and selected backcr oss progeny, had little damage while check cultivars were defoliated in ope n-choice field assays. To further characterize the observed deterrence, we determined foliar glycoalkaloids and conducted no-choice assays with ND2858 -1 backcross progeny genotypes (ND4382-n). Development of neonate L decemli neata in detached leaf assays on resistant progeny genotypes was delayed an d larval weight gain after 4 d was inhibited by 75% relative to larval deve lopment and weight gain on susceptible genotypes. Inhibition of larval deve lopment in detached leaf assays with the selected progeny genotypes was equ ivalent to that of high-leptine genotypes of S. chacoense Bitter. Foliar gl ycoalkaloids of resistant genotypes included low levels of leptines I and I L The unlikely nature of this cross and the presence of leptine in this and resistant progeny selections cast doubt on the recorded pedigree. Molecula r analyses were conducted by restriction fragment length polymorphism. and amplified fragment-length polymorphisms. Both methods established a high de gree of relatedness to S. tuberosum and S. chacoense but not to S. fendleri . We conclude that ND2858-1 did not originate from a cross with S. fendleri , but is likely derived from S. chacoense. Oviposition and larval survival were reduced when adult L decemlineata were placed in cages with resistant genotypes; an effect that was enhanced by inclusion of Perillus bioculatus F. Therefore, the nonpreference previously observed in open-choice field de foliation assays is also associated with antibiotic effects on L. decemline ata. The resistance may be caused by leptines, but is greater than would be expected by the leptine content. This source of host plant resistance coul d be a cost-effective management strategy, especially if combined with othe r resistance mechanisms or compatible control measures to delay development of resistance in the target insects.