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Linkage disequilibrium at the APA insecticidal seed protein locus of common bean (Phaseolus vulgaris L.).

ABSTRACT: BACKGROUND: An interesting seed protein family with a role in preventing insect herbivory is the multi-gene, APA family encoding the alpha-amylase inhibitor, phytohemagglutinin and arcelin proteins of common bean (Phaseolus vulgaris). Variability for this gene family exists and has been exploited to breed for insect resistance. For example, the arcelin locus has been successfully transferred from wild to cultivated common bean genotypes to provide resistance against the bruchid species Zabrotes subfasciatus although the process has been hampered by a lack of genetic tools for and understanding about the locus. In this study, we analyzed linkage disequilibrium (LD) between microsatellite markers at the APA locus and bruchid resistance in a germplasm survey of 105 resistant and susceptible genotypes and compared this with LD in other parts of the genome. RESULTS: Microsatellite allele diversity was found to vary with each of the eight APA-linked markers analyzed, and two markers within the APA locus were found to be diagnostic for bruchid resistance or susceptibility and for the different arcelin alleles inherited from the wild accessions. Arc1 was found to provide higher levels of resistance than Arc5 and the markers in the APA locus were highly associated with resistance showing that introgression of this gene-family from wild beans provides resistance in cultivated beans. LD around the APA locus was found to be intermediate compared to other regions of the genome and the highest LD was found within the APA locus itself for example between the markers PV-atct001 and PV-ag004. CONCLUSIONS: We found the APA locus to be an important genetic determinant of bruchid resistance and also found that LD existed mostly within the APA locus but not beyond it. Moderate LD was also found for some other regions of the genome perhaps related to domestication genes. The LD pattern may reflect the introgression of arcelin from the wild into the cultivated background through breeding. LD and association studies for the arcelin gene, linked genes and other members of the APA family are essential for breaking linkage drag while maintaining high levels of bruchid resistance in common bean.

SUBMITTER: Blair MW

PROVIDER: S-EPMC3095353 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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Linkage disequilibrium at the APA insecticidal seed protein locus of common bean (Phaseolus vulgaris L.).

Blair Matthew W MW Prieto Sergio S Díaz Lucy M LM Buendía Héctor F HF Cardona César C

BMC plant biology 20100429

<h4>Background</h4>An interesting seed protein family with a role in preventing insect herbivory is the multi-gene, APA family encoding the alpha-amylase inhibitor, phytohemagglutinin and arcelin proteins of common bean (Phaseolus vulgaris). Variability for this gene family exists and has been exploited to breed for insect resistance. For example, the arcelin locus has been successfully transferred from wild to cultivated common bean genotypes to provide resistance against the bruchid species Za ...[more]

PMID: 20429910

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Project description:Common bean (Phaseolus vulgaris L.) is a staple food in Brazil with both nutritional and socioeconomic importance. As an orphan crop, it has not received as much research attention as the commodity crops. Crop losses are strongly related to virus diseases transmitted by the whitefly Bemisia tabaci, one of the most important agricultural pests in the world. The main method of managing whitefly-transmitted viruses has been the application of insecticides to reduce vector populations. Compared to chemical vector control, a more sustainable strategy for managing insect-borne viruses is the development of resistant/tolerant cultivars. RNA interference has been applied to develop plant lines resistant to the whitefly in other species, such as tomato, lettuce and tobacco. Still, no whitefly-resistant plant has been made commercially available to date. Common bean is a recalcitrant species to in vitro regeneration; therefore, stable genetic transformation of this plant has been achieved only at low frequencies (<1%) using particle bombardment. In the present work, two transgenic common bean lines were obtained with an intron-hairpin construct to induce post-transcriptional gene silencing against the B. tabaci vATPase (Bt-vATPase) gene, with stable expression of siRNA. Northern blot analysis revealed the presence of bands of expected size for siRNA in leaf samples of the line Bt-22.5, while in the other line (11.5), the amount of siRNA produced was significantly smaller. Bioassays were conducted with both lines, but only the line Bt-22.5 was associated with significant mortality of adult insects (97% when insects were fed on detached leaves and 59% on the whole plant). The expression of the Bt-vATPase gene was 50% lower (p < 0.05) in insects that fed on the transgenic line Bt-22.5, when compared to non-transgenic controls. The transgenic line did not affect the virus transmission ability of the insects. Moreover, no effect was observed on the reproduction of non-target organisms, such as the black aphid Aphis craccivora, the leafminer Liriomyza sp. and the whitefly parasitoid Encarsia formosa. The results presented here serve as a basis for the development of whitefly-tolerant transgenic elite common bean cultivars, with potential to contribute to the management of the whitefly and virus diseases.

Dataset Information

Linkage disequilibrium at the APA insecticidal seed protein locus of common bean (Phaseolus vulgaris L.).

Publications

Linkage disequilibrium at the APA insecticidal seed protein locus of common bean (Phaseolus vulgaris L.).

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