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Genetic mapping and legume synteny of aphid resistance in African cowpea (Vigna unguiculata L. Walp.) grown in California.

Huynh BL, Ehlers JD, Ndeve A, Wanamaker S, Lucas MR, Close TJ, Roberts PA - Mol. Breed. (2015)

Bottom Line: One minor and one major quantitative trait locus (QTL) were consistently mapped on linkage groups 1 and 7, respectively, both with favorable alleles contributed from IT97K-556-6.SNP markers flanking each QTL were positioned in physical contigs carrying genes involved in plant defense based on synteny with related legumes.These markers could be used to introgress resistance alleles from IT97K-556-6 into susceptible local blackeye varieties by backcrossing.

View Article: PubMed Central - PubMed

Affiliation: Department of Nematology, University of California, Riverside, CA 92521 USA.

ABSTRACT

The cowpea aphid Aphis craccivora Koch (CPA) is a destructive insect pest of cowpea, a staple legume crop in Sub-Saharan Africa and other semiarid warm tropics and subtropics. In California, CPA causes damage on all local cultivars from early vegetative to pod development growth stages. Sources of CPA resistance are available in African cowpea germplasm. However, their utilization in breeding is limited by the lack of information on inheritance, genomic location and marker linkage associations of the resistance determinants. In the research reported here, a recombinant inbred line (RIL) population derived from a cross between a susceptible California blackeye cultivar (CB27) and a resistant African breeding line (IT97K-556-6) was genotyped with 1,536 SNP markers. The RILs and parents were phenotyped for CPA resistance using field-based screenings during two main crop seasons in a 'hotspot' location for this pest within the primary growing region of the Central Valley of California. One minor and one major quantitative trait locus (QTL) were consistently mapped on linkage groups 1 and 7, respectively, both with favorable alleles contributed from IT97K-556-6. The major QTL appeared dominant based on a validation test in a related F2 population. SNP markers flanking each QTL were positioned in physical contigs carrying genes involved in plant defense based on synteny with related legumes. These markers could be used to introgress resistance alleles from IT97K-556-6 into susceptible local blackeye varieties by backcrossing.

No MeSH data available.


Related in: MedlinePlus

Variation in aphid damage symptoms measured at different days after planting (DAP) among CB27, IT97K-556-6 and their recombinant inbred line population grown at UC-KARE, Parlier, CA, in 2012 and 2013
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Related In: Results  -  Collection


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Fig2: Variation in aphid damage symptoms measured at different days after planting (DAP) among CB27, IT97K-556-6 and their recombinant inbred line population grown at UC-KARE, Parlier, CA, in 2012 and 2013

Mentions: Aphids began feeding on young cowpea seedlings in the experimental plots about three weeks after planting. Microscopic examination of aphid morphology confirmed that they were typical A. craccivora Koch characterized as shiny-black adults and gray nymphs. Severe symptoms of aphid infestation on cowpea plants included dead or stunted plants with black-mold development caused by honeydew excreted from aphids (Additional File 2); the susceptible parent cultivar CB27 was stunted by aphids, while the African breeding line IT97K-556-6 was fully resistant with no to mild symptoms. Damage symptoms of the RILs in field plots were scored at 60 and 50 days after planting (DAP) in 2012 and 2013, respectively. By those dates, CPA had infested all spreader rows and distinct variation in the symptoms was observed among experimental plots. There were approximately 65,000 aphids/plant (including nymphs and adults) in spreader rows (approximately 1,040,000 aphids/m2). Damage symptoms were scored again 20 days later when most plants in spreader rows were dead (Fig. 1). There were no symptoms of cowpea aphid-borne mosaic virus during the CPA scoring periods. The phenotypic values of the RIL population were highly consistent among blocks and years (repeatability h2 > 0.8) and scoring times (r > 0.8, P < 0.001). Two major groups of RILs had extreme symptoms (resistant vs. susceptible), while other RILs expressed symptoms that were intermediate between the two parents CB27 and IT97K-556-6 (Fig. 2).Fig. 1


Genetic mapping and legume synteny of aphid resistance in African cowpea (Vigna unguiculata L. Walp.) grown in California.

Huynh BL, Ehlers JD, Ndeve A, Wanamaker S, Lucas MR, Close TJ, Roberts PA - Mol. Breed. (2015)

Variation in aphid damage symptoms measured at different days after planting (DAP) among CB27, IT97K-556-6 and their recombinant inbred line population grown at UC-KARE, Parlier, CA, in 2012 and 2013
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4300395&req=5

Fig2: Variation in aphid damage symptoms measured at different days after planting (DAP) among CB27, IT97K-556-6 and their recombinant inbred line population grown at UC-KARE, Parlier, CA, in 2012 and 2013
Mentions: Aphids began feeding on young cowpea seedlings in the experimental plots about three weeks after planting. Microscopic examination of aphid morphology confirmed that they were typical A. craccivora Koch characterized as shiny-black adults and gray nymphs. Severe symptoms of aphid infestation on cowpea plants included dead or stunted plants with black-mold development caused by honeydew excreted from aphids (Additional File 2); the susceptible parent cultivar CB27 was stunted by aphids, while the African breeding line IT97K-556-6 was fully resistant with no to mild symptoms. Damage symptoms of the RILs in field plots were scored at 60 and 50 days after planting (DAP) in 2012 and 2013, respectively. By those dates, CPA had infested all spreader rows and distinct variation in the symptoms was observed among experimental plots. There were approximately 65,000 aphids/plant (including nymphs and adults) in spreader rows (approximately 1,040,000 aphids/m2). Damage symptoms were scored again 20 days later when most plants in spreader rows were dead (Fig. 1). There were no symptoms of cowpea aphid-borne mosaic virus during the CPA scoring periods. The phenotypic values of the RIL population were highly consistent among blocks and years (repeatability h2 > 0.8) and scoring times (r > 0.8, P < 0.001). Two major groups of RILs had extreme symptoms (resistant vs. susceptible), while other RILs expressed symptoms that were intermediate between the two parents CB27 and IT97K-556-6 (Fig. 2).Fig. 1

Bottom Line: One minor and one major quantitative trait locus (QTL) were consistently mapped on linkage groups 1 and 7, respectively, both with favorable alleles contributed from IT97K-556-6.SNP markers flanking each QTL were positioned in physical contigs carrying genes involved in plant defense based on synteny with related legumes.These markers could be used to introgress resistance alleles from IT97K-556-6 into susceptible local blackeye varieties by backcrossing.

View Article: PubMed Central - PubMed

Affiliation: Department of Nematology, University of California, Riverside, CA 92521 USA.

ABSTRACT

The cowpea aphid Aphis craccivora Koch (CPA) is a destructive insect pest of cowpea, a staple legume crop in Sub-Saharan Africa and other semiarid warm tropics and subtropics. In California, CPA causes damage on all local cultivars from early vegetative to pod development growth stages. Sources of CPA resistance are available in African cowpea germplasm. However, their utilization in breeding is limited by the lack of information on inheritance, genomic location and marker linkage associations of the resistance determinants. In the research reported here, a recombinant inbred line (RIL) population derived from a cross between a susceptible California blackeye cultivar (CB27) and a resistant African breeding line (IT97K-556-6) was genotyped with 1,536 SNP markers. The RILs and parents were phenotyped for CPA resistance using field-based screenings during two main crop seasons in a 'hotspot' location for this pest within the primary growing region of the Central Valley of California. One minor and one major quantitative trait locus (QTL) were consistently mapped on linkage groups 1 and 7, respectively, both with favorable alleles contributed from IT97K-556-6. The major QTL appeared dominant based on a validation test in a related F2 population. SNP markers flanking each QTL were positioned in physical contigs carrying genes involved in plant defense based on synteny with related legumes. These markers could be used to introgress resistance alleles from IT97K-556-6 into susceptible local blackeye varieties by backcrossing.

No MeSH data available.


Related in: MedlinePlus