Marker-Assisted Selection for Biotic Stress Resistance in Peanut uri icon

abstract

  • Peanut is the second-most important legume grown worldwide. Cultivated peanut is a disomictetraploid, 2n?4x?40, with limited genetic diversity due to a genetic bottleneck in formation ofthe polyploid from ancestors A. duranensis and A. ipaensis. Consequently, resistance_to biotic stressesis limited in the cultigen; however, wild species possess strong resistances. Transfer o f these resistancesis hindered by differences o f ploidy, but production o f synthetic amphidiploids, coupledwith use o f molecular markers, enables efficient gene transfer. Marker maps have been made frominterspecific crosses, and SSR-based maps from cultivated parents have been developed recently. Atleast 410 resistance gene analogues have been identified. The first markers for biotic stress tolerancewere for root-knot nematode resistance and introgressed from one A. cardenasii chromosome. Theseand improved markers have been used for marker-assisted backcrossing, contributing to release ofthree cultivars. Additional QTLs have been identified since. Early and late leafspots cause significantyield losses worldwide, and resistance depends on multiple genes. Using interspecific populations,five resistance QTLs for early leafspot were identified using greenhouse inoculations, and five QTLsfor late leafspot were identified using detached leaf assays. Using cultivated species populations, 28QTLs were identified for LLS resistance; all but one were minor QTLs; the major QTL was donatedby an interspecific introgression line parent. Rust often occurs alongside leafspots, and rust resistancewas characterized as one major QTL, plus several smaller QTLs. Marker-assisted backcrossing o f thismajor QTL has been performed into different populations. QTLs for resistance to other biotic stresseshave been identified, namely to groundnut rosette virus, Sclerotinia blight, afiatoxin contamination,aphids, and tomato spotted wilt virus. Marker-assisted breeding is still in early stages, and developmento f more rapid and inexpensive markers from transcriptome and genome sequencing is expectedto accelerate progress

publication date

  • 2013