Reproductive efficiency and asymmetric barriers outweigh genetic distance and genome type in the crossability among peanut wild relatives

Peanut (Arachis hypogaea) is an allotetraploid (AABB) globally important crop. While it lacks critical alleles for resistance to many diseases and climate adaptation, wild Arachis species are diverse and possess genes useful for crop improvement. Thus, understanding their reproductive biology and cross-compatibility is critical to the development of viable hybrids suitable for breeding programs. We evaluated factors influencing hybridization effectiveness of peanut wild relatives.

We evaluated species-specific reproductive efficiency through spontaneous and artificial self-pollination, and cross-compatibility, via 5321 artificial pollinations performed across 30 interspecific combinations. We monitored hybrid development through to adult F1. Hybridization effectiveness was measured as absolute and relative parameters, with the latter normalized to the reproductive efficiency of the female parent. We estimated genetic distances using a high-density single-nucleotide polymorphism array to evaluate whether there is a correlation with hybridization success.

Reproductive efficiency after spontaneous pollination differed among species, and manual pollinations did not affect it. Relative hybridization effectiveness was different between intragenomic and intergenomic combinations, and genetic distance was not correlated with cross-compatibility between species. Instead, reproductive efficiency of the female parent and a set of prezygotic and postzygotic reproductive barriers, whose strength varied by species pair, cross direction, and genome type, affected hybridization effectiveness.

The framework we used documented that, beyond genetic distance and genome type, intrinsic biological traits influence hybridization success between peanut wild relatives. This approach may offer a model pathway to enhance the understanding of the hybridization potential of crop wild species and their effective utilization in pre-breeding programs.