Hybridization barriers among the species of Arachis L., namely of the sections Arachis (including the groundnut) and Erectoides

Abstract

Some members of Arachis section Erectoides have been found resistant to early leaf spot disease caused by Cercospora arachidicola (Mycosphaerella arachidis), a serious constraint to groundnut productivity. These accessions do not cross with cultivated species. Crossing between one such diploid species, A. paraguariensis (ICG8130 and ICG8973) of section Erectoides, and the diploids, A. batizocoi and A. duranensis, and the tetraploid A. hypogaea (groundnut) of section Arachis, has helped understand barriers to hybridization between sections. These crosses result in the development of normal pegs and pods, but with of ovule and embryo development restricted or non-existent. Such restricted growth and embryo abortion was due to cessation of early endosperm development in A. duranensis × A. paraguariensis, the non-development of endosperm beyond the coenocytic stage in A. batizocoi × A. paraguariensis, and the overgrowth of nucellar tissue into the embryo sac in case of A. hypogaea × A. paraguariensis. The weak cross-compatibility between the species of two sections suggest relatively closer phylogenetic relationship between them, than with the other incompatible sections of the genus Arachis