Comparison of Embryo Development in Wild and Cultivated Arachis Species

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Abstract
Embryo development following selfing was investigated in two wild diploid peanut species, Arachis batizocoi Krap. et Greg. (coll. K 9484) (2n = 20) and A. duranensis Krap. et Greg. nom. nud. (coll. K 7988) (2n = 20), and one cultivated tetraploid species, A. hypogaea L. NC-Ac 18000 (2n = 40). Rates of peg elongation and sequences of embryo development for each species were compared. Peg elongation rates were similar for the two wild species, but for A. hypogaea it was only one-third to one-half that of the diploid species. Embryos in A. hypogaea showed slightly more rapid cell division than in the wild species. The observed variation in reproductive development between the wild and cultivated species indicate that different control mechanisms may govern development in the different species and may be at least partially responsible for failure to produce viable interspecific hybrids at various ploidy levels. The observations are also important for determining the time at which embryos of different species of Arachis will reach the appropriate stage of development for successful culture on an artificial medium during embryo rescue procedures.