Description

Abstract: Interspecific hybridization in Arachis is difficult between species within sectional groups and nearly impossible among more distantly related species. Embryos usually abort early in the reproductive cycle; thus in vitro techniques are necessary to recover many desirable hybrid combinations in the genus. The objectives of this investigation were to develop techniques whereby mature plants could be recovered from otherwise aborting embryos. First, ovule culture was performed using eight genotypes, three levels of kinetin, and the two basal media Murashige and Skoog (MS) and N6. Two-tenths mg/L kinetin in media resulted in 24% of the ovules swelling to a size of 3-4 mm which could be used for excising embryos. Embryo culture was next performed on five genotypes. The transfer series (I) 0.2 mg/L kinetin for 21 days, (2) 0.5 mg/L 6-benzylamino-purine (BAP) for 14 days and, (3) MS without growth regulators resulted in 34.6% of ovules producing plants across genotypes; other transfer series either resulted in a lower percentage of plant recovery and/or tissues of some genotypes which did not survive to maturity. The BAP medium induced shoot growth, while root growth was induced on the MS without growth regulator medium. Approximately 90% of embryos transferred to a mist system after 7-9 weeks in vitro survived transplanting to soil. Two interspecific hybrids were recovered from incompatible hexaploid x diploid crosses, but only after roots were induced using a MS basal medium with 4 mg/L 1-naphthaleneacetic acid:2 mg/L indole-3-butyric acid in a fourth tissue transfer. The experiments illustrated the feasibility of rescuing embryos of A. hypogaea and interspecific peanut hybrids. The process is slow and will be most applicable to wide crosses which cannot be obtained by more conventional methods.