Description

Abstract: Many species of Arachis fail to produce seeds after self- or cross-pollination. A primary barrier to seed production is pegging for many genotypes; therefore, the effect of applying GA3 (gibberellic acid) to flowers was investigated. Species of Arachis were treated with 0, 88, 176, or 352 ppm GA3 daily for 30 days and the number of flowers and pegs recorded. The species A. chacoense Krap. et Greg. nom. nud., A. villosa Benth., A. correntina (Burk) Krap. et Greg. nom. nud., A diogoi Hoehne, A. stenosperma Greg. et Greg. nom. nud., and A. sp. coll. GK 30006 had a linear response in peg formation to increased levels of GA3 However, A. sp. coll. GKPSc 30108 had a quadratic response. Arachis cardenasii Krap. et Greg, nom. nud. had a cubic response to GA3 levels. The species A. helodes Mart. ex. Krap. et Rig., A. sp. coll. GK 30008, A. sp. coll. GK 30011, A. sp. coll. GK 30017, A. glabrata Benth and A. hypogaea did not have a significant peg response to application of GA3. Flowering was suppressed on all species by 352 ppm GA3. Application of either 88 or 176 ppm GA3 resulted in increased numbers of pegs for all species except A. hypogaea, A. sp. coll. GK 30017 and A. sp. coll. GK 30011. In another experiment, plants of A. chacoense, A. cardenasii, A. villosa, A. helodes, and A. diogoi were treated with 176 ppm GA 3 and pegs were allowed to mature but no seeds were recovered. A crossing program using NC 4 in reciprocal with five species resulted in a significant increase in seeds when GA3 applications were applied, but only for hybrid combinations which are normally successful without GA3. Parthenocarpic development is believed to account for increased numbers of pegs. Because pegging is mandatory before seeds can be obtained in Arachis, applications of GA3 will add significantly toward overcoming a reproductive barrier in Arachis. However, application of additional growth regulators will be necessary to stimulate development of the embryo.