Expansion of a direct shoot organogenesis system in peanut (Arachis hypogaea L.) to include US cultivars

Abstract

Agrobacterium-mediated transformation, employing direct shoot organogenesis, allows for mature transgenic plants to be obtained quickly (3–4 mo). In this study, peanut (Arachis hypogaea L.) cultivars Florida-07, Georgia Green, Georgia Brown, New Mexico Valencia A, and VC-2 were selected to test their shoot induction response for use in future transformation experiments. Two types of cotyledon explants were examined, those that previously had an attached embryo axis upon cotyledon separation (explant A) and those that were embryo axis-free upon separation (explant B). Explants were placed onto a shoot induction medium with N6-benzyladenine concentrations ranging from 10–80 μM for Florida-07, Georgia Green, and VC-2; 10–20 μM for Georgia Brown; and 10–640 μM for New Mexico Valencia A. Following a 4-wk culture period, explants were visually rated based on a scale of 1–4, where 1 indicated slight greening, but no growth, and 4 indicated greening, adventitious bud formation, as well as small leaf expansion. A difference in shoot induction was observed for the cotyledon explants examined (P > t = t = <0.0001). Additionally, cultivars responded to the culture conditions differently (cultivar × N6-benzyladenine interaction). Georgia Green on 10 μM N6-benzyladenine produced the most shoot buds (24.6%) and the highest visual rating (2.1), followed by VC-2 on 10 μM N6-benzyladenine (22.1%, 1.8), New Mexico Valencia A on 640 μM N6-benzyladenine (21.4%, 1.8), Georgia Brown on 80 μM N6-benzyladenine (9.0%, 1.7), and Florida-07 on 40 μM N6-benzyladenine (7.1%, 1.8). Of the tested varieties, Georgia Green, New Mexico Valencia A, and VC-2 were best suited for future transformation experiments based on their shoot bud production.