Peanut regeneration by somatic embryogenesis (SE), involving bulbil-like body (BLB), a new type of SE structure

Abstract

Using cotyledons as explants a new method of peanut regeneration was established via somatic embryogenesis (SE), involving a kind of first-observed SE structure that was shaped like bulbil and therefore named bulbil-like body (BLB). On Murashige and Skoog (MS) media containing a higher concentration of 2,4-D (20.0 mg/L) and incubated in the dark, all the inoculated cotyledon explants formed BLBs with a high frequency of average 26 BLBs per cotyledon explant, and 100.00 % of the formed BLBs spontaneously developed into multiple shoots (3–5 shoots per BLB) without changing induction and incubation conditions. On average, about 103 shoots can be induced from an individual cotyledon explant. On MS media supplemented with 1.0 mg/L NAA all the separated shoots formed normal roots to develop into plantlets. The morphological and histological analyses of BLBs at different development stages revealed that BLB was a special kind of SE structure originated from cortex cells of peanut cotyledon explants, and each individual BLB was composed of multiple embryoids further developing into multiple shoots. To our knowledge, BLB is a novel type of SE structure in peanut different from the known SE structures because of its special shape, induction conditions, somatic embryogenic nature, and multiple-embryoid characteristics.