Development of seed germination and in vitro propagation protocols for Vitex doniana

Abstract

Propagation of Vitex doniana by seeds has been limited by low yield and a prolonged germination period which, along with over-harvesting, has led to a decline in its natural population. The present study aimed to improve seed germination and to establish in vitro organogenesis protocols to conserve superior genotypes. The effects of seed pre-treatments and environmental conditions on seed germination were investigated through conventional germination methods. Removal of the seed coat followed by germination on filter paper resulted in the highest percentage germination (87 %). The best germination temperature range was 25 °C-35 °C (80–87 %). A direct organogenesis protocol was established when in vitro nodal explants were cultured for eight weeks on modified Woody Plant Medium (WPM) supplemented with 0.3 mg/L 6-benzylaminopurine (BAP), resulting in 4 shoots/explant. Shoots were rooted on the modified WPM containing 0.5 mg/L indole-3-acetic acid (IAA), resulting in 80 % rooting and 4 roots/shoot, after four weeks. Successful acclimatisation was achieved, with 93 % survival in the greenhouse. For somatic embryogenesis, pro-embryos that formed from pairing 1 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) with 1 mg/L picloram or each tested auxin with 0.5 mg/L BAP failed to develop into somatic embryos on different maturation media. For time and cost savings and high yield, the present study found that germination be performed using de-coated seeds on filter paper at 25–35 °C followed by transfer to soil upon germination. The present study reports the first direct organogenesis protocol for V. doniana, allowing for clonal propagation of high-value genotypes.