Using ethephon and GA3 to overcome thermoinhibition in 'Jalapeno M' pepper seed

Abstract

'Jalapeno M' pepper (Capsicum annuum L.) seeds were soaked for 40 h in solutions of 0.0, 0.5, 1.0, 2.0, or 3.0 mM GA3 (using Release, 10 % GA3) and 0.0, 1.75, 3.5, 7.0, or 10.5 mM ethephon in all combinations in petri dishes at 25 °C. The seeds were rinsed, dried for 24 hours, then germinated at either 25 or 40 °C. Thermoinhibition was induced at 40 °C, as nontreated seeds failed to germinate, but 99% of the seeds germinated at 25 °C after 7 days. Pretreatment with H2O alone partially alleviated thermoinhibition at 40 °C (41% germination). Pretreatment with ethephon alone resulted in up to 50% germination and with GA3 alone up to 79% germination. The effects of the GA3 and ethephon were additive, as the highest germination percentage (91%) at 40 °C was obtained with 3.5 mM ethephon + 3.0 mM GA3. The percentage of abnormal radicles was <1% in all treatments. Chemicals used: (2-chloroethyl) phosphonic acid (ethephon); gibberellic acid (GA3).