Autopathic Effect of Capsaicin (8-methyl-N-vanillyl-6-nonenamide) on Capsicum annuum L. Seed Germination

Recently, a new class of chile peppers (Capsicum spp.), that rate more than 1,000,000 Scoville heat units have become very popular, in the vernacular these are called “super-hots”. However, it has been observed that germination of “super hot” chile pepper seed is slower and reduced, compared to other chile peppers with lower heat levels. Germination is a principal component of seedling establishment and survival. After imbibition, radicle emergence is the first visible sign of seed germination and is considered a valuable evaluation of seed vigor in crops. The objective of this work was to determine the effect of capsaicin (the compound causing the heat) on chile pepper seed germination. Two no heat cultivars,  ‘Keystone Resistant Giant’ and ‘Pimiento L.’ were chosen.  Seeds were treated with 0, 500, or 1500 ppm capsaicin, and placed in 25 °C for 20 days, and scored daily. A successful germination was recorded when radicle emergence reached ≥2 mm. The osmotic potential of the 500 and 1500 ppm capsaicin solutions was not high enough to act as a salt (0.16 and 0.22 Kpa, respectively), and reduce or prevent germination. We found capsaicin had a major inhibiting effect on seed germination. Capsaicin treatment resulted not only in reduced and delayed germination, but also in inconsistent germination. There was a significant effect of cultivar x treatment, with the control (0 ppm) and 500 ppm capsicin treated seeds of ‘Keystone Resistant Giant’ having higher germination percent than the control and 500 ppm treated seeds of ‘Pimiento L.’ seeds, while the 1500 ppm capsaicin treated seeds of ‘Pimiento L’ had higher germination percent than the 1500 ppm treated seeds of ‘Keystone Resistant Giant’. The major implication of this work is to increase germination percent and uniformity of seeds from “super-hot” chile peppers, whereas a seed wash would be beneficial.