An improved and reliable chili pepper (Capsicum annuum L.) plant regeneration method

Abstract

In this work we report a new method forin vitro chili pepper (Capsicum annuum L.) plant regeneration based on shoot formation from wounded hypocotyls. Chili pepper seeds were surface sterilized and germinated on agar (0.8%) at 25 ± 2°C in the dark. Five factors that may influence shoot regeneration were studied: age of seedlings, hypocotyl wounding site, time elapsed between wounding the hypocotyls and decapitation of seedlings, culture media and cultivars. In order to study the influence of the first three factors on shoot regeneration, the apical, middle or basal hypocotyl regions of seedlings of cv. Mulato Bajio at different stages of development (9, 15, 16, 21 and 28 d old) were wounded with a syringe needle, and the seedlings were cultured on MS semisolid medium without growth regulators at 25 ± 2°C under a 16/8 h light/dark photoperiod (daylight fluorescent lamps; 35 μmol m-(2) s-(-1)) until decapitation. The seedlings were decapitated (3 mm below the cotyledons) at different times after wounding (0, 2, 4, 10, 12 and 14 d), and each explant was evaluated for bud and shoot formation (≥ 5 mm in length) at the wounded site after 30 d of incubation. In general, seedlings at the stage of curved hypocotyl (9 d old) wounded in the apical region of hypocotyl were the best explants for shoot regeneration when inoculated on culture medium without growth regulators. Decapitation after wounding also influenced the shoot regeneration efficiency, with 10-14 d being the best period. Up to 90% shoot regeneration in cv. Mulato Bajio was obtained under these conditions. Statistically significant differences were observed for shoot formation among 21 cultivars tested. Regeneration of whole plants was achieved by rooting the shoots with indole-3-butyric acid pulses of 60 mg L(-1) for 3 h and then subculturing on MS medium without growth regulators.