Callus formation and organogenesis by explants of six Lycopersicon species

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Abstract
Stem and hypocotyl explants of 6 Lycopersicon spp., L. esculentum var. cerasiformae, L. cheesmanii, L. hirsutum, L. pimpinellifolium, L. peruvianum and L. glandulosum, were examined for ability to form callus, adventitious shoots, and adventitious roots on media containing varying levels of IAA and kinetin. Callus growth of L. peruvianum and L. glandulosum explants was better than that of the other species tested. Stem explants tended to form more callus than hypocotyl explants. Shoot formation by hypocotyl explants was superior to stem explants for all species and at nearly all hormone levels. Hypocotyl explants of L. peruvianum and L. glandulosum showed the highest levels of shoot formation, L. cheesmanii and L. esculentum var. cerasiformae hypocotyl explants showed good shoot formation on media containing 3 mg/l kinetin and 0.3 or 1 mg/l IAA. No shoot formation was observed by L. hirsutum explants, and L. pimpinellifolium explants gave only a poor response. Shoot formation by stem explants was obtained only with L. esculentum var. cerasiformae and L. glandulosum. When callus of the 6 spp., subcultured for 63 days on a medium optimal for callus growth, was subcultured on shoot-forming media, only callus of L. peruvianum and L. glandulosum subsequently formed shoots. Callus of L. glandulosum has retained its morphogenic potential for 1 yr in culture and can be used to initiate liquid suspension cultures.