Abstract

In equatorial climates, fibre yield is higher in photo-insensitive kenaf cultivars. To develop a rapid screening method, in vivo and in vitro indices were evaluated. Seven genotypes were grown at natural photoperiod and growth rates before and after flowering, days to flowering and fibre yield were recorded. In vitro, stem and leaf explants of genotypes Tainung and V400 which showed contrasting photoperiodic responses in vivo, were tested for callus induction at 0 and 12 h photoperiod. Calli were transferred to differentiation medium at 12 and 9 h photoperiod and numbers of green spots and embryogenic callus clusters were recorded. Flowering was delayed by at least 27 days in V400 relative to other genotypes. Growth rate reduced by 30% after flowering in all genotypes except V400 where it increased by 60%. Highest yield of 76 g / plant was recorded in V400. Eighty-four percent degree of callus formation by stem was higher than 51% by leaf explants of V400 irrespective of light regime. In Tainung, callus formation varied with explants and photoperiod. Green spots and embryogenic clusters were three times more in Tainung than V400. Both in vivo andin vitro results showed Tainung as photosensitive and V400 as photoinsenstive. Incubating kenaf callus in differentiation medium in 12 h light and evaluating for greenness was useful in screening for photoperiod sensitivity.

Key words: Kenaf, Hibiscus cannabinus, photosensitivity, in vitro screening, somatic embryogenesis.