Effect of plant growth regulators in plant regeneration of Malaysian upland rice

Abstract

This study was carried out to regenerate Malaysian upland rice cultivars; Bario and Hitam by manipulating plant growth regulators. The present study showed that callus induction varied depends on cultivar used. The highest percentage of callus induction for Bario was 76.67% and 75% for Hitam cultivar on MS medium supplemented with 3 mg/L of 2,4-D and 2 mg/L of NAA respectively after 4 weeks culture. Both cultivars produced an embryogenic callus type I from scutellum with yellowish color, dry and compact structure. The embryogenic characteristics were later confirmed using histology. At week seven, highest proliferative mass of callus of Hitam cultivar callus was recorded with 1.73 g average fresh weight with diameter of 9.62 mm2. However, lower average of fresh weight was recorded from Bario cultivar showed 1.6 g with 10.87 mm2 diameter. Then, potential embryogenic callus was selected and transferred to MS medium supplemented with different concentrations of plant growth regulators (BAP, kinetin and NAA) for regeneration studies. The present study showed no shoot formation was recorded from Bario cultivar. The Hitam cultivar callus exhibited first green spot at week 3 and then shoot were formed. The present study showed highest shoot formation (78%) was achieved for Hitam cultivar when placed on MS contained with 1.0 mg/L BAP, 0.5 mg/L kinetin and 0.5 mg/L NAA (optimal shoot regeneration media) after 4 weeks culture. The other treatments showed potential shoot formation was MS media containing 2.0 mg/L BAP, 0.5 mg/L kinetin and 0.5 mg/L NAA and MS supplemented with 0.5 mg/L kinetin and 0.5 mg/L NAA. Similar percentage of shoot formation (33%) showed MS media containing 0.5 mg/L BAP, 1.5 mg/L kinetin and 0.5 mg/L NAA and MS supplemented with 0.5 mg/L BAP, 2.0 mg/L kinetin and 0.5 mg/L NAA. The Hitam cultivar showed 2 average numbers of shoots per callus on optimal shoot regeneration media was recorded after 6 weeks. The present study showed different plant growth regulators for Malaysian upland regeneration system was affected differently with the cultivar tested.