Two phenylurea compounds, thidiazuron (TDZ, 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea) and forchlorfenuron (CPPU, N-(2-chloro-4-pyridyl)-N-phenylurea), were studied for their effect on shoot proliferation in rose. TDZ treatments as a quick dip (100 muM) recorded the highest shoot proliferation multiplication rate for 'Sonia' (16.9 shoots per explant) and 'Raktagandha' (11.1 shoots per explant). A maximum of 12.8 and 10.8 shoots per explant proliferated when CPPU (200 muM) was used as a quick dip for 'Sonia' and 'Raktagandha', respectively. Microshoot quality, i.e. average shoot length, basal stem thickness and total leaf chlorophyll (a + b) content, was appreciably improved as compared with shoots regenerated on normal proliferation medium (PM) containing 6-benzylaminopurine (BAP) 8.88 muM + alpha -naphthalene acetic acid (NAA) 0.54 muM + gibberrellic acid (GA(3)) 0.29 muM. The microshoots regenerated therein rooted normally and the results showed that dual auxins, i.e. indolebutyric acid (IBA) + NAA, acted synergistically to produce functional roots which helped in hardening and whole plantlet recovery. This study suggests that a short exposure of explants to TDZ or CPPU, before subculture onto normal shoot proliferation medium during Stage-II, can significantly enhance axillary shoot proliferation in hybrid tea rose cultivars for their commercial multiplication. (C) 2001 Elsevier Science B.V. All rights reserved.
