Prechill effect on flowering of mature heads of cabbage cultivars

Abstract

Cabbage (Brassica oleracea var. capitata L.) cultivars are diverse with respect to heading, chilling requirement for flowering and winter hardiness. Wiebe (10) categorised cabbage as having obligate requirement for exposure to low temperatures for flowering, 4° to 7°C temperatures as optimum (that led to fastest flowering response), while effective temperature range as 0 to 12°C. Cabbage must attain certain size and more than 16°C temperature was termed as anti or devernalizing. Sheen (5) reported reversal of low temperature effect on sugar accumulation and cancellation of vernalization by either high temperature (20°, 30°C) or alternating temperature (20°/5°C or 30°/5°C day/night temperatures) in radish. He suggested that in sub-tropics, relatively high day temperature in winters prevents bolting. Data (collected at metrological unit of deptt. of Soil Science and Water Management, UHF, Solan) shows anti and devernalizing day temperature (>16°C mid Feb to mid Nov., 2001-2007). Thus, it was planned to initiate flowering in mid seasons heading cabbage cultivars Pusa Mukta and KGAT-I hybrid that fail to flower at Solan due to insufficient exposure to continuous low temperature for complete vernalization, by artificial exposure to low temperature.