EFFECT OF NATURAL AND ARTIFICIAL CHILLING IN CARROT DAUCUS-CAROTA L AT DIFFERENT LOCATIONS IN KENYA .1. EFFECTS ON BOLTING AND FLOWERING

Effect of natural chilling and artificial chilling durations of 2-8 we eks at 9 degrees C on percentage bolting and flowering and on days tak en from planting to the two events in carrot cv. Nantes was observed a t four locations in Kenya in 1991/92. These were; Juja (1500 m above s ea level in a warm Upper Midland (UM) zone) and Mole (2454 m), Kinango p (2558 m) and Marindas (2804 m), all in an Upper Highland (UH) zone. The observation was repeated in 1992/93 but in Juja and Kinangop only. In 1991/92 the lowest bolting and flowering percentage (<25%) was rec orded in carrot plants whose stecklings had received natural chilling at all planted sites while in those whose stecklings had received arti ficial chilling, bolting and flowering percentage increased with artif icial chilling durations within each location. Over 75% flowering was obtained only in those plants grown from carrot stecklings chilled for six and eight weeks within each location and in those given four week s chilling at Kinangop. In 1992/93,the results were quite opposite fro m those of the previous year at Kinangop when 100% bolting and floweri ng was obtained in all chilling treatments including the naturally chi lled plants. But at Juja bolting and flowering in 1992/93 was similar to the previous year. Days from planting to 50% of final bolting and f lowering decreased with increased durations of chilling at all sites, in both years. Days to final bolting and flowering followed a similar pattern. The control plants bolted and flowered earlier than those giv en two weeks of chilling in 1991/92 and at the Kinangop site in 1992/9 3. Significant differences (P<0.05) in days taken to bolting and flowe ring were observed between locations especially in 1992/93 when Juja p lants bolted significantly earlier than those at Kinangop in most trea tments.