TEMPERATURE AND RELATIVE HUMIDITY EFFECTS ON SUGARCANE FLOWERING UNDER NATURAL CONDITIONS IN EGYPT

Abstract

This study consisted of two experiments that were carried out at El-Sabahia Research Station, Sugar Crops Research Institute, (ARC), Egypt, during 2013/2014/2015 (plant cane) and 2015/2016 (ratoon crop) seasons to investigate behavior of selected germplasm (40 genotypes from different origins) under natural flowering and make synchronization for crossing. Results of Individual and combined analysis of variance over two seasons, plant cane and first ratoon revealed significant differences among genotypes for duration of Pre flag leaf stage, duration of flag leaf stage, duration of emergence stage and percent of total flowered plants. The genotypes × inductive cycles interaction was significant for all studied characters. The forty sugar cane genotypes under study were classified into four groups. The first group included fourteen genotypes that flowered in plant cane and first ratoon seasons, and these genotypes ; EI 8-129, M35-157, PS 80-1424, K 81113, L 61-49, AN 56-79, SP 79-2233, G 2009-11, G 2009-10, G 2009-22, G 2009-86, G 2004-27, G 2008-64 and 88/5-27 .The second group consisted of ten genotypes that flowered only under plant cane. These ten genotypes are Koeng Java, SP 72- 5181, G 84-68, G 84-47, G 74-96, G 2008-59, G 2006-3, G 2007-61, GT 54-9 and G 2008- 20.The third group included two genotypes that flowered only under first ratoon and they are EI 242-16 and G 2006-36 . The fourth group included fourteen genotypes that did not show any response neither plant cane nor first ratoon, these genotypes are CO 775, G2003-47, US 59- 161, ROC 10, EI 58-28, EI 8-10, F 161, L 62-96, G 2000-5, G 99-80, SP 80-3250, SP 80- 1842, G 2003-49 and Mex 2001-80. Therefore, the forty evaluated sugarcane genotypes varied considerably among themselves in their response to flowering under plant cane and first ratoon. Flowering for genotypes in plant cane was higher than first ratoon because percentage of daily humidity for plant cane (2014) were higher than first ratoon (2015) during flowering stages and the number of days for flowering under the optimum temperature (18-31 °C) during three month (induction and initiation stage) in plant cane was 63 days higher than first ratoon (33 days), all those factors was reasons of flowering in plant cant was higher than first ratoon, so a better understanding of temperature and relative humidity effects on sugarcane flowering is important to study behavior of genotypes flowering and make synchronization for crossing in future between these genotypes.