Bud dormancy evolution in apple genotypes with contrasting chilling requirements

Abstract This work evaluates how thermal regimes with constant or oscillating temperatures affect the onset and overcome of endodormancy in apple buds with low (‘Castel Gala’) and high (‘Royal Gala’) chilling requirements. Apple twigs were collected in Papanduva-SC orchards during the autumn/winter of 2010 and 2011, and submitted to constant (3°C) or cycling (3/15°C for 6/18h, 12/12h or 18/6h) temperatures for up to 1466 chilling hours (CH). Periodically, a portion of twigs in each treatment was transferred to 25°C, for budburst evaluation. An environmental stress in 2010 caused premature leaf fall on the field, reduced initial budburst in ‘Royal Gala’ samples and interfered with dormancy onset in both cultivars. Cycling temperature treatments with few CH/day decreased partially this effect, allowing buds to enter a dormancy state more efficiently. No significant stress was observed in the orchard in 2011, when dormancy evolution was similar in all thermal treatments, being induced with 54 and 123 CH and overcome with 363 and 662 CH for ‘Castel Gala’ and ‘Royal Gala’, respectively. Apparently, the manner in which apple bud dormancy is induced affects its depth and consequently the total number of chilling hours required to overcome it, making the onset phase fundamental in dormancy studies.

摘要 本研究评估了恒温或变温热环境条件对低需冷量（chilling requirements）品种‘Castel Gala’与高需冷量品种‘Royal Gala’苹果芽内休眠（endodormancy）的启动与解除的影响。2010年与2011年秋冬季节，研究人员从巴西圣卡塔琳娜州帕潘杜瓦的果园采集苹果枝条，将其分别置于恒温（3℃）或变温模式（3/15℃，即3℃处理6小时、15℃处理18小时；或3℃处理12小时、15℃处理12小时；或3℃处理18小时、15℃处理6小时）的环境中处理，直至累积冷时数（chilling hours, CH）达到1466个。定期将各处理组的部分枝条转移至25℃环境下，开展芽萌发（budburst）率评估。2010年的环境胁迫导致田间植株提前落叶，降低了‘Royal Gala’样品的初始芽萌发率，并干扰了两个供试品种的休眠启动进程。每日累积冷时数较少的变温处理可部分缓解该胁迫效应，使芽更高效地进入休眠状态。2011年果园未出现显著环境胁迫，所有热环境处理下的休眠进程均较为一致：‘Castel Gala’与‘Royal Gala’分别在累积54个与123个冷时数时进入休眠，分别在累积363个与662个冷时数时解除休眠。研究表明，苹果芽休眠的诱导方式会影响其休眠深度，进而影响解除休眠所需的总冷时数，因此休眠启动阶段是休眠研究的核心环节。