THERMAL REQUIREMENTS OF CITRUS FRUITS GRAFTED ONTO ROOTSTOCKS IN THE LOW-MIDDLE REGION OF THE SÃO FRANCISCO RIVER BASIN

ABSTRACT To understand the production cycle of a particular cultivar in a given region, it is necessary to obtain information related to its phenology and the accumulated degree days. The purpose of this study was to evaluate the phenological cycle of citrus species grafted onto two rootstocks and grown in the Low-Middle Region of the São Francisco River Basin, in particular with respect to accumulated degree days. The experiment was conducted using ‘Rubi’ and ‘Pera D-12’ oranges and ‘Page’ mandarins. Two rootstocks were used, namely ‘Cravo’ and ‘Volkameriano’ lemon species that were drip irrigated in the Campo Experimental de Bebedouro, an experimental field owned by Embrapa Semiárido. ‘Page’ mandarins with ‘Cravo’ or ‘Volkameriano’ rootstocks exhibited a subperiod (0-10) of 183.32 and 181.24 days, respectively. Meanwhile, ‘Pera D-12’ and ‘Rubi’ oranges with ‘Cravo’ rootstocks had values of 249.57 and 178.58 days, respectively, while those with ‘Volkameriano’ rootstocks had values of 226.35 and 200.41 days, respectively. The accumulated degree days were measured from the initial sprouting to harvesting, which took place when the fruits presented a soluble solids/titratable acidity ratio equal to or greater than 12. ‘Page’ mandarins required 2,720 degree days, whereas ‘Pera D-12’ and ‘Rubi’ oranges required approximately 3,390 and 2,280 degree days, respectively. Finally, ‘Pera D-12’ and ‘Rubi’ oranges with either rootstock presented cycles characterized as mid-season and precocious, respectively, while ‘Page’ mandarins had precocious cycles.

摘要 为明确特定栽培品种在指定区域的生产周期，需获取与其物候期及积温（accumulated degree days）相关的信息。本研究旨在评估种植于圣弗朗西斯科河流域中下段区域、嫁接于两种砧木的柑橘栽培品种的物候周期，重点考察积温指标。本试验供试材料为‘鲁比’橙、‘佩拉D-12’橙及‘佩奇’宽皮橘，采用‘克拉沃’柠檬与‘沃尔卡默’柠檬作为嫁接砧木，试验于贝别杜罗试验场（Campo Experimental de Bebedouro）开展，该试验场隶属于巴西半干旱农业研究公司（Embrapa Semiárido），供试植株均采用滴灌供水。嫁接‘克拉沃’与‘沃尔卡默’砧木的‘佩奇’宽皮橘，其（0-10）物候亚期时长分别为183.32天与181.24天。与此同时，嫁接‘克拉沃’砧木的‘佩拉D-12’橙与‘鲁比’橙，对应物候亚期时长分别为249.57天与178.58天；嫁接‘沃尔卡默’砧木的二者则分别为226.35天与200.41天。积温测算区间为初始萌芽至果实采收期，采收判定标准为果实可溶性固形物与可滴定酸度比值不低于12。‘佩奇’宽皮橘所需积温为2720度日，‘佩拉D-12’橙与‘鲁比’橙则分别约需3390度日与2280度日。最后，嫁接两种砧木的‘佩拉D-12’橙与‘鲁比’橙，其生长周期分别为中熟与早熟类型，而‘佩奇’宽皮橘则均为早熟类型。