RESUMO O objetivo deste trabalho foi caracterizar o comportamento fenológico das diferentes variedades de laranja-doce, tangerinas e híbridos de tangerina que crescem em condições de clima temperado. Os estádios fenológicos foram observados semanalmente, durante cinco anos consecutivos, usando uma escala BBCH (Federal Biological Research Centre for Agriculture and Forestry) adaptada para citros. Todas as variedades apresentaram um período de repouso invernal entre junho e agosto. As primeiras variedades no início de brotação foram ‘New Hall’ e ‘Navelina’, e a última foi ‘Okitsu’. O início da floração ocorreu no período de 13 de agosto a 6 de setembro, e do dia 12 de setembro até 2 de outubro observou-se a plena floração. A colheita dos frutos foi iniciada em março com a cv. ‘Okitsu’ e foi estendida durante sete meses com as outras variedades. A variação interanual na época do início da brotação foi elevada (44 dias), e seu tempo de ocorrência foi correlacionado com o acúmulo térmico (acima 13ºC) e a quantidade de radiação solar durante julho (p<0.0001; r2=0.79). As laranjeiras-de-umbigo e o híbrido ‘Murcott’ apresentaram uma antecipação na floração de 5 a 15 dias, o que pode aumentar a probabilidade de danos ocasionados por geadas tardias.

ABSTRACT The aim of this study was to characterize the phenology of different sweet orange, tangerines and tangerine hybrid varieties growing under the temperate climate conditions of Santa Fe Province, Argentina. Phenological stages were observed weekly during five consecutive years using a BBCH (Biologische Bundesanstalt, Bundessortenamt and Chemical industry) scale adapted for Citrus trees. All varieties showed a winter rest period from June to August. ‘New Hall’ and ‘Navelina’ varieties were the first to reach sprouting stage, whereas ‘Okitsu’ was the last. Inception of flowering occurred from August 13th to September 6th; and full bloom from September 12th to October 2nd. Fruit harvest started with the ‘Okitsu’ cultivar in March, and continued over a 7-month period. Interannual variation for inception of sprouting was high (44 days), and sprouting was correlated with both thermal accumulation (above 13ºC) and the amount of solar radiation measured during July (p<0.0001; r2=0.79). Navel oranges and the ‘Murcott’ hybrid bloomed 5–15 days earlier than other varieties, increasing probability of damage by late frosts.

RESUMO. O objetivo deste trabalho foi avaliar a resposta ao acúmulo de refrigeração artificial de dois cultivares de maça de baixo requerimento de frio. Coletaram-se ramos a campo das cultivares "Caricia" e "Princesa", e da cultivar "Gala" (utilizada como controle), com e sem gemas apicais (ramos intactos e decapitados, respectivamente), as quais foram expostas ao acúmulo de refrigeração artificial (4.0 ± 0.5°C) de zero a 1200 unidades de frio (UF). A brotação das gemas em ambos os tipos de ramos foi maior do que 50% em todo o intervalo de acumulação de frio avaliado em "Caricia" e "Princesa". No entanto, em "Gala·" a brotação excedeu 50% somente nos ramos intactos depois de acumular 900 UF. Observou-se que o tempo médio para a brotação das gemas de "Caricia" e "Princesa" estabilizou-se acima das 600 UF, dependendo do tipo de ramo e do ano de experimentação. As gemas dos cultivares avaliados neste trabalho mostraram uma dormência pouco profunda, no entanto precisaram de acumulação moderada de frio (800 - 1150 UF) para satisfazer seus requerimentos ecofisiológicos. Portanto, apesar da dormência pouco profunda permitir que estes cultivares sejam adequadamente cultivados em zonas com invernos amenos, não podem ser considerados de baixo requerimento de frio.

ABSTRACT. The purpose of this work was to study the response of two apple cultivars bred for low chilling environments to artificial chilling accumulation. Two trials were carried out; in experiment one, excised shoots were randomly taken from "Caricia" and "Princesa", and in experiment two, intact and excised shoots of "Caricia", "Princesa" and "Gala" (control) were collected. After collection, both shoot types were exposed to artificial chilling accumulation (4.0 ± 0.5°C) from 0 to 1200 chill units (CU). Bud break of mixed buds of "Caricia" and "Princesa" was higher than 50% between 0 CU to 1200 CU, irrespective of shoot type. Bud break of "Gala" mixed buds exceeded 50% only in intact shoots after accumulating 900 CU. The mean time to bud break of "Caricia" and "Princesa" diminished with increasing chilling accumulation and stabilized after ~600 CU, depending on the type of shoot and the year of experimentation. The low-chill apple cultivars tested in this work showed shallow dormancy, but they required moderate cold accumulation (800 - 1150 CU) to fully satisfy their chilling requirements. Thus, although their shallow dormancy makes them suitable for cultivation in chill-deficient environments, they cannot be considered low-chill cultivars.

The crop load level of an apple (Malus × domestica Borkh.) tree impacts fruit yield and quality parameters, tree vigor and biennial bearing. The optimal crop load is that which allows for consistent annual cropping and fruit quality acceptable to the market. We evaluated the effect of crop load on yield and fruit quality of two low-chill apples cv. ‘Caricia’ and ‘Eva’, growing in a mild winter area. During 2010 and 2011 crop load was manually adjusted from 2 or 3 to 17 fruits cm−2 of trunk cross-sectional area (TCSA). Fruit yield was positively related to crop load in both cultivars but mean fruit weight diminished as the crop load increased. For both cultivars, the production of non-commercial and small-sized fruit increased, whereas production of middle-sized fruit diminished as the fruit load increased. Shoot length was not affected by crop load in ‘Eva’ whereas it was reduced in ‘Caricia’. Red skin color (RSC %) had a quadratic response to crop load in ‘Caricia’. On the other hand, the RSC % of ‘Eva’ fruit was adjusted to a negative logarithmic model as an effect of crop load increment. No biennial bearing was observed in either cultivar. This research study suggests that the maximum limit of crop load for both cultivars is 7 fruits cm−2 of TCSA, and the lower limit of crop load was 3 fruits cm−2 of TCSA for ‘Eva’ and 5 fruits cm−2 of TCSA for ‘Caricia’.