Damián César Castro

Crop loading studies on ‘Caricia’ and ‘Eva’ apples grown in a mild winter area

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’.

CARGA ÓTIMA DE FRUTOS NA MACIEIRA ‘PRINCESA’ DE BAIXO REQUERIMENTO EM FRIO INVERNAL:RESULTADOS PRELIMINARES

The aim of this study was to evaluate the effect of crop load on yield, fruit size, vegetative growth and return to bloom of low-chill apple (Malus × domestica Borkh.), cv. ‘Princesa’. During 2009 and 2010 crop load was manually adjusted from 1 to 9 fruits per unit of trunk cross-sectional area (TCSA). Fruit yield was positively related tocrop load, but mean fruit weight decreased with increasing crop load. The proportion of small and middle-sized fruits increased with rising crop load reaching 10% and 35% respectively of the total yield at the highest crop load. However the proportion of large-sized fruits did not change with the increase in crop load. Shoot length at 60 days after harvest was negatively related to crop load whereas return to bloom was not affected. These results demonstrates that the optimum crop load for ‘Princesa’ apple ranges between 5 to 9 fruits per unit of TCSA.

FACTORS AFFECTING PHENOLOGY OF DIFFERENT Citrus VARIETIES UNDER THE TEMPERATE CLIMATE CONDITIONS OF SANTA FE, ARGENTINA

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.

Functional dioecy in Gleditsia amorphoides (Fabaceae)

The genus Gleditsia (Fabaceae) comprises woody shrubs and trees that grow in temperate and subtropical regions around the world. This genus is characterised by sexual polymorphism and functionally unisexual flowers. Gleditsia amorphoides is the southernmost species of the genus, and is widely used as a source of timber and derived products for industrial applications (galactomannans are extracted from its seeds and saponins are derived from its fruits). The species is endemic to the Chaquenean Forest of South America. It is described as morphologically androdioecious, with male and perfect flowers appearing on different plants. In the current study, we characterised floral morphology, experimentally tested the breeding system and analysed flower visitors. Results indicated that G. amorphoides staminate flowers produce viable pollen grains and that perfect flowers have a functional gynoecium and empty anthers, where pollen abortion occurs early in floral development. The species relies on outcrossing, which depends mainly on pollen carried by insect pollinators, to produce seeds and fruits. We conclude that G. amorphoides is functionally dioecious, with staminate and pistillate floral morphs.

Can "Caricia" and "Princesa" apples be considered low-chilling cultivars?

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.

Influence of the Environmental Conditions, the Variety, and Different Cultural Practices on the Phenology of Peach in the Central Area of Santa Fe (Argentina)

Phenology is the study of the rhythm of repetitive biological events, the biotic and abiotic causes of these events, and the relationship between phenophases (i.e. periods during which specific phenological events occur) for individual or different species (Lieth, 1974). The knowledge of the phenological patterns of fruit tree crops is essential to estimate their behavior in a new growing area by extrapolation of experimental results from one region to another, or to predict changes in the tree phenology in a given area caused by the variation of the environmental factors between years (Broadhead et al., 2003). Thus, phenological studies can provide criteria for selection of suitable genotypes, helping to improve fruit yield and quality, and reduce environmental risk (Petri et al., 2008).