Chilling injury (CI) is the collective term for various disorders that occur during prolonged cold storage and/or after subsequent ripening of stone fruit. Major symptoms of CI include mealiness, graininess, flesh browning, loss of flavour (off flavour), and red pigmentation (bleeding). These symptoms were evaluated over 2 years in an intra-specific progeny population derived from the cross of cultivars 'Venus' (freestone, melting, yellow-flesh nectarine) and 'BigTop' (clingstone, melting, yellow-flesh nectarine) after storage of fruit at 5 ºC (CI inducing conditions) for 2 and 4 weeks. All the evaluated traits in the progeny showed continuous variation which is typical of quantitative or polygenic inheritance. Longer cold storage periods increased the incidence and severity of CI symptoms, except for bleeding and leatheriness which were not affected by time of storage. CI symptoms showed high and significant heritability or genotype effect in the studied population, with no significant effect of harvesting year. Browning, mealiness and graininess were significantly correlated and were the main CI symptoms observed in this population. Mealiness and graininess were negatively correlated with stone adhesion which reflects the higher susceptibilty to CI disorders of free stone fruit. A genetic linkage map of linkage group 4 (LG4) was constructed with SSR and candidate genes (CGs). Significant quantitative trait loci (QTLs) for mealiness, graininess, leatheriness and bleeding were found in this linkage group, validating QTLs for CI symptoms previously reported in this linkage group from an unrelated progeny population. In addition, QTLs controlling other agronomic and fruit quality traits were also localized in this linkage group.

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Adaptation of two citrus cultivars, Valencia Delta Seedless (VDS) and Valencia Late Frost (VLF) grafted on Forner Alcaide nº 517, to super high-density groves with mechanical harvesting was evaluated in southwest of Spain. Regarding to crop development, both cultivars showed a similar behavior regard to tree growth, good affinity with the rootstock and chlorophyll content in leaf (SPAD units). However, differences were obtained in phenological development and internal quality of the fruit. So, VDS showed a more advanced phenology, while VLF obtained a better-quality juice: higher titratable acidity content with a lower maturity index. On the other hand, it was identified a great potential of the mechanical harvesting in both cultivars, with significant fruit detachment percentages (about 90% or more) and above 8 kg of fruit retention force (FRF). However, VDS obtained a better response to the harvesting equipment evaluated (New Holland BRAUD 9090X DUAL, over-row continuous canopy shaking harvester). So, VDS recorded higher fruit detachment percentages (95-100%) as well as lower levels of physiological and physical damage. Finally, the differences between cultivars, both efficiency of the fruit detachment and tree damage could respond to differences in the structure of the tree and rigidity of the branches. Index terms: super-intensive, dwarfing citrus rootstocks, harvesting efficiency, tree damage, alteration fruits. Adaptação de duas cultivares de citros enxertadas em Forner Alcaide Nº 517 em sistema de plantio super-adensado e avaliação da colheita mecanizada RESUMOA adaptação de duas cultivares de citros, Valencia Delta Seedless (VDS) e Valencia Late Frost (VLF) enxertadas em Forner Alcaide nº 517, foi avaliada em pomares com alta densidade de plantio e colheita mecânica, no sudoeste da Espanha. Em relação ao desenvolvimento das culturas, ambas as cultivares apresentaram comportamento semelhante em relação ao crescimento da planta, boa afinidade com o porta-enxerto e bom conteúdo de clorofila na folha (unidades SPAD). Entretanto, foram obtidas diferenças no desenvolvimento fenológico e na qualidade interna da fruta.

New low and medium vigour Prunus rootstocks compatible with peach cultivars were evaluated under controlled and in field conditions against biotic and abiotic stress factors. Most rootstocks exhibited different levels of resistance to the root-knot nematode Meloidogyne javanica. The plum hybrids ʻPAC 9801-02ʼ and ʻKrymsk 86ʼ ® were the only rootstocks that exhibited a moderate resistance to the lesion nematode. All rootstocks showed a high sensitivity to crown gall. The low vigour plums ʻEvricaʼ and ʻKrymsk 1ʼ ® were sensitive to iron chlorosis. All plum-based materials were moderately tolerant to tolerant to root asphyxia, whereas peach-based rootstocks were sensitive with exception of the peach almond hybrid ʻPAC 0009-01ʼ. Several plums tend to emit an excessive number of root and crown suckers. From the agronomic standpoint, ʻPAC 0009-01ʼ and ʻPAC 9801-02ʼ present a better overall performance taking into account the combined traits.