Abscission study during citrus fruit maturation in Corsica: unfavorable environmental conditions for fruit shedding

Citrus fruit development and ripening are complex processes involving physiological and biochemical changes that are under hormonal, nutritional and environmental control. One of the most evident phenomena in late maturation is shedding of ripe fruit. A previous study on sweet orange abscission supposed that fruit shedding was related to the increase of sugars content of pulp juice. To investigate this potential relationship between fruit abscission and internal maturity parameters we investigated the fruit maturity process of 10 mandarin x clementine hybrids and 9 commercial sweet orange varieties with different maturity time. Morphological and biochemical analyses (acidity, total soluble solids, fruit weight thickness of the flavedo, thickness of the peduncle and external color) were carried out on fruit sets of the different varieties during the maturation process, from December to June. The abscission initiation was evaluated by measuring the force required to detach the fruit of the peduncle. Analysis showed that under our local conditions, abscission was generally not expressed even though fruit maturation was evolving. Therefore, we suppose that even though the local conditions have an important effect, abscission of citrus fruit also results from environmental-genotype interactions. Moreover, evolution of abscission and fruit parameters are not correlated, suggesting the independence in the processing of maturation and abscission. (Résumé d'auteur

L'intranet comme révélateur des libertés : jeux, pouvoirs et stratégies d'acteurs dans les organisations

Les intranets sont d'importants révélateurs des conflits internes dans les organisations, des jeux de pouvoir entre les acteurs et de la volonté managériale. Cet article met en parallèle deux cas, l'un dans une entreprise de grande distribution, l'autre dans une communauté de chercheurs. L'étude menée sur les deux intranets développés dans ces organisations permettent de faire ressortir des constantes et des différences dans le suivi des tels projets technologiques, notamment en terme de jeux de pouvoirs entre les acteurs, mais également en terme de pratiques et de logiques d'acteurs

Physiological analysis of salt stress behaviour of citrus species and genera: low chloride accumulation as an indicator of salt tolerance : S08O07

Tolerant citrus rootstocks are defined as Cl- excluders. However, little is known about the salt tolerance of cultivars used as scions, particularly the tolerance of monoembryonic citrus genotypes. To enhance the genetic resources for generating improved hybrid rootstocks, the evaluation of large samples of citrus species, including both monoembryonic and polyembryonic genotypes, is necessary. In this study, 12 citrus genotypes representing the major Citrus species and all the three genera of the Rutaceae family were subjected to moderate salt stress (75mM) for 12 weeks to characterise their physiological response to salt stress. Various symptoms and physiological parameters were evaluated to characterise their salt sensitivity. These included plant growth (stem diameter), leaf chlorophyll content, leaf flavonoid content, maximum quantum yield of PSII [(Fm-F0)/Fm)], net photosynthesis, stomatal conductance and leaf Na and Cl- contents. The results clearly demonstrated that the most salt sensitive genotypes accumulated high concentrations of Na and Cl- and maintained a fair growth and photosynthetic rate. By contrast, salt-tolerant genotypes accumulated less Na and Cl- and decreased their growth and gas exchange. 'Poncire commun' citron and 'Marumi' kumquat were the most sensitive species, while mandarins, pummelo and 'Australian' sour orange were the most tolerant species. Among the genotypes, 'Engedi' pummelo presented a specific trait for salt tolerance that has not been previously reported. Taken together, the results suggest that low leaf chloride content can be used as an indicator of salt stress tolerance in citrus genotypes. Exploitation of this indicator will enable the improved evaluation of citrus genetic resources and should lead to the identification of new sources of tolerance for rootstock breeding. (Texte intégral

Application of the EXtrapolated Efficiency Method (EXEM) to infer the gamma-cascade detection efficiency in the actinide region

The study of transfer-induced gamma-decay probabilities is very useful for understanding the surrogate-reaction method and, more generally, for constraining statistical-model calculations. One of the main difficulties in the measurement of gamma-decay probabilities is the determination of the gamma-cascade detection efficiency. In [Nucl. Instrum. Meth. A 700, 59 (2013)] we developed the Extrapolated Efficiency Method (EXEM), a new method to measure this quantity. In this work, we have applied, for the first time, the EXEM to infer the gamma-cascade detection efficiency in the actinide region. In particular, we have considered the 238U(d,p)239U and 238U(3He,d)239Np reactions. We have performed Hauser-Feshbach calculations to interpret our results and to verify the hypothesis on which the EXEM is based. The determination of fission and gamma-decay probabilities of 239Np below the neutron separation energy allowed us to validate the EXEM

Evaluation of fruit quality in a lemon cybrid with mandarin mitochondria

Nutritional and organoleptic qualities of fruit are currently very important objectives for plant breeders. Organic acids, sugars and carotenoids were studied by high liquid chromatography on the pulp of a citrus cybrid. This cybrid named 'WLM + EUR' (Citrus deliciosa Ten.) + (Citrus limon (L.) Burm.), inherited nuclear and chloroplasts genomes of Eureka lemon (Citrus limon (L.) Burm.) plus mitochondria from Willow leaf mandarin (Citrus deliciosa Ten.). In our work, impact of new mitochondria on fruit quality was studied during the maturity period. We observed that the cybrid was different from willow leaf mandarin and close to lemon parent. Organic acids level is slightly increased in the cybrid fruit pulp compared to Eureka lemon. No significant difference is observed in sugars and carotenoids between the cybrid and the lemon. The results confirm that mains genetic information for sugars, organic acids and carotenoids biosynthesis are contained in the nucleus. Cybridisation should be used in citrus as a strategy to breed specifie traits associated with mitochondrial genomes such as male sterility without affecting the main organoleptic and nutritional qualities. (Texte intégral