In Loquat (Eriobotrya japonica Lindl.) Return Bloom Depends on the Time the Fruit Remains on the Tree

In loquat (Eriobotrya japonica Lindl.), the comparison of fruiting trees and defruited trees carried out covering a range of developmental fruit stages reveals a significant reduction in flowering due to fruit from its early stage of development, being higher when it changes color and becomes senescent, which coincides with the floral bud inductive period. This effect occurred both at the tree and at the shoot level. Furthermore, although current shoots almost always develop into panicles, those from fruiting trees develop fewer flowers, suggesting that fruit also affects at the floral bud level. In our experiment, the gibberellin concentration at the floral bud inductive period was significantly higher in bark tissues (periderm, cortex and phloem tissues) of fruiting trees, compared with defruited trees that tend to flower more. The lower concentration of IAA in the bark tissues of defruited trees also contributes to increase their flowering intensity. On the contrary, the zeatin concentration was higher. Accordingly, at bud burst, the IAA/zeatin ratio, an indication of effect on flowering, was significantly higher for fruiting trees. Some disruption in the nitrate reduction process in fruiting tree was also observed. The process of floral bud induction and differentiation was not associated with either reducing or translocating and reserve carbohydrate concentration. Hence, loquat flower intensity depends on the time the fruit is maintained on the tree. The intensity is affected indirectly, by reducing the number of shoots, and directly, by reducing the number of flowers per panicle, and these effects are linked to endogenous plant hormone contents.     

Molecular and morphological diversity of Trebouxia microalgae in sphaerothallioid Circinaria spp. lichens1

Three vagrant (Circinaria hispida, Circinaria gyrosa, and Circinaria sp. ‘paramerae’) and one crustose (semi‐vagrant, Circinaria sp. ‘oromediterranea’) lichens growing in very continental areas in the Iberian Peninsula were selected to study the phycobiont diversity. Mycobiont identification was checked using nrITS DNA barcoding: Circinaria sp. ‘oromediterranea’ and Circinaria sp. ‘paramerae’ formed a new clade. Phycobiont diversity was analyzed in 50 thalli of Circinaria spp. using nrITS DNA and LSU rDNA, with microalgae coexistence being found in all the species analyzed by Sanger sequencing. The survey of phycobiont diversity showed up to four different Trebouxia spp. as the primary phycobiont in 20 thalli of C. hispida, in comparison with the remaining Circinaria spp., where only one Trebouxia was the primary microalga. In lichen species showing coexistence, some complementary approaches are needed (454 pyrosequencing and/or ultrastructural analyses). Five specimens were selected for high‐throughput screening (HTS) analyses: 22 Trebouxia OTUs were detected, 10 of them not previously known. TEM analyses showed three different cell morphotypes (Trebouxia sp. OTU A12, OTU S51, and T. cretacea) whose ultrastructure is described here in detail for the first time. HTS revealed a different microalgae pool in each species studied, and we cannot assume a specific pattern between these pools and the ecological and/or morphological characteristics. The mechanisms involved in the selection of the primary phycobiont and the other microalgae by the mycobiont are unknown, and require complex experimental designs. The systematics of the genus Circinaria is not yet well resolved, and more analyses are needed to establish a precise delimitation of the species.     

Climatic factors affecting the occurrence of cloudy stain on the fruit skin of ‘Triumph’ Japanese persimmon

Cloudy stain is a physiological disorder of the Japanese persimmon blemishing the skin and causing a great reduction of fruit quality, thus decreasing its commercial value. The stain starts at or just prior to the fruit colour-break stage, coinciding with the presence of cuticular cracks which increase cuticle water permeability and expose subepidermal cells to air and water, causing oxidation of polyphenol substances of large skin areas that turn almost black. The incidence of the disorder examined over four consecutive years in two growing areas of Spain revealed significant differences from year to year, between areas and even the tree face examined. The data consistently showed that cooler groves and fruit located on the northern face of the canopy were more prone to develop the stain. During the 4 years of the study, the average daily minimum temperature of a period of 15–25 days prior to the onset of staining followed the same order as the yearly staining rate, and accumulated hours below 13°C correlated significantly with the percentage of fruit starting the disorder. No relationship was found between the time-course of relative humidity (RH) and the onset of staining, but once the stain started the lower RH resulted in the lower percentage of affected fruit. Dew point, wind speed, rainfall and evapotranspiration did not correlate either with the onset of staining or with its incidence. Rind of cloudy-stained fruit had higher concentration of N, K, Mg and Fe and lower concentration of Ca than that of healthy fruit, but it is not the cause of the disorder. Accordingly, we conclude that cloudy stain of Japanese persimmon starts after a period of low temperature (≤ 13°C) and, afterwards, RH is responsible for its development and severity.     

Biosynthesis and Contents of Gibberellins in Seeded and Seedless Sweet Orange (<Emphasis Type="Italic">Citrus sinensis</Emphasis> L. Osbeck) Cultivars

In this work, we study the capacity to biosynthesize gibberellins (GA) of ovules (either fertilised or unfertilised), developing seeds and pericarp from fruitlets and their relation with fruit set capacity. Experiments were performed in adult, 12-year-old trees of seeded (Pineapple) and seedless parthenocarpic (Washington navel) sweet orange [Citrus sinensis L. Osbeck] cultivars. The activity of GA20-, GA3- and GA2-oxidases and gibberellin levels were measured in the ovules and pericarp of fruitlets in different development states. The results indicate that ovules are the main sites of gibberellin synthesis in fruitlets during the post-anthesis period. The most intense GA₁ synthesis—coincident with the highest expression of GA20ox2, GA3ox1 and GA2ox1—was detected in the ovules of the seeded cultivar, probably induced by fecundation and associated with low early fruitlet abscission rates. By contrast, the low activity detected in the sterile cultivar appears to be rather developmentally or constitutively regulated. As a fruitlet develops, the GA₁ concentration is augmented in the pericarp in comparison to ovules or developing seeds, and levels therein did not exhibit noticeable differences between varieties. Furthermore, developing seeds from pineapple had higher GA₁ content than the unfertilised abortive ovules from Washington navel. Taken together, data suggest a main role for this hormone in the control of fruitlet abscission, and also demonstrate a function in seed development.     

A functional genetic marker for apple red skin coloration across different environments

The red skin color desired by most apple consumers is not easy to achieve in warm climates, as the expression of MYB10, which regulates red pigmentation in apple, is influenced negatively by high temperatures. We describe the development and validation of a genetic marker for red skin coloration that effectively predicts color in a warm summer environment in Spain, as well as more temperate climates in New Zealand and Italy. Following the determination of a major-effect quantitative trait locus (QTL) controlling red skin coloration on linkage group (LG)9, using four segregating populations grown in New Zealand, and screened using the IRSC apple 8-K single-nucleotide polymorphism (SNP) array, the most significant SNP marker (ss475879531) was transformed into a marker suitable for use in a real-time PCR assay. This marker was validated using five apple seedling populations growing in a warm summer environment in Spain, demonstrating that the marker system efficiently predicts red skin coloration and can be used for marker assisted selection, even under conditions considered adverse for skin color development.     

Evidence for rolling-circle replication in a major satellite DNA from the South American rodents of the genus Ctenomys

A major PvuII satellite DNA has been cloned from a South American octodontid rodent of the genus Ctenomys (C. porteousi). The satellite monomer, termed RPCS, is 337 bp in size and 42% G + C. Analysis of the nucleotide sequence demonstrates that RPCS is not composed of a series of shorter repeats. RPCS-related sequences were found in 11 of 12 Ctenomys species analyzed by hybridization under high-stringency conditions. The only negative species, C. opimus, was reactive under low-stringency conditions. RPCS-related sequences were not found under high- or low-stringency conditions in Calomys musculinus and Mus musculus. However, under low-stringency conditions, RPCS-related sequences were found in the octodontid Octodontomys gliroides, which is thought to have diverged from the genus Ctenomys more than 10 Myr ago. The pattern of periodicities observed, by restriction analysis, between Ctenomys species in the satellite array can be mainly accounted for by a rolling-circle amplification mechanism but cannot be solely accounted for by unequal crossing-over.     

A new fossil genus of South American cricetid rodents allied to Wiedomys, with an assessment of the Sigmodontinae

A new genus and species of sigmodontine cricetids, Cholomys pearsonl , from the Lower Pleistocene Vorohué Formation of south-eastern Buenos Aires Province. Argentina, is described. Its closest relative among the extant and extinct cricetids proved to be the living Wiedomys pyrrhorhinus of Brazil. Wiedomys and Cholomys are included in a new tribe of the Sigmodontinae, Wiedomyini. The distinction between the North American and the South American cricetids is stressed, the two groups being postulated to pertain to different subfamilies. The names Neotominae and Sigmodontinae are chosen for these two taxa, respectively. A tribal classification of the Sigmodontinae is advanced. Oryzomyini, Akodontini, Scapteromyini, Phyllotini, Sigmodontini, lehthyomyini and Wiedomyini are recognized as natural tribes of the Sigmodontinae. This broad array of suprageneric groupings reflecting different adaptive types strongly supports the hypothesis that the differentiation of the Sigmodontinae took place in South America from a primitive cricetid immigrant stock which entered South America, probably from North America, not later than during Miocene times.