Linking ascorbic acid production in Ribes nigrum with fruit development and changes in sources and sinks

Background and Aims

Understanding the synthesis of ascorbic acid (l-AsA) in green tissues in model species has advanced considerably; here we focus on its production and accumulation in fruit. In particular, our aim is to understand the links between organs which may be sources of l-AsA (leaves) and those which accumulate it (fruits). The work presented here tests the idea that changes in leaf and fruit number influence the accumulation of l-AsA. The aim was to understand the importance of leaf tissue in the production of l-AsA and to determine how this might provide routes for the manipulation of fruit tissue l-AsA.

Methods

The experiments used Ribes nigrum (blackcurrant), predominantly in field experiments, where the source–sink relationship was manipulated to alter potential leaf l-AsA production and fruit growth and accumulation of l-AsA. These manipulations included reductions in reproductive capacity, by raceme removal, and the availability of assimilates by leaf removal and branch phloem girdling. Natural variation in fruit growth and fruit abscission is also described as this influences subsequent experimental design and the interpretation of l-AsA data.

Key Results

Results show that fruit l-AsA concentration is conserved but total yield of l-AsA per plant is dependent on a number of innate factors many of which relate to raceme attributes. Leaf removal and phloem girdling reduced fruit weight, and a combination of both reduced fruit yields further. It appears that around 50 % of assimilates utilized for fruit growth came from apical leaves, while between 20 and 30 % came from raceme leaves, with the remainder from ‘storage’.

Conclusions

Despite being able to manipulate leaf area and therefore assimilate availability and stored carbohydrates, along with fruit yields, rarely were effects on fruit l-AsA concentration seen, indicating fruit l-AsA production in Ribes was not directly coupled to assimilate supply. There was no supporting evidence that l-AsA production occurred predominantly in green leaf tissue followed by its transfer to developing fruits. It is concluded that l-AsA production occurs predominantly in the fruit of Ribes nigrum.     

Dieter Seidel‐65 Jahre

Fruit extract of Solanum xanthocarpum was evaluated for its toxicity against Alternaria brassicae, the causal agent of Alternaria blight of Indian mustard [Brassica juncea (L.) Czern. &; Coss]. The mass obtained after vacuum drying of the crude methanolic extract was utilised for further sequential fractionation using n-hexane, ethyl acetate, n-butanol and methanol. Among the crude and different fractions tested, methanolic fraction was most effective with a minimum inhibitory concentration (MIC) of 62.5 μg/ml. The methanolic fraction was further fractionated using open column liquid chromatography into five subfractions (I–V) to identify the antifungal bioactive compounds. Among the five subfractions (SFs) tested SF IV was most effective at inhibiting A. brassicae conidial germination and thereby inhibited lesion development of Alternaria blight at a concentration of 15.625 μg/ml or higher. Furthermore, bioautography of SF IV with Alternaria alternata and diagnosis with Dragendorff reagent indicated that SF IV contains a mixture of bioactive alkaloids, namely a₁ (R_f = 0.12) and a₂ (R_f = 0.22). The potential of using S. xanthocarpum as a resource for the development of biofungicides is discussed.     

Epidemiology and prediction of brown leaf rust of mulberry caused by Peridiopsora mori

Brown leaf rust (BLR) caused by Peridiopsora mori is one of the major foliar diseases of mulberry (Morus sp.) in the subtropical hills of eastern India. The disease appeared in first week of August and continued up to September with maximum severity in second and third week of September. The disease symptoms appeared at atmospheric temperature (27.00–20.07°C), relative humidity (92.14–82.43%), rainfall (11.20 cm) and rainy days (7) of the preceding week. Disease severity (>50 PDI) was observed at temperature (26.29–19.29°C), relative humidity (94.14–80.14%), rainfall (4.12 cm) and number of rainy days (2–3 days). Apparent rate of infection was found high at temperature (27.00–19.83°C), relative humidity (94.67–85.00%), rainfall (4.6 cm) and rainy days (2) of the preceding week. The correlation coefficient between disease severity and average meteorological factors of the preceding 7 days revealed that BLR disease severity showed significant negative correlation with minimum temperature. It was also revealed that contribution of maximum and minimum temperature 42.23% and 35.21%, maximum and minimum relative humidity (RH) 11.23% and 10.69% and rainfall and number of rainy days 0.11% and 0.50%, respectively towards development of BLR disease severity. Multiple regression analysis revealed that average of maximum and minimum temperatures and minimum RH of preceding 7 days were found to maximally influence BLR disease severity.     

Infection process of Colletotrichum dematium on mulberry leaves: An unusual method of sporulation

Abstract

The pre-penetration and infection process of Colletotrichum dematium on mulberry leaf was investigated by scanning electron microscope. Conidia produced on germination appressoria directly or at the end of short germ tubes. Appressoria were formed mostly over cuticle, but sometimes over stomata also. At 72 h post-inoculation, an extensive network of sub-cuticular runner hyphae (RH) was produced. The RH were traceable by the cuticular bulgings on leaf surface. The RH emerged to leaf surface through ruptured cuticle to form secondary infection hyphae (SIH). The SIH re-entered the leaf tissue by sending penetration branches through stomata. Conidia were formed singly on short conidiophores from the RH and SIH, at short intervals. The conidia developed on RH were exposed to leaf surface through ruptured cuticle. Some times conidia were released through stomata also. The RH and SIH had thick knots from which hyphal branches and conidia were developed. Definite acervuli were not developed.     

Leaf yield loss assessment due to Macrophomina root rot disease in mulberry gardens of south India

Abstract

Leaf yield loss in mulberry due to Macrophomina root rot disease was assessed in three different states of south India at field level. The highest leaf yield loss recorded was in V-1 variety (34.74%), whereas the lowest leaf yield loss was in K-2 variety (28.54%). However, the leaf yields losses in other varieties viz., MR-2 (32.90%), S-36 (32.06%), RFS-175 (31.75%) and S-13 (29.0%) recorded were medium. The average leaf yield loss was 31.49% due to root rot disease caused by M. phaseolina in mulberry.     

Wolbachia endosymbiont in a species of the Anastrepha fraterculus complex (Diptera: Tephritidae)

Summary

In Anastrepha sp.2 aff. fraterculus, the egg-cell harbours a large population of endosymbionts. The bacteria were identified as belonging to genus Wolbachia by PCR assay using primers of the ftsZ gene followed by sequencing of the amplified band. Newly deposited eggs stained in toto by Hoechst show that the bacteria are unevenly dispersed throughout the egg-cell, with a higher accumulation at the posterior pole, and that the degree of infestation varies from egg to egg. Analysis by transmission electron microscopy shows that bacteria are present in the female germ line of embryonic and larval stages, as well as in the different cell types of the ovaries at the adult stage. Mature ova within the follicles harbour a large population of the symbionts. The results indicate the existence of a transovarian transmission of the endosymbionts in this fly.     

Membrane Processing of Fruit Juices and Beverages: A Review

ABSTRACT:?

Membrane technology for the processing of fruit juices and beverages has been applied mainly for clarification using ultrafiltration and microfiltration, and for concentration using reverse osmosis. The effects of product preparation, membrane selection, and operating parameters are important factors influencing filtration rate and product quality. Technological advances related to the development of new membranes, improvement in process engineering, and better understanding of fruit beverage constituents have expanded the range of membrane separation processes. Developments in novel membrane processes, including electrodialysis and pervaporation, increased the array of applications in combination with other technologies for alternate uses in fruit juices and beverages.     

Prey Spectra of Jaguar (Panthera onca) and Puma (Puma concolor) in Tropical Forests of Mexico

At the Calakmul Biosphere Reserve in Campeche, Mexico, the prey spectra of sympatric jaguars (Panthera onca) and pumas (Puma concolor) were studied by examination of their scats. 10 vertebrate species were identified for jaguars and 7 for pumas, mainly mammals and some birds. Based on these diet analyses, we conclude that jaguars and pumas coexist at Calakmul by means of different food habits.     

Phylogenetic relationships of Andean-Ecuadorian populations of Anastrepha fraterculus (Wiedemann 1830) (Diptera: Tephritidae) inferred from COI and COII gene sequences

Phylogenetic relationships among Andean-Ecuadorian and other Neotropical populations of Anastrepha fraterculus and related species have been studied using two regions of mtDNA : 405 base pairs within Cytochrome Oxidase I ( COI) and 224 base pairs within Cytochrome Oxidase II (COII). Phylogenetic relationships were inferred using Maximun Parsimony (MP) method and haplotype networks. Andean-Ecuadorian populations of A. fraterculus are monomorphic at the COI locus and fall within a clade of South-American lowland populations of A. fraterculus. They appear to be unrelated with populations of northern Andes of Colombia and Venezuela also assigned to A. fraterculus, meaning that this species, as currently circumscribed, is not monophyletic and is composed of different biological entities that are little differentiated morphologically. At the COII locus, Andean-Ecuadorian populations of A. fraterculus show a major haplotype with a few variants, and form a clade with the lowland populations of southern Brazil an Argentina, but are clearly differentiated from them. Andean-Ecuadorian populations of Anastrepha fraterculus appear to be homogeneous with respect to their mitochondrial genome and thus their identity as members of a single gene pool is confirmed by these results.