Increasing water stress negatively affects pear fruit growth by reducing first its xylem and then its phloem inflow

Drought stress negatively affects many physiological parameters and determines lower yields and fruit size. This paper investigates on the effects of prolonged water restriction on leaf gas exchanges, water relations and fruit growth on a 24-h time-scale in order to understand how different physiological processes interact to each other to face increasing drought stress and affect pear productive performances during the season. The diurnal patterns of tree water relations, leaf gas exchanges, fruit growth, fruit vascular and transpiration flows were monitored at about 50, 95 and 145 days after full bloom (DAFB) on pear trees of the cv. Abbé Fétel, subjected to two irrigation regimes, corresponding to a water restitution of 100% and 25% of the estimated Etc, respectively. Drought stress progressively increased during the season due to lower soil tensions and higher daily vapour pressure deficits (VPDs). Stem water potential was the first parameter to be negatively affected by stress and determined the simultaneous reduction of fruit xylem flow, which at 95 DAFB was reflected by a decrease in fruit daily growth. Leaf photosynthesis was reduced only from 95 DAFB on, but was not immediately reflected by a decrease in fruit phloem flow, which instead was reduced only at 145 DAFB. This work shows how water stress negatively affects pear fruit growth by reducing first its xylem and then its phloem inflow. This determines a progressive increase in the phloem relative contribution to growth, which lead to the typical higher dry matter percentages of stressed fruit.

Effects of specific organs on seed oil accumulation in Brassica napus L

Seed oil content is an important agricultural characteristic in rapeseed breeding. Genetic analysis shows that the mother plant and the embryo play critical roles in regulating seed oil accumulation. However, the overwhelming majority of previous studies have focused on oil synthesis in the developing seed of rapeseed. In this study, to elucidate the roles of reproductive organs on oil accumulation, silique, ovule, and embryo from three rapeseed lines with high oil content (zy036, 6F313, and 61616) were cultured in vitro. The results suggest that zy036 silique wall, 6F313 seed coat, and 61616 embryo have positive impacts on the seed oil accumulation. In zy036, our previous studies show that high photosynthetic activity of the silique wall contributes to seed oil accumulation (Hua et al., 2012). Herein, by transcriptome sequencing and sucrose detection, we found that sugar transport in 6F313 seed coat might regulate the efficiency of oil synthesis by controlling sugar concentration in ovules. In 61616 embryos, high oil accumulation efficiency was partly induced by the elevated expression of fatty-acid biosynthesis-related genes. Our investigations show three organ-specific mechanisms regulating oil synthesis in rapeseed. This study provides new insights into the factors affecting seed oil accumulation in rapeseed and other oil crops.

Evidence for a radial strain gradient in apple fruit cuticles

The morphological outer side of the apple fruit cuticle is markedly more strained than the inner side. This strain is released upon wax extraction. This paper investigates the effect of ablating outer and inner surfaces of isolated cuticular membranes (CM) of mature apple (Malus × domestica) fruit using cold atmospheric pressure plasma (CAPP) on the release of strain after extraction of waxes. Strain release was quantified as the decrease in area of CM discs following CAPP treatment and subsequent solvent extraction of wax. Increasing duration of CAPP treatment proportionally decreased CM mass per unit area. There was no difference in mass loss rate between CAPP treatments of outer or inner surfaces. Also, there was no difference in surface area of CMs before and after CAPP treatment. However, upon subsequent wax extraction, surface area of CMs decreased indicating the release of strain. Increasing the duration of CAPP treatment resulted in increasing strain release up to 47.7 ± 8.0 % at 20 min when CAPP was applied to the inner surface. In contrast, strain release was independent of CAPP duration averaging about 12.1 ± 0.6 % when applied to the outer surface of the CM. Our results provide evidence for a marked gradient of strain between the outer side (strained) and the inner side of the CM (not strained) of mature apple fruit.

Factors Limiting Peach as a Potential Host for Drosophila suzukii (Diptera: Drosophilidae)

The spotted wing drosophila, Drosophila suzukii Matsumura, has widely established in North America and become an economic concern for a variety of fruit crops. To better understand fruit susceptibility, we evaluated peach surface characteristics on the pest's oviposition success. The number of D. suzukii eggs laid into the fruit flesh was tested on 1) peaches with or without indumenta (commonly referred to as peach fuzz), 2) peaches physically damaged by harvest operations, 3) peaches damaged by the peach twig borer Anarsia lineatella Zeller or the forktailed bush katydid, Scudderia furcata Brunner von Wattenwyl, and 4) peaches with punctures that simulated stink bug damage. Female D. suzukii did not lay eggs in intact fuzzy sections of the fruit or into small punctures (0.3 or 0.5 mm), but readily laid eggs in sections without fuzz, with insect damage, and with large punctures (1 mm). The number of eggs per treatment was positively related to the area of the damaged section; the overall fruit firmness and sugar content was not related to the number of eggs laid in treated or damaged spots. Direct observations of D. suzukii oviposition confirmed that peach fuzz appeared to be an obstacle for the fly's oviposition success, and female flies ceased ovipositional attempts on fuzzy peach sections after a short period of time. Successful oviposition times were associated with substrate firmness, with shorter oviposition time in damaged spots than in cherry fruit or shaved spots of the peach. The results indicate that intact, preharvest peach fruit are unlikely to be infested by the fly, but any surface damage could render the fruit susceptible to the fly.

Spatial Distribution of Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Injury at Harvest in Mid-Atlantic Apple Orchards

Brown marmorated stink bug, Halyomorpha halys (Stål), injury to late-season apple cultivars was measured at harvest in 2011 and 2012 in commercial orchards in four mid-Atlantic states. In each orchard block, a border zone (adjacent to woods), an interior zone (near orchard center), and an intermediate zone (between border and interior zones) comprised 1-3 tree rows per zone, depending on block size. Just before commercial harvest, 10 fruit were sampled from the upper, middle, and lower third of the canopy from five trees in each zone. After 3-5 wk in cold storage, fruit were examined for external and internal injury, and severity of internal injury (number of injury sites per fruit) from H. halys. A zero-inflated negative binomial model accounted for significant variation among the orchards and showed that apples from the upper canopy of border zone trees had the highest probability of experiencing external and internal injury. A minor interaction was detected among the orchards and zones for injury prevalence and severity, but there was no evidence of an orchard showing less expected injury in the border zone compared with other zones. Adjusting for orchard-to-orchard variation, differences in injury distributions among the zones and canopies were primarily due to injury prevalence rather than expected injury severity. The implications of these results to scouting and managing H. halys in eastern apple orchards are discussed.

[Effects of irrigation threshold on soil temperature in blossom and fruit-set periods of muskmelon under mulching-drip irrigation in greenhouse]

It is very significant for muskmelon growth and production to maintain optimal conditions of soil moisture and temperature, especially during blossom and fruit-bearing periods. The object of this study was to analyze the effects of different soil water thresholds (T1: 55% of the field capacity, T2: 65% of the field capacity, T3: 75% of the field capacity, CK: 85% of the field capacity) on soil temperature under mulching-drip irrigation in greenhouse. Moreover, effects of the ratio of soil moisture to heat in the plough layer (0-20 cm) on muskmelon growth and fruit setting were investigated. Results indicated that during the flowering and fruit bearing periods, the order of mean soil temperature in the plough layer for the different treatments was T1 > T2 > T3 > CK. There was an inverse correlation between soil temperature in the plough layer and moisture. The maximum one-day variations for soil temperature on sunny day, rainy day and after irrigation were observed in the soil surface under the plastic film mulch, while the minimum happened in the soil layer of 20 cm outside the mulch. The soil temperature extreme was closely related with soil depth, and the difference in the extreme soil temperature between the soil surface and the soil layers of 10 and 20 cm was significant. The treatment T3, with the fastest plant growth rate, the minimum duration of fruit bearing and the maximum fruit setting rate, could be selected as the optimal treatment, and the ratio of soil moisture to heat in T3 was 1.62 mm · °C(-1). Therefore, taking into consideration the relationship between soil moisture and temperature during flowering and fruit bearing periods of muskmelon under mulching-drip irrigation, the ratio of soil water to heat in the plough layer should be kept at 1.62 mm · C(-1). The result would be very meaningful for drip-irrigated muskmelon production and management in greenhouse in North China.

Evaluation of the Host Status of Mature Green Papayas 'Maradol' for the Mexican Fruit Fly (Diptera: Tephritidae)

The suitability of mature green 'Maradol' papaya as a host of Anastrepha ludens (Loew) was studied under field and laboratory conditions. Field tests were conducted on commercial-ripened and spot-ripened fruit in two orchards and during two seasons in the state of Chiapas. Fruits at exportation ripeness are in "commercial ripeness", while fruits that are harvested immediately preceding exportation ripeness are in "spot ripeness." The field tests consisted of forced infestation experiments that evaluated papayas at two ripeness stages: the commercial- or exportation-ripened fruit (green fruits with one or two yellow stripes) and fruit before exportation ripeness called "spot ripeness." These tests were conducted in two orchards and during two seasons in the state of Chiapas, Mexico. Laboratory trials were performed with commercial-ripened fruit only. Fruit from four different postharvest periods (3, 24, 48, and 72 h) were exposed to groups of gravid flies. No larvae emerged from the fruit that was collected in the field experiments. However, some larvae and several fertile flies were obtained from the commercial-ripened fruit 72 h postharvest but not 3, 24, and 48 h postharvest in the laboratory. The results of this study indicate that the commercially ripe fruits of papaya Maradol were resistant to or free from infestation of A. ludens flies under field conditions, though these fruits must be considered nonnatural, conditional host because they became infested in the laboratory.

Fruit softening and pectin disassembly: an overview of nanostructural pectin modifications assessed by atomic force microscopy

BACKGROUND

One of the main factors that reduce fruit quality and lead to economically important losses is oversoftening. Textural changes during fruit ripening are mainly due to the dissolution of the middle lamella, the reduction of cell-to-cell adhesion and the weakening of parenchyma cell walls as a result of the action of cell wall modifying enzymes. Pectins, major components of fruit cell walls, are extensively modified during ripening. These changes include solubilization, depolymerization and the loss of neutral side chains. Recent evidence in strawberry and apple, fruits with a soft or crisp texture at ripening, suggests that pectin disassembly is a key factor in textural changes. In both these fruits, softening was reduced as result of antisense downregulation of polygalacturonase genes. Changes in pectic polymer size, composition and structure have traditionally been studied by conventional techniques, most of them relying on bulk analysis of a population of polysaccharides, and studies focusing on modifications at the nanostructural level are scarce. Atomic force microscopy (AFM) allows the study of individual polymers at high magnification and with minimal sample preparation; however, AFM has rarely been employed to analyse pectin disassembly during fruit ripening.

SCOPE

In this review, the main features of the pectin disassembly process during fruit ripening are first discussed, and then the nanostructural characterization of fruit pectins by AFM and its relationship with texture and postharvest fruit shelf life is reviewed. In general, fruit pectins are visualized under AFM as linear chains, a few of which show long branches, and aggregates. Number- and weight-average values obtained from these images are in good agreement with chromatographic analyses. Most AFM studies indicate reductions in the length of individual pectin chains and the frequency of aggregates as the fruits ripen. Pectins extracted with sodium carbonate, supposedly located within the primary cell wall, are the most affected.

Genetic, metabolite and developmental determinism of fruit friction discolouration in pear

BACKGROUND

The unattractive appearance of the surface of pear fruit caused by the postharvest disorder friction discolouration (FD) is responsible for significant consumer dissatisfaction in markets, leading to lower returns to growers. Developing an understanding of the genetic control of FD is essential to enable the full application of genomics-informed breeding for the development of new pear cultivars. Biochemical constituents [phenolic compounds and ascorbic acid (AsA)], polyphenol oxidase (PPO) activity, as well as skin anatomy, have been proposed to play important roles in FD susceptibility in studies on a limited number of cultivars. However, to date there has been no investigation on the biochemical and genetic control of FD, employing segregating populations. In this study, we used 250 seedlings from two segregating populations (POP369 and POP356) derived from interspecific crosses between Asian (Pyrus pyrifolia Nakai and P. bretschneideri Rehd.) and European (P. communis) pears to identify genetic factors associated with susceptibility to FD.

RESULTS

Single nucleotide polymorphism (SNP)-based linkage maps suitable for QTL analysis were developed for the parents of both populations. The maps for population POP369 comprised 174 and 265 SNP markers for the male and female parent, respectively, while POP356 maps comprised 353 and 398 SNP markers for the male and female parent, respectively. Phenotypic data for 22 variables were measured over two successive years (2011 and 2012) for POP369 and one year (2011) only for POP356. A total of 221 QTLs were identified that were linked to 22 phenotyped variables, including QTLs associated with FD for both populations that were stable over the successive years. In addition, clear evidence of the influence of developmental factors (fruit maturity) on FD and other variables was also recorded.

CONCLUSIONS

The QTLs associated with fruit firmness, PPO activity, AsA concentration and concentration of polyphenol compounds as well as FD are the first reported for pear. We conclude that the postharvest disorder FD is controlled by multiple small effect QTLs and that it will be very challenging to apply marker-assisted selection based on these QTLs. However, genomic selection could be employed to select elite genotypes with lower or no susceptibility to FD early in the breeding cycle.

[Sex structure and seed productivity of Mentha canadensis L. from natural flora of primorye of Russia]

The sex structure and seed productivity of Mentha canadensis L. from different climatic regioins of Primorye of Russia was studied. We established that M. canadensis is characterized by a homogeneous population structure due to the formation of vegetative clones. The ratio of female and androgynous individuals was 1:5, and it is possible that this is a species-specific trait. Both sexual forms produced fruits under conditions of isolation from cross-pollination. We discuss the possibility of apomixis and the influence of climatic conditions on seed productivity and morphometric characteristics of plants.

'Movers and shakers' in the regulation of fruit ripening: a cross-dissection of climacteric versus non-climacteric fruit

Fruit ripening is a complex and highly coordinated developmental process involving the expression of many ripening-related genes under the control of a network of signalling pathways. The hormonal control of climacteric fruit ripening, especially ethylene perception and signalling transduction in tomato has been well characterized. Additionally, great strides have been made in understanding some of the major regulatory switches (transcription factors such as RIPENING-INHIBITOR and other transcriptional regulators such as COLOURLESS NON-RIPENING, TOMATO AGAMOUS-LIKE1 and ETHYLENE RESPONSE FACTORs), that are involved in tomato fruit ripening. In contrast, the regulatory network related to non-climacteric fruit ripening remains poorly understood. However, some of the most recent breakthrough research data have provided several lines of evidences for abscisic acid- and sucrose-mediated ripening of strawberry, a non-climacteric fruit model. In this review, we discuss the most recent research findings concerning the hormonal regulation of fleshy fruit ripening and their cross-talk and the future challenges taking tomato as a climacteric fruit model and strawberry as a non-climacteric fruit model. We also highlight the possible contribution of epigenetic changes including the role of plant microRNAs, which is opening new avenues and great possibilities in the fields of fruit-ripening research and postharvest biology.

Banana fruit NAC transcription factor MaNAC1 is a direct target of MaICE1 and involved in cold stress through interacting with MaCBF1

Our previous studies have indicated that the banana ripening-induced MaNAC1, a NAC (NAM, ATAF1/2 and CUC2) transcription factor (TF) gene, is regulated by ethylene during fruit ripening, and propylene, a functional ethylene analogue, induces cold tolerance of banana fruits. However, the involvement of MaNAC1 in propylene-induced cold tolerance of banana fruits is not understood. In the present work, the possible involvement of MaNAC1 in cold tolerance of banana fruits was investigated. MaNAC1 was noticeably induced by cold stress or following propylene treatment during cold storage. Transient protoplast assays showed that MaNAC1 promoter was activated by cold stress and ethylene treatment. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA) and transient expression assays demonstrated MaNAC1 as a novel direct target of MaICE1, and that the ability of MaICE1 binding to MaNAC1 promoter might be enhanced by MaICE1 phosphorylation and cold stress. Moreover, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses revealed physical interaction between MaNAC1 and MaCBF1, a downstream component of inducer of C-repeat binding factor (CBF) expression 1 (ICE1) in cold signalling. Taken together, these results suggest that the cold-responsive MaNAC1 may be involved in cold tolerance of banana fruits through its interaction with ICE1-CBF cold signalling pathway, providing new insights into the regulatory activity of NAC TF.

Different mechanisms are responsible for chlorophyll dephytylation during fruit ripening and leaf senescence in tomato

Chlorophyll breakdown occurs in different green plant tissues (e.g. during leaf senescence and in ripening fruits). For different plant species, the PHEOPHORBIDE A OXYGENASE (PAO)/phyllobilin pathway has been described to be the major chlorophyll catabolic pathway. In this pathway, pheophorbide (i.e. magnesium- and phytol-free chlorophyll) occurs as a core intermediate. Most of the enzymes involved in the PAO/phyllobilin pathway are known; however, the mechanism of dephytylation remains uncertain. During Arabidopsis (Arabidopsis thaliana) leaf senescence, phytol hydrolysis is catalyzed by PHEOPHYTINASE (PPH), which is specific for pheophytin (i.e. magnesium-free chlorophyll). By contrast, in fruits of different Citrus spp., chlorophyllase, hydrolyzing phytol from chlorophyll, was shown to be active. Here, we enlighten the process of chlorophyll breakdown in tomato (Solanum lycopersicum), both in leaves and fruits. We demonstrate the activity of the PAO/phyllobilin pathway and identify tomato PPH (SlPPH), which, like its Arabidopsis ortholog, was specifically active on pheophytin. SlPPH localized to chloroplasts and was transcriptionally up-regulated during leaf senescence and fruit ripening. SlPPH-silencing tomato lines were impaired in chlorophyll breakdown and accumulated pheophytin during leaf senescence. However, although pheophytin transiently accumulated in ripening fruits of SlPPH-silencing lines, ultimately these fruits were able to degrade chlorophyll like the wild type. We conclude that PPH is the core phytol-hydrolytic enzyme during leaf senescence in different plant species; however, fruit ripening involves other hydrolases, which are active in parallel to PPH or are the core hydrolases in fruits. These hydrolases remain unidentified, and we discuss the question of whether chlorophyllases might be involved.

Challenges in predicting climate change impacts on pome fruit phenology

Climate projection data were applied to two commonly used pome fruit flowering models to investigate potential differences in predicted full bloom timing. The two methods, fixed thermal time and sequential chill-growth, produced different results for seven apple and pear varieties at two Australian locations. The fixed thermal time model predicted incremental advancement of full bloom, while results were mixed from the sequential chill-growth model. To further investigate how the sequential chill-growth model reacts under climate perturbed conditions, four simulations were created to represent a wider range of species physiological requirements. These were applied to five Australian locations covering varied climates. Lengthening of the chill period and contraction of the growth period was common to most results. The relative dominance of the chill or growth component tended to predict whether full bloom advanced, remained similar or was delayed with climate warming. The simplistic structure of the fixed thermal time model and the exclusion of winter chill conditions in this method indicate it is unlikely to be suitable for projection analyses. The sequential chill-growth model includes greater complexity; however, reservations in using this model for impact analyses remain. The results demonstrate that appropriate representation of physiological processes is essential to adequately predict changes to full bloom under climate perturbed conditions with greater model development needed.

Role of the FUL-SHP network in the evolution of fruit morphology and function

Arabidopsis research in the last decade has started to unravel the genetic networks directing gynoecium and fruit patterning in this model species. Only recently, the work from several groups has also started to address the conservation of these networks in a wide number of species with very different fruit morphologies, and we are now beginning to understand how they might have evolved. This review summarizes recent advances in this field, focusing mainly on MADS-box genes with a well-known role in dehiscence zone development, while also discussing how these studies may contribute to expand our views on fruit evolution.

Genome-wide identification, characterization and expression analysis of the auxin response factor gene family in Vitis vinifera

Our study has identified and analyzed the VvARF gene family that may be associated with the development of grape berry and other tissues. Auxin response factors (ARFs) are transcription factors that regulate the expression of auxin responsive genes through specific binding to auxin response elements (AuxREs). The ARF genes are represented by a large multigene family in plants. Until now, many ARF families have been characterized based on genome resources. However, there is no specialized research about ARF genes in grapevine (Vitis vinifera). In this study, a comprehensive bioinformatics analysis of the grapevine ARF gene family is presented, including chromosomal locations, phylogenetic relationships, gene structures, conserved domains and expression profiles. Nineteen VvARF genes were identified and categorized into four groups (Classes 1, 2, 3 and 4). Most of VvARF proteins contain B3, AUX_RESP and AUX_IAA domains. The VvARF genes were widely expressed in a range of grape tissues, and fruit had higher transcript levels for most VvARFs detected in the EST sources. Furthermore, analysis of expression profiles indicated some VvARF genes may play important roles in the regulation of grape berry maturation processes. This study which provided basic genomic information for the grapevine ARF gene family will be useful in selecting candidate genes related to tissue development in grapevine and pave the way for further functional verification of these VvARF genes.

There's more than one way to skin a fruit: formation and functions of fruit cuticles

As with all aerial plant organs, fleshy fruits are encased in a hydrophobic cuticle that must fulfil multiple functions, including limiting desiccation and preventing microbial infection, which in the case of fruits maintains palatability and promotes seed dispersal. Fruit cuticles have many features in common with those of vegetative organs, but also have unique characteristics, including the fact that they are often astomatous, thicker than those of most leaves, and can be relatively easily isolated. These attributes provide a valuable experimental system to address questions related to cuticle structure, function, and the relationships between composition, architecture, permeability, and biomechanical properties. Here we provide an overview of insights into cuticle biology that have resulted from studies of those of fleshy fruits, as well as the diversity and dynamic nature of fruit cuticle composition and architecture, the environmental factors that influence those features, and the roles that they play in fruit ontogeny.

[Effects of environmental factors at different altitudes on leaves and fruit quality of Fuji apple]

To inquire the different performances of the leaves and fruit quality of Fuji apple tress at various altitudes and their responses to the environmental factors, indices including leaf morphology, anatomy, δ13 C, and fruit quality of the Fuji apple trees at respective altitudes of 1375 m, 1575 m and 1715 m were investigated and their responses to environmental factors were determined following stepwise regression analysis. The results showed that 6 factors like the warmth index, Bailey's index, photosynthetically active radiation (PAR), coldness index, ultraviolet B and the annual precipitation dominantly affected the characteristic parameters of leaves and fruit. Elevation increase was matched by the decreasing warmth index, rising Bailey' s index, intenser PAR, higher coldness index, stronger ultraviolet B and heavier annual precipitation; meanwhile, the leaf structure and fruit quality parameters also displayed evident trends of change accordingly, namely, leaf parameters like leaf thickness, cuticle thickness, ratio of palisade and spongy, maximum conduit diameter, δ13C and nitrogen content per unit area increased gradually, and oppositely, leaf length-width ratio, specific leaf area, stoma length-width ratio and ratio of upper and lower epidermis to the leaf thickness decreased gradually; similarly, fruit parameters such as fruit shape index, fruit hardness, sugar-acid ratio, total color and the a/b-value ascended while the titratable acid and the hue angle descended. With increasing the altitude, the photosynthetic rate and water use efficiency of leaves were enhanced, and the fruit sugar-acid ratio climbed and the fruit flavor and color improved. Therefore, it could be safely concluded that within the altitude range between 1375 and 1715 m, environmental factors at a higher altitude favored Fuji apple growth.

Simultaneous application of ethylene and 1-MCP affects banana ripening features during storage

BACKGROUND

In order to avoid the ripening blocking effect of 1-MCP (1-methylcyclopropene) on bananas when applied before ethylene commercial treatment, 1-MCP in combination with 'CD ethylene' (ethylene-cyclodextrin complex) was used in gas formulations: 300 nmol mol(-1) 1-MCP + 1200, 2400 or 4800 nmol mol(-1) ethylene (ETH). Control bananas received 1-MCP alone or 4800 nmol mol(-1) ethylene alone or no treatment. Treatments were done on overseas shipped bananas, at 14 °C, 90% relative humidity (RH), for 16 h; the bananas were stored under the same atmospheric conditions. After 4 or 12 days the bananas were commercially treated with 500 µmol mol(-1) ethylene.

RESULTS

A 300 nmol mol(-1) 1-MCP treatment significantly blocked banana ripening in terms of physiological and technological parameters, inhibiting ethylene production and respiration, despite the commercial ethylene treatment. The application of 300 nmol mol(-1) 1-MCP + 1200 or 2400 nmol mol(-1) ethylene delayed ripening but with a regular pattern. A 300 nmol mol(-1) 1-MCP + 4800 nmol mol(-1) ethylene application did not delay ripening as did 4800 nmol mol(-1) ethylene treatment. The development of black spots was closely associated with advanced ripening/senescence of fruits.

CONCLUSION

The combined 300 nmol mol(-1) 1-MCP + 1200 or 2400 nmol mol(-1) ethylene treatment appears to be a promising treatment to extend banana storage, following overseas shipping.

Characterization of an uncharacterized aldo-keto reductase gene from peach and its role in abiotic stress tolerance

The aldo-keto reductase (AKR) superfamily is a large enzyme group of NADP-dependent oxidoreductases with numerous roles in metabolism, but many members in this superfamily remain uncharacterized. Here, PpAKR1, which was cloned from the rosaceous peach tree (Prunus persica), was investigated as a member of the superfamily. While PpAKR1 had amino acids that are important in AKRs and which belonged to the AKR4 group, PpAKR1 did not seem to belong to any of the AKR4 subgroups. PpAKR1 mRNA abundance increased with abscisic acid, oxidative stress, and cold and salt stress treatments in peach. NADP-dependent polyol dehydrogenase activity was increased in Arabidopsis thaliana transformed with PpAKR1. Salt tolerance increased in Arabidopsis transformed with PpAKR1. PpAKR1, which was a previously uncharacterized member of the AKR superfamily, could be involved in the abiotic stress tolerance.

Increasing tomato fruit quality by enhancing fruit chloroplast function. A double-edged sword?

Fruits are generally regarded as photosynthate sinks as they rely on energy provided by sugars transported from leaves to carry out the highly demanding processes of development and ripening; eventually these imported photosynthates also contribute to the fruit organoleptic properties. Three recent reports have revealed, however, that transcriptional factors enhancing chloroplast development in fruit may result in higher contents not only of tomato fruit-specialized metabolites but also of sugars. In addition to suggesting new ways to improve fruit quality by fortifying fruit chloroplasts and plastids, these results prompted us to re-evaluate the importance of the contribution of chloroplasts/photosynthesis to fruit development and ripening.

Nectar robbing positively influences the reproductive success of Tecomella undulata (Bignoniaceae)

The net consequence of nectar robbing on reproductive success of plants is usually negative and the positive effect is rarely produced. We evaluated the influence of nectar robbing on the behaviour of pollinators and the reproductive success of Tecomella undulata (Bignoniaceae) in a natural population. Experimental pollinations showed that the trees were strictly self-incompatible. The three types of floral colour morphs of the tree viz. red, orange and yellow, lacked compatibility barriers. The pollinators (Pycnonotus cafer and Pycnonotus leucotis) and the robber (Nectarinia asiatica) showed equal preference for all the morphs, as they visited each morph with nearly equal frequency and flower-handling time. The sunbirds caused up to 60% nectar robbing, mostly (99%) by piercing through the corolla tube. Although nectar is replenished at regular intervals, insufficient amount of nectar compelled the pollinators to visit additional trees in bloom. Data of manual nectar robbing from the entire tree showed that the pollinators covered lower number of flowers per tree (5 flowers/tree) and more trees per bout (7 trees/bout) than the unrobbed ones (19 flowers/tree and 2 trees bout). The robbed trees set a significantly greater amount of fruits than the unrobbed trees. However, the number of seeds in a fruit did not differ significantly. The study shows that plant-pollinator-robber interaction may benefit the self-incompatible plant species under conditions that increases the visits of pollinators among the compatible conspecifics in a population.

Enhancement of crop photosynthesis by diffuse light: quantifying the contributing factors

BACKGROUND AND AIMS

Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation.

METHODS

Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied.

KEY RESULTS

The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when global irradiance was high.

CONCLUSIONS

Diffuse light enhanced crop photosynthesis. A more uniform horizontal PPFD distribution played the most important role in this enhancement, and a more uniform vertical PPFD distribution and higher leaf photosynthetic capacity contributed more to the enhancement of crop photosynthesis than did higher values of LAI.

Essential oil composition and antifungal activity of aerial parts of Ballota nigra ssp foetida collected at flowering and fruiting times

The present study reports the results of gas chromatographic-mass spectrometric (GC/MS) analyses of the essential oils from the aerial parts of Ballota nigra L. ssp foetida (Lamiaceae) collected at flowering and fruiting times, as well as their in vitro antifungal activity against nine plant pathogenic fungi. Moreover, the essential oils were evaluated for their antifungal activity using the agar dilution method, and also MICs (minimum inhibitory concentrations) and MFCs (minimum fungicidal concentrations) were determined. The major compounds identified in the flowering and fruiting aerial parts oils respectively were beta-caryophyllene (22.6% and 21.8%), caryophyllene oxide (18.0% and 20.5%) and germacrene-D (16.5 and 13.1%). The oils showed in vitro antifungal activity against some species of Fusarium, Botrytis cinerea, and Alternaria solani. Our study indicates that the oil of B. nigra ssp foetida could be used as a control agent for plant pathogenic fungi in natural formulations.

The chimeric repressor version of an Ethylene Response Factor (ERF) family member, Sl-ERF.B3, shows contrasting effects on tomato fruit ripening

Fruit ripening involves a complex interplay between ethylene and ripening-associated transcriptional regulators. Ethylene Response Factors (ERFs) are downstream components of ethylene signaling, known to regulate the expression of ethylene-responsive genes. Although fruit ripening is an ethylene-regulated process, the role of ERFs remains poorly understood. The role of Sl-ERF.B3 in tomato (Solanum lycopersicum) fruit maturation and ripening is addressed here using a chimeric dominant repressor version (ERF.B3-SRDX). Over-expression of ERF.B3-SRDX results in a dramatic delay of the onset of ripening, enhanced climacteric ethylene production and fruit softening, and reduced pigment accumulation. Consistently, genes involved in ethylene biosynthesis and in softening are up-regulated and those of carotenoid biosynthesis are down-regulated. Moreover, the expression of ripening regulators, such as RIN, NOR, CNR and HB-1, is stimulated in ERF.B3-SRDX dominant repressor fruits and the expression pattern of a number of ERFs is severely altered. The data suggest the existence of a complex network enabling interconnection between ERF genes which may account for the pleiotropic alterations in fruit maturation and ripening. Overall, the study sheds new light on the role of Sl-ERF.B3 in the transcriptional network controlling the ripening process and uncovers a means towards uncoupling some of the main ripening-associated processes.