Effect of Ultraviolet Radiation Environment on Leaf Quantum Efficiencies and Photosynthesis for Tropical and Temperate Species

ABSTRACT

Ultraviolet radiation has detrimental effects on plants and levels are expected to rise through mid-century. Photosystem II is the most vulnerable site in chlorophyll affecting productivity. The purpose of this study was to evaluate leaf-level interactions with UV radiation in tropical and temperate crops. The species sampled were (1) citrus, (2) banana, (3) coffee, (4) pineapple, (5) olive, (6) grape, (7) apple, and (8) tobacco. Plants of each species were placed beneath a polycarbonate structure that excluded 98% of UV radiation, but maintained ambient environmental conditions and transmitted 96% PAR (UV– treatment). Plants of each species were maintained nearby under ambient conditions (i.e., without a UV filter; UV+ treatment). The maximum quantum efficiency (F_v/F_m) was measured with and without UV radiation at the time of measurement. Photosynthesis (A) and quantum efficiency (Φ_II) were measured in the same experimental system using only apple, citrus, banana, and coffee. Only banana and coffee did not fully recover their F_v/F_m potential when they had not been previously exposed to UV, indicating that these species probably had not induced background repair mechanisms. The ΔF_v/F_m is small in magnitude for banana and coffee due to UV treatment but when A is measured, the treatment impact has greater magnitude and banana and coffee A do not recover and coffee Φ_II continues to decline while banana Φ_II appears to stabilize. Banana and coffee have the potential to benefit from cultural practices that reduce the UV irradiance to the leaf or canopy surface.     

Study of the Solar Drying of Pears

ABSTRACT

Four pear cultivars originating from Portugal (‘Amêndoa’, ‘Amorim’, ‘Carapinheira Branca’ and ‘S. Bartolomeu’) were dried in a solar drier, following a traditional sun drying method normally used in Portugal for the production of dried pears. The temperature and relative humidity inside the drier were recorded hourly throughout the whole process, while the moisture loss in the pears was evaluated with a variable frequency along the drying process, according to the drying rate. From the results obtained, it was possible to conclude that the conditions inside the drier are very favorable to drying, with periods in which the atmosphere is characterized by very high temperatures and very low relative humidities. Furthermore, the drying rates of the four cultivars of pears used in this study were investigated and it was observed that all of them present a similar kinetic behavior, thus enabling the use of alternative cultivars for the production of dried pears.     

A combination of gum arabic and chitosan can control anthracnose caused by Colletotrichum musae and enhance the shelf-life of banana fruit

Summary

Anthracnose, caused by Colletotrichum musae, is the major disease affecting the quality of banana fruit during storage. To control banana anthracnose, the combined effects of coatings with gum arabic [GA; at 5, 10, 15 or 20% (w/v)] and 0.75% (w/v) chitosan (CH) were investigated and compared to untreated controls. In vitro results showed significant (P < 0.05) inhibition of mycelial growth and conidial germination of C. musae in all combined treatments compared to the untreated controls after 7 d of incubation at room temperature (25°C). However, potato dextrose agar (PDA) plates amended with 10% (w/v) GA gave the most promising results among all test treatments in suppressing mycelial growth (86%) and inhibiting conidial germination (80%), while no effective inhibition of conidial germination was observed in the controls. In vivo results confirmed that 10% (w/v) GA was the optimum concentration to control fruit decay (70%), while showing efficacy on the reduction of growth of C. musae on artificially inoculated banana fruit. The combined coatings of GA + CH also significantly delayed ripening in terms of weight loss, fruit firmness, soluble solids content, and titratable acidity. These results support the possibility of using 10% (w/v) GA combined with 0.75% (w/v) CH as an alternative strategy to control post-harvest anthracnose disease in banana fruit.     

Modified atmosphere packaging of ‘Kolikuttu’ bananas at low temperature

Summary

Mature `Kolikuttu' bananas were packed under modified atmosphere (M.A.) conditions using low density polyethylene (LDPE) bags and stored at 14°C and 94% r.h. The effect of ethylene scavengers on storage life of banana was examined. The in-package concentrations of oxygen, carbon dioxide and ethylene were measured during storage. Percentage weight loss, changes in firmness, total soluble solids (TSS), pH and sugar: acid during storage were also determined. Based on the in-package gaseous composition, the optimum storage period was defined. After termination of storage, bananas were allowed to ripen naturally, and the physico-chemical properties of ripened banana were analysed. `Kolikuttu' bananas could be packed in LDPE (0.075 mm) and stored at 14°C and 94% r.h. for 24.d. Storage life could be further extended up to 30.d by using ethylene scavengers. Physico-chemical properties of M.A. stored banana after ripening were similar to those held under ambient conditions. Therefore, packaging of `Kolikuttu' banana as individual hands in LDPE (0.075.mm) bags of 1:1 surface to weight ratio (cm² g^-1) with 50 ml of saturated potassium permanganate absorbed onto suitable porous matrices could be recommended to increase storage lifeat 14°C.     

Benzothiadiazole- or methyl jasmonate-induced resistance to Colletotrichum musae in harvested banana fruit is related to elevated defense enzyme activities

Summary

The ability of benzothiadiazole (BTH) or methyl jasmonate (MeJA) to induce disease resistance in harvested banana fruits was investigated in relation to the activities of several defense-related enzymes. Harvested banana fruit were sprayed with BTH or MeJA solution before being stored at 22°C. Disease development and the activities of six defense-related enzymes were monitored during storage. Compared with untreated fruits, BTH or MeJA treatment significantly reduced the severity of disease in non-inoculated bananas, and lesion diameters and the incidence of disease in bananas inoculated with Colletotrichum musae. The activities of the defense-related enzymes peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), β1,3-glucanase, and chitinase were all enhanced in BTH- and in MeJA-treated banana fruit whether inoculated with the pathogen or not. The results suggest that post-harvest decay in bananas can be controlled by BTH or MeJA, and involves activation of the disease defense system. In non-inoculated bananas, MeJA and BTH had similar effects on the three defense enzymes (CAT, PPO and PAL), but different effects on the three PR proteins (POD, β1,3-glucanase and chitinase). In inoculated bananas, MeJA and BTH had similar effects on all six enzymes.     

Fermentative metabolism in ‘Conference’ pears under various storage conditions

Summary

The aim of this work was to investigate the fermentative metabolism of ‘Conference’ pears during different storage regimes. Fruits were stored at 0°C in the following controlled atmosphere (CA) conditions: 6 kPa CO₂ + 0.5 kPa O₂;3 kPa CO₂ + 1 kPa O₂; or 1 kPa CO₂ + 2 kPa O₂; and also in regular air (RA) as a control. Pears kept in RA showed low pyruvate decarboxylase (PDC) and alcohol dehydrogensase (ADH) activities, and correspondingly low levels of ethanol and acetaldehyde production as long as the fruits were maintained at low temperatures. During shelf-life at 20°C, RA-fruits released higher amounts of acetaldehyde, while ethanol production remained low. Lactate concentrations in RA-stored pears increased continuously in the second part of the storage period and during shelf-life, while lactate dehydrogenase (LDH) activity remained low. During CA-storage, ‘Conference’ pears showed continuous increases in the activities of PDC and ADH, mainly in fruits stored under high CO₂ and/or low O₂ partial pressures. The production of ethanol and acetaldehyde was not influenced in fruits stored in 6 kPa CO₂ + 0.5 kPa O₂. LDH activity in CA-stored pears increased during storage, while lactate concentrations diminished. During shelf-life at 20°C, the concentrations of all measured fermentation products increased, particularly acetaldehyde and lactate. We conclude that PDC, ADH, and LDH activities are not rate-limiting factors in the accumulation of fermentation products in ‘Conference’ pears during storage and shelf-life at 20°C.     

基于VAR模型的北京市西瓜市场的替代与整合

西瓜是我国重要的鲜活农产品之一。利用北京市批发市场中香蕉、梨子、哈密瓜、菠萝4种典型水果的价格数据,建立向量自回归模型探究香蕉、梨子、哈密瓜、菠萝4种水果在水果市场对西瓜的替代作用和动态影响,进而分析各种水果对西瓜的替代效果与水果市场的整合效应。结果表明:在不考虑季节因素的影响时,哈密瓜、香蕉、梨子与西瓜之间存在着较强的替代关系,强弱依次为哈密瓜>香蕉>梨子,而菠萝对西瓜不具有明显的替代作用。当价格受到正向的外部冲击时,西瓜自身价格会上涨,以分担这种压力,哈密瓜、香蕉和梨子这些存在替代关系的水果对西瓜价格分担上涨压力的贡献率比没有替代关系的水果高。在推动北京市西瓜市场发展的同时也要顾全整体水果市场的大局,充分考虑到各种水果之间的相互影响的替代关系。     

Growth and mineral nutrient content of developing fruit on banana plants (Musa acuminata AAA, ‘Grand Nain’) subjected to water stress and recovery

Summary

The effects of progressive water stress and subsequent re-hydration on fruit growth and mineral nutrient content were investigated in banana plants (Musa acuminata AAA, ‘Grand Nain’) under field conditions. Water stress was imposed by suspending irrigation from flower emergence for 63 d, then continuous re-watering was restored. These adverse conditions reduced fruit growth, fruit size, yield, and delayed fruit maturation. Fruit fresh and dry weights decreased with photosynthetic rate and soil moisture content during the stress period. In relation to nutrient accumulation, the main effect of drought was to reduce potassium levels, which is the major mineral nutrient in banana. In contrast, all the other minerals analysed either increased (i.e., calcium, sodium, iron and zinc), or remained stable (i.e., nitrogen, phosphorus, magnesium, manganese and copper) under the drought treatment, which generated a positive effect on the organoleptic properties of the fruit. After re-hydration, the mineral nutrient content of banana fruit was similar between stressed and non-stressed plants. The data illustrate the ability of banana to maintain relatively normal mineral contents and functional fruit tissues, which continued to expand after re-hydration, despite the long period of water stress. However, banana fruit lost commercial value, with a reduction in size and biomass after the water stress period.     

Re-initiating softening ability of 1-methylcyclopropene-treated ‘Bartlett’ and ‘d’Anjou’ pears after regular air or controlled atmosphere storage

Summary

‘Bartlett’ and ‘d’Anjou’ pears treated with 300 nl l^–1 1-methylcyclopropene (1-MCP) did not soften to eating quality within 7 d, a desirable ripening period. A pre-conditioning method was evaluated as a means to re-initiate the softening ability of pears prior to marketing. Fruit were treated with 1-MCP and stored at –1°C in regular air, or in a controlled atmosphere for 2 – 9 months. After storage, fruit were pre-conditioned with nine temperature (10°, 15° or 20°C) and time (5, 10 or 20 d) combinations. Pre-conditioned fruit were then assessed for ripening ability following storage for 14 d at 20°C. The ripening ability of 1-MCP-treated ‘Bartlett’ fruit recovered in response to many pre-conditioning combinations of 10° – 20°C for 10 – 20 d, as indicated by a decrease in flesh firmness to 27 N or lower. The requirements for pre-conditioning regimes are storage atmosphere- and time-dependent. For ‘d’Anjou’ pears, no pre-conditioning combination resulted in re-initiating the ripening of fruit treated with 300 nl l^–1 1-MCP. However, when the 1-MCP dose was 50 nl l^–1, ‘d’Anjou’ pears ripened over an extended shelf-period with a substantial decrease in superficial scald. The results indicate that treatment with 1-MCP at approx. 50 nl l^–1, combined with a pre-conditioning prior to marketing, is a potential means to control scald in ‘d’Anjou’ fruit. Re-initiation of ripening occurred concomitantly with a substantial increase in ethylene production. The control of superficial scald by 1-MCP in ‘d’Anjou’ pears was due to the inhibition of the biosynthesis of -farnesene and conjugated trienes.     

Effects of short-term N2 treatments on ripening of banana fruit

Summary

Experiments were conducted to evaluate the effects of anoxia treatments on banana fruit ripening. Pre-climacteric banana fruit were exposed to pure N₂ for 0, 6, 9, 12 or 24 h, then stored for up to 3 weeks at 20°C and approx. 90% relative humidity. Changes in peel colour, fruit firmness and post-harvest life were evaluated. Ripening was inhibited most effectively in fruit exposed to N₂ for 9 h. Furthermore, exposure of banana fruit to pure N₂ gas for 9 h reduced the rates of ethylene production and respiration, as well as the activities of polygalacturonase and pectin methyl esterase. These results suggest that anoxia treatment is a feasible technology to inhibit ripening and extend the shelf-life of banana fruit.     

Grouping of banana clones based on genomic groups,ploidy, and seasons of planting for sucker production in Musa spp.

ABSTRACT

Sucker production of important clones belonging to different ploidy levels and genomic groups were assessed in three different planting seasons at Kerala Agricultural University, Thrissur, India. The study revealed that morphological characters such as plant height, collar girth, and total number of leaves recorded very strong, significant, and positive correlation with sucker production characters but negative correlation was observed with average leaf production interval and bunch weight. The number of dead suckers was found to be positively correlated with plant height, collar girth, “D” leaf area, bunch weight, and average leaf production interval. In a cluster analysis, six banana varieties that were planted in different three seasons (18 entries) and their pooled data (6 entries) were grouped into four distinct clusters each. In factor/principle component analysis, the first three major factors/principle components amounted to a total of 85.9% of the variability. The communality values of the factor analysis revealed that collar girth was the major relative contributory trait for deciding the sucker yield and production in banana.

Abbreviations: EVS: Early vegetative stage; AVS: Active vegetative stage; FBI: Flower bud initiation; FBD: Flower bud differentiation; PCA: Principle component analysis; FA: Factor analysis     

Genome composition and genetic diversity of Musa germplasm from China revealed by PCR-RFLP and SSR markers

Banana (Musa spp.) is one of the most important crops in the world. In this study, 216 banana accessions, 184 from the National Banana Germplasm Collection of China (NBGCC) and 32 from the International Network for the Improvement of Banana and Plantain (INIBAP), were used to determine the genome composition of banana plants in these collections and to estimate their genetic diversity. The genome composition was examined using PCR-RFLP markers. The molecular data for all but one accession (ITC 1231) from INIBAP were in agreement with the initial records based on phenotypic characteristics. Microsatellite (SSR) markers were used to investigate the genetic variability and relationships among these banana accessions. Ten of the 47 primer pairs tested consistently produced reproducible and discrete fragments. We identified a total of 92 alleles, ranging from 5 to 15 per locus. The genetic similarity between the accessions ranged between 0.1 and 1, when estimated using Jaccard's coefficient. The UPGMA method based on genetic similarities, grouped the NBGCC accessions according to those containing the ‘A’ and ‘B’ genomes. However, this analysis could not separate all the accessions, especially the somatic mutations, using the primers in this study. These data indicated that limited genetic variation exists within these accessions and the collections of NBGCC should include a much wider range of banana plant material.     

A novel method for Citrus propagation: Seed grafting

Summary

We have developed a novel technique for grafting citrus seeds onto citrus rootstock plants that resulted in successful graft-take with normal vascular connections between the emerging seedling stem tissues and the rootstock plant. The method was found to be suitable for producing grafted plants from seeds of six cultivars and hybrids of Citrus and the citrus relative Murraya paniculata, using four common Citrus rootstocks. Plants produced by this method developed normally and were established in the field more rapidly than those produced by the common practice of grafting the rootstocks with budwood derived from seedlings prepared from seed in soil-based media. Seed grafting is expected to find a range of uses in breeding programmes; for example, by reducing the time required for the evaluation of hybrid seedlings, in cases where the female parent is mono-embryonic, for testing for vertical transmission of pathogens, and for screening for pathogen resistance among hybrid and mutagenised seed sources.     

Forest proximity rather than local forest cover affects bee diversity and coffee pollination services

Context

As agricultural demands for land continues to expand, strategies are urgently needed to balance agricultural production with biodiversity conservation and ecosystem service provision in agricultural landscapes.

Objectives

We used a factorial landscape design to assess the relative contributions of forest proximity and local forest cover to bee diversity and the provision of coffee pollination services.

Methods

We quantified bee diversity and fruit set in 24 sun-grown coffee fields in Southeast Region of Brazil that were selected following a factorial sampling design to test the independent effects of local forest cover (in a radius of 400 m) and proximity to forest fragments. To assess the impact of landscape simplification, we also evaluated local coffee cover.

Results

Bee richness and abundance were higher in the proximity of forest fragments, but only bee abundance decreased when the coffee cover dominated the surrounding landscapes. Coffee fruit set was 16% higher overall with bee visitations compared with bee exclusion and increased to 20% when coffee bushes were near forest fragments, and the coffee cover was low. Surprisingly, local forest cover did not affect the bee community or coffee fruit set.

Conclusion

Our results provide clear evidence that the proximity of coffee crops to forest fragments can affect the abundance and richness of bees visiting the coffee flowers and thereby facilitate the provision of pollination services. The positive association between forest proximity and fruit set reinforces the importance of natural vegetation in enhancing bee diversity and, therefore, in the provision of pollination services. The negative effect of coffee cover on fruit set at the local scale suggests that the service demand can surpass the capacity of pollinators to provide it. These effects were independent of the local forest cover, although all studied landscapes had more than 20% remaining forest cover (within a 2 km radius), which is considered the extinction threshold for Atlantic Forest species. Interspersion of forest fragments and coffee plantations in regions with more than 20% of forest cover left could thus be a useful landscape management target for facilitating pollinator flows to coffee crops and thus for increasing coffee yields.

     

The influence of the topographic position within highlands of Western Rwanda on the interactions between banana (Musa spp. AAA-EA), parasitic nematodes and soil factors

Soil properties vary according to the topography. They affect water uptake and root exploration in the soil. Consequently, they may also influence the spread of plant–parasitic nematodes. This study reports on the effect of toposequence-related variations in soil on banana yields, foliar nutrient status, and nematode impact. Twenty banana plots were visited within 6 hills/valleys at each of the three toposequence positions: valley bottom, mid-slope and crest. Important variability in plant growth, nutrition and soil properties was observed within the toposequence. Significantly better plant growth (height and girth) was observed in the valley bottoms, where banana bunch weight was 1.7–3.4 kg higher (although not significant) than at upper toposequence positions. Best plant growth was observed in valley bottoms in contrast to the highest N and K foliar deficiencies in this position. Plants in the valley bottoms had higher foliar Ca and Mg, and K compared to those in the crest. Plants in the mid-slope had greater percentage of dead roots (19.1%), compared to the plants in the valley bottoms (12.3%) and the crest (14.2%). Soils in the valley bottoms were deeper, sandier, with lower organic matter, lower N, and K compared to the soils at higher toposequence. Nematodes likely play a key role in banana root damage, however, their effect appear to be in relation to various soil factors at each position. The abundance of Pratylenchus goodeyi had generally limited impact on banana yields in fields having less than 5% slope (crest and valley bottom) where soil conditions were more optimal for root growth. However, in the presence of increased run-off on steeper middle slopes, root death was increased even under moderate pressure from P. goodeyi.     

Relationships Among some Pears Genotypes (Pyrus Communis L.) Based on ISSR and RAPD Analysis

Thirty one pears genotypes from east blacksea region were evaluated for genetic relationships by using Randomly Amplified Polymorphic DNA (RAPD) and ISSR (Inter-Simple Sequence Repeats) markers from total 70 RAPD and ISSR primer investigated, 22 could amplify clearly and consistently. Cluster analysis of the pears genotypes was performed based on data from polymorphic bands RAPD and ISSR by using Jaccard’s similarity coefficient and the Unweighted pair-group method with arithmetic average (UPGMA) clustering method. The 31 pear genotypes were classified into two major groups. Cluster A was divided into 2 subclusters: Gumushane pears and Trabzon pears. Cluster B consisted of Artvin pears. The similarity matrix values ranged between 0.105 and 0.968.     

In vitro culture of albedo tissue from fruits of Citrus sinensis cv. Washington Navel: Effect of fruit age and orange juice

SUMMARY

Callus from citrus fruit explants has been used to study different aspects of fruit physiology. However, growth responses of callus derived from citrus fruit tissues are not always comparable with those of intact fruit; there are, for example, differences in nutritional requirements. Results with tissues cultivated in vitro seem to depend on a variety of environmental and internal factors. In the present work albedo tissue from fruits of Citrus sinensis cv. Washington Navel of different age has been used as a source of explants. The growth (fresh weight) of the calli was dependent on the age of the fruit from which the explants were taken, as well as on the addition of orange juice to the plant growth medium. Orange juice stimulated the growth of the calli and this growth was greater as the fruit age increased. The highest values were obtained when the albedo was isolated from fruits 30 to 45 mm in diameter and grown on medium supplemented with 20% orange juice.     

Somaclonal variation with early juice-sac granulation obtained by inter-specific protoplast fusion in citrus

Summary

Six plants with an early juice–sac granulation trait derived from inter-specific protoplast fusions between embryogenic calli of ‘Bonanza’ navel orange (Citrus sinensis [L.] Osbeck) and mesophyll protoplasts of ‘Dahongpao Red’ tangerine (C. reticulata Blanco) were analysed by flow cytometry and by using molecular markers, including simple sequence repeats (SSR) and restriction fragment length polymorphism (RFLP). The results indicated that all six plants were diploids and had inherited their nuclear DNA from the embryogenic callus parent ‘Bonanza’ navel orange. However, an analysis of morphological and fruit characteristics, and measurements of components of the cell walls in the juice-sacs, showed that they were not true-to-type for ‘Bonanza’ navel orange, especially for fruit traits such as juice-sac granulation and navel structure. These results confirmed that these plants were not hybrids, and were more likely to be somaclonal variants that arose during the regeneration of the navel orange protoplasts. These plants will provide material for studying the mechanism of granulation in juice-sacs, a common phenomenon during the storage of pummelo and other citrus fruits.     

Land cover and climate changes drive regionally heterogeneous increases in US insecticide use

Context

Global environmental change is expected to dramatically affect agricultural crop production through a myriad of pathways. One important and thus far poorly understood impact is the effect of land cover and climate change on agricultural insect pests and insecticides.

Objectives

Here we address the following three questions: (1) how do landscape complexity and weather influence present-day insecticide use, (2) how will changing landscape characteristics and changing climate influence future insecticide use, and how do these effects manifest for different climate and land cover projections? and (3) what are the most important drivers of changing insecticide use?

Methods

We use panel models applied to county-level agriculture, land cover, and weather data in the US to understand how landscape composition and configuration, weather, and farm characteristics impact present-day insecticide use. We then leverage forecasted changes in land cover and climate under different future scenarios to predict insecticide use in 2050.

Results

We find different future scenarios—through modifications in both landscape and climate conditions—increase the amount of area treated by ~ 4–20% relative to 2017, with regionally heterogeneous impacts. Of note, we report large farms are more influential than large crop patches and increased winter minimum temperature is more influential than increased summer maximum temperature. However, our results suggest the most important determinants of future insecticide use are crop composition and farm size, variables for which future forecasts are sparse.

Conclusions

Both landscape and climate change are expected to increase future insecticide use. Yet, crop composition and farm size are highly influential, data-poor variables. Better understanding of future crop composition and farm economics is necessary to effectively predict and mitigate increases in pesticide use.

     

Harvest date affects the antioxidative systems in pear fruits

Summary

Pears (Pyrus communis L. cv. Conference) were picked 7 d before (27 d), during (0) or 7 d (+7 d) after the estimated ideal time for commercial harvest. Changes in antioxidant content (ascorbate and glutathione) and in the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), total peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR) were estimated immediately after harvest for each picking time. Ascorbate and non-protein thiols (glutathione) content significantly decreased with increasing maturity. Concommitantly, the activity of SOD and CAT fell about five-fold and two-fold, respectively, when the fruit was picked more mature, indicating a higher potential for the accumulation of cytotoxic O₂^.2 and H₂O₂ respectively. POX activity remained relatively constant until the optimal harvest date but increased later. APX activity increased 2.5-fold in the more mature fruit but GR remained stable. Collectively, these results provide evidence that harvest date is accompanied by a decline in the non-enzymic and enzymic systems responsible for catabolism of active oxygen species. This may contribute to explain the widely described influence of harvest date on the occurrence of physiological disorders in pears.