Poor Fruit Quality Research Articles

Characterization of aphid resistance loci in black raspberry (Rubus occidentalis L.)

Viruses vectored by the aphid Amphorophora agathonica cause decline in black raspberry plant health resulting in a shortened life and poor fruit quality of the infected plantings. New aphid resistant cultivars could increase the longevity of plantings providing growers and processors with consistent fruit production. Recent exploration of the native range of black raspberry identified three sources of aphid resistance: Ag4 from Ontario (ON), Canada, Ag5 from Maine (ME), and a third source from Michigan (MI) with no formal designation. The objectives of this study were to assess segregation of these three sources of aphid resistance in populations with single and combined sources and develop markers that can identify each source of resistance. A genetic linkage map constructed for ORUS 4305 placed the ON aphid resistance locus on Rubus linkage group (RLG) 6. Segregation ratios in populations with single and combined sources, and linkage mapping in two populations (ORUS 4304 and ORUS 4812) segregating for the Ag5 and MI sources, respectively, indicated that these three sources of resistance are each conferred by single dominant genes/alleles that are linked on RLG6. Confirmation of marker association in 16 validation populations identified four markers that could be used to predict resistance; however, none could distinguish between the ON and MI sources. These four markers may be useful for screening populations to enrich the field-planted progeny for aphid resistance. Fine mapping of the resistance loci is needed to develop functional markers at each of the resistance loci to enable pyramiding and durable aphid resistance.

Tree age influences nutritional, pectin, and anatomical changes in developing ‘Kinnow’ mandarin (Citrus nobilis Lour × Citrus deliciosa Tenora) fruit

ABSTRACTAn understanding of variation in fruit quality in relation to tree age can help understand the issue of poor fruit quality in young orchards; however, limited information is available on the citrus fruit. In this study, the endogenous nutritional status in rind, rag, and leaves; pectin status in rind and rag; and anatomical fruit growth parameter in rind tissues were studied in ‘Kinnow’ mandarins fruit during their development on trees from three age (6-, 18-, and 35-year-old) groups. In older (35-year-old) trees, rind, rag, and leaf nitrogen (N), phosphorus (P), and potassium (K) concentrations were superior. In fruit from all tree age groups, total pectin and protopectin reduced; however water-soluble pectin (WSP) improved. In rind tissues harvested from young (6-year-old) trees, cell density was more while cell size was less. In all tree age groups, cell density in rind tissues correlated negatively with rind WSP.

Evaluation of Host Resistance to Botrytis Bunch Rot in Vitis spp. and Its Correlation with Botrytis Leaf Spot

Botrytis cinerea, the causal agent of Botrytis bunch rot and gray mold, is the number one postharvest disease of fresh grapes in the United States. Fungicide applications are used to manage the disease, but fungicide-resistant isolates are common and postharvest losses occur annually. Host resistance is needed for long-term management of the disease. Sources of resistance in grape have been identified, but often have poor fruit quality. In this study, 27 grape lines (cultigens and species), including high fruit–quality Vitis vinifera, were evaluated for fruit and leaf susceptibility to two isolates of B. cinerea. No significant differences in virulence or pathogenicity were detected between the two isolates, but differences in disease incidence were evident among lines in leaves and berries. Most V. vinifera cultivars evaluated had high disease incidence in berries, whereas complex hybrids, Vitis aestivalus and Vitis arizonica, had low- to moderate disease incidence. Two V. vinifera breeding lines had moderate susceptibility (<50% disease) to Botrytis bunch rot when inoculated with either isolate. Only one V. vinifera line had little (<5%) to no berry or leaf disease when inoculated with either isolate. Moderate resistance (10% to 25%) was detected in Vitis spp., and a single V. vinifera line. Correlations were examined among soluble solids, leaf susceptibility, and fruit susceptibility. No correlations between soluble solids and disease susceptibility (leaves or berries) were identified, but moderate correlations between leaf and berry susceptibility were observed. Moderate resistance to Botrytis bunch rot and leaf spot were detected in Vitis breeding lines, suggesting these may be useful for developing grape cultivars with high fruit quality and resistance to B. cinerea.

Disease Resistance to Multiple Fungal and Oomycete Pathogens Evaluated Using a Recombinant Inbred Line Population in Pepper.

Incorporating disease resistance into cultivars is a primary focus of modern breeding programs. Resistance to pathogens is often introgressed from landrace or wild individuals with poor fruit quality into commercial-quality cultivars. Sites of multiple disease resistance (MDR) are regions or "hot spots" of the genome with closely linked genes for resistance to different pathogens that could enable rapid incorporation of resistance. An F2-derived F6 recombinant inbred line population from a cross between 'Criollo de Morelos 334' (CMM334) and 'Early Jalapeno' was evaluated in inoculated fruit studies for susceptibility to oomycete and fungal pathogens: Phytophthora capsici, P. nicotianae, Botrytis cinerea, Fusarium oxysporum, F. solani, Sclerotinia sclerotiorum, Alternaria spp., Rhizopus oryzae, R. stolonifer, and Colletotrichum acutatum. All isolates evaluated were virulent on pepper. Significant differences in disease susceptibility were identified among lines for each of the pathogens evaluated. P. capsici was the most virulent pathogen, while R. oryzae and one Sclerotinia isolate were the least virulent. Quantitative trait loci associated with resistance were identified for Alternaria spp. and S. sclerotiorum. Positive correlations in disease incidence were detected between Alternaria spp. and F. oxysporum, F. solani, and C. acutatum, as well as between C. acutatum and Botrytis spp., F. oxysporum, F. solani, and P. capsici. No sites of MDR were identified for pathogens tested; however, positive correlations in disease incidence were detected among pathogens suggesting there may be genetic linkage among resistance genes in CM334 and Early Jalapeno.

MicroRNA-mediated responses to long-term magnesium-deficiency in Citrus sinensis roots revealed by Illumina sequencing

BackgroundMagnesium (Mg)-deficiency occurs most frequently in strongly acidic, sandy soils. Citrus are grown mainly on acidic and strong acidic soils. Mg-deficiency causes poor fruit quality and low fruit yield in some Citrus orchards. For the first time, we investigated Mg-deficiency-responsive miRNAs in ‘Xuegan’ (Citrus sinensis) roots using Illumina sequencing in order to obtain some miRNAs presumably responsible for Citrus Mg-deficiency tolerance.ResultsWe obtained 101 (69) miRNAs with increased (decreased) expression from Mg-starved roots. Our results suggested that the adaptation of Citrus roots to Mg-deficiency was related to the several aspects: (a) inhibiting root respiration and related gene expression via inducing miR158 and miR2919; (b) enhancing antioxidant system by down-regulating related miRNAs (miR780, miR6190, miR1044, miR5261 and miR1151) and the adaptation to low-phosphorus (miR6190); (c) activating transport-related genes by altering the expression of miR6190, miR6485, miR1044, miR5029 and miR3437; (d) elevating protein ubiquitination due to decreased expression levels of miR1044, miR5261, miR1151 and miR5029; (e) maintaining root growth by regulating miR5261, miR6485 and miR158 expression; and (f) triggering DNA repair (transcription regulation) by regulating miR5176 and miR6485 (miR6028, miR6190, miR6485, miR5621, miR160 and miR7708) expression. Mg-deficiency-responsive miRNAs involved in root signal transduction also had functions in Citrus Mg-deficiency tolerance.ConclusionsWe obtained several novel Mg-deficiency-responsive miRNAs (i.e., miR5261, miR158, miR6190, miR6485, miR1151 and miR1044) possibly contributing to Mg-deficiency tolerance. These results revealed some novel clues on the miRNA-mediated adaptation to nutrient deficiencies in higher plants.

Remote hyperspectral imaging of grapevine leafroll-associated virus 3 in cabernet sauvignon vineyards

Grapevine leafroll disease (GLD) is considered to be one of the most economically destructive viral diseases of grapevines worldwide, resulting in reduced vine vigor, yield reductions, and poor fruit quality. Five pathogens (grapevine leafroll-associated viruses) are recognized as causal agents of this disease, of which Grapevine leafroll-associated virus 3 (GLRaV-3) is the most common. Although there is no cure for the disease, management strategies (including vigilant removal of infected vines) can drastically limit its spread and economic impact. Comprehensive mapping (total population sampling) of disease presence on the ground is cumbersome and cost prohibitive in many situations. In addition, the practice of identifying diseased vines requires individuals to be highly trained to recognize symptoms. Compared to more traditional detection methods, airborne hyperspectral imaging offers a potentially valuable alternative for monitoring the disease that is cost effective, reliable and automatable. This study tests the use of hyperspectral imaging to aid in the management of GLD.Over the span of two years we monitored five Cabernet Sauvignon vineyards: ground surveys recorded the incidence of visual symptoms of disease in the field during the same months in which hyperspectral maps recorded disease incidence from the air. A customized Geographic Information System (GIS) methodology was developed to compare the visual symptoms to the results of the hyperspectral imaging technique. For a select number of vines, disease incidence was then confirmed by laboratory assays. On average, detection sensitivity was 94.1%, with a range of 88% to greater than 99% per vineyard. Various vineyard-specific factors appear to compromise detection sensitivity. Overall, our results show that remote hyperspectral imaging of GLRaV-3 infected Cabernet Sauvignon vineyards can be a useful and cost-effective approach to mapping diseased vines. Future studies should focus on the use of this tool for detecting GLRaV-3 in other grape varieties, as well as other grapevine pathogens.

Evaluation of fruit quality and antioxidant activity of kiwifruit during ripening and after storage

BACKGROUND: In the Northern hemisphere kiwifruit harvest time is conditioned by low temperatures occurring during the harvesting season while in Southern Italy minimum temperatures in autumn are high enough to support fruit growth and ripening. To evaluate the influence of delayed harvest time on kiwifruit quality attributes. METHODS: The experiment was carried out in a commercial kiwifruit, ‘Hayward’, orchard located in Southern Italy. In this area, the conventional harvest time occurs 160 days after full bloom (DAFB), during the first decade of November. Fruits were collected from 130 DAFB to 192 DAFB. Fresh fruit and dry weight, flesh color, firmness, total soluble solids content (TSS), titratable acidity (TA), ascorbic acid (AA), total polyphenols content (TPH) and antioxidant capacity (TAC) were determined. After 120 days of storage, fruit harvested 178 DAFB, had higher fresh and dry weight, flesh firmness, TSS, TA and lower water loss than fruit harvested at 160 DAFB, with no significant differences in AA, TPH and TAC. TAC was correlated more to TPH than to AA. Early (130–158 DAFB) harvests, resulted in poor fruit quality and scarce post harvest maintenance. Delaying fruit harvest time, in mild winter areas such as Southern Italy, resulted in an improved fruit

Breeding Perennial Fruit Crops for Quality Improvement

Fruits play a crucial role in human diets and as a commercial commodity in trade. The consumers have considered fruit quality as the most important criteria that decides its acceptability. Fruit quality-based overall acceptability determines the success of any breeding programme, as a number of improved varieties with desired traits including resistance to stresses could not be popularized due to their poor quality fruits. However, breeding for quality improvement in perennial fruit crops is hampered by a number of limitations including large size of the plant, long juvenile phase and environmental problems (e.g. fruit drops due to natural calamities). Besides, fruit quality is a polygenic trait, which is quantitatively inherited and thus making breeding programme complicated in quality improvement of fruit crops. Several attempts have been made to improve the quality characters in annual staple crops, however this aspect is conveniently ignored in case of perennial fruit crops. A balanced approach combining conventional and non-conventional breeding techniques could help in addressing this issue. The biotechnological approaches provide precision, reliability and are considered to reduce the breeding cycle in long duration crops. Efficacy of approaches like marker assisted selection, candidate gene, genomics, trangenics, cisgenics has shown to be advantageous when dealing with cumbersome crops. This review would focus on problems in fruit breeding and present status of different breeding approaches for fruit quality improvement in fruit trees.

Somatic Embryogenesis of Date Palm (Phoenix dactylifera L.) Through Cell Suspension Culture.

Date palm (Phoenix dactylifera L.) is the oldest and most economically important plant species distributed in the hot arid regions of the world. Propagation of date palm by seeds produces heterogeneous offspring with inferior field performance and poor fruit quality. Traditionally, date palm is propagated by offshoots, but this method is inefficient for mass propagation because of limited availability of offshoots. Plant regeneration through tissue culture is able to provide technologies for the large-scale propagation of healthy true-to-type plants. The most commonly used technology approach is somatic embryogenesis which presents a great potential for the rapid propagation and genetic resource preservation of this species. Significant progress has been made in the development and optimization of this regeneration pathway through the establishment of embryogenic suspension cultures. This chapter focuses on the methods employed for the induction of callus from shoot tip explants, establishment of cell suspension culture, and subsequent somatic embryogenesis and plant regeneration.

Trade-Offs of Flowering and Maturity Synchronisation for Pineapple Quality.

In the pineapple sector of Benin, poor fruit quality prevents pineapple producers to enter the European market. We investigated effects of common cultural practices, flowering and maturity synchronisation, (1) to quantify the trade-offs of flowering and maturity synchronisation for pineapple quality and the proportion of fruits exportable to European markets, and (2) to determine the effect of harvesting practice on quality attributes. Four on-farm experiments were conducted during three years using cultivars Sugarloaf and Smooth Cayenne. A split-split plot design was used in each experiment, with flowering induction practice as main factor (artificial or natural flowering induction), maturity induction practice as split factor (artificial or natural maturity induction) and harvesting practice as the split-split factor (farmers’ harvest practice or individual fruit harvesting at optimum maturity). Artificial flowering induction gave fruits with lower infructescence weight, higher ratio crown: infructescence length, and a lower proportion of fruits exportable to European markets than natural flowering induction. The costs of the improvements by natural flowering induction were huge: the longer durations from planting to flowering induction and harvesting, the higher number of harvestings of the fruits increasing the labour cost and the lower proportion of plants producing fruits compared with crops from artificially flowering-induced plants. Artificial maturity induction decreased the total soluble solids concentration in the fruits compared with natural maturity induction thus decreasing the proportion of fruits exportable to European markets, at a benefit of only a slightly shorter time from flowering induction to harvesting. Harvesting individual fruits at optimum maturity gave fruits with higher total soluble solids in naturally maturity induced fruits compared with the farmers’ harvest practice. Given the huge costs of natural flowering induction, options to use artificial flowering induction effectively for obtaining high fruit quality are discussed.

Water deficit effects on tomato quality depend on fruit developmental stage and genotype

Many studies have advocated that water deficit (WD) may exert beneficial effects on fruit quality. However, the fruit response to WD at specific developmental stages was seldom investigated, although different mechanisms could be involved at each stage and lead to different effects on final fruit quality. In the present study, a moderate WD (−60% of water supply compared to control) was applied during each of the three major phases of fruit development, namely cell division (CD), cell expansion (CE) and maturation (MT). Two cocktail tomato (Solanum lycopersicum L.) genotypes were studied, one producing poor quality fruits (LA1420), and the other one producing tasty fruits (PlovdivXXIVa named Plovdiv). Contrasted responses were observed between the two genotypes. For both of them, fruit fresh mass and size were not significantly reduced by WD, whatever the developmental phase affected. Osmotic regulations were likely involved in the CD treatment for LA1420 fruits, which accumulated more sugars (both on a dry and fresh matter basis) and less acids (on a dry matter basis). In the CE treatment, other adaptive strategies involving sugar metabolism and sub-cellular compartmentation were suggested. In contrast, the composition of Plovdiv fruits changed only under the MT treatment, with less sugars, acids and carotenoids compared to control fruits (both on a dry and fresh matter basis). Total ascorbic acid (AsA) was not significantly influenced by treatments in both genotypes. On their whole, results suggest that, depending on genotypes, fruits are sweeter and less acidic under WD, but that the nutritive value related to vitamin and carotenoid contents may be lessened. The sensitivity of each developmental phase highly depends on the genotype. All phases were sensitive to WD for LA1420, but only the ripening phase for Plovdiv. Interestingly, major changes in fruit composition were observed in LA1420 which presents poor fruit quality under control conditions. This suggests the onset of fast adaptive response to WD at the fruit level in this genotype.

A Novel Regeneration System for Tamarillo (Cyphomandra betacea) via Organogenesis from Hypocotyl, Leaf, and Root Explants

Cyphomandra betacea (Cav.) is commonly known as Tamarillo or tree tomato. This species is mainly used for its edible fruits which have a high nutritional value and contain relatively high amounts of proteins, vitamins B6, C, E, and provitamin A. The cultivation of Tamarillo in Rwanda is facing major challenges caused mainly by viral diseases such as Tamarillo mosaic virus (TaMV). These diseases are difficult to control and are transferred through vegetative propagation, often resulting in heavy productivity losses and poor-quality fruits. Thus, this study was conducted to evaluate the possibility of using tissue culture as an alternative propagation method. Tamarillo seeds were sterilized using a commercial bleach and germinated in vitro to get clean starting explants. Explants (hypocotyls, leaves, and roots) were cultured on semisolid Murashige and Skoog (MS) media supplemented with 6-benzylaminopurine (BA), N6-2-isopentyl adenine (2iP), 6-furfurylaminopurine (kinetin) evaluated at 5, 10, 20, 40 µM, and thidiazuron (TDZ), evaluated at 0.1, 0.5. 1.0 1.5 µM in separate experiments. Data were collected on the number of microshoots and roots 2 months after culture and analyzed using the Statistical Software for Social Sciences (SPSS) Software version 8. The results showed that the growth regulators evaluated had a significant (P ≤ 0.05) effect on plantlet regeneration from leaf and hypocotyl explants. The media supplemented with BA 40 μM was the most effective in inducing multiple shoots from leaf explants producing 4.67 ± 0.15 shoots per explant. Root explants showed the least morphogenic responses for all the parameters evaluated. The regenerated plantlets were transplanted to the greenhouse and a survival rate of 90% was recorded. During this study, a simple, reproducible, single-step protocol was developed. These results would be useful for mass propagation of Tamarillo.

Effect of Time and Level of Pruning on Vegetative Growth, Flowering, Yield, and Quality of Guava

Poor quality fruit production in the rainy season and failure to manipulate production periods are common problems for guava production in India and Nepal. As a possible management to overcome these problems, a field experiment was conducted to understand the effect of time and level of pruning on growth, flowering, yield, and quality of guava. An experiment was laid out with split-pot design allocating three pruning times (mid-April, early May, and mid-May) and four pruning levels (0-, 10-, 20-, and 30-cm tip removal) with three replications in each treatment. Increased level of pruning in early May increased the leaf number and area both in rainy and winter seasons. Similarly, an increased level of pruning and delayed pruning increased the fruit size and fruit weight in both seasons. In the winter season, fruit yield per tree was increased by plants pruned in early May. Total soluble sugar (%) of fruits increased with the increased level of pruning in both seasons irrespective of timing of pruning, but fruit acidity was not affected by both treatments. In conclusion, pruning plants at a 20 cm pruning level in early May was the most effective management to reduce yield in the rainy season and to enhance yield and quality in the winter season.

Effect of Pruning Severity on V egetative, Physiological, Yield and Quality Attributes in Grape (Vitis vinifera L.): A Review

Grape is one among the most delicious, refreshing and nourishing fruits of the world. It is one of the earliest fruits grown by man. The berries are a good source of sugars and minerals like Ca, Mg, Fe, and vitamins like B1, B2, and C. Grape has so many uses and is so unique that no fruit can challenge their superiority. Crop load is the most important factor affecting yield and cluster quality as well as vine vigor of both seeded and seedless varieties. Hence, an optimum canopy size and bunch number per vine are to be maintained for achieving better fruit Quality which warrants proper balancing between vigour and capacity. The pruning requirement of different varieties differs as per their growth behaviour. Therefore, variety-specific standardization of pruning is essential for any grape cultivars for harnessing potential yield and quality. In this view, it is essential to get scientific information on the pruning requirement of grapes. Pruning all the matured canes to fruit bud level, as adopted by local grape growers results in more exploitation of reserved food material leading to loss of vigour, quality and early setting of senility in vines. Heavy bearing of vines results in poor quality fruits with low TSS and high fruit acidity.

SCREENING CONTROLLED POLLINATION PEACH SEEDLINGS FOR MILDEW AND BROWN ROT RESISTANCE AT CRA-FRF IN THE FRAME OF THE FRUITBREEDOMICS EU PROJECT

Obtaining high quality fruit cultivars endowed with genetic resistances to various pests and diseases is one of the challenges of peach breeding and a strategy to improve the European fruit consumption and reduce the negative impacts of pesticides on the human health and on the environment. In peach orchards, on average 15 to 20 chemical sprays are required to control pathogens such as brown rot caused by Monilinia spp, powdery mildew (Sphaerotheca pannosa), leaf curl (Taphrina deformans) and green aphids (Myzus persicae). The CRA-FRF breeding activity aim is to increase peach resistance to these pathogens, particularly brown rot and powdery mildew agents. To avoid excessive depletion in fruit quality caused by the use of resistant sources with poor fruit quality, such as ‘Bolinha’, we started the breeding activity using as initial parents, cultivars such as ‘Suncrest’, ‘Fireprince’, ‘Glohaven’, ‘Cresthaven’, ‘Fayette’ and ‘Contender’, that have some tolerance and good commercial fruit quality. Tolerance level was then progressively increased by crossing the most tolerant selections, exploiting the additive heritability variance. The Mexican cultivar ‘Oro A’ has been used as a source of resistance to mildew and was back-crossed several times with cultivars of superior fruit quality to regain commercial value. Recently, sources of resistance from other inter-compatible species, such as P. davidiana and almond, were used in controlled crosses with peach. Currently, this breeding activity is carried out in the framework of the Fruitbreedomics EU Project. The goal of this activity is to find and evaluate resistant germplasm to brown rot and powdery mildew and to release pre-breeding material with pyramided resistant genes for these diseases.

Proteomic analysis of Citrus sinensis roots and leaves in response to long-term magnesium-deficiency.

BackgroundMagnesium (Mg)-deficiency is frequently observed in Citrus plantations and is responsible for the loss of productivity and poor fruit quality. Knowledge on the effects of Mg-deficiency on upstream targets is scarce. Seedlings of ‘Xuegan’ [Citrus sinensis (L.) Osbeck] were irrigated with Mg-deficient (0 mM MgSO4) or Mg-sufficient (1 mM MgSO4) nutrient solution for 16 weeks. Thereafter, we first investigated the proteomic responses of C. sinensis roots and leaves to Mg-deficiency using two-dimensional electrophoresis (2-DE) in order to (a) enrich our understanding of the molecular mechanisms of plants to deal with Mg-deficiency and (b) understand the molecular mechanisms by which Mg-deficiency lead to a decrease in photosynthesis.ResultsFifty-nine upregulated and 31 downregulated protein spots were isolated in Mg-deficient leaves, while only 19 upregulated and 12 downregulated protein spots in Mg-deficient roots. Many Mg-deficiency-responsive proteins were involved in carbohydrate and energy metabolism, followed by protein metabolism, stress responses, nucleic acid metabolism, cell wall and cytoskeleton metabolism, lipid metabolism and cell transport. The larger changes in leaf proteome versus root one in response to Mg-deficiency was further supported by our observation that total soluble protein concentration was decreased by Mg-deficiency in leaves, but unaffected in roots. Mg-deficiency had decreased levels of proteins [i.e. ribulose-1,5-bisphosphate carboxylase (Rubisco), rubisco activase, oxygen evolving enhancer protein 1, photosynthetic electron transfer-like protein, ferredoxin-NADP reductase (FNR), aldolase] involved in photosynthesis, thus decreasing leaf photosynthesis. To cope with Mg-deficiency, C. sinensis leaves and roots might respond adaptively to Mg-deficiency through: improving leaf respiration and lowering root respiration, but increasing (decreasing) the levels of proteins related to ATP synthase in roots (leaves); enhancing the levels of proteins involved in reactive oxygen species (ROS) scavenging and other stress-responsive proteins; accelerating proteolytic cleavage of proteins by proteases, protein transport and amino acid metabolism; and upregulating the levels of proteins involved in cell wall and cytoskeleton metabolism.ConclusionsOur results demonstrated that proteomics were more affected by long-term Mg-deficiency in leaves than in roots, and that the adaptive responses differed between roots and leaves when exposed to long-term Mg-deficiency. Mg-deficiency decreased the levels of many proteins involved in photosynthesis, thus decreasing leaf photosynthesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1462-z) contains supplementary material, which is available to authorized users.

Transcriptome sequencing of Prunus sp. rootstocks roots to identify candidate genes involved in the response to root hypoxia

Root hypoxia in fruit trees affects growth, vegetative development, and reproductive development, which is reflected in low productivity, poor fruit quality, and premature decay of trees. Using Illumina Hiseq2000, we performed transcriptome analysis of roots from two different rootstocks, ‘Mariana 2624’ and ‘Mazzard F12/1,’ which are tolerant and sensitive to hypoxia, respectively. Transcriptomes from control and hypoxia-stressed plants (6, 24, and 72 h) were compared, using Prunus persica (L.) as reference genome. Hypoxic conditions altered the transcription in both genotypes. There were a high number of common differentially expressed genes (DEG) between the two genotypes for each sampling time, but also exclusive DEG for each genotype, with a few DEG that presented opposite modes of regulations during the hypoxia treatment. An important group of DEGs exclusively upregulated in the tolerant genotype are associated to enzymes of posttranslational protein modifications, such as leucine-rich repeat (LRR), kinases and ubiquitin-protein ligases, regulation of transcription, and process of oxide reduction. Singular enrichment analysis of gene ontology (GO), detected at least 115 GOs involved in the response to root hypoxia in the sensitive and/or tolerant genotypes. At least 25 GOs were identified as part of the baseline differences between the genotypes, most GO were disturbed in the sensitive genotype. The contribution from the baseline gene expression to the differential response between the Prunus genotypes is evidence that the resistant genotype is already “prepared” for a hypoxia event. An example are GO BP:0042221 of response to chemical stimulus; BP:0006979 of response to oxidative stress; MF:0016209 of antioxidant activity; MF:0016684 of oxidoreductase activity, acting on peroxide as acceptor; and MF:0004601 of peroxidase activity, which were disturbed only in the sensitive genotype, but not in the tolerant.

Virulence diversity of anthracnose pathogens (Colletotrichum acutatum and C. gloeosporioides species complexes) on eight olive cultivars commonly grown in Portugal

Olive anthracnose, caused by Colletotrichum acutatum and C. gloeosporioides species complexes, is a major disease affecting fruits at maturity, causing significant yield losses, and poor fruit and oil quality. Diverse genetic groups, particularly belonging to C. acutatum s.l. have been reported among the pathogens, with recent research proposing these genetic groups as distinct species. In this work, the virulence diversity of isolates representing different populations of C. acutatum s.l. and C. gloeosporioides s.s. was studied using a set of eight olive cultivars. Higher disease severity was produced by isolates belonging to groups A2 and A5 of C. acutatum s.l. (=C. nymphaeae and C. acutatum s.s., respectively) compared to C. gloeosporioides s.s. isolates as well as isolates of C. acutatum s.l. group A4 (=C. godetiae). Anthracnose severity was higher on the cultivars ‘Cobrancosa’, ‘Macanilha de Tavira’ and ‘Galega Vulgar’ and lower in ‘Azeitoneira’, ‘Blanqueta’, ‘Negrinha de Freixo’ and ‘Picual’, but results indicate the occurrence of isolate × cultivar interactions. Differences in severity could be related to differences in conidia germination and appressoria formation, suggesting that early host-pathogen recognition events can in part explain disease severity under favourable environmental conditions. Overall results revealed the higher virulence and fitness levels of genotypes belonging to certain genetic groups within C. acutatum suggesting their ability to adapt to diverse agro-climatic conditions including specific hosts.

Physiological and genetic factors influencing fruit cracking

One of the main disorders that widely limit fruit quality and quantity is fruit cracking or splitting that is observed on the fruit skin and flesh in the preharvest phase. Besides, cracking can occur during postharvest in some fruits, mostly attributable to the environmental conditions of storage. Value of cracked fruits is reduced and these fruits are not marketable because of the poor fruit quality. Many fruits such as apple, sweet cherry, grape, plum, pomegranate, grape, persimmon, litchi, avocado, pistachio, citrus, banana as well as tomato can crack or split. There are many factors that influence fruit cracking. In this work, genetic, morphological, environmental and physiological aspects of fruit cracking are reviewed. Under the same environmental conditions, fruits from different cultivars show differences in cracking susceptibility. Some correlations have been observed between susceptibility of fruit cracking and some fruit traits (fruit shape, fruit size, fruit firmness; anatomy and strength of the fruit skin, stomata in fruit skin, cuticular properties, osmotic concentration, water capacity of the fruit pulp and growth stage of the fruit). Also, orchard management (such as irrigation and nutrition) and environmental condition (such as temperature, wind and light) can influence fruit cracking. Besides, fruit cracking is quantitative trait and is controlled by several genes. The best way to reduce fruit cracking at present would be a suitable orchard management that takes into account and try to minimize stress of the water, nutrition and physiological factors that contribute to fruit cracking. Also, the most resistant cultivars to fruit cracking that have desirable fruit quality can be selected for cultivation.

COMPARATIVE STUDY ON PRODUCTIVITY OF SOME ARABIAN AND LOCAL DATE PALM CULTIVARS GROWN IN THE DESERT REGION AT GIZA GOVERNORATE

Eight Arabian date palm cultivars i.e. Madjool (Majhool), Bahree, Nabtet-Seif, Halawy, Braym,Khalas, succary and Lolo in comparison with the commercial cv. Hayany (locally grown date palm) in the desert region at Giza Governorate.Fruit set percentage, date of harvest, average number of bunches/palm, bunch weight, yield per palm as well as physical and chemical properties of fruitsand Numerical evaluation were recordedand calculatedfor some tested soft date palm cultivars. Significant differences were observed for fruit set percentage of some tested date palm cvs. Highest fruit set percentages were obtained from Madjool (95.40 – 97.50%), and Hayany (81.00 & 80.00) in comparison with other tested cvs. as well as Nabtet-Seif which produced the lowest fruit set percentage (55 – 58.5%).Braym,Barhee and Halawy were earlyin harvest by the first half of Aug., Madjool, Hayany and Khalas as midseason (September), while Nabtet-Seif, Succary and Lolo are late in harvest (October). Barhee, Nabtet-Seif, Halawy, Braym, Khalas, Succary, Lolo and Hayanyfruits are eatable at Khalal and rutab stage, while Madjool was not eatable atkhalal stage increase tannins and acid content in the khalal fruits, Madjool was suitable for raw eating at rutaband tamer stage.Among the physical fruit characteristics are, fruit weight (18.00 &18.74 gm), fruit length (4.00 & 4.00 cm) and seed weight (1.64&1.59gm) were the highest in theHayany in tested seasons.Fruitflesh percentage was the highest with Barhee and lowest with Hayany. As for chemical fruit characteristics, total soluble solids and total sugars contents recorded the highestin the Halawy and Succary. Fruits of Halawy and Barhee had lower tannins and acidity percentage, while it reached the highest content in Hayany.The numerical evaluation (total unit 100) of some tested soft date palm showed that, they were ranked as follows:Barhee (89.77unit), Madjool (84.25 unit), Hayany(80.96 unit), Succary (77.52 unit), Halawy (75.56 unit), Khalas (71.28 unit),Nabtet-Seif (69.82unit), Lolo (75.23 unit) and Braym (65.95 unit) in average both tested seasons. In addition, total score of fruit quality (70 unit)of tested soft date palm was ranked as follows:Madjool (63.25 unit), Barhee (59.47unit), Succary (58.28unit), Lolo (56.28unit), Hayany (55.18 unit), Halawy (54.65 unit ), Khalas (54.23unit), Nabtet-Seif (50.79 unit) and Barym (48.09 unit) inaverage both tested seasons. Generally, the obtained herein results proved that Madjool, BarheeandHayany showed better results and could be recommended to be cultivated in the desert region at Giza Governorate, due to their high yield and fruits physiochemical characteristicsthan the other tested soft date palm cultivars.Although the yield of date palm cvs., Succary and Lolo grown in desert region Giza Governorate was relatively low in comparing with Hayany cv. (local date palm) which showed hight physiochemical characteristics for its fruits. On the contrary, Nabtet-Seif and Braym showed less yield and poor fruit quality than the standard studied cv. Hayany.