The effect of root restriction on the incidence of blossom-end rot in bell pepper (Capsicum annuum L.)

Summary

Water and calcium uptake are important factors affecting the incidence of fruit blossom-end rot (BER) in tomato and pepper. In the present study an attempt was made to manipulate these factors by severe root pruning and to examine the effect on BER in greenhouse-grown bell pepper (Capsicum annuum L., cv. Mazurka). Pepper plants were transplanted, with the root system split into four separated compartments, each containing a single root quarter. Removal of half, or three quarters, of the root from fruit-bearing plants significantly reduced fruit BER incidence compared with plants with intact roots, especially in fruits which were at the rapid expansion stage at the beginning of the treatments. Removal of three quarters of the root reduced midday leaf water potential, stomatal conductance, and plant height. The number and weight of fruits were not affected by these treatments. Root pruning caused only a slight reduction in stem sap flow, as measured by the heat pulse technique. Calcium concentrations in the distal part of fruits from quarter-root-plants were higher than in fruits from non-pruned plants, whereas magnesium and potassium concentrations were not affected. On the other hand, in the leaves, calcium, magnesium and potassium concentrations were all reduced by root pruning. The K/Ca ratio decreased in the blossom-end of the fruits and increased in the leaves of root-pruned compared with control plants. The results suggest that root pruning did not affect the total uptake of calcium, apparently driven by transpiration, but did enhance calcium partitioning to the developing fruit. Root pruning also affected calcium distribution within the fruit and therefore attenuated BER incidence.     

Apoplastic anti-oxidants in pepper (Capsicum annuum L.) fruit and their relationship to blossom-end rot

Summary

The aim of the present research was to study changes in the major anti-oxidative enzyme activities known to be associated with the apoplast, during the induction of blossom-end rot (BER) in bell pepper (Capsicum annuum L.) fruits grown under saline conditions. Pepper plants of the BER-sensitive cv. ‘Mazurka’ and less-sensitive cv. ‘Selica’ were grown under control, low- and high-salinity irrigation regimes. Fruits were harvested continuously and, after approx. 7 months under these conditions, BER symptoms started to appear (in the Spring season) and fruits were sampled for biochemical measurements. The intercellular washing fluid (IWF; apoplast fraction) of the fruit pericarp was prepared and enzyme activities in that fraction were determined. The results showed that production of reactive oxygen species (ROS) in the fruit apoplast was higher in ‘Mazurka’ than in ‘Selica’. Apoplastic peroxidase and superoxide dismutase (SOD) activities, and the concentration of ascorbic acid, increased during ‘Selica’ fruit development, whereas the concentration of H₂O₂ decreased. During the stage of rapid growth, when fruits are most susceptible to BER, apoplastic peroxidase activity was greatly enhanced in the healthy pericarp of BER-affected fruits compared to healthy fruits. Under saline conditions, apoplastic peroxidase and SOD activities, as well as ascorbic acid and H₂O₂ levels, increased in healthy fruits of the resistant cultivar ‘Selica’; whereas, in healthy fruit of the BER-sensitive cultivar ‘Mazurka’, apoplastic peroxidase activity decreased while the level of ascorbic acid increased, but to a much lesser extent than in ‘Selica’. SOD activity and H₂O₂ levels increased similarly in both cultivars with increasing levels of salinity. It is proposed that apoplast-associated peroxidase activity and ascorbic acid concentration are increased coordinately in response to salt stress and may be part of a protective anti-oxidation mechanism that determines cultivar sensitivity to BER.     

Comparison of anti-oxidant activities and fruit quality attributes in four sweet bell pepper (Capsicum annuum L.) cultivars grown in two soilless media

This work was carried out to study the effects of two soilless media consisting of 80:20 [volume/volume (v/v)] mixtures of mosspeat and perlite, or cocopeat and perlite, on fruit quality and anti-oxidant activities in four cultivars of bell pepper (Capsicum annuum L.): ‘Traviata’ (green), ‘Inspratian’ (red), ‘Aracia’ (orange), and ‘Taranto’ (yellow). The results showed that the composition of the medium had a significant effect on the anti-oxidant composition and activities of the bell pepper fruit. Plants grown on 80:20 (v/v) mosspeat and perlite had significantly higher pericarp firmness, titratable acidity, total phenolic compound concentrations, 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability, and the hydroxy free-radical (?OH) scavenging ability. Fruit on plants grown on 80:20 (v/v) cocopeat and perlite had significantly higher vitamin C concentrations. Among the four cultivars tested, ‘Inspratian’ (red) was superior in more factors including pericarp thickness, dry matter content, titratable acidity, total soluble solids content, total phenolic concentration, DPPH scavenging ability, and vitamin C concentration. There was a significant interaction between cultivar and soilless medium composition, indicating that the response of bell pepper cultivars varied in the different media. The results of the present study highlight the importance of comparing soilless media in terms of their effect on fruit crop quality and anti-oxidant activity.     

Effects of greenhouse cooling method on growth,fruit yield and quality of tomato (Solanum lycopersicum L.) in a tropical climate

A tomato (Solanum lycopersicum L.) crop was grown in four greenhouses during the dry season 2005/06 in Central Thailand. Sidewalls and roof vents of two greenhouses were covered with nets and these greenhouses were mechanically ventilated when air temperature exceeded 30 °C (NET). The other two greenhouses were covered with polyethylene film and equipped with a fan and pad cooling system (EVAP). Overall mean air temperature was significantly reduced by 2.6 and 3.2 °C (day) and 1.2 and 2.3 °C (night) in EVAP as compared to NET and outside air, respectively. Temperature maxima in EVAP averaged about 4 °C lower than in NET and outside. The relative humidity was around 20 and 30% (day) and 10 and 15% (night) higher in EVAP than in NET or outside, respectively. Vapour pressure deficit averaged 0.25 kPa in EVAP, 1.03 kPa in NET and 1.48 kPa outside. The crop water-consumption was significantly lower in EVAP (1.2) than in NET (1.8 L plant⁻¹ day⁻¹), which is ascribed to reduced transpiration in EVAP. Total fruit yield was similar in NET (6.4 kg plant⁻¹) and EVAP (6.3 kg plant⁻¹). The quantity of undersized (mostly parthenocarpic) and blossom-end rot (BER)-affected fruits was reduced in EVAP. However, the proportion of marketable yield was significantly higher in NET (4.5 kg plant⁻¹) than in EVAP (3.8 kg plant⁻¹), owing largely to an increased incidence of fruit cracking (FC) in EVAP. Higher FC but lower BER incidence coincided with higher fresh weight and Ca concentration in the fruits in EVAP. It is concluded that in regions with high atmospheric relative humidity evaporative cooling without technical modifications allowing dehumidification will not improve protected tomato production.     

Abortion of reproductive organs in sweet pepper (Capsicum annuum L.): a review

Summary

Levels of abortion of reproductive organs (i.e., buds, flowers, and young fruits) in sweet pepper plants (Capsicum annuum L.) are high, and cyclical fluctuations occur in fruit set. Stages susceptible to abortion are very young buds (< 2.5 mm), buds close to anthesis, and flowers and fruits up to 14 d after anthesis. An overview of factors and processes involved in flower and fruit abortion in sweet peppers is presented. More light, higher CO₂ concentrations, and lower planting density, increase the availability of assimilates per plant, and decrease fruit abortion. The cyclical pattern in fruit set is caused by changes in demand for assimilates. High flower abortion occurs when fast growing fruit (at approx. 3 weeks after anthesis) are present, due to competition for assimilates. Fruit set increases when fast growing fruit are almost mature and have a low assimilate demand. Prior to abortion, auxin export from the reproductive organ diminishes, ethylene production increases, and lower levels of activity of sucrose-cleaving enzymes are found. Severe water stress and low nutrient supply also increase abortion levels. Low night- and high day-time temperatures hamper pollen development, causing low seed set, which can result in fruit abortion. Two theories have been used to explain abortion: unbalanced demand for and supply of assimilates, and hormonal dominance of developing fruit over young fruit. Attempts to prevent abortion or to diminish the cyclical pattern of fruit set have not yet been successful, but new suggestions are presented.     

Heterosis studies in chilli (Capsicum annuum L.)

By top-crossing 12 different homozygous chilli varieties with a genetic male sterile (MS), 12 hybrids were produced. Heterosis over mid-parent (MP) and superior parent (SP) was studied for days to flower, plant height, number of primary branches, length of fruit, number of fruits per plant and fruit yield per plant. Degree and direction of heterosis varied greatly for different characteristics and crosses studied. The hybrid MS × K-2 exhibited significant positive heterosis for fruit yield over its SP (157%), followed by MS × Pant-C-1, MS × Japanese bunch variety and MS × Bhiwapur local, indicating that male sterility can be utilised for commercial exploitation of hybrid vigour. Heterosis was observed for days to flower, plant height, number of primary branches, fruit length and number of fruits per plant.     

Blossom-end rot is associated with impairment of sugar metabolism and growth of pepper (Capsicum annuum L.) fruits

Summary

Blossom-end rot (BER) in pepper fruits is known as a “physiological” disease which is evoked by climatic and osmotic stresses (e.g., high temperatures and salinity) and by deficit irrigation management. The physiological and biochemical mechanisms involved in the stimulation of BER are still a matter of dispute. It has been proposed that BER occurs under cultivation conditions that accelerate fruit growth beyond calcium supply to the growing tissue. In the present study, we investigated this hypothesis by recording fruit growth and sugar metabolism under normal and BER-inducing conditions.The results showed that pepper fruits grown in a ventilated-cooled greenhouse, which ameliorated BER, had a higher initial growth rate than those grown in a non-cooled greenhouse, but had lower calcium concentrations in the fruit pericarp. Fruits that grew without ventilation-cooling had higher concentrations of apoplastic and symplastic sucrose and reducing sugars, and higher levels of symplastic starch than those that developed in a cooled greenhouse. Concomitantly, fruits that developed in a non-cooled greenhouse had lower acid invertase, sucrose synthase and fructokinase activities than those that developed in a cooled greenhouse. Accordingly, the non-necrotic part of BER-affected fruits had higher concentrations of symplastic starch, reducing sugars and sucrose than healthy fruits. These findings indicate that the occurrence of BER in pepper fruits was associated with impaired sucrose metabolism in fruit tissues, which led to reductions in growth rate and final size. Thus, the present findings negate the notion that BER occurs when fruit growth rate is stimulated, and favour the idea that direct impairment of fruit sugar metabolism and of normal fruit growth are involved.     

Evaluation of new rootstocks for resistance to soil-borne pathogens and productive behaviour of pepper (Capsicum annuum L.)

Summary

An evaluation of five rootstocks for pepper (Capsicum annuum L.) was carried out over a 3-year period on three farms in Campania (Italy). Pepper is very susceptible to soil-borne pathogens, especially Phytophthora capsici, Verticillium dahliae and Meloidogyne spp. (root-knot nematode). The lack of resistant hybrids and of crop rotation, and the longterm survival of propagules of the pathogen, have increased the risk of damage that so far has been controlled by pre-planting soil treatment with methyl bromide. The use of pepper grafted onto rootstocks resistant to the main soil-borne pathogens is not undertaken commercially in Italy because the available rootstocks are unsatisfactory. P. capsici, V. dahliae, Fusarium oxysporum, F. solani and M. incognita have been detected on farms where the new rootstocks were tested. Trials were performed on the same sites for 2 or 3 years in order to provide favourable conditions for parasites. Two rootstocks, ‘Graffito’ and ‘Gc 1002’, were found to be resistant to P. capsici. In the presence of an early, high population density of M. incognita, ‘Graffito’ showed good tolerance, while ‘Gc 1002’ was susceptible to the root-knot nematode. In addition, both rootstocks showed good compatibility with the different scions tested and did not decrease vegetative growth, fruit yield or the size of the scions. In contrast, in the presence of V. dahliae, F. oxysporum and F. solani, none of the rootstocks tested was sufficiently resistant to vascular or crown and root rot damage.     

辣椒GMS育性相关miRNA的鉴定和表达分析

研究辣椒花药中sRNA分布,筛选育性相关miRNA,通过miRNA及其靶基因的表达分析探讨miRNA对雄性育性的调控。利用高通量测序技术对辣椒细胞核雄性不育两用系处于小孢子单核靠边期的花药进行sRNA测序,同时分析两材料间miRNA的表达差异。通过qRT-PCR技术验证差异分析结果,并对miRNA及其靶基因在小孢子发育不同时期的表达模式进行分析。在构建的不育株和可育株两个文库中共发掘出857个可信度高的miRNA;筛选得到42个表达差异显著的miRNA;通过靶基因预测与注释,预测出的差异表达miRNA的靶基因中与繁殖有关的基因有152个,与生殖过程有关的基因有151个。通过qRT-PCR验证了选出的9条miRNA的存在,其表达差异与测序分析结果基本一致;单核靠边期多数miRNA负调控其靶基因,不同发育时期其调控模式会发生变化。本研究为揭示辣椒miRNA与雄性育性的关系提供了重要信息。     

辣椒离体培养及再生体系的研究

以"韩国甜椒"为试材,研究外植体种类、苗龄、基本培养基种类、激素组合等多种因素对辣椒组织再生的影响。结果表明:带柄子叶再生能力较子叶和下胚轴切段强,14d苗龄幼苗的外植体芽分化率较高,最佳芽分化培养基为MB+4.5mg/L BA+0.5mg/L IAA+4mg/L AgNO3+200mg/L Cef,最佳芽伸长培养基为MS+3mg/L BA+0.3mg/L IAA+2mg/L GA3+4mg/L AgNO3+200mg/L Cef,生根培养基先用1/2MS+0.4mg/L NAA+4mg/L AgNO3,继代用1/2MS+0.4mg/L NAA+0.2%活性炭。     

辣椒品质育种研究进展

对国内外有关辣椒果实辣椒素、维生素C和干物质等品质性状的遗传特性及相关因素的研究进展作了综述,指出了今后的研究方向.     

Flowering,fruit set and development of the fruit and seed of sweet pepper (iCapsicum annuum L.) cultivated under conditions of high ambient temperature

Sweet pepper (Capsicum annuum L.) cvs E-84066 and Yolo Wonder were grown under ambient conditions in plastic covered greenhouses. Anthesis commenced five and six weeks after planting and rose to a peak of 39 (E-84066) and 19 (Yolo Wonder) flowers per week respectively after which there was a rapid fall. Temperatures throughout anthesis were high (>38°C (maximum) and >16°C (minimum)) and this is likely to have contributed to the magnitude of the flux. Fruit set was highest in the early stages of the crop, but subsequently declined as the majority of flowers aborted. Overall, fruit weight was correlated with seed weight and seed number, and declined throughout the life of the crop. By contrast, seed size and the percentage germination remained constant. The latter is of particular importance for seed crops where seed quality is of primary concern.     

辣（甜）椒果实相关性状遗传研究进展

果实是辣椒最主要的经济产出品,因此在长期的栽培选育过程中,较注重对辣椒果实大小、形状、颜色、辛辣味等重要经济性状的选择。通过对有益等位基因及有益突变的利用,可以创新辣椒种质资源,获得综合性状优良的辣椒新品种。本文综述了近年来国内外在辣（甜）椒果实质量、形状、颜色、硬度、辛辣性的基因定位及分子生物学方面的研究成果及进展,并对辣椒果实性状基础研究方向进行了展望。     

辣椒成熟果实中辣椒红素含量的QTL定位

以83-58×Perennial构建的包括138个单株的重组自交系(RIL)群体为作图群体,利用142个SSR标记、24个CAPS标记以及果实辣味、果柄着生方向(pun和up)2个形态标记构建遗传连锁图谱并进行了辣椒成熟果实中辣椒红素的QTL定位。生理成熟期(花后70d)辣椒果实的辣椒红素含量测定值作为QTL定位时的表型数据,利用复合区间作图法共检测到3个QTL位点,分别位于辣椒的第2、10、12条染色体上,分别解释了表型变异的7.6%、8.2%、6.5%。     

辣椒始花节位遗传研究

 应用植物数量性状主基因+多基因混合遗传模型和经典遗传学方法对特早熟辣椒‘B₉₄₃₁ ’与‘吉林长椒’杂交组合多个世代群体始花节位进行了联合分析, 结果表明: ‘B₉₄₃₁ ’始花节位受1对隐性等位主基因控制, B₉₄₃₁ ×吉林长椒始花节位遗传符合1对主基因+多基因混合遗传模型。该杂交组合的B₁、B₂ 和F₂ 群体主基因遗传率分别为83.72%、76.56%和86.63% , 多基因遗传率分别为10.96%、18.58%和7.94%。     

Growth,gas exchange,and nutrient status in pepper (Capsicum annuum L.) grown in recirculating nutrient solution as affected by salinity imposed to half of the root system

Pepper plants grown in recirculating nutrient solution were exposed to NaCl-salinity (60 mM NaCl, 8 dS m⁻¹) imposed either to the entire or to half of the root system and compared to plants supplied with a standard nutrient solution (1.9 dS m⁻¹). The saline solution was obtained by adding NaCl to the standard nutrient solution. In the split-root treatment, the root compartment not exposed to salinity was supplied with raw water (0.38 dS m⁻¹). Both the stem and the root dry weights were markedly restricted by salinity, irrespective of salinizing half or the entire root system. In the split-root treatment, the dry weight of the root compartment receiving raw water did not differ significantly from that exposed to salinity. The net photosynthesis and the leaf chlorophyll content were restricted by both salinity treatments, but the decrease was more marked when the entire root system was exposed to salinity. In contrast, the stomatal conductance and the transpiration rate were equally reduced, regardless of salinizing the entire or part of the root system. The leaf Na and Cl concentrations were raised by the NaCl-salinity, but only in one sampling date the increase was significantly higher when the entire root zone was exposed to salinity, as compared with salinization of half of the root system. Salinity reduced significantly the leaf K, Ca, and Mg uptake but not to levels that could cause nutrient deficiencies. These results indicate that pepper is susceptible to high salinity, predominantly due to reduced stomatal conductance. However, after long-term exposure to salinity the growth may be suppressed due also to inhibition of photosynthesis at chloroplast level. The adverse effects of high NaCl-salinity are hardly mitigated when only a part of the root system is salinized, which indicates that the response is governed by root exposure to high NaCl concentrations and not by inefficiency of the roots to take up water.     

辣椒抗黄瓜花叶病毒QTL分析

利用辣椒抗黄瓜花叶病毒材料perennial与园艺性状优良的感病材料茄门,及其F2群体146个单株、F3 146个株系为试材,采用SRAP和SSR分子标记技术,利用JoinMap 3.0软件构建了包含76个标记、13个连锁群,覆盖长度为830.4 cM的辣椒分子遗传图谱。对F3株系（4 380个单株）进行人工接种鉴定黄瓜花叶病毒,其病情指数呈正态分布。结合分子遗传图谱的结果,利用MapQTL 4.0软件进行分析,将抗病基因的QTL定位在第1、4、7连锁群上,抗性贡献率分别为12.7%、38.8%、11.0%。     

辣椒产量和品质性状Hayman遗传分析

 将辣椒(Capsicam annuum L. ) 6个亲本, 按(1 /2) n ( n - 1) 双列杂交法配制15个杂交组合, 用Hayman双列杂交分析法估算5个关于产量、品质性状的遗传参数。Wr对Vr的回归分析结果表明,单株产量、小区产量、辣椒素和干物质含量的遗传符合“加性—显性”模型; 早期产量的遗传不符合“加性—显性”模型。Wr +Vr与Yr间相关分析表明, 单株产量、小区产量、早期产量和干物质含量呈负相关,说明含有更多显性基因的亲本具有较小的Wr +Vr值; 辣椒素含量呈正相关, 说明含有较多辣椒素显性基因的亲本具有较大的Wr +Vr值。遗传参数估算表明, 辣椒素和干物质含量的遗传是加性效应方差明显大于显性效应方差; 单株产量和小区产量的遗传加性效应方差明显小于显性效应方差; 早期产量的遗传是显性效应方差显著大于加性效应方差, 同时还存在显著的、复杂的上位性效应。     

辣椒基因组DNA提取方法研究

本项研究采用SDS法、CTAB法和高盐低pH法对辣椒(CapsicumannuumL.)叶片基因组DNA进行提取;紫外吸收检测法与琼脂糖凝胶电泳法对DNA的纯度进行检测。紫外吸收检测结果表明,SDS法提取的辣椒叶片DNA具有典型的天然DNA分子的标准紫外吸收光谱特点,其A260/A280在1.771～1.912之间。SDS法提取的DNA经琼脂糖凝胶电泳检测得到一条迁移率很低的整齐清晰的DNA谱带,所提取DNA的质量和产率均较高,用该法提取的辣椒DNA进行RAPD分析,DNA扩增效果较好,带形清晰、整齐,说明SDS法提取的DNA分子较为完整,能用作PCR模板来开展辣椒分子水平的研究。     

辣椒AFLP反应体系的优化与建立

以5个辣椒（Clapsjcum annuum L.）材料为研究对象,对AFIJP反应体系中的DNA用量、酶切连接时间、预扩增产物的稀释倍数等关键因素进行优化分析,建立了适宜辣椒作物的AFLP反应体系。研究结果：酶切连接反应中,基因组DNA适宜用量为100ng,反应时间是6h最为合适,预扩增产物适宜稀释倍数在30-50倍时较为理想。