Development of pepper (Capsicum annuum) seed quality

Changes in seed quality in pepper (Capsicum annuum L.) were monitored during seed development and maturation in two seasons. Seed quality was assessed by a number of different tests, but principally by determining seed storage longevity in laboratory tests and seedling growth in glasshouse tests. Mass maturity (defined as the end of the seed-filling phase) occurred 49–53 days after anthesis (DAA) in 1989 (varying among fruit layers) and 53 DAA in 1990 when seed moisture contents were 51–53%. The onset of both germinability and desiccation tolerance occurred either just before or at mass maturity. Maximum potential longevity (assessed by the value of the seed lot constant K_i) was achieved 63–65 DAA, i.e. not until 10–12 days after mass maturity (DAMM), in both years. Seedling dry weights in the glasshouse growth tests were maximal later still - for seeds harvested 17–21 DAMM in 1989 and 17 DAMM in 1990; the effects on seedling weight arose from differences in times from sowing to emergence (P < 0.005) among different seed harvests, with no significant differences in subsequent relative growth rates (P > 0.25). Seed priming reduced mean germination times for seeds harvested at all stages of development, but had little effect on germination capacity and potential longevity, and did not affect the pattern of changes in potential longevity during seed development and maturation. The results contradict the hypothesis that seed quality is maximal at the end of the seed-filling phase and that viability and vigour begin to decline immediately thereafter.     

Chromoplast differentiation in bell pepper (Capsicum annuum) fruits

We report here a detailed analysis of the proteome adjustments that accompany chromoplast differentiation from chloroplasts during bell pepper (Capsicum annuum) fruit ripening. While the two photosystems are disassembled and their constituents degraded, the cytochrome b₆f complex, the ATPase complex, and Calvin cycle enzymes are maintained at high levels up to fully mature chromoplasts. This is also true for ferredoxin (Fd) and Fd-dependent NADP reductase, suggesting that ferredoxin retains a central role in the chromoplasts’ redox metabolism. There is a significant increase in the amount of enzymes of the typical metabolism of heterotrophic plastids, such as the oxidative pentose phosphate pathway (OPPP) and amino acid and fatty acid biosynthesis. Enzymes of chlorophyll catabolism and carotenoid biosynthesis increase in abundance, supporting the pigment reorganization that goes together with chromoplast differentiation. The majority of plastid encoded proteins decline but constituents of the plastid ribosome and AccD increase in abundance. Furthermore, the amount of plastid terminal oxidase (PTOX) remains unchanged despite a significant increase in phytoene desaturase (PDS) levels, suggesting that the electrons from phytoene desaturation are consumed by another oxidase. This may be a particularity of non-climacteric fruits such as bell pepper that lack a respiratory burst at the onset of fruit ripening.     

Shikimate dehydrogenase from pepper (Capsicum annuum) seedlings. Purification and properties

Shikimate dehydrogenase (SKDH, EC 1.1.1.25) was extracted from seedlings of pepper ( Capsicum annuum L.) and purified 347-fold. The purification procedure included precipitation with ammonium sulphate and chromatography in columns of Reactive Red-agarose, Q-Sepharose and Sephadex G-100. Pepper SKDH isozymes are separable only using PAGE. The purified enzyme has a relative molecular mass of 67 000 as estimated by gel filtration. The optimum pH of enzyme activity is 10.5 and the optimum temperature is 50°C, but the enzyme is quickly inactivated at temperatures higher than 40°C. The purified enzyme exhibited typical Michaelis-Menten kinetics and K_m values are 0.087 m M for shikimic acid and 0.017 m M for NADP. The mechanism of reaction is sequential considering NADP as a cosubstrate. Ions such as Ca²⁺, Mg²⁺ and Mn²⁺ activate the enzyme, but Zn²⁺ and Cu²⁺ are strong inhibitors. Some phenolic compounds such as guaiacol, protocatechuic acid and 2,4-D are competitive inhibitors of pepper SKDH, showing K_i values of 0.38 m M , 0.27 m M and 0.16 m M , respectively.     

Carbohydrate metabolism during fruit development in sweet pepper (Capsicum annuum) plants

Growth, accumulation of sugars and starch, and the activity of enzymes involved in sucrose mobilization were determined throughout the development of sweet pepper fruits. Fruit development was roughly divided into three phases: (1) an initial phase with high relative growth rate and hexose accumulation, (2) a phase with declining growth rate and accumulation of sucrose and starch, and (3) a ripening phase with no further fresh weight increase and with accumulation of hexoses, while sucrose and starch were degraded. Acid and neutral invertase (EC 3.2.1.26) were closely correlated to relative growth rate until ripening and inversly correlated to the accumulation of sucrose. Acid invertase specifically increased during ripening, concurrently with the accumulation of hexoses. Sucrose synthase (EC 2.4.1.13) showed little correlation to fruit development, and in periods of rapid growth the activity of sucrose synthase was low compared to the invertases. However, during late fruit growth sucose synthase was more active than the invertases. We conclude that invertase activities determine the accumulation of assimilates in the very young fruits, and a reactivation of acid invertase is responsible for the accumulation of hexoses during ripening. During late fruit growth, before ripening, sucrose synthase is transiently responsible for the sucrose breakdown in the fruit tissue. Results also indicate that pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90) and its activator fructose-2,6-bisphosphate (Fru2,6bisP) are involved in the regulation of the sink metabolism of the fruit tissue.     

EMS-induced lincomycin resistance in red pepper (Capsicum annuum L.)

Summary Ethyl methane sulphonate (EMS) is a potential mutagen to induce lincomycin resistance in Capsicum annuum. Mutagenized cotyledons were cultured on shoot regenerating medium containing lincomycin (100 mgl⁻¹). Approximately 14% of regenerated shoots were chlorophyll deficient and about 4% of regenerated shoots were green from mutaganized cotyledons. The regenerated green plants were resistant to lincomycin but sensitive to chloramphenicol, kanamycin, spectinomycin, and streptomycin. Reciprocal crosses were made between resistant and sensitive plants. Inheritance of lincomycin resistance was transmitted as a non-Mendelian trait. Lincomycin resistance is a first selectable and maternally inherited organelle encoded genetic marker described in chili pepper. Such mutants should be useful in designing biochemical selection schemes to recover somatic hybrids and cybrids.     

Defence response of pepper (Capsicum annuum) suspension cells to Phytophthora capsici

Cell suspension cultures of three cultivars of Capsicum annuum L., with different degrees of sensibility to the fungus Phytophthora capsici, responded to elicitation by both lyophilized mycelium and fungus filtrate. They showed conductivity changes, browning, production of the phytoalexin capsidiol and synthesis or accumulation of pathogenesis-related (PR) proteins with glucanase (EC 3.2.1.39) and chitinase (EC 3.2.1.14) activities. The cultivation medium was optimised for growth of both the plant and the fungus in order to avoid any stress during their combination. The resistant cv. Smith-5, showed a more rapid and intense response to the elicitor preparations than the sensitive cvs Americano and Yolo Wonder. This was particularly evident when the cell suspensions were elicited with the filtrate, when differences became clearly visible after only 6 h incubation. The greatest rate of capsidiol accumulation occurred after 18 h in the mycelium-elicited cells and after 12 h in those elicited with the filtrate. These times are the optimal for capsidiol accumulation, and the phytoalexin is produced much more rapidly than it can be excreted into the extracellular medium. The inhibition threshold of fungal growth (300 µg capsidiol [g dry weight]^?1) was reached only in the resistant cultivar. The induction of an intracellular glucanase (pI 8.9 and R_f 0.18) and an extracellular chitinase (pI 5.4 and R_f 0.70) only in the resistant cultivar 24 h after elicitation suggests that these enzymes are involved in the resistance to Phytophthora capsici, while other hydrolases common to all three cultivars form part of a more general defence. The results indicate that elicitation of pepper cell suspension cultures by signal molecules from P. capsici exhibits properties of a multicomponent dynamic system in which different protective mechanisms play complementary roles in the overall expression of the defence reaction. We confirm that the differential responses of resistant and susceptible pepper cultivars to P. capsici previously seen in plant stem sections are retained in suspension culture.     

Evolution of Capsaicinoids in Peter Pepper (Capsicum annuum var. annuum) During Fruit Ripening

The evolution of individual and total contents of capsaicinoids present in Peter peppers (Capsicum annuum var. annuum) at different ripening stages has been studied. Plants were grown in a glasshouse and the new peppers were marked in a temporal space of ten days. The extraction of capsaicinoids was performed by ultrasound‐assisted extraction with MeOH. The capsaicinoids nordihydrocapsaicin (n‐DHC), capsaicin, dihydrocapsaicin, homocapsaicin, and homodihydrocapsaicin were analyzed by ultraperformance liquid chromatography (UHPLC)‐fluorescence and identified by UHPLC‐Q‐ToF‐MS. The results indicate that the total capsaicinoids increase in a linear manner from the first point of harvest at ten days (0.283 mg/g FW) up to 90 days, at which point they reach a concentration of 1.301 mg/g FW. The evolution as a percentage of the individual capsaicinoids showed the initial predominance of capsaicin, dihydrocapsaicin, and n‐DHC. Dihydrocapsaicin was the major capsaicinoid up to day 50 of maturation. After 50 days, capsaicin became the major capsaicinoid as the concentration of dihydrocapsaicin fell slightly. The time of harvest of Peter pepper based on the total capsaicinoids content should be performed as late as possible. In any case, harvesting should be performed before overripening of the fruit is observed.     

Phenylalanine ammonia-lyase activity and capsaicin-precursor compounds in p-fluorophenylalanine-resistant and -sensitive variant cells of chili pepper (Capsicum annuum)

Cell suspension cultures of chili pepper ( Capsicum annuum L. cv. Tampiqueño 74) displaying differences in their resistance to p -fluorophenylalanine (PFP) and in their contents of capsaicin (the compound which is responsible for the hot taste of chili pepper fruits) were characterized in relation to the activity of phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), the levels of free l -phenylalanine, phenolics and the phenylpropanoid acids involved in capsaicin biosynthesis. A nonselected cell line, a sensitive line (CA-02), a moderately resistant cell line (CA-29) and two resistant cell lines (CA-04 and CA-16) were studied. Higher PAL activities and higher levels of phenylalanine and phenolics were found in the PFP-resistant cells even after a minimum of 9 subcultures (15 days each) in the absence of the analog, indicating that the selected trait was stable. PFP-resistant chili pepper cells accumulated higher amounts of capsaicin precursors (cinnamic, caffeic and ferulic acids) than either the nonselected cells or the sensitive cell line. p -Coumaric acid was not detected at significant levels in any of the cell cultures. Overall, accumulation of free phenyl-alanine correlated well with PAL activity, phenolics, phenylpropanoids and capsaicin levels, suggesting an active flow through the phenylpropanoid pathway in PFP-resistant cells of chili pepper.     

高温干旱对不同品种辣椒生长及呼吸作用的影响

研究了高温干旱胁迫对不同品种辣椒生长及呼吸作用的影响。结果表明,高温胁迫对正椒13号的生长无影响,对鸡爪×吉林的生长稍有抑制;干旱及高温干旱严重地抑制了辣椒的生长。干旱导致叶片相对电导率的增加高于高温,而高温加剧了干旱伤害程度,并且对鸡爪×吉林的伤害更大。高温处理引起了辣椒总呼吸、细胞色素呼吸和交替呼吸的增加。干旱胁迫抑制了细胞色素呼吸,但诱导了交替呼吸的增强;高温干旱共同胁迫加剧了总呼吸和细胞色素呼吸的下降,交替呼吸只在胁迫第一天被促进,随后立即下降。高温、干旱和高温干旱胁迫下正椒13号表现出了较鸡爪×吉林更强的交替呼吸和总呼吸。说明高温、干旱和高温干旱胁迫下辣椒保持较高的总呼吸和交替呼吸与其抗高温和/或干旱能力相关。     

Identification and development of polymorphic EST-SSR markers by sequence alignment in pepper, Capsicum annuum (Solanaceae)

? Premise of the study: The redundancies in expressed sequence tags (ESTs) in the National Center for Biotechnology Information sequence database were used to identify and develop polymorphic simple sequence repeat (SSR) markers for pepper (Capsicum annuum). ? Methods and Results: Sixty-eight polymorphic SSR loci were identified in the contigs (containing redundant ESTs) generated by assembling 118060 pepper ESTs from the public sequence database. Thirty-three SSR markers exhibited polymorphism among 31 pepper varieties, with alleles per SSR marker ranging from two to six. The mean observed and expected heterozygosity were 0.28 and 0.39, respectively. There were 18 SSR markers with a motif repeat number of less than five, accounting for 55% of the total. ? Conclusions: We demonstrated the value of mining the redundant sequences in public sequence databases for the development of polymorphic SSR markers, which can be used for marker-assisted breeding in pepper.     

Microspore-derived embryogenesis in pepper (Capsicum annuum L.): subcellular rearrangements through development

Background information. In vitro-cultured microspores, after an appropriate stress treatment, can switch towards an embryogenic pathway. This process, known as microspore embryogenesis, is an important tool in plant breeding. Basic studies on this process in economically interesting crops, especially in recalcitrant plants, are very limited and the sequence of events is poorly understood. In situ studies are very convenient for an appropriate dissection of microspore embryogenesis, a process in which a mixture of different cell populations (induced and non-induced) develop asynchronically.Results. In the present study, the occurrence of defined subcellular rearrangements has been investigated during early microspore embryogenesis in pepper, an horticultural crop of agronomic interest, in relation to proliferation and differentiation events. Haploid plants of Capsicum annuum L. (var. Yolo Wonder B) have been regenerated from in vitro anther cultures by a heat treatment at 35 degrees C for 8 days. Morphogenesis of microspore-derived embryos has been analysed, at both light and electron microscopy levels, using low-temperature-processed, well-preserved specimens. The comparison with the normal gametophytic development revealed changes in cell organization after embryogenesis induction, and permitted the characterization of the time sequence of a set of structural events, not previously defined in pepper, related to the activation of proliferative activity and differentiation. These changes mainly affected the plastids, the vacuolar compartment, the cell wall and the nucleus. Further differentiation processes mimicked that of the zygotic development.Conclusions. The reported changes can be considered as markers of the microspore embryogenesis. They have increased the understanding of the mechanisms controlling the switch and progression of the microspore embryogenesis, which could help to improve its efficiency and to direct strategies, especially in agronomically interesting crops.     

辣椒资源及其加工利用

综述了辣椒的起源、传播、栽培种分类、生产和加工利用的概况,介绍了辣椒的化学组成、辣椒红色素和辣椒碱的药理作用及其开发利用价值。     

Graft-induced genetic changes and the inheritance of several characteristics in pepper (Capsicum annuum L.)

 The general characteristics of several graft-induced changes in pepper were investigated in a cross experiment. F₁, F₂, and BC₁ progenies derived from crosses of the original stock and scion cultivars ‘Spanish Paprika’ and ‘Yatsubusa’, respectively, as well as their graft-induced variant strain G₅S₂₅ were analyzed for inheritance of the most conspicuous graft-induced variant traits. As part of a research program with the aim of revealing the mechanism of graft induction, the present study was carried out to examine the stability of the phenotypic changes and the characteristics of the graft-induced variants. For the fruit apex, a two-gene system was suggested, with other factors having a modifying influence. One of the two apex genes acted for pointed fruits and the other for inverted-blunt fruits. The inverted-blunt gene, the apex gene of the stock, was unambiguously present in the graft-induced variants, while the pointed gene that acted in the dominant mode in the original scion was inactive and expressed only under certain conditions in a mosaic state. The stable inverted-blunt cultivar used for the stock maintained certain factor(s) for pointed fruit, but the presence of that factor(s) could not be detected in graft-induced variants. The results of pungency analysis suggested a gene for non-pungency that appeared to be introduced in the graft-induced variants. The fruiting habit and fruiting direction that appeared in a mosaic state in graft-induced variants were found to combine factors of the stock with the appropriate characteristics of the scion asymmetrically. The bushy plant type appeared in a transgressive state in the variants, showing a definitely higher number of branches on the main stem and more frequent ramifications on the complete plant than on either the stock and scion cultivars or the progency derived from sexual crosses. A change in mature fruit color from red to yellow occurred in an early generation of graft-induced variants. Our results demonstrate that some of the characteristics of the stock were introduced into the progeny obtained from selfed seeds of the scion and that novel characteristics appeared as a result of graft induction. Received: 30 December 1997 / Accepted: 3 March 1998     

Aerated hydration treatment for improved germination and seedling growth in aubergine (Solarium melongena) and pepper (Capsicum annuum)

Aerated hydration treatment of aubergine and pepper seeds at 25°C (42 h for aubergine, 48 h for pepper) followed by drying increased percent germination across a range of test temperatures (18°C, 25°C and 35°C). The increase in germination obtained by the treatment was retained in storage for up to 4 months. In a glasshouse experiment, aerated hydration decreased mean emergence time but increased seedling dry weight in both species and decreased the proportion of abnormal seedlings in pepper. This work suggests that aerated hydration treatment can improve establishment of these crops in a range of planting temperatures.     

Differences on the microsporogenesis and tapetal development of male fertile and cytoplasmic male sterile pepper (Capsicum annuum L.)

To clarify the time and cause of pollen abortion, differences on the microsporogenesis and tapetum development in the anthers of male fertile maintainer line and cytoplasmic male sterile (CMS) line pepper were studied using transmission electron microscopy. The results showed that CMS line anthers appeared to have much greater variability in developmental pattern than male fertile maintainer line ones. The earliest deviation from normal anther development occurred in CMS line anthers at prophase I was cytomixis in some microspore mother cells (MMCs), and vacuolisation in tapetal cells. Then, MMCs in CMS line anthers developed asynchronously and a small part of ones at the different stage degenerated in advance appearing to have typical morphological features of programmed cell death (PCD). Most MMCs could complete the meiosis, but formed non-tetrahedral tetrad microspores with irregular shape and different size and uncertain number of nuclei, and some degenerated ahead of time as well. Tapetal cells in CMS line anther degenerated during meiosis, and were crushed at the tetrad stage, which paralleled the collapse of pollens. Pollen abortion in CMS line anthers happened by PCD themselves, and the premature PCD of tapetal cells were closely associated with male sterility.     

Tapetum Dimorphism and Its Histochemical Study in Sweet Pepper (Capsicum annuum L. Var. grossum)

In sweet pepper, the portion of tapetum toward the interior of the anther comprising large cells is derived from cells of connective of anther whereas the remaining tapetum on the outside of the anther comprising comparatively small cells is derived from the parietal layer. Those ceils of the former prosessing large vacuoles and large nuclei are stained weaker than the cells of the latter by methyl green-pyronin and mercuric-bromophenol blue staining. Large spherical grains which contain acid phosphatase appear in the vacuoles in both kinds of tapetum at sporogenesis stage. During meiosis of pollen mother cells, DNA, RNA and protein sysntheses increase in tapetum. The tapetum derived from connective accumulates more DNA than that derived from parietal layer. The activity of acid phosphatase becomes higher in tapetum when it degenerates. The degeneration of two kinds of tapetum is similar. There are no starch grains in tapetum through its whole course of development.     

Flower and nectar attributes of pepper (Capsicum annuum L.) plants in relation to their attractiveness to honeybees (Apis mellifera L.)

Flower morphology, nectary structure, nectar traits and rates of honeybee foraging on pepper plants were studied. The nectary appears as swellings on the basal part of the ovary. The nectariferous cells are smaller and denser than the neighbouring parenchyma. Stomata are present in the nectary epidermis, but do not appear on the other parts of the ovary epidermis. Seven pepper breeding lines were grown near a bee yard in Rehovot. Five to six fold differences in nectar volume were found between the extreme genotypes. Nectar volumes were higher during noon and afternoon hours, as compared with morning hours. High correlation coefficients between nectar volume and sugar concentration were found. These were significant for the four high nectar yielding genotypes, ranging between r = 0.65 to r = 0.94. Male-fertile flowers produced more nectar and higher sugar concentration than sterile ones. Skewed distribution was observed in nectar volume of F₂ populations, but relatively low heritability values were calculated. Pepper nectar contains fructose and glucose only. The former occupies 52–82 % of the total sugar content. Pepper genotypes varied in frequency of honeybee visits and significant correlation between sugar quantity and number of honeybee visits per flower was evident. Fertile pepper flowers are not very attractive to honeybees and male-sterile flowers are even less so. The considerable variation in nectar characteristics can be exploited to increase attractiveness to honeybees, thus facilitating bee pollination in commercial production of F₁hybrid seeds and improve fruit quality.     

QTL mapping of fruit-related traits in pepper (Capsicum annuum)

QTL analysis of pepper fruit characters was performed in an F₃ population derived from a cross between two Capsicum annuum genotypes, the bell-type cultivar Maor and the Indian small-fruited line Perennial. RFLP, AFLP^®1, RAPD and morphological markers (a total of 177) were used to construct a comparative pepper-tomato genetic map for this cross, and 14 quantitatively inherited traits were evaluated in 180 F₃ families. A total of 55 QTL were identified by interval analysis using LOD 3.0 as the threshold for QTL detection. QTL for several traits including fruit diameter and weight, pericarp thickness and pedicel diameter were often located in similar chromosomal regions, thus reflecting high genetic correlations among these traits. A major QTL that accounts for more than 60% of the phenotypic variation for fruit shape (ratio of fruit length to fruit diameter) was detected in chromosome 3. This chromosome also contained QTL for most of the traits scored in the population. Markers in linkage groups 2, 3, 8 and 10 were associated with QTL for multiple traits, thereby suggesting their importance as loci that control developmental processes in pepper. Several QTL in pepper appeared to correspond to positions in tomato for loci controlling the same traits, suggesting the hypothesis that these QTL may be orthologous in the two species.     

Fructokinase and hexokinase from pollen grains of bell pepper (Capsicum annuum L.): possible role in pollen germination under conditions of high temperature and CO2 enrichment

The processes of pollen grain development and germination depend on the uptake and metabolism of pollen sugars. In pepper (Capsicum annuum L.), initial sugar metabolism includes sucrose hydrolysis by invertase and subsequent phosphorylation of glucose and fructose by hexose kinases. The main objective of this study was to investigate changes in fructokinase (EC 2.7.1.4) and hexokinase (EC.2.7.1.1) activities in pepper flowers during their development, and to study the possible roles of these enzymes in determining pollen germination capacity under high temperature and under CO(2) enrichment, previously shown to modify sugar concentrations in pepper pollen (Aloni et al., 2001 Physiologia Plantarum 112: 505-512). Fructokinase (FK) activity was predominant in pepper pollen, and increased during pollen maturation. Pollen hexokinase (HK) activity was low and did not change throughout pollen development. High-temperature treatment (day/night, 32/26 degrees C) of pepper plants reduced the percentage of pollen that germinated compared with that under normal temperatures (26/22 degrees C), and concomitantly reduced the activity of FK in mature pollen. High temperature also reduced FK and HK activity in the anther. Under high ambient CO(2) (800 micro l l(-1)) pollen FK activity was enhanced. The results suggest that pollen and anther FK may play a role in the regulation of pollen germination, possibly by providing fructose-6-phosphate for glycolysis, or through conversion to UDP-glucose (UDPG) to support the biosynthesis of cell wall material for pollen tube growth. High temperature stress and CO(2) enrichment may influence pollen germination capacity by affecting these pathways.     

辣椒优良自交系间遗传差异的分子分析

作物自交系间遗传差异的分析与评价是杂种优势育种和杂交育种成功的基础。鲜食尖椒类(Capsicum an-nuumvar.longum)品种是我国辣椒生产的主要品种类型之一。针对我国鲜食尖椒的育种目标,以国内外10份尖椒优良自交系为材料,利用相关序列扩增多态性(SRAP)和简单序列重复(SSR)标记技术对其进行了遗传差异分析。结果显示:SRAP技术具有较高的位点和多态性检测能力,平均每次检测的位点数和多态性位点数分别为34个和10个,是SSR的10倍和5倍;辣椒自交系间基于SRAP标记的遗传距离和基于SSR标记的遗传距离之间的相关程度较低(r=0.144);基于SRAP标记和SSR标记联合数据计算的遗传距离,10个尖椒自交系被分为3大类,这种分类结果与辣椒杂种优势育种实践相一致。本研究结果表明,SRAP具有较高的遗传分析效力;基于不同分子标记遗传分析结果的差异与标记间共享位点的多少有关;10个尖椒自交系的分类结果可用于指导育种实践。