Influence of growing season and donor plant age on anther culture response of some pepper cultivars (Capsicum annuum L.)

The effects of growing season and donor plant age on anther culture in Capsicum were investigated. Pepper cultivars Kekova and Sera Demre 8 were grown under unheated greenhouse conditions in winter season and field conditions in summer season. Flower buds were collected and cultured in weekly intervals from November to May in winter and from April to December in summer. The results of this study indicated that anthers from these two pepper genotypes gave different embryogenic response to seasonal effects. Kekova cultivar gave the highest embryogenic yield in summer season while this was occurred in winter season for Sera Demre 8 cultivar. The results of the study revealed that the effect of donor plant age was also an important factor in anther culture of pepper. Since 4-month-old plants gave the highest embryo yield in both cultivars in each seasons, it is possible to say that anthers collected from old plants have sufficient embryogenic response when the optimum developmental stage is selected.     

Genetics and distribution of fertility restoration associated RAPD markers in inbreds of pepper (Capsicum annuum L.)

Experiments were conducted to study genetics of fertility restoration and to examine distribution of RAPD markers (OPW19₈₀₀ and OPP13₁₄₀₀) linked with fertility restoration gene (Rf) in pepper (Capsicum annuum L.) inbreds. Forty-two hot and five sweet pepper inbreds were crossed on a cytoplasmic male sterile (cms) line CCA-4261 and F₁s were evaluated for fertility restoration under open field conditions. DNA of 5 plants of CCA-4261 and individual plants of 47 inbreds was isolated and PCR reaction was performed using OPW19 and OPP13 primers. The results revealed that most of the hot pepper lines posses Rf gene. The Rf gene associated two markers, viz., OPW19₈₀₀ and OPP13₁₄₀₀ were not frequently distributed in the restorer inbred lines because presence of marker bands often does not coincide with the presence of Rf gene identified in many restorer inbreds. The case specific applications of both the RAPD markers have been described.     

Effectiveness of water pillow irrigation method on yield and water use efficiency on hot pepper (Capsicum annuum L.)

A study was conducted to elucidate the effect of water pillow (WP) irrigation method, a new alternative method to furrow irrigation, on the yield and water use efficiency (WUE) of hot pepper in a semi-arid climatic condition. In this research, treatments used were: (i) WP method and its 7-day irrigation interval (WP₇), (ii) WP method and its 9-day irrigation interval (WP₉), (iii) WP method and its 11-day irrigation interval (WP₁₁) and (iv) furrow irrigation (FI) method and its 5-day irrigation interval (control) were employed. Although the plants were grown under different irrigation methods and interval conditions, there were no statistical differences in yield and biomass of hot pepper plants between FI and WP treatments (P < 0.05). Water use efficiency (WUE) and irrigation water use efficiency (IWUE) values significantly increased with the application of WP irrigation method (P < 0.05). The highest WUE and IWUE values obtained from WP₁₁ treatment in both years. As a result, we conclude that WP method is a way to save water and increase the yield in semi-arid areas where climatic conditions require repeated irrigation in the hot pepper production area.     

A SCAR marker linked to the N gene for resistance to root knot nematodes (Meloidogyne spp.) in pepper (Capsicum annuum L.)

The root-knot nematodes (Meloidogyne spp.) are important nematode pests and cause serious diseases in pepper in the world. No molecular markers linked to the nematodes resistance N gene have been reported. In this paper, ‘Carolina Wonder’ (Capsicum annuum L.), a sweet pepper line resistant to root-knot nematode with N gene, ‘20080-5-29’ (C. annuum L.), an inbred line susceptible to root-knot nematode with good horticultural characteristics, and their F₂ progeny with 320 individuals were used as materials. Evaluation of resistance and susceptibility of parental lines, F₁ and F₂ progeny inoculated with root-knot nematodes (Meloidogyne incognita) were carried out. ‘Bulked segregant analysis’ method was used to search for polymorphic markers from 512 pairs of AFLP primers. Based on the assessment of resistance and susceptibility and polymorphism of the AFLP marker in F₂ population, the genetic linkage distance between the AFLP marker and the N gene was estimated. One AFLP marker E39/M41-339 was obtained and transferred to a SCAR marker amplifying a 315 bp DNA fragment linked to the N resistant allele and a 331 bp fragment linked to the N⁺ susceptible allele. The distance between the molecular marker and the nematodes resistance N gene is 6.3 cM. This research delivered a valuable tool for the marker assisted selection of nematodes resistance in pepper.     

Refinement of shed-microspore culture protocol to increase normal embryos production in hot pepper (Capsicum annuum L.)

A low percentage of normal-looking embryos (20%) is still a problem in an efficient shed-microspore culture of hot pepper (Capsicum annuum L.) and it is more a serious problem in other androgenesic culture systems of pepper. Therefore, several factors were investigated to refine the protocol in order to increase the percentage of normal-looking embryos. The most important factors which improved the protocol and resulted in a significantly higher percentage of normal-looking embryos produces (>50%), were delayed enrichment of the liquid upper layer medium with 2.5 μM Zeatin and 5 μM IAA, and reduced incubation temperature from 28 °C to 21 °C, both after 3 weeks of culture. Addition of 1% activated charcoal in the solid lower layer of the medium enhanced the total embryo yield only, while an application of abscisic acid and increased osmolality medium had a detrimental effect on embryo production. The use of doubled haploid lines as anther donor plants has clearly decreased the variability and improved the statistical analysis of treatment effects. A higher percentage of normal embryos are produced with this refined protocol, and is therefore more suitable for implementation in the breeding programs of hot pepper.     

Fruits are more sensitive to salinity than leaves and stems in pepper plants (Capsicum annuum L.)

The effects of NaCl stress on plant growth, gas-exchange, activity of superoxide dismutase (SOD), rate of lipid peroxidation, and accumulation of Na⁺ ion and sugar were investigated in leaves and fruits of pepper plants (Capsicum annuum L.). Especially, the gene expression of l-galactono-1,4-lactone dehydrogenase (GalLDH), which is the last enzyme of ascorbic acid (AsA) biosynthesis, and the relationships between AsA level and Na⁺ concentration in plant tissue were investigated with increasing salinity. Plants were treated with three treatments: the control (0 mM NaCl) and two salinity levels (50 and 100 mM NaCl) for 21 days under greenhouse conditions. Plant growth was markedly restricted due to the reduction of photosynthetic rate and the increase of Na⁺ accumulation in leaves with the increasing intensity of NaCl stress. Salinity had more effect on fruit growth comparing to leaf growth, suggesting that fruits could be more sensitive to salinity than leaves. In comparison with the control, salt stress significantly increased lipid peroxidation (as measured as malondialdehyde content) but decreased SOD activity in both fruits and leaves although the effect was larger in fruits; and the rate of the decrease in SOD activity was greater than that of the increase in lipid peroxidation. The AsA concentration transiently increased first 7 days but it slightly decreased from the initial level in the end of treatment day 21. The change in GalLDH gene expression was similar to AsA concentration. The accumulation of Na⁺, the reduction of AsA level at severe salinity stress were greater in fruits than in leaves; and AsA level had a negative relationship with Na⁺ concentration in both leaves and fruits. These results suggest that the difference in salt sensitivity between fruits and leaves in pepper plants can be related to the difference in inhibition of AsA synthesis, which in turn is probably due to the toxicity of extreme accumulation of Na⁺.     

Agronomic characteristics and carotenoid content of five Bola-type paprika red pepper (Capsicum annuum L.) cultivars

The production of sweet paprika in Spain uses exclusively fruit of Bola-type Capsicum annuum L. This work describes the evaluation of the agronomic behaviour of five new cultivars of the Bola-type paprika red pepper, selected in the Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), and grown in Extremadura for 3 years. The colour and the pigment content of the paprika elaborated following the traditional procedure of La Vera were also studied.     

The genetics of non-virus vein-banding in aromatic pepper Capsicum annuum L.

Vein-banding is a genetically inherited trait controlled by one locus, Vb, which is expressed as a wave-like banding of the main and side veins of pepper leaves. It was studied as a morphological defect always present in the ‘Nsukka Yellow’ pepper, Capsicum annuum L., and was shown to be inherited as an incompletely dominant characteristic with an F₂ segregation ratio of 1:2:1. The F₁ population was uniformly mild in expression of the vein-handing characteristic of the parent ‘Nsukka Yellow’ pepper. VbVb was designated as the genetic constitution of severe vein-banding, and vbvb as a normal genotype, the F₁ being Vbvb. A selection of normal plants from the back-cross with the normal-leafed parent yield a stable normal-leafed strain of ‘Nsukka Yellow’ christened ‘UN-Yellow’.     

Defence responses in leaves of resistant and susceptible pepper (Capsicum annuum L.) cultivars infected with different inoculum concentrations of Phytophthora capsici Leon

Three pepper cultivars (PM-702: resistant, Demre-8 and KM-hot: susceptible) with different resistances to Phytophthora capsici-22 (P. capsici-22) were inoculated with different concentrations of zoospores to analyze the time course of phenylalanine ammonia lyase (PAL) activity, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), proline and total protein.     

Evaluation of crucial factors for implementing shed-microspore culture of Indonesian hot pepper (Capsicum annuum L.) cultivars

A shed-microspore culture protocol was developed in Wageningen for producing doubled haploid plants in several genotypes of Indonesian hot pepper (Capsicum annuum L.). For transfer of technology to Indonesia, three factors were studied that appeared crucial for successful implementation in practice. First, application in the culture medium of a combination of the antibiotics timentin and rifampicin at the concentrations of 200 and 10 mg/l, respectively, prevented bacterial contamination from the donor explants. Second, in vitro application of colchicine (100 μM) during the first week of culture was highly effective in increasing the percentage of doubled haploid plants. Third, a comparative analysis of the ploidy level of plants regenerated from shed-microspore-derived embryos using chloroplast counts in guard cells of leaf stomata and flow cytometric measurement of leaf nuclear DNA content, revealed that the first procedure is a reliable and an easy to use method for ploidy determination with hot pepper.     

Manganese nutrition of pepper (Capsicum annuum L.): Growth,Mn uptake and fruit disorder incidence

This research included two independent yet build up objectives: (i) to examine the effects of Mn concentration in the irrigation water on the yield and fruit quality of greenhouse-grown bell pepper exposed to heat stress; and (ii) to investigate in a laboratory experiment the role of Mn addition on oxidative and anti-oxidative components of fruit apoplast. The field experiment included four concentrations of Mn in the irrigation water (0, 0.2, 0.6 and 1.0 mg L⁻¹). The effect of Mn application rate on vegetative growth and total fruit yield was insignificant and despite low Mn concentrations in zero-Mn-fed plants, no visible foliar Mn symptoms were observed. A quadratic regression was obtained between high-quality fruit yield and Mn concentration in fruit. Based on the quadratic equation, maximum high-quality yield was obtained when fruit-Mn concentration approached 44 mg kg⁻¹ DW. The correlation also indicates that variations in high-quality yield could be explained by differences in fruit-Mn concentration. The combination of low-Mn nutrition and high air temperature which prevailed during the experiment (summer season) induced severe pale spots and blemished fruits; approximately 50% of fruits were infected in zero-Mn-fed plants. In a laboratory experiment with detached-fruit under high temperature the H₂O₂ concentration increased whereas ascorbic acid concentration decreased in the apoplast. In Mn-fed fruit the H₂O₂ concentration was attenuated and the activity of ascorbate oxidase was suppressed, with the result that apoplastic ascorbic acid concentration increased. In light of the known crucial role of Mn in enzyme activities and in detoxification of oxygen free-radicals, the pale spots might be related to Mn effect on oxidative stress-related apoplastic activities. The relationships between incidence of pale spots and plant-Mn concentration may support this hypothesis, but further research is needed to validate it.     

Effect of arbuscular mycorrhizal fungal inoculation on root system architecture of trifoliate orange (Poncirus trifoliata L. Raf.) seedlings

Plant root system architecture is essential characteristics in relation to nutrient acquisition by root system from soil volume. Many environmental factors can affect the establishment of root system architecture, e.g. arbuscular mycorrhizal (AM) fungi. We inoculated the trifoliate orange (Poncirus trifoliata L. Raf.) seedlings with four AM fungal species in rhizoboxes, with non-inoculated seedlings as control. Using the WinRHIZO^® image analysis system, the root system architecture of seedlings was characterized. Results indicated that AM colonization did not affect the tap root length, the average root diameter, the basal root growth angle in spite that four AM fungal species exerted differential influence on the plant growth. Contrastingly, AM colonization significantly reduced the total root length, the root volume, the root surface area, but promoted the formation of lateral roots of high order. In addition, AM colonization induced more fine roots and less coarse roots. To our knowledge, it is the first report on the influence of AM fungi on the distribution of root diameter size classes. The mechanisms and implication of AM fungi on root system architecture is discussed.     

Towards crop improvement in bell pepper (Capsicum annuum L.): Transgenics (uid A::hpt II) by a tissue-culture-independent Agrobacterium-mediated in planta approach

Agrobacterium tumefaciens-mediated transformation has been one of the methods used to generate transgenic plants in bell pepper. An alternate transformation method that avoids/minimizes tissue culture would be beneficial for the improvement of bell pepper due to its recalcitrant nature. In this report, transgenic bell pepper plants have been developed by a tissue-culture-independent A. tumefaciens-mediated in planta transformation procedure. In the present study, two open pollinated varieties viz., Arka Gaurav and Arka Mohini were used for transformation. Agrobacterium strain EHA105 harboring the binary vector pCAMBIA1301 that carries the genes for β-glucuronidase (uid A) and hygromycin phosphotransferase II (hpt II) was used for transformation. GUS histochemical analysis of T₀ and T₁ plants at various stages of growth followed by molecular analysis using PCR, Southern analysis and RT-PCR allowed selection of transgenics. The method resulted in 17.8% and 11.4% of the T₀ plants in Arka Gaurav and Arka Mohini being selected as chimeric and 35.0% and 29.7%, respectively, were identified as stable transformants in the T₁ generation based on PCR analysis.     

Enriched production of N-hydroxycinnamic acid amides and biogenic amines in pepper (Capsicum annuum) flowers

The biosynthesis of N-hydroxycinnamic acid amides (HCAAs), such as feruloyltyramine, p-coumaroyltyramine, feruloylserotonin, and p-coumaroylserotonin, in pepper plants was investigated in view of the activity of their corresponding enzymes and substrate levels. Almost all HCAAs were found in flowers, whereas the enzyme activity essential for HCAA biosynthesis seemed to be expressed constitutively in all tissues tested. The highest levels of the biogenic amines tyramine and serotonin, the key amine substrates, were also found in flowers, indirectly suggesting that the amine substrates play an important regulatory role in the synthesis of HCAAs.     

The response of chilli (Capsicum annuum L.) plants to early inoculation with mycorrhizal fungi at different levels of phosphorus

Summary

Chilli plants cv. Pusa Jwala were inoculated in the nursery beds with three mycorrhizal fungi, Gigaspora calospora, G. margarita and Glomus fasciculatum and transplanted to plots supplied with 0, 25 and 50% of a recommended P level (65 kg ha^?1). Uninoculated plants were also transplanted at 0 (Control) and 100% of.the recommended P level. Plant growth, height, shoot dry weight, uptake of P, root colonization and yield of green chillies were measured. Chilli responded well to inoculation and P. G. margarita best improved growth and yield. Inoculation plus 25 and 50% P were equally better than the control and equal to uninoculated plants at 100% P. As much as 50–75% P can be dispensed with by inoculation with mycorrhizal fungi and this represents a considerable economic saving in cost.     

Sensitive stages of fruit and seed development of chili pepper (Capsicum annuum L. var. Shishito) exposed to high-temperature stress

The sensitivity of developmental stages to high temperature was investigated in chili pepper (Capsicum annuum L. var. Shishito). Plants were subjected to heat stress (38/30 °C day/night) immediately after anthesis for 5 or 10 days, or from 10 to 30 days after anthesis (DAA), from 30 DAA until harvest of the seeds, or immediately after anthesis until harvest of the seeds. Control plants were grown at 30/22 °C (day/night). Exposure to high temperature (heat stress) during different periods of development after anthesis adversely affected fruit growth, seed yield, and seed quality in chili pepper. Heat stress for the whole period after anthesis, and from 30 DAA until harvest reduced the growth period of chili fruits by 15 and 10 days, respectively. Heat stress from 10 to 30 DAA reduced fruit width and fruit weight. The early stage of seed development from anthesis until 10 DAA was sensitive to high temperature, which affected fruit length, fruit weight and seed set. Applying high temperatures to plants for 10 DAA increased the proportion of abnormal seeds per fruit. High temperatures from 10 DAA until 30 DAA inhibited carbohydrate accumulation and adversely affected seed germinability and vigor. These results suggest that the stage of development at which chili peppers are exposed to high temperatures is an important factor in fruit and seed growth and in seed quality.     

Field response of papaya (Carica papaya L. cv. Coorg Honey Dew) to inoculation with arbuscular mycorrhizal fungi at different levels of phosphorus

Summary

Papaya (Carica papaya L.) cv. Coorg Honey Dew is one of the most popular cultivars grown in Southern India, but it requires high doses of inorganic phosphorus (P) fertilisation for growth. Arbuscular mycorrhizal fungi (AMF) are known to improve plant growth and nutrient uptake, especially the uptake of P and micronutrients. As papaya plants respond well to high levels of P, inoculation with AMF was studied to see if AMF could fulfill the requirement for P in plants grown under field conditions. Papaya seedlings (n = 36 per AMF) were colonised separately, in polybags, for 45 d by two species of AMF, Glomus mosseae and G. fasciculatum. Seedlings were then transplanted to the field, with uninoculated seedlings as controls, in a replicated randomised block design. Three levels of P were applied [50, 75, or 100% of the recommended dose (240 g plant^–1 year^–1) of P fertiliser, as super-phosphate]. Plants were studied for root colonisation by AMF, for growth parameters, and for leaf nutrient contents (especially, P, Zn, and Cu). Acidic and alkaline phosphatase activities in the roots of AMF-colonised plants were recorded as these enzymes are involved in the mobilisation of P. The yields of plants up to 18 months-old, and fruit quality, measured by total soluble solids contents (TSSC) and β-carotene contents, were recorded. AMF-inoculated plants performed better than uninoculated control plants at all levels of P applied. G. mosseae was more effective at improving plant growth, fruit yield, and P and Zn contents than G. fasciculatum at the 75% and 50% P-levels. Cu contents increased at all P-levels in G. fasciculatum-colonised plants. Total soluble solids contents showed marginal improvements at the 75% P level with both fungi. β-carotene contents increased significantly in G. mosseae-colonised plants at the 50% and 75% P-levels, and in G. fasciculatum-colonised plants at the 75% P-level. The feasibility of applying on-farm produced AMF inoculum to improve papaya cultivation and to save 25% of the P applied during papaya cultivation is discussed.     

Evaluating variability of root size system and its constitutive traits in hot pepper (Capsicum annum L.) under water stress

The importance of root size system has long been recognized as crucial to cope with drought conditions. This investigation was conducted to: (i) evaluate the variability in root size system of hot pepper at maturity; (ii) estimate the effect of root size system on yield under drought conditions; and (iii) effect of water stress on xylem vessel development and total xylem cross-sectional area in roots of hot pepper cultivars. Twelve diverse hot pepper cultivars were grown in wooden boxes with two different water treatments, normal and in 50% water application as water deficit condition. Mean primary root length (PRL) showed a significant positive correlation with final fruit yield at normal as well as stressed condition. Total dry mass of fruit was reduced by 34.7% in drought treatments (DI) compared to full watered treatment (FI). At harvest, water-stressed plants had 21% lower root dry weight mass but higher root:shoot ratio other than FI. PRL, lateral root density, total xylem area per root cross-section showed a significant positive relationship with fruit yield. Also, lateral root density was higher in cultivars with higher xylem density, particularly in tolerant cultivars. Lateral root density (r = 0.847, P < 0.001) and total xylem cross-sectional area in root (r = 0.926, P < 0.001) were tightly related with total biomass production. The importance of root traits contributing to withstand drought in hot pepper is discussed.     

RAPD markers reveal polymorphism among some Iranian pomegranate (Punica granatum L.) genotypes

In this study RAPD markers were used to determine the diversity level among 24 Iranian pomegranate genotypes. One hundred decamer random primers were used for PCR reactions, among which 16 showed reliable polymorphic patterns. These primers produced 178 bands, of which 102 were polymorphic. Cluster analysis of the genotypes was performed based on data from polymorphic RAPD bands, using Jaccard's similarity coefficient and UPGMA clustering method. The highest and lowest similarities detected between genotypes were 0.89 and 0.29, respectively. At a similarity of 60%, the genotypes were divided into four sub-clusters. Cophenetic correlation coefficient between similarity matrix and cophenetic matrix of dendrogram was relatively high (r = 0.9) showing the goodness of fit of the dendrogram. RAPD markers showed to be a useful tool for studying the genetic diversity of pomegranate.     

Selection of ethylene-resistant carnations (Dianthus caryophyllus L.) by video recording system and their response to ethylene

We used conventional cross-breeding techniques to develop a carnation with low ethylene sensitivity. A time-lapse video recording system for evaluating ethylene sensitivity of flowers, developed in our earlier study, proved useful for this breeding. We selected 10 new ethylene-resistant lines, in addition to the previously selected line 64–54. Lines 902–48a, 234–43S, and 234–36S showed extremely low ethylene sensitivity. The response time to 10 μL L⁻¹ ethylene of these three lines exceeded 50 h in two independent experiments (2004 and 2005), whereas that of three sensitive control cultivars (‘White Sim’, ‘Excerea’, and ‘Scania’) was 6.2–8.0 h. The mean vase life of the ethylene-resistant lines ranged from 7.6 to 12.7 days (1.4–2.3 times that of ‘White Sim’). The application of ethylene to carnation flowers induced autocatalytic ethylene production in both petals and gynoecia of 9 of the 11 ethylene-resistant lines without petal wilting, indicating that the autocatalytic ethylene production was regulated independently of the petal wilting reaction. This result further suggests that these lines have normal ethylene receptors and produce ethylene autocatalytically, but their petal wilting reaction stops at a point beyond the receptor. Two lines (118–64S and 120–69S) showed extremely low ethylene production at flower senescence and very low autocatalytic ethylene production from petals and gynoecia.