Production of inter-section hybrids between Primula filchnerae and P. sinensis through ovule culture

Inter-section hybrids were obtained in the reciprocal crosses between Primula filchnerae (2n = 2x = 24) of Sect. Pinnatae and P. sinensis ‘Fanfare’ (2n = 2x = 24) of Sect. Auganthus by rescuing ovules on half-strength (1/2) Murashige and Skoog's (MS) medium supplemented with 50 g l⁻¹ sucrose, 2.5 g l⁻¹ gellan gum, 0.1 mg l⁻¹ α-naphthaleneacetic acid (NAA), 0.1 mg l⁻¹ 6-benzyladenine (BA) and 50 mg l⁻¹ gibberellic acid (GA₃). In ovule culture, germination occurred with radicle elongation but no plumule was observed. The radicle kept on the initial medium showed root proliferation with callus formation. When the calluses were transferred to (1/2)MS media containing 30 g l⁻¹ sucrose and 3 g l⁻¹ gellan gum, without plant growth regulators (PGRs) or with 1 mg l⁻¹ zeatin and 0.1 mg l⁻¹ NAA, plantlets were regenerated. The plants thus obtained were confirmed to be hybrids through flow cytometry (FCM) and random amplified polymorphic DNA (RAPD) analyses. The hybrid obtained when P. filchnerae was used as the maternal parent was diploid, whereas hexaploid hybrid was obtained when using P. sinensis as the maternal parent. The hexaploid hybrid might be produced through chromosome doubling of a triploid originated from the fertilization of P. sinensis with unreduced pollen of P. filchnerae.     

Eggplant relatives as sources of variation for developing new rootstocks: Effects of grafting on eggplant yield and fruit apparent quality and composition

We propose the utilization of eggplant (Solanum melongena L.) interspecific hybrids derived from crosses with closely related species as an approach for developing new improved rootstocks for eggplant. Here we investigate rootstock effects on fruit yield, apparent quality and proximate and mineral composition of S. melongena ‘Black Beauty’ (BB) scions grafted on interspecific hybrid rootstocks developed from crosses of S. melongena with Solanum incanum L. (SI × SM) and Solanum aethiopicum L. (SM × SA). The results are compared with non-grafted (BB control) and self-grafted (BB/BB) controls and with S. melongena ‘Black Beauty’ scions grafted onto Solanum torvum Sw. (STO) and Solanum macrocarpon L. (SMA) rootstocks. All treatments were grown in a soil naturally infested with root-knot nematodes (mostly Meloidogyne incognita (Kofoid and White) Chitwood). SI × SM and SM × SA interspecific hybrids had high germination (≥90%) and total graft success (100%). Contrary to what occurred with all other treatments, no plants from scions grafted onto these hybrid rootstocks died during the experiment. In particular, the SI × SM hybrid rootstock conferred the highest vigour to the scion, which resulted in the highest values for fruit earliness and early and total yield. Little difference was observed among treatments for apparent fruit quality traits, except for a greater fruit calyx length and prickliness of fruit grafted onto SMA rootstocks. A similar result was obtained for fruit composition where phenolics content was higher in fruit from plants grafted onto SMA rootstocks. Grafting eggplant onto interspecific eggplant hybrids, especially on the SI × SM hybrid, has proved advantageous for eggplant production, as the high vigour and good compatibility of the rootstock with scion results in improved early and total yield without negative effects on apparent fruit quality or composition. Interspecific hybrids represent an alternative to the commonly used STO rootstock, which is a wild species with irregular germination.     

Maintaining product quality in raisins throughout the introgression of powdery mildew resistance

The availability of powdery mildew-resistant raisin accessions will lower grower production costs and enhance the environment through reduced fungicide use. To achieve this objective, backcrossing has been employed with Vitis romanetii as the source of non-race-specific powdery mildew resistance. Initial crosses of powdery mildew-resistant F₁ hybrid B36-45 with seeded raisin cultivars ‘Rangspray’ and ‘Raisin de Palestine’ yielded seedless powdery mildew-resistant first-generation backcross selections C87-41 and C87-106, which were used to develop second-generation backcross populations. Principal component analyses consistently identified ‘wrinkle,’ ‘meatiness,’ ‘product attractiveness’ and ‘skin persistence’ as being the quality characteristics most important in discriminating among powdery mildew-resistant raisin accessions and commercial raisin cultivars. Raisin quality ratings were much improved across most evaluated characters in second-generation backcross families as compared with parental powdery mildew- resistant accessions C87-41 and C87-106. After two generations of backcrossing, powdery mildew-resistant raisin selections were identified with product quality characteristics similar to those of commercial raisin cultivars.     

Cybrid/hybrid plants regenerated from somatic fusions between male sterile Satsuma mandarin and seedy tangelos

Somatic hybridization provides an alternative for transferring mitochondria-encoded cytoplasmic male sterility (CMS). Herein, symmetric protoplast electrofusion was conducted between embryogenic callus protoplasts of Citrus unshiu Marc. cv. Guoqing No. 1 (G1), a CMS cultivar, and mesophyll-derived protoplasts of seedy ‘Page’ tangelo [C. reticulata Blanco × (C. reticulata Blanco × C. paradisi Macf.)] or ‘Nova’ tangelo [C. reticulata Blanco × (C. reticulata Blanco × C. paradisi Macf.)], to transfer CMS trait. Flow cytometry analysis showed that 14 plants recovered from G1 + ‘Page’ tangelo that displayed typical morphological character of ‘Page’ were diploid, and 6 plants regenerated from G1 + ‘Nova’ tangelo were tetraploid. Genetic compositions of regenerated plants from the two fusions were determined by SSR, CAPS and chloroplast-SSR analysis. Cybrid nature of diploids from G1 + ‘Page’ tangelo with nuclear DNA from ‘Page’, mitochondrial DNA (mtDNA) from the G1 and chloroplast DNA (cpDNA) derived from either parent was confirmed. Tetraploid plants from G1 + ‘Nova’ tangelo were identified as somatic hybrids with random cpDNA inheritance. The regenerated cybrid and hybrid plants hold great potential for Citrus seedless breeding at diploid or triploid levels.     

Pollination with laser-irradiated pollens breaks cross-incompatibility between zicaitai (Brassica campestris var. purpurea) and ornamental kale (Brassica oleracea var. acephala) to produce hybrids with the aid of ovule culture

The objective of this study was to produce interspecific hybrids between an Ogura-cytoplasmic male sterile (CMS) line of zicaitai (Brassica campestris var. purupurea, 2n = 20) and cultivars of ornamental kale (Brassica oleracea var. acephala, 2n = 18) to develop a CMS system for hybrid seed production. Pollination with pollen grains of ornamental kales irradiated at a power output of 9.0 mW with a He–Ne laser for 3 min could overcome the cross-incompatibility between the species concerned. Intact hybrids could be efficiently produced from ovules cultured on Murashige and Skoog media supplemented by 0.2 mg l⁻¹ 6-benzyladenine. Chromosome number of hybrids was confirmed to be 2n = 19. Hybrids resembled ornamental kales in leaf morphology and in vernalization response. Pollens of hybrids had a sterile appearance. Moreover the hybridity of the putative hybrids was confirmed by RAPD data on a DNA fragment of 820 bp.     

Stoloniferous shoot protoplast,an efficient cell system in potato for somatic cell genetic manipulations

The present study reports that protoplasts isolated from stoloniferous shoots (SS) of potato represent an efficient system for somatic cell genetic manipulations. SS were established from single-node cuttings on MS medium supplemented with either 0.1 or 0.2 M sucrose (Suc), and protoplasts were isolated and cultured within the alginate strip, following an improved method. SS induced by 0.1 M Suc yielded 8–22 × 10⁵ protoplasts g⁻¹ fresh mass, with a high morphogenic competence. However, 0.2 M Suc-induced SS yielded protoplasts that contained large amounts of starch grains, resulting in their high degree of fragility, delayed cell division and poor morphogenic competence. For symmetric somatic hybridization (electrofusion) between Solanum tuberosum Gp. Tuberosum androgenic (di)haploid (2n = 2x = 24) ‘C-13’ and diploid (2n = 2x = 24) wild species S. pinnatisectum, protoplasts isolated from 0.1 M Suc-induced SS were also found to be most responsive. Out of several putative somatic hybrids, there were two tetraploids and five diploids, with 48 and 24 chromosomes, respectively at all the three shoot layers (L₁–L₃). This precluded the occurrence of mixoploidy vis-à-vis chimaerism in regenerants, as common in somatic fusion involving mesophyll protoplasts of S. pinnatisectum. Nuclear microsatellite analyses based on the two single-locus nSSR loci (STM0037 and STM2030) confirmed that one of the tetraploids was a true nuclear hybrid (heterokaryon), while the other a homokaryon of the Tuberosum parent ‘C-13’. The use of 0.2 M Suc-induced SS protoplasts for fundamental studies on tissue- and/or cell type-specific transient gene expression underlying tuberization has been discussed.     

The influence of desiccation and rehydration on the survival of polyembryonic seed of Citrus suhuiensis cv. limau madu

A study was carried out to investigate the influence of desiccation and freezing followed by various presowing rehydration procedures on the desiccation sensitivity of the seed of Citrus suhuiensis cv. limau madu. The freshly harvested seeds of limau madu were desiccated under a broad range of relative humidity (RH) to various equilibrium water contents (g H₂O g⁻¹ dw). The desiccated and desiccated–frozen seeds were either directly sown under germination conditions or subjected to presowing rehydration procedures: seed preheating, prehumidification and osmoconditioning. The hydrated and desiccated seeds were sown in controlled germination conditions and the survival was evaluated 4–6 weeks after sowing. The results showed that desiccation progressively reduced the percentage of normal seedling of the seeds of limau madu and the viability is almost lost at water contents below 0.08 g H₂O g⁻¹ dw. The estimated desiccation sensitivity was substantially high (WC₅₀ = 0.143 g H₂O g⁻¹ dw) when the desiccated seeds were rapidly rehydrated (uncontrolled rehydration). In contrast, seed prehumidification, preheating and osmoconditioning (controlled rehydration procedures) markedly enhanced normal seedling percentages decreasing the estimated values of WC₅₀ (between 0.08 and 0.127 g H₂O g⁻¹ dw). While the rapidly rehydrated desiccated–frozen seeds were almost killed at water content of 0.15 g H₂O g⁻¹ dw, prehumidification and preheating have noticeably increased percentage of frozen seeds survival at the same water content. However, at water content of 0.21 g H₂O g⁻¹ dw preheating significantly (P < 0.05) increased percentage of normal seedling of the frozen seeds. Seed desiccation markedly reduced the percentages of germinated seeds with multiple seedlings. Seed controlled rehydration remarkably increased the survival of polyembryos. The beneficial effect of seed controlled rehydration on the survival of the desiccated seeds was pronounced at medium water contents (0.08–0.25 g H₂O g⁻¹ dw).     

Genetic transformation of Prunus domestica L. using the hpt gene coding for hygromycin resistance as the selectable marker

The study and development of transformation technology with new selection schemes is important for various fundamental studies and for crop trait improvement via genetic engineering. Here we have shown that hygromycin resistance is an effective system for plum genetic transformation. Embryonic axes of mature seeds were co-cultivated with Agrobacterium strain LBA4404 containing the pC1381 plasmid carrying the hygromycin phosphotranferase gene (hpt) and β-glucuronidase (GUS) gene or with strain EHA105 containing the plasmid pC1301 carrying the same marker and reporter genes. The latter strain containing a pC2301 plasmid carrying the neomycin phosphotransferase gene (nptII) gene was used as a control. Infected explants were placed on shoot induction medium containing either 5 mg L⁻¹ hygromycin or 75 mg L⁻¹ kanamycin for selection. Green shoots developed from the explants under hygromycin pressure. These shoots showed continued and vigorous growth and development upon transfer onto fresh hygromycin medium. PCR using hpt sequence primers, and Southern blot analysis using a probe from the hpt gene, confirmed the presence of the transgenes and their stable integration in regenerated plants. Full transgenic plants were obtained in a greenhouse. Hygromycin selection was very effective and no escapes were observed. The study demonstrated that hygromycin resistance can be used as an effective selectable marker for plum transformation. The new system developed here is important and useful for multiple gene transformation in plum.     

Breaking the intergeneric hybridization barrier in Carica papaya and Vasconcellea cauliflora

The present investigation was undertaken to develop PRSV (Papaya ringspot virus) resistant hybrids through intergeneric hybridization. Intergeneric hybridization was done involving nine Carica papaya cultivars as female and Vasconcellea cauliflora as male. To break the intergeneric hybridization barrier, various nutrient combinations were used. Among the combinations used, sucrose 5%, sucrose 5% + boron 0.5% and sucrose 5% + CaCl₂ 0.5% improved the fruit set and seed set percentage. A total number of 1197 flowers were pollinated and 308 fruits were obtained. On extraction, 721 seeds were obtained from CO 7, Pusa Nanha and CP 50. Out of 721 F₀ seeds (crossed seeds) sown, 419 seeds germinated and artificial screening for PRSV was carried out 27 days after sap inoculation. Out of 29 F₁ hybrid plants from CO 7 x V. cauliflora cross, only six plants namely CO 7V1 to CO 7V6 were found free from PRSV symptoms. Similarly, out of 55 F₁ hybrids from cross involving Pusa Nanha x V. cauliflora only 23 plants namely PNV1 to PNV23 were found free from the symptoms and 70 plants namely CPV1 to CPV70 out of 335 plants of CP50 x V. cauliflora cross were found free from PRSV symptoms. Among the crosses, Pusa Nanha x V. cauliflora had higher yield under PRSV infected conditions, however, total soluble solids and total sugars were found lesser than the CO 7 x V. cauliflora cross. The hybridity of the progenies were confirmed by using ISSR (Inter Simple Sequence Repeats) primers by the amplification of DNA from progenies and their parents. ISSR primers UBC 856, UBC807 and ISSR primer combinations UBC 856-817, UBC 810-817, UBC 861-817, UBC 856-810, UBC 861-810 and UBC 856-817 clearly amplified specific bands of the male parent, which were present in F₁ progenies, but it was absent in female parents.     

Direct regeneration of plants derived from in vitro cultured shoot tips and leaves of three Lysimachia species

The regenerability of three ornamental species—Lysimachia christinae, Lysimachia rubinervis and Lysimachia nummularia ‘Aurea’, were investigated using in vitro leaves and shoot tips. 6-Benzylaminopurine (BAP) and α-naphthalene acetic acid (NAA) added to Murashige and Skoog (MS) medium were tested for their effect on organogenesis. On the medium, shoot regeneration occurred directly without callus formation. In these species, L. christinae developed the highest regeneration rate and numbers of shoots/explant from shoot tips (100%, 12.25) and leaf bases (100%, 13.01) on the MS medium containing 3.0 mg l⁻¹ BAP and 0.1 mg l⁻¹ NAA. For L. rubinervis, the highest shoot induction rate and number of shoots/explant were obtained from shoot tip (100%, 16.87–17.20) on the MS medium with 0.1 mg l⁻¹ NAA and 3.0–5.0 mg l⁻¹ BAP. L. nummularia ‘Aurea’, however, showed the highest regeneration rate and number of shoots/explant (100%, 12.73) from leaf bases on MS medium supplemented with 1.0 mg l⁻¹ BAP and 0.1 mg l⁻¹ NAA. All in vitro shoots rooted well on half macronutrient MS medium containing 0.1 mg l⁻¹ NAA. After acclimatization, transplanted plantlets grew normally and flowered in the field.     

Genetic diversity and population's structure in Tunisian strawberry tree (Arbutus unedo L.)

A growing interest in the use of the Strawberry tree (Arbutus unedo L., Ericaceae) has been recently reported for industrial, pharmaceutical and chemical fields. However, the bulk material comes from natural populations because of the lack of selection of interesting cultivars. In Tunisia, A. unedo populations are severely destroyed due to deforestation and over-collecting. The species occurs in small scattered populations decreasing progressively in size. Yet, no conservation or improvement programs are attempted to preserve and promote the potential value of this resource. In this work, we assessed the genetic diversity of nine Tunisian populations of A. unedo L. from different bioclimates, using 65 polymorphic RAPD loci. The analysis of the genetic variation within and among populations is primordial to elaborate conservation and improvement programs. A low genetic diversity within a population estimated by both Nei's (He) and Shannon's diversity (H′) indices (0.155 < He < 0.248; 0.229 < H′ < 0.364) was observed due to genetic drift and selfing. At the species level, the amount of the within population variation estimated by Shannon's index (H_POP/H_SP = 0.686) and the molecular variance (80.67%) was higher than that among populations. A moderate genetic differentiation among populations (Φ_ST = 0.193 and G_ST = 0.314) which could be attributed to the long seed distance dispersal was detected. The UPGMA dendrogram based on Φ_ST values showed three clusters each including populations without relationship to bioclimatic or geographical origin indicating that differentiation occurs at a local space scale. The in situ protection measures should be made appropriately according to a population within bioclimates. The ex situ conservation and the selection of genotypes should involve extensive collection of seeds or cuttings from the within populations rather than among them.     

Effects of plant growth promoting rhizobacteria (PGPR) on yield,growth and nutrient contents in organically growing raspberry

During 2003 and 2005, plant growth promoting effects of two Bacillus strains OSU-142 (N₂-fixing) and M3 (N₂-fixing and phosphate solubilizing) were tested alone or in combinations on organically grown primocane fruiting raspberry (cv. Heritage) plants in terms of yield, growth, nutrient composition of leaves and variation of soil nutrient element composition in the province of Erzurum, Turkey. The results showed that Bacillus M3 treatment stimulated plant growth and resulted in significant yield increase. Inoculation of raspberry plant roots and rhizosphere with M3 and/or OSU-142 + M3, significantly increased yield (33.9% and 74.9%), cane length (13.6% and 15.0%), number of cluster per cane (25.4% and 28.7%) and number of berries per cane (25.1% and 36.0%) compared with the control, respectively. In addition, N, P and Ca contents of raspberry leaves with OSU-142 + M3 treatment, and Fe and Mn contents of the leaves of raspberry with M3 and OSU-142 + M3 applications significantly improved under organic growing conditions. Bacterial applications also significantly effected soil total N, available P, K, Ca, Mg, Fe, Mn, Zn contents and pH. Available P contents in soil was determined to be increased from 1.55 kg P₂O₅/da at the beginning of the study to 2.83 kg P₂O₅/da by OSU-142, to 5.36 kg P₂O₅/da by M3 and to 4.71 kg P₂O₅/da by OSU-142 + M3 treatments. The results of this study suggest that Bacillus M3 alone or in combination with Bacillus OSU-142 have the potential to increase the yield, growth and nutrition of raspberry plant under organic growing conditions.     

Development of seedless and Mal Secco tolerant mutant lemons through budwood irradiation

Mal secco (caused by Phoma tracheiphila (Petri) Kantsch. and Gik.) is the most destructive fungal disease of lemon plantations worldwide and seedless lemons would be preferred by most consumers. Five dosage levels, 0, 3, 5, 7, and 9 kiloradian (krad), of cobalt (⁶⁰Co) gamma irradiation were applied to budstick of ‘Kutdiken’ lemon (Citrus limon (L.) Burm. f.) clone KT-2A. Mutations were stabilized in three vegetative generations. Three hundred fifty-eight and 478 M1V3 (mutation one and vegetation three) plants were evaluated for seed number and mal secco tolerance in the field and the greenhouse, respectively. LD₅₀ was around 5 krad gamma irradiation for ‘Kutdiken’ lemon. The seed number varied from 0 to 34 per fruit. The level of mal secco tolerance also varied significantly among the plants from 1.0 (no symptom) to 4.3 (high level of disease occurance). The stable seedless and mal secco tolerant plants were obtained from 5 and 7 krad irradiation: the three mutants from 5 krad irradiation gave more lemon-like fruits, while 7 krad irradiation caused altered tree morphology and early maturation of fruits. This study shows considerable potential for lemon cultivar improvement aiming to obtain seedless and mal secco tolerant lemons.     

Evaluation of the effectiveness of soil-applied plant derivatives of Meliaceae species on nitrogen availability to peach trees

We assessed the effect of soil-applied derivatives of melia (Melia azedarach L.) and neem (Azadirachta indica A. Juss) on nitrogen (N) soil availability, root uptake and peach (Prunus persica L.) growth. First we evaluated the effectiveness of experimentally prepared amendments made with fresh ground melia leaves or commercial neem cake incorporated into the soil as nitrification inhibitors, then we evaluated the effect of fresh ground melia fruits and neem cake on growth and N root uptake of potted peach trees, and on soil microbial respiration. Soil-applied fresh ground melia leaves at 10 and 20 g kg⁻¹ of soil as well as commercial neem cake (10 g kg⁻¹) were ineffective in decreasing the level of mineral N after soil application of urea-N as a source of mineral N, rather they increased soil concentration of nitric N and ammonium N. The incorporation into the soil of fresh ground melia fruits (at 20 and 40 g kg⁻¹) and neem cake (at 10 and 20 g kg⁻¹) increased N concentration in leaves of GF677 peach × almond (Prunus amygdalus) hybrid rootstock alone or grafted with one-year-old variety Rome Star peach trees. An increase in microbial respiration, leaf green color and plant biomass compared to the control trees were also observed. The Meliaceae derivatives did not affect, in the short term (7 days), N root uptake efficiency, as demonstrated by the use of stable isotope ¹⁵N, rather they promoted in the long term an increase of soil N availability, N leaf concentration and plant growth.     

Midday depression of photosynthesis is related with carboxylation efficiency decrease and D1 degradation in bayberry (Myrica rubra) plants

Diurnal patterns of photosynthesis in two-year-old Myrica rubra young trees under natural conditions were studied by measuring gas exchange, chlorophyll fluorescence parameters and D1 protein. When measured on a clear day, the diurnal changes of net photosynthetic rate (P_n), stomatal conductance (G_s) and apparent quantum yield (AQY) show two daily maxima; the maximum value occurred at about 09:00 h, then declined, and reached the lowest values at about 13:00 h then increased to reach the second maxima at about 15:00 h. However, with the consistent decline of P_n and G_s in the afternoon, the ratio of intercellular CO₂ concentration (C_i) to atmospheric CO₂ concentration (C_a) increased. In addition, carboxylation efficiency (CE) and RUBP regeneration declined as the afternoon progressed. In the morning, the maximum yield of fluorescence after dark adaptation (F_m) and maximal photochemical efficiency of PSII (F_v/F_m) decreased continuously until it reached its minimum at 13:00 h, while the reverse occurred in the later afternoon. The quantum yield of PSII (Φ_PSII) declined after 09:00 h; in contrast, initial fluorescence (F_o) increased. A decrease in the rate of Q_A reduction and an increase in inactive PSII reaction centers was observed as the day progressed. Non-photochemical quenching (qN) and its slow-relaxing (qS) component increased at about midday, while the fast-relaxing component (qF) declined. The amount of inactive PSII centers was significantly enhanced, while F_v/F_m, Φ_PSII, qS and rate of Q_A reduction were significantly reduced by DTT (dithiothreitol), an inhibitor of the xanthophyll cycle. The D1 protein was significantly degraded at 13:00 h relative to that at 09:00 h during the course of the day. These results suggest that stomatal and non-stomatal limitations, which decreased carboxylation and photochemical efficiency, may cause the midday depression; and that non-stomatal limitations may be due to the decrease in RuBPCase activity and degradation of D1 protein, which causes decreased photoprotection at midday.     

Taxonomic revision of Dendrobium moniliforme complex (Orchidaceae)

Taxonomic revision of Dendrobium moniliforme complex is presented. D. moniliforme complex is characterized by the even slim stems, bracts with brownish zone, semi-spherical anther cap and the hairy disc of lip. Dendrobium tosaense, Dendrobium officinale and Dendrobium guangxiense were excluded by having membranous bracts lacking brownish zone, anther cap conical and bifid. Two species are recognized in this complex, i.e., D. moniliforme and Dendrobium wilsonii. D. wilsonii differs from D. moniliforme by having elliptic leaves about 1.3–2 cm wide, dorsal sepal 3.0–4.0 cm long, 0.6–0.9 cm wide, petals elliptic to oblong, 3.0–4.0 cm long, 1.0–1.5 cm wide, lip elliptic to ovate–lanceolate, 2.6–3 cm long, 1.2–1.5 cm wide.     

Effects of intracanopy lighting on photosynthetic characteristics in cucumber

Plants of cucumber (Cucumis sativus L. cv. Euphorbia) were grown in a traditional high-wire cultivation system to investigate the effects of three lighting regimes on photosynthetic characteristics, leaf area and yield. The lighting regimes included overhead lighting (OH), where all the lamps were mounted above the canopy and overhead + intracanopy lighting (OH + IC) which comprised 65% of overhead lamps and 35% of lamps mounted vertically along the plant rows. All overhead lighting was provided for 20 h day⁻¹ and intracanopy lighting was provided for either 20 h or 24 h day⁻¹ lighting period. Intracanopy lighting improved the light distribution in the canopy. Gas exchange measurements showed that intracanopy lighting increased net photosynthesis (P_N) and photosynthetic capacity (P_max). Parameters calculated from CO₂ response (A/C_i) curves showed that in vivo estimate of the maximum rate of Rubisco carboxylation (Vc_max) and the maximum rate of electron transport (J_max) were affected by light regime. Intracanopy light increased yield by 11% compared to traditional overhead light.     

Development of a male sterile eggplant by utilizing the cytoplasm of Solanum virginianum and a biparental transmission of chloroplast DNA in backcrossing

To develop a male sterile line of eggplant (Solanum melongena L.) utilizing the cytoplasm of S. virginianum, an interspecific F₁ hybrid between S. virginianum and S. melongena ‘Senryo Nigou’ was continuously backcrossed to S. melongena ‘Uttara’ using ‘Uttara’ as a recurrent pollen parent and four backcross generations, BC₁, BC₂, BC₃ and BC₄ were produced. All the plants in backcross generations were anther indehiscent although the F₁ hybrid, S. virginianum and S. melongena were dehiscent. Pollen stainability with acetic carmine and in vitro germination ability of pollen in all the backcross progenies were quite lower than those of the parental species. Fruit set percentage, number of seeds per fruit and seed germination rate were high in all the backcross progenies. The present results indicate that anther indehiscent type of functional male sterile line of eggplant could be developed by utilizing the cytoplasm of S. virginianum. PCR-RFLP analysis of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) were performed to identify the organelle inheritance. The F₁ hybrid and all the backcross progenies displayed maternal inheritance of mtDNA. The cpDNA of the examined single BC₁ plant exhibited the recombinant cpDNA pattern of the parental F₁ hybrid and ‘Uttara’, indicating occurrence of the biparental inheritance of cpDNA. As all the BC₂, BC₃ and BC₄ progenies showed the same recombinant cpDNA patterns of the BC₁ plant, the recombinant cpDNA might be stable and harmonize with the nuclear genome of S. melongena. The present male sterile line can contribute to expand the male sterility source of eggplant.     

Responses of eight chile peppers to saline water irrigation

Salt tolerance of five cultivars of Capsicum annuum L. Early Jalapeno, Golden Treasure, NuMex Sweet, NuMex Joe E. Parker, and Santa Fe Grande, two cultivars of C. chinense Jacq. Habanero and Pimienta De Chiera, and one accession of C. annuum, NMCA 10652, were evaluated in a field study. Seedlings were transplanted in late May to field raised beds containing loamy sand soils in a semi-arid environment. Plants were well irrigated throughout the experiment. Three saline solution treatments, prepared by adding NaCl, MgSO₄, and CaCl₂ to tap water at different amounts to create three salinity levels of 0.82 dS m⁻¹ (control, tap water), 2.5 dS m⁻¹, and 4.1 dS m⁻¹ electrical conductivity (EC), were initiated on 15th June and ended in late August. Among the eight varieties, NMCA 10652 had the highest survival percentage at 100% in the 4.1 dS m⁻¹ treatment, followed by ‘Early Jalapeno’, ‘NuMex Sweet’, ‘Pimienta De Chiera’, ‘Santa Fe Grande’, ‘Golden Treasure’, and ‘NuMex Joe E. Parker’. ‘Habanero’ had the lowest survival at 28%. Compared to control, final shoot dry weight of the plants irrigated with saline solution at 4.1 dS m⁻¹ was reduced by 92% in ‘Habanero’, followed by ‘Golden Treasure’ at 80%. For fruit fresh weight in 4.1 dS m⁻¹ vs. control, ‘Habanero’ had the highest reduction at 86%, followed by ‘Golden Treasure’ at 74%, while NMCA 10652 and ‘Santa Fe Grande’ had the least at 26% and 19%, respectively. NMCA 10652, the most tolerant to salinity, had the lowest leaf Na⁺ accumulation, while ‘Habanero’, the most sensitive to salinity, had the highest Na⁺ in the leaves. For leaf Cl⁻, ‘Early Jalapeno’ had the highest, while ‘Habanero’ had the lowest Cl⁻ accumulation in the leaves. Generally, sensitive varieties accumulated more Na⁺ and/or Cl⁻ in leaves, except for ‘Early Jalapeno’, which was relatively tolerant to salinity but had high Na⁺ and Cl⁻ accumulation in leaves.     

Effects of elevated CO2 on growth and morphological characteristics of ornamental bromeliads

Three ornamental bromeliads, i.e. Aechmea ‘Maya’ (CAM), Aechmea fasciata ‘Primera’ (CAM) and Guzmania ‘Hilda’ (C₃) were grown under greenhouse conditions at ambient (380 ppm) and elevated (750 ppm) CO₂. The effects of long-term exposure (34 weeks) to elevated CO₂ on growth and morphological traits constituting the ornamental value were assessed.