Effect of Glomus mosseae and Entrophospora colombiana on plant growth,production, and fruit quality of ‘Maradol’ papaya (Carica papaya L.)

The effect of inoculating ‘Maradol’ papaya plants with arbuscular mycorrhizal fungi (AMF) Glomus mosseae (GM) and Entrophospora colombiana (EC) was assessed. The results showed that both mycorrhizae species increased the number of fruits and yield in papaya plants by 41.9 and 105.2% for GM and 22.1 and 44.1% for EC, respectively, with respect to control plants. GM significantly increased plant height. Sugar content, firmness, color (°Hue), and ripening process of mycorrhized plant fruits were similar to those of the control. Weight loss of mycorrhized plant fruits was considerably less than that of the control. Inoculation of papaya with AMF is recommended, particularly with GM since it increases yield, and fruit weight (45.1%), furthermore, it reduced fruit weight loss during ripening.     

Agrobacterium × plant factors influencing transformation of ‘Joseph's coat’ (Amaranthus tricolor L.)

A protocol is developed for Agrobacterium-mediated genetic transformation of Amaranthus tricolor via explant co-cultivation with Agrobacterium rhizogenes. Bacteria-plant specific factors which influenced transformation were optimized. Of the two Agrobacterium strains employed, LBA9402 was more infectious compared to A4. Bacterial suspensions grown overnight with 100 μM acetosyringone and experiencing O.D.₆₆₀ = 0.6 followed by dilution to a density of 10⁹ cells ml⁻¹ were the most effective. Explants from garden-grown plants were more responsive than those from in vitro cultures; stem internodes being better than leaves. Immersion of the pre-pricked explants in bacterial suspension resulted in a markedly higher transformation frequency compared to the direct injection method. The infection of internode explants with the LBA9402 strain followed by co-cultivation on growth regulator-free MS medium (MS0) for 5 days resulted in emergence of hairy roots up to a maximum frequency of 97.22%. Roots were individually cultured in MS0, but fortified with bactericidal antibiotic (500 μg ml⁻¹ cefotaxime). Rhizoclones showing prolific growth were renewed through successive subcultures in MS0. Opine gene expression was revealed by positive agropine and mannopine synthesis in all selected transformed rhizoclones. Shoot regeneration from root clones, capable of auxin-independent growth and opine proficiency, was stimulated in MS augmented with 2.0 mg l⁻¹ zeatin. pRi TL–DNA rolB and pRi TR–DNA man2 ORF were detected in leaf tissues of regenerated plants from selected hairy root clones through PCR amplification. The implication of such findings is discussed on the possibility of conferring protection to crop amaranths against biotic stress challenges, particularly due to insects, viruses or fungal pathogens.     

Effect of high temperature stress on the reproductive growth of strawberry cvs. ‘Nyoho’ and ‘Toyonoka’

High temperatures are known to reduce fruit size and fruit weight in strawberry, but cultivar differences in the response to high temperature stress during the reproductive stage up to the second inflorescence have not been sufficiently reported. We examined the effect of two day/night temperature regimes on fruit set and fruit growth in two cultivars, ‘Nyoho’ and ‘Toyonoka’. A high day/night temperature of 30/25 °C reduced the number of inflorescences, flowers, and fruits in both cultivars compared with plants grown at 23/18 °C. The percentage of fruit set in ‘Nyoho’ was not significantly different between the two temperature treatments, while that in ‘Toyonoka’ was much lower at 30/25 °C than at 23/18 °C. Days to ripening was shorter at 30/25 °C than at 23/18 °C, and no cultivar differences were observed. Fresh weight of primary, secondary, and tertiary fruits was greater at 23/18 °C than at 30/25 °C in both cultivars, and no cultivar differences were observed, except in tertiary fruits. The diameter of fruits from all positions was also reduced at 30/25 °C in both cultivars. Relative growth rates of fruits showed two peaks in both cultivars and in both temperature treatments. Both peaks appeared earlier at 30/25 °C than at 23/18 °C. Percentage of fruit set at 30/25 °C in the second inflorescence was also significantly lower in ‘Toyonoka’ than in ‘Nyoho’. These results indicate that high temperature stress negatively affects the reproductive process in strawberry and that plant response to high temperature stress is cultivar-related in such responses.     

The effect of sucrose on the expression of the VvTFL1 and VFL genes during flower development in the “Xiangfei” grapevine

VFL and VvTFL1 genes expression patterns and the effects of sucrose on the expression of VFL and VvTFL1 genes in different organs of the “Xiangfei” grapevine (Vitis vinifera L.) were investigated. VvTFL1 gene expression was detected in the meristem of the apical bud and lateral bud, but was not detected during inflorescence differentiation and flower organ development. After sucrose treatment, VvTFL1 gene expression increased in the apical bud, but decreased in the lateral bud. These results suggested that the VvTFL1 gene might be mainly involved in the apical growth process of shoots, and exogenous sucrose had an effect on the VvTFL1 gene by increasing shoot apical meristem initiation of apical buds. The VFL gene was expressed primarily during inflorescence differentiation and early flower organ development, but it gradually reduced in later flower development. After sucrose treatment, VFL gene expression increased in the inflorescence and small or middle flower, but a little change was seen in the large flower. These results suggested that the VFL gene plays important roles in the initiation of inflorescence meristems and the morphological formation of flower organs. Exogenous sucrose had an effect on VFL gene expression at the early stage of flower development.     

Effect of fruit-load on the growth,absorption, and partitioning of inorganic nutrients in young ‘Fuyu’ persimmon trees

Tree growth and the increase in inorganic nutrients during a growing season were studied in 3-year-old, container-grown ‘Fuyu’ persimmon trees with different levels of fruit-load. Fruit-load was varied by adjusting the leaf–fruit ratio to 10, 20, 30, and 60 on July 5. Some trees were completely defruited. The whole trees were harvested on November 5 of that year, and increases in dry weight and inorganic elements in different tree parts during the season were measured. A lower leaf–fruit ratio resulted in a higher yield but also decreased fruit weight, soluble solids, and fruit color. Dry weight of the aerial woods and root increased significantly with a greater ratio. However, total dry weight including the fruits was higher in the lower ratio trees than in the higher ratio trees; the weight of a tree that maintained the ratio of 10 was 35% higher than a tree without fruit. Fruits accounted for 62% of total dry weight when the ratio was 10 and 27% when the ratio was 60. The leaf–fruit ratio did not significantly alter the total increase in P, K, Ca, and Mg content. N tended to decrease with an increasing leaf–fruit ratio. Of the total increases of N, P, and K during the season, the fruits accounted for 30%, 50%, and 54% at the ratio of 20, respectively, and the percentages increased to 44, 81, and 74 at the ratio of 10. The inorganic element content in the aerial woods and root tended to increase with greater ratios, especially in the root. When trees were defruited, N and K increases in the root accounted for 44% and 35% of the total increase, respectively. These results indicated that persimmon orchard fertilization programs with different fruit-load levels should accommodate the proportion of nutrients partitioned to fruits that are removed permanently from the tree.     

Identification of S-alleles in pear (Pyrus communis L.) cv. ‘Rocha’ and other European cultivars

In this work we report the cloning and identification of S-RNase alleles responsible for gametophytic self-incompatibility (GSI) of ‘Rocha’ pear and of 13 other European pear cultivars that might be used as its pollinators. Partial sequences of S-RNase alleles were amplified by PCR with specific primers hybridising in conserved regions of previously identified S-RNase alleles of Pyrus communis, cloned and sequenced and the S-genotype of eight pear cultivars was fully determined. Three cultivars (‘General Léclerc’ (SqSl), ‘Tosca’ (SbSl) and ‘Alexandrine Douillard’ (SbSk)) shared no S-alleles with ‘Rocha’ (SaSe) and shall be totally compatible with this cultivar. None of the cultivars analysed showed an identical amplification pattern to the one observed in ‘Rocha’, so the other cultivars shall be at least semi-compatible. One new allele was identified in P. communis cv. ‘Beurré d’Avril’ (designated as St). The determination of both S-RNase alleles of cvs ‘Rocha’, ‘Beurré Precoce Morettini’ (SeSk) and ‘Tosca’ and the identification of one S-RNase allele in cvs ‘Carapinheira’ (Sb), ‘Amêndoa’ (Se), ‘Pérola’ (Sk) and ‘Beurré d’Avril’ (St) are important contributions for the effort recently developed worldwide to establish groups of sexual compatibility among European pears.     

Postharvest changes in pigment concentrations in ‘Fuji’ apples with ‘Fuji’ stain

’Fuji’ apples (Malus domestica Borkh cv. ‘Fuji’) sometimes develop a discolouration in the peel during cold storage, typically in the periphery of sunburned peel. We refer to this particular postharvest disorder as ‘Fuji’ stain as we have not observed it in any cultivar other than ‘Fuji’ and the discolouration looks like a stain on the peel. Because peel discolouration occurs, peel pigments are thought to be involved. Hence the concentrations of anthocyanins, epicatechin, quercetin glycosides, chlorogenic acid, chlorophylls, and carotenoids in peel disks taken from areas exhibiting ‘Fuji’ stain were compared to concentrations observed in peel disks not exhibiting ‘Fuji’ stain. In 2005, peel from sunburned apples exhibiting ‘Fuji’ stain was compared to peel from three areas of sunburned apples not exhibiting stain [i.e. sunburned peel, the area around the sunburned peel (halo), and the area around the halo (OH)]. Additionally, stained peel was compared to the sun-exposed side of non-stained non-sunburned apples (NSNB). The second year, 2006, we compared stained peel to NSNB peel and the area outside the stained area (OS) on those fruit with stain. The concentrations of idaein, epicatechin, and quercetin glycosides were consistently low in the stained peel both years. This is in contrast to our earlier studies in which sunburned ‘Fuji’ apples had high concentrations of quercetin glycosides and epicatechin and low concentrations of idaein, and non-sunburned apples had low concentrations of quercetin glycosides and epicatechin and high concentrations of idaein. The consistent and unique characteristic of stained peel reported here indicates an association of these compounds with the incidence of stain. In 2005, chlorogenic acid concentrations in the stain peel were lower than other peel types, but in 2006 they were higher. Differences in chlorophyll and carotenoid concentrations were observed among many of the peel types. However, there is not a clear association between stain development and changes in chlorophyll and carotenoid concentrations due to significant differences not being observed in both years. While our research provides insight into pigment changes associated with ‘Fuji’ stain formation, more work is needed to help clarify the inconsistencies observed between the 2 years.     

Seed abortion of ‘Tosa-Buntan’ pummelo pollinated with soft-X-irradiated pollens

Cross-pollination was performed with soft-X-irradiated hyuga-natsu pollens (1000 Gy) for ‘Tosa-Buntan’ pummelo (Citrus grandis (L.) Osbeck). This resulted in the transformation of large and complete seeds into small and empty ones (practically seedless). Although fruit set, fruit retention, total soluble solids content (TSS) and titratable acidity of the juice were not affected, decrement in the fruit size was observed. Two weeks after the pollination, endosperm cell division with free nuclei began in both the non-irradiated and irradiated pollen treatment conditions. Seven weeks after pollination, endosperm division with the cell wall occurred in the non-irradiated pollen treatment conditions; however, the endosperm development ceased in most ovules that underwent the irradiated pollen treatment, and the ovules remained in their free nuclear stage. The delayed degeneration of the ovules, following successful fertilization and commencement of endosperm cell division, allow these seedless fruits to be categorized as pseudo-parthenocarpic.     

In vitro proliferation from axillary buds and ex vitro protocol for effective propagation of Syringa × hyacinthiflora ‘Luo Lan Zi’

As a precondition for lilac mass propagation, the optimal shoot-multiplication medium for Syringa × hyacinthiflora ‘Luo Lan Zi’ was ascertained mainly based on clustered microshoot inducement and large leaf area establishment in 6-benzyladenine (BAP) (1.00 mg L⁻¹) and zeatin (Z) (0.10 mg L⁻¹) combination. Medium supplied with lower level of BAP (0.50 mg L⁻¹) and auxin (IAA) (0.25 mg L⁻¹) was not suitable for lilac shoot proliferation, but it could be competent for long-term preservation of the un-rooted shoots so that subsequent proliferation culture could be carried out at anytime. In addition, excess height growth which resulted in low transplanting survival rate was effectively controlled by decrease in node number when paclobutrazol (PBZ) was applied in rooting medium at a concentration of 1.00 mg L⁻¹ after taking into account the effects on shoot height, rooting, persistent leaf area and PBZ carry-over. An important overwintering treatment was to use a plastic chamber covering for plants in the greenhouse prior to field planting to ensure adequate biomass of stem and underground parts not only in the current growing season but also in the subsequent years.     

Study on nutraceutical properties of different cultivars Ipomoea aquatica Forsskal (‘Chunbai’ and ‘Liulv’) in an eutrophic water body

Ipomoea aquatica Forsskal is a fast-growing aquatic economic plant and has been applied widely to purify eutrophic water, but little is known about the edible safety of it for humans or animals. The main purpose of our research was to assess the metal (copper, zinc, lead, cadmium and chromium) concentration and nutritional quality in the edible part of I. aquatica Forsskal (‘Chunbai’ and ‘Liulv’) growing in eutrophic water. The results showed that all levels of these metals were within the acceptable levels in our present studies, and the metal accumulating potential varied mainly depending upon levels of metal contamination in the water body in which they were growing. In the present investigation, nitrate content (NO₃–N) had no significant differences between ‘Chunbai’ and ‘Liulv’, but had significant differences (p < 0.001) between eutrophic water and Hoagland nutrient solution. Soluble protein, soluble sugar, and vitamin C content were affected greatly by variety and solution (treatments). The soluble protein and vitamin C content in ‘Liulv’ were one time higher but the soluble sugar content was one time lower than that in ‘Chunbai.’ The soluble protein and soluble sugar of plants cultivated in nutrient solutions were one time lower than that in eutrophic water. In addition, the vitamin C content of plants grown in Hoagland nutrient solution was approximately two times higher than that in eutrophic water. The possible utilization of these aquatic vegetables to meet the demands of food and health perspectives for consumers is discussed.     

Re-constructing data of leaf area increment in the greenhouse pot chrysanthemum cultivar ‘Lompoc’

A dynamic model was developed for re-constructing data of shoot leaf area increment in pot chrysanthemum. From specified final areas of individual leaves and time of anthesis of the terminal flower, the model can re-construct dynamic growth of each leaf on side shoots using a modified Richards function. In the model, leaf growth is related to a relative time index ranging from zero to unity, where zero is the start of short day treatment and unity corresponds to anthesis of the terminal flower. Experiments were conducted under greenhouse conditions to collect data for parameter estimation, model verification and model validation. An allometric relationship between leaf length and leaf area was used to estimate leaf area non-destructively from leaf length recordings. When compared with the data used for parameter estimation, the model simulations fitted the data with R² values ranging from 0.979 to 0.998. In the validation trial the model showed a tendency of over estimation early leaf growth but could explain variations in the data with R² values ranging from 0.899 to 0.993.     

Identification of parental species of the Alstroemeria cv. ‘Jubilee’ using AFLP marker technique

Twelve Alstroemeria species, two hybrids, one cv. ‘Jubilee’, an anther-cultured plant from cultivar ‘Jubilee,’ and Bomarea salsilla and Leontochir ovallei (the latter two were chosen as outgroup) were evaluated using the AFLP marker technique in order to identify putative parental genotypes of the Alstroemeria cv. ‘Jubilee’ and of known interspecific hybrids, and to estimate their genetic relationships within the genus Alstroemeria. A total of 297 AFLP markers were scored by using the primer combination (E + ACCA/M + CTAG). In order to discriminate all Alstroemeria genotypes, cluster analysis (UPGMA) and principal coordinates analysis were performed. The Alstroemeria cv. ‘Jubilee’, of which the parents are unknown, had genetic distance (GD) 0.54 from Alstroemeria exserens, GD 0.57 from Alstroemeria garaventae, GD 0.62 from Alstroemeria gayana, and GD 0.66 from Alstroemeria hookeri cumminghiana. Thus, these four species are considered as putative parental genotypes. An interspecific hybrid (Alstroemeria aurea × Alstroemeria inodora), showed the smallest genetic distance from A. aurea (GD 0.56) and A. inodora (GD 0.45). The Alstroemeria ligtu group was distantly allocated from other Chilean species. We conclude that the AFLP marker technique appears to be a satisfactory tool for identifying the parental genotypes of interspecific hybrids in Alstroemeria.     

Effect of distance from early flowering pollinizers ‘Maypole’ and ‘Dolgo’ on ‘Fiji’ fruit set

An apple orchard consisting of a single cultivar under the condition of natural pollination must have suitable pollinizers such as Crab apples to ensure stable fruit production. We selected ‘Maypole’ and ‘Dolgo’ as pollinizers for the cultivar ‘Fuji’, and investigated the rate of fruit and seeds in ‘Fuji’ fruits produced by pollen of the pollinizers. We developed a method for tracing pollen flow based on the leaf color of progeny and S-RNase allele of ‘Maypole’, and on Simple Sequence Repeat (SSR) analyses of ‘Maypole’ and ‘Dolgo’. These were powerful tools for determining the distance insects (mainly Osmia cornifrons) carry pollen from the pollinizers to ‘Fuji’. Although the fruit set of ‘Fuji’ apples was not reduced with increasing distance between ‘Fuji’ apple trees and pollinizers (probably due to pollen flow from other commercial cultivars planted outside the area), the rate of ‘Fuji’ apple fruit produced by the pollen of the pollinizers decreased with increasing distance. The rate of fruit produced by the pollinizers was 84% and 77% when ‘Fuji’ was 2.5 m from ‘Maypole’ and ‘Dolgo’, respectively, and 71% and 64% when ‘Fuji’ was 5 m from ‘Maypole’ and ‘Dolgo’, respectively, but was reduced to 47% and 39% when ‘Fuji’ was 10 m from ‘Maypole’ and ‘Dolgo’, respectively. However, the spacing could cause reduced fruit size, and require extra fruit thinning for producing large fruits. It could also cause reduction of the yield for increasing the planting area of pollinizers. We recommend that pollinizers should be planted not more than 10 m from ‘Fuji’.     

Performance of ‘Tahiti’ lime on twelve rootstocks under irrigated and non-irrigated conditions

Faced with new challenges, such as emerging diseases, shortening of orchard longevity, and larger social and environmental demands from consumers, practices such as rootstock diversification, irrigation and high density plantings have become relevant for the Brazilian citrus industry. This research had the objective to evaluate the performance of irrigated and non-irrigated ‘Tahiti’ lime trees grafted on 12 rootstocks and one interstock. Plots were distributed following a randomized block design, with four replicates and one plant per plot. Rootstocks influenced plant vigor, especially ‘Flying Dragon’ trifoliate, which reduced tree height by approximately 47% compared to the ‘Rangpur’ lime. Trees that were budded on more vigorous rootstocks showed higher yield when grown without irrigation than with irrigation. The ‘1646’ citradia and ‘Morton’ citrange rootstocks performed particularly well. On the other hand, the plants on less vigorous rootstocks showed better performance in terms of yield under irrigation than the same combinations without irrigation, especially those grafted on the tetraploid ‘Carrizo’ and ‘Troyer’ citranges, ‘Swingle’ citrumelo, ‘Davis A’ trifoliate and ‘Flying Dragon’ trifoliate. Plants budded on the ‘1708’ citradia had high yields under irrigated and non-irrigated conditions. The effect of interstock on plant vigor was dependent of rootstock. Interstocked plants on ‘Davis A’ trifoliate were higher than those without interstock. On the other hand, interstocked plants on Catania 2 ‘Volkamer’ lemon were less vigorous than those without interstock.     

Vegetative and productive responses of ‘Conference’ and ‘Williams’ pear trees planted at different in-row spacings

The effect of in-row spacing on the vegetative and productive performance of 4-year-old ‘Conference’ (CON) and ‘Williams’ (WIL) pear trees was studied. Analysis of digital images was used to estimate canopy growth and conformation. Fruit quality was determined by measuring fruit weight, flesh firmness, peel color, soluble solid content, and titratable acidity. WIL produced more and more efficiently than CON, especially at closer spacings. WIL canopies were generally bigger than CON canopies, and reduced spacing penalized stem growth and influenced canopy conformation. Root growth and conformation was similar for both cultivars, whereas decreasing in-row spacing reduced root dry weight, length, volume, and spread area only in WIL. Also, WIL trees partitioned more to fruit and leaves compared to CON, and increasing spacing resulted in a relative shift toward vegetative growth. CON fruit was smaller but sweeter and less acidic than WIL fruit. Increasing spacing influenced negatively WIL fruit quality parameters, with the only exception of fruit weight, which was increased. For the range of in-row spacing considered, our results indicate that WIL may represent a more efficient and competitive option than CON for high-density plantings, at least in the early stages of orchard life.