Competition of redroot pigweed (Amaranthus retroflexus L.) and nettle-leaved goosefoot (Chenopodium murale L.) with tomato (Lycopersicon esculentum Mill.) cultivars

Competition of 31 tomato (Lycopersicon esculentum Mill) cultivars with Amaranthus retroflexus and Chenopodium murale was investigated at different growing periods under natural conditions, University of Jordan, during 2008–2010. Cultivars were varied in their competitiveness with weeds; some tolerated while others were highly susceptible and exhibited great growth (shoot dry weight) and fruit yield reductions. A. retroflexus was more competitive than C. murale at most growing periods. Weeds attained high growth in the spring and summer but were much reduced in autumn. A. retroflexus requires relatively higher temperature for growth and competitiveness than C. murale. Gardners Delight and Special Back cultivars showed tolerance and their growth and yield either increased or least reduced in competition with weeds. In contrast, growth of First in the Field, Back More, Orient and Tiny Tim was reduced by 65–75% of their controls. Highest growth of weeds was in competition with The Amateur and lowest with First in the field and Back More. Fruit yield of all cultivars was reduced in competition, especially with A. retroflexus. Reduction was up to 100% in the spring. Both weeds reduced growth of cultivars most during the spring while A. reteroflexus eliminated certain cultivars.     

A modified green-grafting technique for large-scale virus indexing of grapevine (Vitis vinifera L.)

A modified method of green-grafting was investigated for use in viral indexing of grapevine stock. Cabernet franc and Cabernet sauvignon scions infected with grapevine leafroll-associated virus 3 (GLRaV3) were cleft-grafted on to virus-free indicator rootstocks LN33 and C. sauvignon, and were maintained in polystyrene containers containing vermiculite soaked with Huglin and Julliard solution. Using this method plants could be transferred to soil 3–4 weeks following grafting. Leafroll symptoms: reddening of leaves, leaf rolling, and interveinal discolouration, were scored at 3–4 weeks and again at 12 weeks. Double antibody sandwich–enzyme linked immunosorbent assay (DAS–ELISA) was used to validate the visual symptoms of disease. At both times it was clear that C. sauvignon was a more sensitive indicator of GLRaV3 than LN33, with 80% of grafts showing symptoms at 3–4 weeks and 90% showing symptoms at 12 weeks. The results indicate that the technique described here is effective and suitable for large-scale indexing of grapevine stock for viral contamination.     

A comparison of conventional cloning options for annatto (Bixa orellana L.)

Summary

Annatto (Bixa orellana L.) is a tree indigenous to tropical America that has been naturalised throughout the Indian sub-continent. The plant is chiefly valued for its carotenoid pigments, annatto. Methods for the clonal propagation of hardwood and softwood cuttings, air-layering, budding, and grafting of annatto were investigated. Hardwood cuttings collected during the wet Summer months (June-July) were treated with indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), or naphthaleneacetic acid (NAA) at varying concentrations. The highest percentage rooting (63.4%), along with highest number of roots (8.33 per cutting) were achieved by hardwood cuttings after 12 h of 2.5 mM IAA treatment. Among the various auxin treatments of softwood cuttings, 5.0 mM IBA in combination with 5.0 mM NAA for 5 min resulted in a significant (P < 0.05) rooting percentage (56.7%). The responses of softwood cuttings to an auxin analogue (boric acid) and/or to thiamine hydrochloride (vitamin B) were inferior to synthetic auxins. When subjected to air-layering, hardwood branches gave 100% rooting without any application of hormone. Among the different types of budding methods attempted (patch, T, or I), patch budding produced the highest efficiency (78%) of propagation. Splice-grafting could also be used for conventional propagation of annatto, with a 50% survival rate. Annatto can therefore be cloned by adopting these methods. Propagation based on softwood cuttings facilitated moderate-scale cloning of this valuable, elite germplasm.     

Genetic diversity and relationships within Citrus and related genera based on sequence related amplified polymorphism markers (SRAPs)

Sequence related amplified polymorphism (SRAP) markers were used to detect molecular marker polmorphisms among 86 citrus and their relatives in Aurantioidea. Twenty-one SRAP primer combinations produced a total of 376 polymorphic fragments with an average of 17.9 per primer combination and an average polymorphism information content (PIC) of 0.86. The unweighted pair group method arithmetic average (UPGMA) analysis demonstrated that the accessions had a similarity range from 0.28 to 1.00 with a mean of 0.64. The subtribe Clauseninae (tribe Clauseneae) separated from the subtribes of the tribe Citreae. The subtribe Balsamocitrinae (tribe Citreae) was the most distant from the others. In the Citrinae, ‘primitive citrus fruit trees’ and ‘near citrus fruit trees’ groups did not clearly separate from each other but all genera in these groups were distinct. On the other hand, subgenus Papeda and subgenus Citrus were not separated clearly in the dendrogram. C. maxima, C. medica and C. reticulata separated into three distinct clusters in agreement with three ‘true basic species’ thesis. Similarity-based analyses supported the theory of few ancestral species in Aurantioidea.     

Sana Physiological responses of two grapevine (Vitis vinifera L.) cultivars to CycocelTM treatment during drought

The plant growth regulator Cycocel^TM [(2-chloroethyl)trimethylammonium chloride] can be used to produce drought tolerance in grapevine (Vitis vinifera L.) due to a reduction in the ratio between vegetative growth and fruit production. To evaluate the physiological responses of two grapevine cultivars to drought and Cycocel^TM treatment, a factorial experiment was conducted in a greenhouse. The factors included irrigation frequency (at 5-, 10-, or 15-day intervals corresponding to no, mild, or severe drought stress), Cycocel^TM concentration (0, 500, or 1000 mg l^–1), and cultivar (‘Rasheh’ or ‘Bidane-Sefid’). Stomatal conductance (g_s) the net rate of CO₂ assimilation (A_net), the rate of transpiration (T_r), and chlorophyll a and b concentrations decreased in plants exposed to mild or severe water-deficit stress, whereas carotenoid, proline, and total soluble sugar concentrations increased compared to plants with no drought stress. The relative water content (RWC) of leaves declined only under severe drought stress. A reduction in intercellular CO₂ concentrations (C_i) occurred under mild drought stress; however, under severe drought stress, C_i values increased. Under mild drought stress, the reduction in the net rate of photosynthesis was related to stomatal closure, whereas under severe drought stress, non-stomatal factors were dominant. Water-use efficiency (WUE) improved under mild drought stress relative to non-stressed plants, but under severe drought, it declined. Foliar applications of Cycocel^TM resulted in increased A_net, g_s, T_r, and WUE values, as well as proline and soluble sugar concentrations. ‘Rasheh’ was more tolerant to drought stress than was ‘Bidane-Sefid’. Foliar applications of Cycocel^TM, particularly at 1000 mg l^–1, mitigated the negative effects of drought stress by increasing A_net, WUE, RWC, compatible solute concentrations, such as proline, soluble sugar, and chlorophyll a and b concentrations.     

Genetics and molecular mapping of gynoecious (F) locus in cucumber (Cucumis sativus L.)

Gynoecious is an important economic trait of cucumber for determinant of earliness and yield, yet genetic mechanism is not well understood for this trait. The experiment was conducted using F₂ mapping population by crossing of PPC-2, a gynoecious and parthenocarpic line with Pusa Uday (monoecious and non-parthenocarpic cultivar). Out of 179 SSR markers screened, 39 markers differentiated the gynoecious and monoecious parents. However, only 17 markers were segregating with F₂ mapping population, those were used for genotyping and linkage map analysis and these markers were placed along with F locus on chromosome 6 covering a total distance of 100.4cM. The SSR markers, SSR13251 and UW020605 were found to be closely linked to gynoecious (F) locus at 1.0 and 4.5 cM, respectively. The segregation of F₂ population of PPC-2 × Pusa Uday and GPC-1 × Punjab Naveen and test crosses for sex type herein suggested that single dominant gene controlled the gynoecious sex expression in cucumber particularly in gynoecious genotypes PPC-2 and GPC-1. Therefore, the monogenic dominant nature of gynoecious sex identified in the present experiment and SSR markers closely linked to the F locus will be useful in marker-assisted backcross breeding for transfering gynoecious trait into horticulturally desirable varieties.     

Patterns of 14C-sucrose translocation in egg plant (Solanum melongena L.)

Summary

Patterns of distribution of ¹⁴C-sucrose were determined in egg plant (Solanum melongena L.) cv. Arka Shirish at the vegetative, flowering and fruit development stages. 5 μCi of ¹⁴C-sucrose was fed to the fifth leaf from the top at each growth stage and the plants were harvested, 48 h after feeding or at later stages, and the distribution of ^l4C-sucrose determined. Results indicated bidirectional transport of assimilates to both apical and basal portions of the stem. Within 48 h ¹⁴C moved to all the plant parts; roots, stem and leaves appeared to be strong sinks until the fruit began to develop. In plants fed at the fruit development stage, the fruit below the fed leaf were a major sink, although considerable activity was traced in other plant parts also. Only at later stages of crop growth did the fruit become a strong sink. Even at the fruit development stage, about 5-8% of the activity was still found in the roots and no retranslocation to fruit was observed.     

Association analysis of fruit traits in mulberry species (Morus L.)

Improvement of fruit traits is an important objective in current mulberry breeding programs. In this study, 93 mulberry accessions of diverse origin were genotyped using 15 ISSR markers to identify marker–trait associations with fruit traits. Fifteen ISSR primers generated a total of 104 amplification products, of which 94 were polymorphic, revealing 90.38% polymorphism; the mean PIC value was 0.2698. UPGMA cluster analysis showed clear genetic relationships between the 93 mulberry cultivars, and the major clusters were related to known pedigree relationships and their ecotype. The mean r² value for all intra-chromosomal loci pairs was 0.0210. Marker–trait associations were investigated using the unified mixed-model approach, considering both population structure (Q) and kinship (K). In total, 24 marker–trait associations (p < 0.01) were identified using different ISSR markers. The results suggest that association mapping in mulberry is a viable alternative to quantitative trait loci mapping, and detection of associations between markers and mulberry fruit traits will also provide important information for marker-assisted breeding.     

Changes in apical morphology during floral initiation and development in pyrethrum (Tanacetum cinerariaefolium L.)

Summary

Changes in apical morphology during floral initiation and development in pyrethrum (Tanacetum cinerariaefolium L.) were investigated by scanning electron microscopy. The sequence of events may be divided into eleven stages of apical development which are distinctive in both morphology and size. The environmental stimulus promoting rapid flower initiation was demonstrated to be vernalization. Flower initiation occurred after four months under non-vernalizing conditions through an autonomous flower induction process. Devernalization was observed under short day (10 h daylength), low photon flux density (200 µmol m² s^?1) conditions. Apices were never observed to revert to vegetative growth after the initiation of the first involucral bract and therefore this was considered to be the developmental stage at which the apex was committed to generative development.     

Using precocious trifoliate orange (Poncirus trifoliata [L.] Raf.) to establish a short juvenile transformation platform for citrus

The precocious trifoliate orange (Poncirus trifoliata [L.] Raf.), an early flowering mutant of P. trifoliata, has a short juvenile phase of about 14 months, significantly shorter than other citrus. In this report, using the stems of precocious trifoliate orange seedlings as explants, an improved protocol mediated by Agrobacterium tumefaciens was developed to evaluate regeneration and transformation frequency. The transformed plants continued to reveal the precocious trait of non-transgenic mature precocious trifoliate orange, and as such could prove to be an efficient system for the verification of gene function in the fruits/flower via genetic transformation in woody plants.     

Effects of fruit thinning,pollination and paclobutrazol on fruit set and size of persimmon (Diospyros kaki L.) in subtropical Australia

Summary

A factorial combination of three cultural factors (± hand-pollination, ± growth retardant, ± fruit thinning) were evaluated for their effects on fruit set and fruit size of ‘Fuyu’ persimmon (Diospyros kaki L.) in subtropical Australia (Lat. 27° S). Treatments were applied to individual shoots on mature seven year old trees. Fruit set of pollinated flowers was high compared with non-pollinated flowers (91% vs. 47%). Pollinated fruit also grew faster at all stages of fruit development and, at harvest, fresh weights were 25% heavier. Palcobutrazol significantly (P<0.05) increased fruit weight by 7% compared with controls but did not increase fruit set. Irrespective of treatment, fruit weight was not correlated (r<0.3, n.s.) with shoot length, number of nodes per shoot, fruit nodal position, shoot dry weight, leaf area per shoot, and number of leaves per shoot. Fruit fresh weight was only poorly correlated with shoot base diameter (r = 0.41*). Pollinated fruit had significantly (P<0.05) higher concentrations of nutrients (N, K, Ca, and Zn).     

Some physiological characteristics of fruits of jujube (Zizyphus spina-christi L., Willd.) at different stages of maturity

Summary

Jujube fruits (Z. spina-christi L., Willd.) of the three cvs Bambawi, Zaytoni and Mallasey were harvested at three stages of maturity and their physiological characteristics measured. Moisture content, titratable acidity, total chlorophyll and pectic substances decreased with fruit maturity. Total soluble solids, carotenoids and vitamin C contents increased as the fruit matured.     

Cold and heat requirements of the apricot tree (Prunus armeniaca L.)

Summary

The cold units (CU) and heat units (HU) required for the flowering of 13 apricot cultivars (Prunus armeniaca L.) cultivated in AbaraÂn (Murcia) have been established. The end of the dormancy period was determined on the basis of the dry-weight increase of the flower buds. The tests in which the dry weight was measured after forcing the flower buds at 208C turned out to be more precise in detecting the beginning of the reactivation phase than those in which they were not forced.     

Effects of post-harvest storage conditions on the levels of glucosinolates in broccoli sprouts (Brassica oleracea var. italica) grown under different temperature regimes

Summary

Broccoli sprouts have been recognised as a rich source of glucosinolates, particularly 4-methylsulphinylbutyl glucosinolate, the precursor of the potent anti-cancer compound, sulphoraphane. Previous results have shown that temperature can significantly affect the levels of glucosinolates. In this study, we showed how sprout age and storage temperature affected glucosinolate levels in broccoli sprouts grown under different temperature regimes. Experiments were conducted in growth cabinets with day/night temperature regimes of 30°/15°C, 22°/15°C and 18°/12°C. At 9, 10 and 11 d after sowing in the first temperature regime, 10, 11 and 12 d in the second, and 12, 13 and 14 in the third, sprouts were submitted to 4°C or 20°C to simulate refrigerated and room temperature storage. Sampling was done after 1 d or 2 d of exposure to these conditions. The results showed that total glucosinolate levels and the potential health effects of broccoli sprouts depended on the growth temperature regime (P < 0.05), the age of the sprouts (P < 0.001), and the storage conditions (P < 0.01). The highest total glucosinolate levels (65.7 µmoles g^–1 dry weight) were obtained under the 30º/15°C temperature regime for the youngest sprouts (harvested 9 d after emergence), after being submitted to a storage temperature of 4°C for 24 h. However, these levels were much lower than in 3-d-old sprouts. Consuming old sprouts provides less health-protective effects due to reduced levels of glucosinolates.     

The importance of male red mason bee (Osmia rufa L.) and male bufftailed bumblebee (Bombus terrestris L.) pollination in blackcurrant (Ribes nigrum L.)

Summary

Male wild bees visit flowers to feed and, despite their lack of specialised organs for carrying pollen, simultaneously pollinate them. We analysed the pollinating efficiency of the males of two bee species for blackcurrant (Ribes nigrum L.): red mason bee (Osmia rufa L.) and bufftailed bumblebee (Bombus terrestris terrestris L.). Both bee species are commercial pollinators and many males are produced during their rearing. Gauze sleeves were used to isolate the inflorescences and to keep the males inside (one per sleeve). In each experimental group, there were six shoots with four neighbouring inflorescences (n = 24). The sleeves were also used to prevent other bees from reaching the flowers, and to allow self-pollination. Non-isolated flowers were pollinated by free-range bees. The effect of male bee pollination was similar to that of free-range bee pollination. The percentages of flowers that developed into fruit were as follows: male bufftailed bumblebee pollination, 79.5%; free-range bee pollination, 71.1%; male red mason bee pollination, 65.1%; and self-pollination, 46.4%; while the mean numbers of fruit per raceme were 5.0, 4.4, 3.6, and 2.4, respectively. The number of non-pollinated flowers per raceme (ranging from 1.3 – 2.8) exhibited an inverse relationship to these numbers of fruit. Our observations showed that male wild bees can pollinate blackcurrant flowers successfully, and could potentially be useful in other crops.     

Photosynthetic and physiological responses to high temperature in grapevine (Vitis vinifera L.) leaves during the seedling stage

To study the effects of high temperature (HT) on grape growth, a controlled experiment with grapevine (Vitis vinifera L., cv. Hongti) was conducted from July to October, 2015. The HT treatments were 34, 36, 38, and 40°C, with 28°C as control. The changes to photosynthetic pigment characteristics, antioxidant enzyme activities, and relative water content (RWC) under different HTs were investigated. Severe chlorosis was observed during the late stages of HT treatment. Chlorophyll a (Chl a), chlorophyll b (Chl b), photosynthetic rate at irradiation saturation (P_max), light saturation point (LSP), apparent quantum efficiency (AQE), peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activity in grape leaves increased at first, and then decreased under high-temperature stress (HTS), but the light compensation point acted contrary to the LSP. The carotenoid, malondialdehyde and relative electrical conductivity (REC) increased under HTS; and the Chl/carotenoid ratio and RWC were contrary to the REC. The results suggested that grapes subjected to 38°C for 4 d decreased their RWC, but Chl a, Chl b, P_max, AQE, LSP, SOD, POD, and CAT reached their maximums. Therefore, the high-temperature limit of Hongti was 38°C and the duration time was 4 d.     

Temperature requirements for the germination of olive seeds (Olea europaea L.)

Summary

Olive seeds cv Chondrolia Chalkidikis were subjected to temperatures of 5°, 10°, 15°, 20°, 25° and 30°C for one, two or three months, and were then transferred to 20°C. Exposure to 10° and 15° for one month or more caused higher emergence percentages compared to that at a constant 20°C. The highest germination rate was observed when seeds subjected to 10°C for one month were then transferred to 20°C. Seeds at 5°, 25° and 30°C did not germinate while being held to these temperatures; even when transferred to 20°C the percentage and rate of emergence were lower than those of seeds held at constant 20°C. In another experiment, in which seeds were subjected to 10°C for 0, 2, 4, 6 and 8 weeks before being transferred to 20°C, it was found that four weeks exposure to 10°C was near optimal. Emergence percentages of seeds at constant 10°C or at diurnally alternating temperatures of 10° for 16 h/20° for 8 h were high and equal (92%), but emergence in the latter treatment was slower. Alternating 10° with 25°C resulted in a 95% reduction of the emergence percentage. Transferring seeds immediately after chilling at 10°C for three or four weeks to 25°C, partially reversed the effect of the low temperature. However, the chilling effect could not be reversed when the seeds were subjected to 10°C for five weeks.     

Cold treatments enhance responsiveness to gibberellin in stock (Matthiola incana (L.) R. Br.)

Summary

Endogenous GAs have been suggested as regulators of stem elongation and flowering of cold-requiring plants. Here, the relationship between temperature conditions and responsiveness to GA₄ on stem elongation and flowering of stock (Matthiola incana) was investigated. The optimum temperature for induction of flower bud initiation was 10°C, and the minimum duration was 20 d in the late flowering cv. Banrei; the type of cold treatment effect on flowering was classified as a “direct effect”. Stem elongation was markedly promoted by cold treatment regardless of flower bud initiation. The cold treatment amplified the stem elongation response to GA₄. The GA₄ level necessary for flower bud initiation was lower in the 10°C treatment than in the 15°C treatment, and it became lower at longer durations of cold treatment. These results indicate that the cold treatments enhance responsiveness to GA₄ not only in the stem elongation process but also in the flower bud initiation process and that the development of responsiveness to GA₄ may correlate with the temperature and duration of cold treatment.     

Effects of CO2 on greenhouse grown eggplant (Solanum melongena L.) I. Leaf conductance

Leaf conductance of eggplant (Solanum melongena L., cv. Cosmos) was measured comparatively in two glasshouse compartments, with continuously low or high C02 (on average 415 or 685 μmol mol^-1, respectively). Measurements were carried out on eight days between February and June 1991 in an early planted crop. A regression equation was fitted to the data to account for the effects of PAR, air humidity and C02 on leaf conductance. Calculations with this equation demonstrated that leaf conductance was reduced by 10.2% per 100 |imol mol1 increase in C02, which is a three to four times stronger response than in other fruit vegetable crops. When, on some occasional days, C02 was kept equal in the two compartments, leaf conductance was not different, indicating that stomatal behaviour had not adapted to long lasting C02 conditions. The rate of crop transpiration, as estimated with the Penman-Monteith combination equation, was reduced by elevated C02 by only a few percent on average and by about 15% in a period of some weeks in spring.