bluuebunny/crossref_metadata_2025 huggingface dataset:
Postharvest Ascorbate Metabolism in Two Cultivars of Spinach Differing in Their Senescence Rates
Authors: Hodges D. Mark , Forney Charles F.
Published: January 2019

Rapidly declining levels of ascorbate (vitamin C) have been associated with advancing senescence and postharvest quality loss in spinach (Spinacia oleracea L.). To further explore the association between ascorbate metabolism and senescence, two cultivars of spinach previously shown to differ in their postharvest senescence rates were grown under controlled conditions (18 °C, 14 light: 10 dark photocycle) and harvested 6 weeks after planting. Detached leaves of `Spokane F1' (relatively fast senescence rate) and `BJ412 Sponsor'(relatively slow senescence rate) were bagged and placed in the dark at 10 °C. Samples were removed on days 0, 7, 14, 21, and 28, and analyzed for activities of L-galactono-γ-lactone dehydrogenase (GLDH), ascorbate peroxidase (ASPX), ascorbate oxidase (AAO), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR), and levels of ascorbate [reduced (AsA) and oxidized (DHA)] and malondialdehyde (MDA) (estimator of lipid peroxidation). Oxidative stress, as estimated by MDA levels, steadily increased in both spinach cultivars during storage, but increased more in `Spokane'than in `Sponsor'. GLDH activities peaked on day 14 for both cultivars and leveled off thereafter, while activities of ASPX, DHAR, and MDHAR declined during storage. ASPX activities were lower in `Spokane'than in `Sponsor'after day 21. No difference in AAO activities was noted between `Sponsor'and `Spokane'during storage. Total ascorbate concentrations declined in both cultivars on day 14 after which no further decreases were noted, while DHA/AsA ratios increased during storage. Early in the storage regime (days 0 and 7), ascorbate levels were lower in `Spokane'than in `Sponsor. GLDH activities may have increased as part of a strategy to maintain the ascorbate pool during escalating oxidative stress. However, decreased levels of ascorbate suggests that, even though ascorbate biosynthesis was increased, ascorbate was being degraded, possibly through hydrolysis of DHA to 2,3-diketogulonate. Initially lower levels of ascorbate (days 0 and 7) and lower activities of ASPX (day 28) in `Spokane' may have resulted in comparatively greater susceptibility of this cultivar to oxidative stress than `Sponsor'.
Rootstock Effects on Growth, Cell Number, and Cell Size of `Gala' Apples
Authors: Al-Hinai Yahya K. , Roper Teryl R.
Published: January 2019

The effects of rootstock on growth of fruit cell number and size of `Gala' apple trees (Malus domestica Borkh) were investigated over three consecutive seasons (2000-02) growing on Malling 26 (M.26), Ottawa-3, Pajam-1, and Vineland (V)-605 rootstocks at the Peninsular Agricultural Research Station near Sturgeon Bay, WI. Fruit growth as a function of cell division and expansion was monitored from full bloom until harvest using scanning electron microscopy (SEM). Cell count and cell size measurements showed that rootstock had no affect on fruit growth and final size even when crop load effects were removed. Cell division ceased about 5 to 6 weeks after full bloom (WAFB) followed by cell expansion. Fruit size was positively correlated (r2 = 0.85) with cell size, suggesting that differences in fruit size were primarily a result of changes in cell size rather than cell number or intercellular space (IS).
The Effect of Water Deficit during Early Fruit Development on Olive Fruit Morphogenesis
Authors: Rapoport Hava F. , Costagli Giacomo , Gucci Riccardo
Published: January 2019

Water deficit was applied between 4 and 9 weeks after full bloom by withholding irrigation from 3-year-old Olea europaea L. (`Leccino') plants grown in 2 L containers in a greenhouse. At 6, 8, and 22 weeks after full bloom (AFB), fruit were sampled for fresh weight and volume determinations, and then fixed for anatomical studies. Structural observations and measurements were performed on transverse sections at the point of widest fruit diameter using image analysis. Water deficit applied between 4 and 9 weeks AFB produced a significant decrease in predawn leaf water potential, which reached minimum values of -3.1 MPa. The applied water deficit reduced fruit fresh weight and volume at 8 and 22 weeks AFB. Fruit transverse area of the water deficit treatment was 50%, 33%, and 70% of the irrigated one at the 6-, 8-, and 22-week sampling dates, respectively. Mesocarp growth occurred for both irrigated and water deficit plants between 8 and 22 weeks AFB. At 22 weeks AFB differences between treatments were significant for mesocarp transverse area, but not for endocarp area. Mesocarp cell size, indicated by area, was significantly different between treatments at 8 and 22 weeks AFB. However, the mesocarp cell number was similar for both treatments at all times, and most mesocarp cells were produced by 6 weeks AFB. The growth of endocarp area showed the greatest shift in timing in response to the early water deficit. Ninety percent of endocarp growth had occurred by 8 weeks AFB in the irrigated treatment, but only 40% when the deficit irrigation treatment was imposed.
Changes in Jasmonates of Mangoes during Development and Storage after Varying Harvest Times
Authors: Kondo Satoru , Yazama Futoshi , Sungcome Kasinee , Kanlayanarat Sirichai , Seto Hideharu
Published: January 2019

Jasmonic acid (JA) and methyl jasmonate (MeJA) were quantified in the skin, pulp, and seeds of `Nam Dok Mai' and `Nang Klangwan' mangoes (Mangifera indica L.). JA showed similar changes during development in both cultivars of fruit. JA concentrations were high in the early growth stages of skin and pulp development, decreased with days after full bloom (DAFB), and then increased again during ripening. JA concentrations in the skin were higher than those in the pulp. 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations in the skin and pulp of both cultivars increased toward harvest. Differing with JA, ACC concentrations in the pulp were high compared with the skin. This fact suggests that although JA and ACC are associated with the ripening of mangoes, they may play different roles. JA concentrations in the seeds of both cultivars decreased toward harvest, possibly suggesting a lack of dormancy in mango seeds. Changes in jasmonates during storage were also examined. JA content in the skin and pulp increased in stored fruit. In addition, the increase in JA content was largest in fruit that lost the most fresh weight. This suggests that JA accumulation that occurs during fruit senescence is associated with moisture loss.
Influence of Rate, Timing, and Method of Nitrogen Fertilizer Application on Uptake and Use of Fertilizer Nitrogen, Growth, and Yield of June-bearing Strawberry
Authors: Strik Bernadine , Righetti Timothy , Buller Gil
Published: January 2019

Fertilizer nitrogen (FN) recovery, and changes in nitrogen (N) and dry weight partitioning were studied over three fruiting seasons in June-bearing strawberry (Fragaria ×ananassa Duch. `Totem') grown in a matted row system. Fertilizer nitrogen treatments were initiated in 1999, the year after planting. The standard ammonium nitrate N application at renovation (55 kg·ha-1 of N) was compared to treatments where additional N was applied. Supplemental treatments included both ground-applied granular ammonium nitrate (28 kg·ha-1 of N) applied early in the season and foliar urea [5% (weight/volume); 16 kg·ha-1 of N] applied early in the season and after renovation. When labeled N was applied (eight of nine treatments) it was applied only once. The impact of no FN from the second through the third fruiting season was also evaluated. Fertilizer nitrogen treatment had no impact on total plant dry weight, total plant N, yield or fruit quality from the first through the third fruiting seasons. Net dry matter accumulation in the first fruiting season was 2 t·ha-1 not including the 4 t·ha-1 of dry matter removed when leaves were mowed during the renovation process. Seasonal plant dry weight and N accumulation decreased as the planting aged. Net nitrogen accumulation was estimated at 40 kg·ha-1 from spring growth to dormancy in the first fruiting season (including 30 kg·ha-1 in harvested fruit, but not including the 52 kg·ha-1 of N lost at renovation). Recovery of fertilizer N ranged from 42% to 63% for the broadcast granular applications and 15% to 52% for the foliar FN applications, depending on rate and timing. Fertilizer N from spring applications (granular or foliar) was predominantly partitioned to leaves and reproductive tissues. A large portion of the spring applied FN was lost when plants were mowed at renovation. Maximum fertilizer use efficiency was 42% for a granular 55 kg·ha-1 application at renovation, but declined to 42% just before plant growth the following spring, likely a result of FN loss in leaves that senesced. In June, ≈30% of the N in strawberry plants was derived from FN that was applied at renovation the previous season, depending on year. This stored FN was reallocated to reproductive tissues (22% to 35%) and leaves (43% to 53%), depending on year. Applying fertilizer after renovation increased the amount of remobilized N to new growth the following spring. The following June, 15% of plant nitrogen was derived from fertilizer applied at renovation 2 years prior.
Effects of Extended Daylength on Shoot Growth and Carbohydrate Metabolism for Creeping Bentgrass Exposed to Heat Stress
Authors: Xu Qingzhang , Huang Bingru , Wang Zhaolong
Published: January 2019

Heat injury in creeping bentgrass (Agrostis stolonifera var. palustris Huds) has been associated with decreases in carbohydrate availability. Extending light duration may increase carbohydrate availability and thus improve growth of creeping bentgrass under heat stress. The objective of this study was to investigate whether turf performance and carbohydrate status could be improved by extending daily light duration for creeping bentgrass exposed to supraoptimal temperature conditions. `Penncross' plants were initially grown in growth chambers set at a day/night temperature of 20/15 °C and 14-hour photoperiod and then exposed to a day/night temperature of 33/28 °C (heat stress) and three different light durations: 14 (control), 18, and 22 hours (extended light duration) for 30 days. Turf quality and tiller density decreased with the duration of heat stress, as compared to the initial level at 20 °C, regardless of the light duration. However, both parameters increased with extended light duration from 14 to 18 or 22 hours. Extended light duration, particularly to 22 hours, also improved canopy net photosynthetic rate from -1.26 to 0.39 μmol·m-2·s-1 and daily total amount of carbon assimilation from -6.4 to 31.0 mmol·m-2·d-1, but reduced daily total amount of carbon loss or consumption to 50% through dark respiration compared to 14 hours treatment by the end of experiment. In addition, extending light duration from 14 to 22 hours increased water-soluble carbohydrate content in leaves both at the end of light duration and the dark period. These results demonstrated that extending light duration improved turf performance of creeping bentgrass under heat stress, as manifested by the increased tiller density and turf quality. This could be related to the increased carbohydrate production and accumulation. Supplemental lighting could be used to improve performance if creeping bentgrass is suffering from heat stress.
Practical Factors Controlling in vitro Adventitious Root Formation from Walnut Shoot Microcuttings
Authors: Dolcet-Sanjuan Ramon , Claveria Elisabet , Gruselle Robert , Meier-Dinkel Adreas , Jay-Allemand Christian , Gaspar Thomas
Published: January 2019

Various factors were found to influence the in vitro induction and elongation of adventitious roots from walnut shoot microcuttings. Diverse walnut genotypes (Juglans regia, J. nigra × J. regia hybrids) and selected elite J. regia clones were micropropagated throughout the establishment of in vitro shoot-tip cultures. New evidence is presented here that demonstrates the importance of the genotype and juvenility of the plant material on the in vitro rooting ability. Selection of the best adapted genotypes to multiplication and rooting, and rejuvenation of mature clones through repetitive subcultures or micrografting were examined. Adult J. regia clones were rejuvenated through subsequent subcultures and their rooting was consequently improved. The same results were not accomplished by micrografting on juvenile shoots. A differential response to auxin type and concentration was observed for Juglans regia or J. nigra × J. regia clones. A short prerooting culture in multiplication medium, lowering the sucrose concentration in the root elongation medium and increasing the atmospheric carbon dioxide during the root elongation phase affected the number of shoots forming roots as well as the quality of plantlets and roots.
Merging Carrot Linkage Groups based on Conserved Dominant AFLP Markers in F2 Populations
Authors: Santos Carlos A. F. , Simon Philipp W.
Published: January 2019

Markers were placed on linkage groups, ordered, and merged for two unrelated F2 populations of carrot (Daucus carota L.). Included were 277 and 242 dominant Amplified fragment-length polymorphism (AFLP) markers and 10 and eight codominant markers assigned to the nine linkage groups of Brasilia × HCM and B493 × QAL F2 populations, respectively. The merged linkage groups were based on two codominant markers and 28 conserved dominant AFLP markers (based upon sequence and size) shared by both populations. The average marker spacing was 4.8 to 5.5 cM in the four parental coupling phase maps. The average marker spacing in the six merged linkage groups was 3.75 cM with maximum gaps among linkage groups ranging from 8.0 to 19.8 cM. Gaps of a similar size were observed with the linkage coupling phase maps of the parents, indicating that linkage group integration did not double the bias which comes with repulsion phase mapping. Three out of nine linkage groups of carrot were not merged due to the absence of common markers. The six merged linkage groups incorporated similar numbers of AFLP fragments from the four parents, further indicating no significant increase in bias expected with repulsion phase linkage. While other studies have merged linkage maps with shared AFLPs of similar size, this is the first report to use shared AFLPs with highly conserved sequence to merge linkage maps in carrot. The genome coverage in this study is suitable to apply quantitative trait locus analysis and to construct a cross-validated consensus map of carrot, which is an important step toward an integrated map of carrot.
Evaluation of Long-day Onions for Resistance to White Rot Infection Using Greenhouse and Laboratory Techniques
Authors: Hovius Marilyn H.Y. , Goldman Irwin L.
Published: January 2019

Breeders have found field screening for onion white rot resistance to be unreliable since consistently moderate to high disease levels that significantly differentiate cultivars, do not occur over field sites and years. The objective was to see if a greenhouse or laboratory technique could predict field reaction of onion accessions. Onion (Allium cepa) accessions were grown in fields naturally infested with the white rot causing fungus (Sclerotium cepivorum) in 1999 and 2000 (New Zealand) and in 2000 and 2001 (Canada). The field disease levels were low at three sites, moderate at two and high at one. Field screening was not a reliable predictor of white rot reaction when disease incidence was low. Onion accessions were screened for resistance in the greenhouse using nonsterile muck soil (NSMS) and sterile muck soil (SMS) with S. cepivorum sclerotia as the inoculum source. Total disease incidence was significantly higher in the NSMS compared to the SMS and accessions showed significant variability for white rot reaction in both soils. Two laboratory-based techniques were used to test the effect of onion volatiles on mycelium growth in culture. The volatiles from susceptible accessions resulted in faster radial growth of S. cepivorum mycelium (on water agar) and height of aerial mycelium (on potato dextrose agar) than volatiles from resistant accessions. Disease incidence in the greenhouse, S. cepivorum culture growth rates on water agar media and aerial mycelial height were all good predictors of field disease incidence in a covariance analysis. The best predictor was aerial mycelial height, which was predictive of field disease incidence in four out of six field sites. Onion breeders can use the methods described in this study in breeding for white rot resistance.
Diurnal Operation of the Xanthophyll Cycle and the Antioxidant System in Apple Peel
Authors: Cheng Lailiang , Ma Fengwang
Published: January 2019

Xanthophyll cycle conversion and the antioxidant system in the peel of apple fruit (Malus ×domestica Borkh. `Liberty') were monitored in the field over a diurnal course at about 3 months after full bloom. Compared with leaves, sun-exposed peel of apple fruit had much lower photosystem II operating efficiency at any given photon flux density (PFD) and a larger xanthophyll cycle pool size on a chlorophyll basis. Zeaxanthin (Z) level increased with rising PFD in the morning, reached the highest level during midday, and then decreased with falling PFD for the rest of the day. At noon, Z accounted for >90% of the xanthophyll cycle pool in the fruit peel compared with only 53% in leaves. Efficiency of excitation transfer to PSII reaction centers (Fv′/Fm′) was negatively related to the level of Z in fruit peel and leaves throughout the day. In fruit peel, the antioxidant enzymes in the ascorbate-glutathione cycle, ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) showed a diurnal pattern similar to that of incident PFD. In contrast, the activities of APX and GR in leaves did not change significantly during the day although activities of both MDAR and DHAR were higher in the afternoon than in the morning. In both fruit peel and leaves, superoxide dismutase activity did not change significantly during the day; catalase activity showed a diurnal pattern opposite to that of PFD with much lower activity in fruit peel than in leaves. The total ascorbate pool was much smaller in fruit peel than in leaves on an area basis, but the ratio of reduced ascorbate to oxidized ascorbate reached a maximum in the early afternoon in both fruit peel and leaves. The total glutathione pool, reduced glutathione and the ratio of reduced glutathione to oxidized glutathione in both fruit peel and leaves also peaked in the early afternoon. We conclude that the antioxidant system as well as the xanthophyll cycle responds to changing PFD over the course of a day to protect fruit peel from photooxidative damage.
Exploring the Limits of Crop Productivity: Beyond the Limits of Tipburn in Lettuce
Authors: Frantz Jonathan M. , Ritchie Glen , Cometti Nilton N. , Robinson Justin , Bugbee Bruce
Published: January 2019

The productivity of lettuce in a combination of high light, high temperature, and elevated CO2 has not been commonly studied because rapid growth usually causes a calcium deficiency in meristems called tipburn, which greatly reduces quality and marketability. We eliminated tipburn by blowing air directly onto the meristem, which allowed us to increase the photosynthetic photon flux (PPF) to 1000 μmol·m-2·s-1 (57.6 mol·m-2·d-1); two to three times higher than normally used for lettuce. Eliminating tipburn doubled edible yield at the highest PPF level. In addition to high PPF, CO2 was elevated to 1200 μmol·m-2·mol-1, which increased the temperature optimum from 25 to 30 °C. The higher temperature increased leaf expansion rate, which improved radiation capture and more than doubled yield. Photosynthetic efficiency, measured as canopy quantum yield in a whole-plant gas exchange system, steadily increased up to the highest temperature of 32 °C in high CO2. The highest productivity was 19 g·m-2·d-1 of dry biomass (380 g·d-1 fresh mass) averaged over the 23 days the plants received light. Without the limitation of tipburn, the combination of high PPF, high temperature, and elevated CO2 resulted in a 4-fold increase in growth rate over productivity in conventional environments.
Molecular Characterization of Kiwifruit (Actinidia) Cultivars and Selections Using SSR Markers
Authors: Zhen Yiqi , Li Zuozhou , Huang Hongwen , Wang Ying
Published: January 2019

Forty-eight kiwifruit cultivars and selections, representing more than 90% of total world kiwifruit production, were investigated using nine SSR markers to establish genetic identities, and evaluate genetic diversity and relatedness. These nine SSRs were polymorphic and a total of 213 alleles were detected, resulting in a mean number of 23.7 alleles per locus, ranging from nine to 38 alleles. One hundred and thirty-three alleles were found to be common to both A. chinensis and A. deliciosa, while 33 and 36 were specific to A. chinensis and A. deliciosa, respectively. In addition, 34 alleles were specific to one single genotype and provided a set of valuable alleles for cultivar identification. A single SSR locus UDK 96-414 could differentiate all 48 genotypes except two presumable clones. Mean number of alleles per locus (A), percentage of polymorphic loci (P), and direct count heterozygosity (Ho) assessed for each genotype over all loci revealed considerable differences among these 48 genotypes. On average, A = 2.6, P = 89.4% and Ho = 0.546 were found in A. chinensis cultivars, while A = 3.5, P = 97.0% and Ho = 0.671 in A. deliciosa cultivars. Consensus fingerprint profiling using SSR markers is a useful and reliable method for establishing genetic identities of kiwifruit cultivars and selections. It also improves evaluation effectiveness of genetic diversity and relatedness compared to RAPD markers.
Factors Affecting Seed Production in Transgenic Ethylene-insensitive Petunias
Authors: Clevenger Donna J. , Barrett James E. , Klee Harry J. , Clark David G.
Published: January 2019

Pollen viability, in-vivo pollen tube growth, fruit ripening, seed germination, seed weight, whole plant vigor, and natural flower senescence were investigated in homozygous and heterozygous transgenic ethylene-insensitive CaMV35S::etr1-1 petunias (Petunia ×hybrida `Mitchell Diploid'). Homozygous or heterozygous plants were used to determine any maternal and/or paternal effects of the CaMV35S::etr1-1 transgene. All experiments except for those used to determine natural flower senescence characteristics were conducted in both high and low temperature greenhouses to determine the effect of temperature stress on transgenic plants when compared to wild-type. Results indicated that ethylene-insensitive plants had a decrease in pollen viability, root dry mass, seed weight, and seed germination. Fruit ripening, seed germination, and seed weight were maternally regulated. In contrast, the CaMV35S::etr1-1 transgene is completely dominant in its effect on natural flower senescence.
Uptake, Partitioning, and Storage of Fertilizer Nitrogen in Red Raspberry as Affected by Rate and Timing of Application
Authors: Rempel Hannah G. , Strik Bernadine C. , Righetti Timothy L.
Published: January 2019

The effects of 15N-labeled fertilizer applied to mature summer-bearing red raspberry (Rubus idaeus L. `Meeker') plants were measured over 2 years. Four nitrogen (N) treatments were applied: singularly at 0, 40, or 80 kg·ha-1 of N in early spring (budbreak), or split with 40 kg·ha-1 of N (unlabeled) applied at budbreak and 40 kg·ha-1 of N (15N-depleted) applied eight weeks later. Plants were sampled six times per year to determine N and 15N content in the plant components throughout the growing season. Soil also was sampled seven times per year to determine inorganic N concentrations within the four treatments as well as in a bare soil plot. There was a tendency for the unfertilized treatment to have the lowest and for the split-N treatment to have the highest yield in both years. N application had no significant effect on plant dry weight or total N content in either year. Dry weight accumulation was 5.5 t·ha-1 and total N accumulation was 88 to 96 kg·ha-1 for aboveground biomass in the fertilized plots in 2001. Of the total N present, averaged over 2 years, 17% was removed in prunings, 12% was lost through primocane leaf senescence, 13% was removed through fruit harvest, 30% remained in the over-wintering plant, and 28% was considered lost or transported to the roots. Peak fertilizer N-uptake occurred by July for the single N applications and by September for the last application in the split-N treatment. This uptake accounted for 36% to 37% (single applications) and 24% (last half of split application) of the 15N applied. Plants receiving the highest single rate of fertilizer took up more fertilizer N while plants receiving the lower rate took up more N from the soil and from storage tissues. By midharvest, fertilizer N was found primarily in the fruit, fruiting laterals, and primocanes (94%) for all fertilized treatments; however, the majority of the fertilizer N applied in the last half of the split application was located in the primocanes (60%). Stored fertilizer N distribution was similar in all fertilized treatments. By the end of the second year, 5% to 12% of the fertilizer acquired in 2001 remained in the fertilized plants. Soil nitrate concentrations increased after fertilization to 78.5 g·m-3, and declined to an average of 35.6 g·m-3 by fruit harvest. Seasonal soil N decline was partially attributed to plant uptake; however, leaching and immobilization into the organic fraction may also have contributed to the decline.
Prohexadione-calcium Decreases Fall Runners and Advances Branch Crowns of `Chandler' Strawberry in a Cold-climate Annual Production System
Authors: Black Brent L.
Published: January 2019

Balancing vegetative growth with fruiting is a primary concern in strawberry (Fragaria ×ananassa Duch.) production. Where nursery plant selection and preconditioning are inadequate for runner control, additional approaches are needed. The gibberellin biosynthesis inhibitor prohexadione-Ca (commercial formulation Apogee) was tested over two seasons for suppressing fall runners of `Chandler' plug plants in a cold-climate annual hill production system. Prohexadione-Ca was applied as a foliar spray at active ingredient concentrations ranging from 60 to 480 mg·L-1, either as a single application 1 week after planting, or repeated at 3-week intervals. The lowest rate resulted in inadequate runner control, with some runners producing malformed daughter plants. Higher rates resulted in 57% to 93% reductions in fall runner numbers, with a concomitant increase in fall branch crown formation. There were no effects of the prohexadione-Ca treatments on plant morphology the following spring, and no adverse effects on fruit characteristics or yield. Chemical names used: prohexadione-calcium, calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene-carboxylate.
Seedling Emergence of Common Bean Accessions under Suboptimal Temperature
Authors: Balasubramanian Parthiba M. , Vandenberg Albert , Hucl Pierre J.
Published: January 2019

Suboptimal seedbed temperatures in early spring limit common bean (Phaseolus vulgaris L.) seedling emergence. This field study evaluated emergence of cultivated and wild common bean when subjected to suboptimal seedbed temperature. One hundred and eighty common bean accessions and three control cultivars were planted on 3 May at Saskatoon, Sask., in 2000 and 2001. Percent emergence, cumulative thermal units to 50% anthesis and to 50% maturity, and seed yield were determined. The seedbed temperature during the 2 weeks after planting ranged between 1 and 18 °C in 2000, and 5 and 17 °C in 2001. At 20 days after planting, emergence in accession G8823 was significantly greater than the control cultivars in 2000. `CDC Nighthawk', a black bean control cultivar was comparable in emergence to G8823 at 30 days after planting. A similar trend was observed in 2001 with the exception that emergence was greater at 30, 40, and 50 days after planting due to a warmer seedbed. `CDC Nighthawk' was among the earliest to mature, although it required a significantly higher cumulative thermal unit to anthesis compared to most other accessions. G8823 could serve as a parent to develop elite bean cultivars with emergence at suboptimal seedbed temperatures.
Building a Replacement Sour Orange Rootstock: Somatic Hybridization of Selected Mandarin + Pummelo Combinations
Authors: Grosser Jude W. , Medina-Urrutia Victor , Ananthakrishnan Govindarajulu , Serrano Patricia
Published: January 2019

Sour orange has been a premier citrus rootstock worldwide due to its ability to perform on challenging soils and to produce and hold high-quality fruit. However, increasingly widespread quick-decline isolates of citrus tristeza virus (CTV) have destroyed entire industries on sour orange in some countries, and are in the process of destroying millions of trees on sour orange in Florida. CTV also threatens other citrus locations planted heavy to sour orange, including Texas and Mexico. An acceptable alternative rootstock to replace sour orange is in high demand but has yet to be developed. Molecular analyses have recently determined that sour orange is probably a hybrid of pummelo and mandarin. We report the production of 12 new mandarin + pummelo somatic hybrids produced by protoplast fusion from selected superior mandarin and pummelo parents, in efforts to develop a suitable replacement sour-orange-like rootstock that is resistant to CTV-induced quick decline. Somatic hybrids from all 12 parental combinations were confirmed by a combination of leaf morphology, flow cytometry, and RAPD analyses (for nuclear hybridity). These new mandarin + pummelo somatic hybrids are being propagated by rooted cuttings as necessary to conduct quick-decline resistance assays and to assess horticultural performance in replicated field trials.
The Effect of Light-dependent Application of Nitrate on the Growth of Aeroponically Grown Lettuce (Lactuca sativa L.)
Authors: Demšar Jernej , Osvald Jože , Vodnik Dominik
Published: January 2019

With a high nitrate supply, and most frequently under low-light conditions, lettuce accumulates relatively large amounts of NO3-as a result of an excess of uptake over reduction. Different approaches, which are used to reduce leaf nitrate, often result in a yield loss. A computerized aeroponic system, which supplies different nitrate concentrations in accordance with the changeable light conditions (dynamic light-dependent application of nitrate), was used to reduce nitrate accumulation in lettuce (Lactuca sativa L.) var. Capitata cv. Vanity. Under unfavorable light conditions nitrate was supplied at limited rates (slight, medium, and strong reduction) to the plants. In response to given light conditions the nitrate supply was reduced close to one-half or one-fourth of the full nutrient solution (8 mmol·L-1 NO3-). Controlled nutrition resulted in efficient reduction in leaf nitrate. In the early-spring experiment the average nitrate content in outer leaves was decreased by 9%, 63%, and 92% and in the late-spring experiment the decrease was 23%, 58%, and 76% compared to control. At the same time, the controlled, light-dependent nitrate deprivation did not result in a loss of a lettuce yield (except in the treatment with strong nitrate reduction) and had limited effects on photosynthesis (PN-Ci measurements) and photosynthetic pigments.
Changes in Cutting Composition during Early Stages of Adventitious Rooting of Miniature Rose Altered by Inoculation with Arbuscular Mycorrhizal Fungi
Authors: Scagel C.F.
Published: January 2019

Many changes in metabolism are known to occur during adventitious root formation, including changes in amino acids, proteins, and carbohydrates. The influence of arbuscular mycorrhizal fungi (AMF) on adventitious rooting of rose was tested by inoculating four cultivars with Glomus intraradices Schenck & Smith. Changes in cutting composition were measured during the initial stages of adventitious root formation. Although there were cultivar-specific differences in response, AMF inoculation generally increased the biomass and number of adventitious roots on cuttings before root colonization was detected. Application of rooting hormone increased this effect. Inoculation with AMF washings also increased the root biomass and number, but only when cuttings were treated with hormone. Changes in cutting composition in response to AMF were detected at 7 to 14 days. Differences in protein concentrations in response to AMF or hormone application were similar, while differences in amino acid and reducing sugar concentrations were not. Concentrations of proteins and amino acids in cuttings at the beginning of the experiment were positively correlated with adventitious rooting, while concentrations of reducing sugars and nonreducing sugars were not correlated with rooting. These results suggests that nitrogen-containing compounds play an important role in adventitious rooting, and that changes in amino acids associated with AMF inoculation were potentially different than those that occurred when cuttings were treated with rooting hormone alone. Carbohydrate concentrations in cuttings were not strongly related to initiation of adventitious roots, but reducing sugar may play a role in regulating part of the response of cuttings to AMF. The response of rose cuttings prior to colonization by G. intraradices suggests that AMF-plant signaling events occurred prior to rooting.
Dehardening Kinetics, Bud Development, and Dehydrin Metabolism in Blueberry Cultivars during Deacclimation at Constant, Warm Temperatures
Authors: Arora Rajeev , Rowland Lisa J. , Ogden Elizabeth L. , Dhanaraj Anik L. , Marian Calin O. , Ehlenfeldt Mark K. , Vinyard Bryan
Published: January 2019

Loss of freeze tolerance, or deacclimation, is an integral part of winter survival in woody perennials because untimely mid-winter or spring thaws followed by a hard freeze can cause severe injury to dehardened tissues. This study was undertaken to investigate deacclimation kinetics, particularly the timing and speed, of five blueberry (Vaccinium L.) cultivars (`Bluecrop', `Weymouth', `Ozarkblue', `Tifblue', and `Legacy'), with different germplasm compositions and mid-winter bud hardiness levels, in response to an environmentally controlled temperature regime. Based upon bud cold hardiness evaluations in 2000 and 2001, `Tifblue', a Vaccinium ashei Reade cultivar, was one of the least hardy and the fastest to deacclimate; `Bluecrop', a predominantly V. corymbosum L. cultivar, was the most hardy and the slowest to deacclimate; and `Ozarkblue', a predominantly V. corymbosum cultivar but including southern species V. darrowi Camp. and V. ashei, was intermediate in speed of deacclimation. `Weymouth' (predominantly V. corymbosum) and `Legacy' (73.4% V. corymbosum and 25% V. darrowi) were slow to intermediate deacclimators. Deacclimation rates did not correlate strictly with mid-winter bud hardiness. Data suggest that the southern germplasm component V. ashei may be responsible for the observed faster deacclimation whereas both southern species, V. darrowi and V. ashei, may contribute genes for cold sensitivity. Strong positive correlations between stage of bud opening and bud cold hardiness existed in both years (r = 0.90 and 0.82 in 2000 and 2001 study, respectively). Previously identified major blueberry dehydrins, 65-, 60-, and 14-kDa, progressively decreased in their abundance during incremental dehardening in `Bluecrop', `Weymouth', and `Tifblue'. However, down-regulation of the 14-kDa dehydrin most closely mirrored the loss in cold hardiness during deacclimation, and, therefore, may be involved in regulation of bud dehardening. Because differences in deacclimation rate were clearly evident among the genotypes studied, rate of deacclimation of the flower buds of blueberry should be an important consideration in breeding to improve winter survival.
Supercooling and Cold Hardiness in Sour Cherry Germplasm: Flower Buds
Authors: Mathers H.M.
Published: January 2019

Flower buds of two sweet cherry (Prunus avium L.), 12 sour cherry (Prunus cerasus L.) and one ground cherry (P. fruticosa Pall.) were collected monthly from Aug. 1990 to Mar. 1991, and subjected to freeze tests to determine the level of cold hardiness. LT50 values (temperatures at which 50% of the flower buds were killed) summed over all months were significantly correlated (r = 0.6844, P ≤ 0.01) to the flower bud low temperature exotherms (LTEs). Correlation of LTEs to LT50 values was highest, r = 0.85, P ≤ 0.01 for the acclimation and midwinter period, November to February collections. During this period the average LT50 occurred before and within 2.5 °C of the LTE, indicating tissue injury before the LTE occurrence. During deacclimation, represented by the March collection, the LT50 began within 2.0 °C, on average, of the LTE, and in 11 of 12 cultivars and seedlings preceded the LTE. In March, the correlation of LTEs to LT50 values was less, r = 0.69, P ≤ 0.05, indicating possible changes flower bud deep supercooling. LTE values were selected as a measure of flower bud hardiness in sour cherry. Exotherms were not detected in the flower buds of all germplasm tested on all evaluation dates, but were the best means of separating selections. While LTE analyses expressed significant differences in November, December, and March at P ≤ 0.01, the LT50 analyses expressed differences only in December and February at P ≤ 0.05. The relationship between ambient temperatures and floral tissue hardiness indicated that November and March are two critical times for flower bud injury. November injury would occur in years when sudden low temperatures occur without sufficient pre-exposure to freezing temperatures. March injury would occur in years when sudden freezing temperatures follow warm days. This type of injury would be most pronounced in southern genotypes. Spring freeze injury could be significantly reduced by the selection of cultivars and seedlings that have delayed deacclimation. Exotherm occurrence and bud volume were correlated (r = 0.95, P ≤ 0.05). In January, when exotherms were least prevalent, they were generally present only in the five cultivars and seedlings with large bud volumes. The LTEs in midwinter, occurred within 3 °C of the reported average annual minimum temperature for the northern range of Prunus commercial production (Zone 6). The results of the principal component analysis of flower bud LTEs indicated that other selection criteria as flowering time might have played a more significant role in the hardiness range of sour cherry than simply geographic origin. The first principal component (PC1), which accounted for 77% of the total variance was used to separate among cultivars and seedlings. Selections at the positive end of PC1 had flower buds that were more cold susceptible than selections at the negative end of PC. This concurs with other research showing that flower bud hardiness is related more to commercial range (i.e., the range of commercial production) than to geographic distribution.
Variation for Antioxidant Activity and Antioxidants in Tomato
Authors: Hanson Peter M. , Yang Ray-yu , Wu Jane , Chen Jen-tzu , Ledesma Dolores , Tsou Samson C.S. , Lee Tung-Ching
Published: January 2019

Tomato (Lycopersicon esculentum Mill.) is among the most widely consumed vegetables worldwide and an important source of certain antioxidants (AO) including lycopene, β-carotene, and vitamin C. Improvement of tomato for content of AO and overall antioxidant activity (AOA) could potentially benefit human health in many countries. We evaluated 50 L. esculentum and three L. pimpinellifolium (L.) Mill. entries for contents of lycopene, β-carotene, ascorbic acid, total phenolics, and two assays for antioxidant activity [anti-radical power (ARP) and inhibition of lipid peroxidation (ILP)] for 2 years during the same period in south Taiwan. We detected high levels of genetic diversity for the AO and AOA measured in this study. Group means of the L. pimpinellifolium entries were significantly higher than L. esculentum group means for ARP, ILP, lycopene, ascorbic acid, phenolics, and soluble solids concentration, suggesting that introgression of alleles from L. pimpinellifolium may have potential to improve cultivated tomato for these traits. Ranking of entries for ILP and ARP were consistent between years, particularly for those entries with the highest means and these assays could be adopted by tomato breeders. Results from ILP and ARP assays were highly correlated (r = 0.82**) and it would be unnecessary to use both assays for tomato. Lycopene, β-carotene, ascorbic acid, soluble solids, and total phenolics were all positively correlated with ARP. Among AO, total phenolics content was most closely associated with ARP (r = 0.90**) and ILP (r = 0.83**); this suggests that phenolics make a major contribution to AOA in tomato fruit. Fruit size was negatively correlated with ARP (r = -0.74**) and ILP (r = -0.71**), indicating that combining large fruit size and high AOA will be challenging.
A Rapid and Accurate Method for Estimating Tomato Lycopene Content by Measuring Chromaticity Values of Fruit Purée
Authors: Hyman Joshua R. , Gaus Jessica , Foolad Majid R.
Published: January 2019

Lycopene is the red pigment and a major carotenoid in tomato (Lycopersicon esculentum Mill.) fruit. It is a potent natural antioxidant, and the focus of many tomato genetics and breeding programs. Crop improvement for increased fruit lycopene content requires a rapid and accurate method of lycopene quantification. Among the various available techniques, high-performance liquid chromatography (HPLC) can be accurate, however, it is laborious and requires skilled labor and the use of highly toxic solvents. Similarly, spectrophotometric methods, although easier than HPLC, also require time-consuming extractions and may not be as accurate as HPLC, as they often overestimate fruit lycopene content. Colorimetric estimation of fruit lycopene using chromaticity values has been proposed as an alternative rapid method. Previous studies that examined the utility of this technique, however, were confined to the evaluation of only one or few cultivars and, therefore, lacked broad applicability. The purpose of the present study was to examine the utility of chromaticity values for estimating lycopene and β-carotene contents in tomato across diverse genetic backgrounds. Measurements of the chromaticity values (L*, a*, b*, C*, h*) were taken on whole fruit and purée of 24 tomato genotypes and were compared with HPLC measurements of fruit lycopene and β-carotene. Examination of different regression models indicated that a model based on the transformed value a*4 from purée measurements explained up to 94.5% of the total variation in fruit lycopene content as measured by HPLC. When this model was applied to a second set of fruit harvested at a later date from the same 24 genotypes, it explained more than 90% of the total variation in lycopene, suggesting its reliability. The best estimation for β-carotene content was obtained by using the b* chromaticity value from whole fruit measurements or the transformed a*2 value from purée measurements. Neither model, however, could explain more than 55% of the variation in β-carotene content, suggesting that chromaticity values may not be appropriate for estimating tomato β-carotene content. The overall results indicated that fruit lycopene content could be measured simply and rather accurately across a wide range of tomato genotypes using chromaticity values taken on fruit purée.
Location and Anatomy of Nodules on Alnus maritima Subjected to Flooding
Authors: Kratsch Heidi A. , Graves William R.
Published: January 2019

Although many species of Alnus Miller grow in wet soils, none is as closely associated with low-oxygen, waterlogged soils as Alnus maritima (Marsh.) Muhl. ex Nutt. (seaside alder). An actinorhizal species with promise for use in horticultural landscapes, land reclamation, and sustainable systems, A. maritima associates with Frankia Brunchorst, thereby forming root nodules in which gaseous nitrogen is fixed. Our objective was to determine how root-zone moisture conditions influence the occurrence, location, and anatomy of nodules on A. maritima. Plants of Alnus maritima subsp. maritima Schrader and Graves were established in root zones with compatible Frankia and subjected to four moisture regimens (daily watered/drained, partially flooded, totally flooded, and totally flooded with argon bubbled through the flood water) for 8 weeks. Oxygen content of the root zone, number and location of nodules on root systems, and dry weight and nitrogen content of shoots were determined. Root-zone oxygen content ranged from 17.3 kPa for daily watered/drained plants to 0.9 kPa for argon-treated plants. Across all treatments, 87% of the nodules were within the upper one-third (4 cm) of the root zone. Although shoot dry weights of daily watered/drained and partially flooded plants were not different, daily watered/drained plants had more nitrogen in their leaves (2.53 vs. 2.21 mg·g-1). Nodulation occurred in all treatments, but nodules on totally flooded roots (with or without argon) were limited to a single lobe; in contrast, multilobed nodules were prevalent on partially flooded and daily watered/drained plants. Frankia infection within submerged nodule lobes was limited to one or two layers of cortical cells. Submerged nodules developed large air spaces between cortical cells, and phenolic-containing cells appeared to inhibit Frankia expansion within the nodule. These data suggest that access to root-zone oxygen is critical to the Frankia-A. maritima subsp. maritima symbiosis, and that plants of this subspecies in the drained soils of managed landscapes may benefit more than plants in native wetland habitats from nodulation and nitrogen fixation.
Gene Flow between Parents with Different Ploidy Levels in a Natural Population of Leucocoryne Lindley
Authors: Salas P. , Mansur L.
Published: January 2019

Gene flow between species of different ploidy levels is important in plant evolution and breeding. A cytological study was conducted on a natural population with individuals belonging to the diploid L. purpurea Gay (2n = 10) and to the tetraploid L. coquimbensis F. Phil (2n = 18) species, as well as intermediate phenotypes of apparent hybrid origin. The genus Leucocoryne is endemic to Chile and it exhibits heterogeneity, presumably genetic, for shape, size, and color of its flowers. The objective of the study was to determine if there is gene flow between species having different ploidy levels. From the karyotypic analyses of the seeds, only parental types having 2n = 10 and 2n = 18 individuals were observed. However, from the bulb analyses, 2n = 10, 2n = 18, 2n = 14, and 2n = 22 individuals were encountered. The karyotypes of the 2n = 14 and 2n = 22 individuals suggest the occurrence of natural interespecific hybridization between species with different ploidy levels in nature. Models which may account for the origin of these genotypes are proposed.