Distribution and function of LMW glutenins,HMW glutenins,and gliadins in wheat doughs analyzed with ‘in situ’ detection and quantitative imaging techniques

The different gluten subunits, gliadins, LMW glutenins, and HMW glutenins have been reported to play different key roles in different type of wheat products. This paper studied the interaction between gliadin, LMW and HMW glutenins in soft, hard and durum semolina flour doughs during different stages of mixing. In order to see how do the gluten subunits (gliadin, LMW glutenin and HMW glutenin) redistribute during mixing, dough samples were taken at maximum strength and 10 min after maximum strength. The doughs have been mixed with the same level of added water (55%), therefore they all have different strengths values due to their changes in proteins content. Oscillatory rheological measurements were performed on the doughs. It has been found that HMW glutenins are relatively immobile because of their less molecular mobility and do no redistribute themselves especially at high strength for doughs such as hard wheat flour. LMW glutenins and gliadins on the other hand redistribute themselves at even at high dough strengths forming a more stable network. In weaker doughs such as soft wheat, the breakdown of the three proteins subunits is responsible for the decay in dough strength. We have also visualized how the greater amount of LMW glutenins in semolina is in constant interaction with HMW glutenins and gliadins allowing the dough to maintain a stable strength for an extended mixing time. Finally, we have found the ‘in situ’ detection and quantitative analysis techniques to be more sensitive to the changes occurring in the gluten network of the dough than the oscillatory rheological analysis.     

Effect of Allelic Variation of Glutenin Subunits and Gliadins on Baking Quality in the Progeny of Two Biotypes of Bread Wheat cv. Ulla

During the determination of the HMW glutenin subunit composition of Finnish varieties, the variety Ulla was observed to contain two biotypes which differed from each other at two loci:Glu-A1andGlu-A3/Gli-A1. One of them, called Ulla 1, contained subunit 2* (Glu-A1b) andGlu-A3o/Gli-A1o, and Ulla 2 contained the null allele (Glu-A1c) andGlu-A3a/Gli-A1c. In order to determine the effect of this allelic variation on quality, the two biotypes were crossed and random lines were produced from the progeny by single seed descent. In total, 95 F6 lines were analysed from four bulked Ulla progeny lines. Significant interaction between the allelic variants of HMW glutenins and LMW gluten proteins affected the SDS-sedimentation volume at the mean flour protein level of 13·1% (dmb); the effect of LMW gluten variants was larger in the lines deficient of a HMW glutenin subunit than in lines having a HMW glutenin subunit (2*). At the higher flour protein levels (mean=15·1%, dmb) the effect on SDS-sedimentation volume was additive; progeny carrying alleles b (subunit 2*) and o/o atGlu-A1andGlu-A3/Gli-A1had significantly greater sedimentation volumes than the progeny carrying alleles c (no subunit) and a/c, respectively. The SDS-sedimentation volumes indicated differences in the quantities of the polymeric glutenins, gel proteins which have been shown to reflect dough strength. In the four bulked Ulla progeny lines, the variation in HMW glutenin subunits affected the dough strength values of the Extensigraph. However, the variation in LMW glutenin subunits did not affect Extensigraph dough strength values, as was predicted by SDS-sedimentation volumes. In the Ulla progeny, adding a HMW glutenin subunit affected Extensigraph dough strength more than adding a LMW glutenin subunit, although both increased the SDS-sedimentation volumes. Moreover, the variation in LMW gluten proteins affected the dough mixing stability in the Farinograph and test baking results of the Ulla progeny.     

Correlations of the Amount of Gluten Protein Types to the Technological Properties of Wheat Flours Determined on a Micro-scale

Flour samples of 14 wheat cultivars previously characterised by rheological measurements and by baking tests on a micro-scale (Kieffer et al.: Journal of Cereal Science27 (1998) 53–60) were analysed for the relative amounts of gluten protein types using a combined extraction/HPLC procedure. Regression analysis was used to find relations between wheat properties and protein quantities. The results indicated that the maximum resistance of dough and gluten and the gluten index were strongly dependent on the quantity of glutenin subunits (GS) in flour; additionally they were influenced by the ratio of gliadin to glutenin subunits. Within the family of glutenin proteins, the correlation coefficients for high-molecular-weight (HMW) and low-molecular-weight (LMW) GS were in a similar range, but twice the amount of LMW GS was necessary to get the same resistance as with HMW GS. Among HMW GS, the contribution of x-type GS was more important than those of y-type GS. The extensibility of dough and gluten was mainly dependent on the ratio of gliadin to total glutenin subunits, to HMW GS and LMW GS. Dough development time showed the highest correlation with total HMW GS and x-type HMW GS. Bread volume was influenced by the total amount of gluten protein more than by the amount of protein in different groups or of different types, probably because of the rather low range of flour protein content (8·7–12·0 %) within the set studied. Significant differences between gliadins and glutenins with respect to their effects on bread volume could not be detected. The correlation between bread volumes and the quantity of gluten proteins was higher, when dough was mixed to optimum.     

Expansion profiles of wheat doughs fermented by seven commercial baker's yeasts

Commercial baker's yeast consists of Saccharomyces cerevisae, however the strain can vary in each baker's yeast, which might influence the dough fermentation time. The scope of this research was to investigate the dough expansion of wheat doughs fermented by seven commercial baker's yeasts at different yeast concentrations (2.88·10¹¹, 5.76·10¹¹ and 8.64·10¹¹ colony forming units/kg flour) and fermentation temperatures (5 °C, 15 °C, 25 °C and 35 °C). Dough expansion was investigated by monitoring the dough height and it was found to be described well by a first order kinetic model. Doughs fermented with four of the seven yeasts generally had higher kinetic rate constants and hence shorter fermentation times compared to fermentation with the other three yeasts. The shortest fermentation times were found for doughs fermented at 25 °C and the highest yeast concentration, a trend found for all the yeasts tested. The differences in the kinetic rate constants indicate a differentiation in yeast strain among the commercial baker's yeasts emphasising the great importance of the choice of baker's yeast for the dough fermentation time.     

Control of citrus postharvest penicillium molds with sodium ethylparaben

The curative antifungal activity of postharvest sodium ethylparaben (SEP) treatments against citrus green mold (GM) and blue mold (BM) was determined on different citrus species and cultivars artificially inoculated with Penicillium digitatum or Penicillium italicum and incubated at 20 °C and 90% RH for 7 d or stored at 5 °C and 90% RH for 8 weeks plus 7 d of shelf-life at 20 °C. The best concentration was selected in in vivo primary screenings with ‘Valencia’ oranges. SEP at 80 mM was tested at 20, 50 or 62 °C for 30, 60 or 150 s in small-scale trials to determine the best dip treatment conditions. Dips of 80 mM SEP at 20 °C for 60 s were selected and applied alone or in combination with 25 μL L⁻¹ of the conventional fungicide imazalil (SEP + IMZ 25). Imazalil at the very low concentrations of 25 (IMZ 25) or 50 μL L⁻¹ (IMZ 50) was also tested. Effectiveness of SEP alone at 20 °C for 60 s was significantly higher on oranges (cvs. ‘Valencia’ and ‘Lanelate’) than on mandarins (cvs. ‘Clemenules’, ‘Nadorcott’ and ‘Ortanique’), with GM and BM incidence reductions of up to 57–73% after 7 d at 20 °C. SEP was compatible with IMZ 25 and consistently improved its performance, irrespective of citrus cultivars and storage conditions. All treatments were less effective on ‘Clemenules’ mandarins. On ‘Valencia’ oranges stored for 8 weeks at 5 °C and 7 d at 20 °C, the combined treatment was significantly more effective than the single treatments (reductions of GM and BM incidence of about 96–93% and 55–39%, respectively). In additional tests, SEP, IMZ 25 and the combination applied at 20 °C for 60 s prevented GM on ‘Valencia’ oranges treated, inoculated with P. digitatum 24 h later and incubated at 20 °C for 7 d. It can be concluded from these results that SEP might be an integrating nonpollutant control alternative to be included in citrus postharvest disease control programs in the future.     

Hydration,polymerization and rheological properties of frozen gluten-water dough as influenced by thermostable ice structuring protein extract from Chinese privet (Ligustrum vulgare) leaves

The effects of thermostable ice structuring proteins (TSISPs) extracted from Chinese privet (Ligustrum vulgare) leaves on water molecular state, dehydration of gluten proteins, secondary structure of proteins, glutenin subunit of glutenin macropolymer (GMP) and rheological properties of gluten doughs during frozen storage were investigated by nuclear magnetic resonance (NMR), attenuated total reflectance-Fourier transform infrared reflectance (ATR-FTIR), reversed phase-high performance liquid chromatography (RP-HPLC) and dynamic rheometry. After frozen storage for 5 weeks, the control sample showed dehydration of gluten proteins and mobility of water molecules in gluten dough increased, significantly indicating ice formation and water redistribution. Secondary structure of gluten proteins changed significantly, α-helix decreased and β-sheet increased. Glutenin subunits depolymerized, indicated by the decrease in high molecular weight glutenins/low molecular weight-glutenins (HMW/LMW) ratio. The decrease in elastic moduli (G′) and viscous moduli (G′') showed the deterioration of rheological properties of gluten dough. The addition of TSISPs inhibited the dehydration of gluten proteins, decrease in α-helix, increase in β-sheet and HMW/LMW ratio, resulting in improved rheological properties of gluten dough.     

Improved viscoelastic zein–starch doughs for leavened gluten-free breads: Their rheology and microstructure

Gluten-free bread was prepared from commercial zein (20 g), maize starch (80 g), water (75 g), saccharose, NaCl and dry yeast by mixing above zein's glass transition temperature (T_g) at 40°C. Addition of hydroxypropyl methylcellulose (HPMC, 2 g) significantly improved quality, and the resulting bread resembled wheat bread having a regular, fine crumb grain, a round top and good aeration (specific volume 3.2 ml/g). In model studies, HPMC stabilized gas bubbles well. Additionally, laser scanning confocal microscopy (LSCM) revealed finer zein strands in the dough when HPMC was present, while dynamic oscillatory tests showed that HPMC rendered gluten-like hydrated zein above its T_g softer (i.e. |G*| was significantly lower). LSCM revealed that cooling below T_g alone did not destroy the zein strands; however, upon mechanical impact below T_g, they shattered into small pieces. When such dough was heated above T_g and then remixed, zein strands did not reform, and this dough lacked resistance in uniaxial extension tests. When within the breadmaking process, dough was cooled below T_g and subsequently reheated, breads had large void spaces under the crust. Likely, expanding gas bubbles broke zein strands below T_g resulting in structural weakness.     

Investigation of the high-amylose maize starch gelatinization behaviours in glycerol-water systems

The effect of glycerol on gelatinization behaviours of high-amylose maize starch was evaluated by confocal laser scanning microscopy (CLSM), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), texture analyzer (TPA) and rheometer. Gelatinization of the high-amylose maize starches with glycerol content of 10% (w/w) began at 95.4 °C (T_o), peaked at 110.3 °C (T_p), and completed at 118.9 °C (T_c). The birefringence began to disappear at around 100 °C and finished at 120 °C which corresponded well to the onset and conclusion temperatures obtained by DSC. The high-amylose maize starch granules maintained original morphological structure at 100 °C and swelled to a great degree at 110 °C. The high-amylose maize starch paste formed at 100 °C showed the lowest hardness (39.92 g), while at 120 and 130 °C, showed the highest hardness (610.89 g and 635.43 g, respectively). It should be noted that in going from 100 °C to 110 °C there is a significant increase in the viscosity of the slurry solution. The identical apparent viscosity was observed when the shear rate exceed 100 s⁻¹, resulting from the high-amylose maize starch granules were completely gelatinized at 120 °C, which was consistent with DSC analysis.     

A temperature-based phenology model for predicting development,survival and population growth potential of the mealybug,Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

The temperature-dependent population growth potential of Phenacoccus solenopsis Tinsley, a highly polyphagous and invasive mealybug species, was studied on sprouted potatoes under laboratory conditions at six constant temperatures (15–40 °C). Several non-linear equations were fitted to the obtained data to model temperature-dependent population growth and species life history. The established equations for each life age/stage of the species were compiled to obtain an overall temperature-dependent phenology model. The life table parameters of P. solenopsis were estimated using stochastic simulation centred on a rate summation and cohort up-dating approach. The theoretical lower development threshold temperatures estimated using linear regressions applied to mean development rates were 11.2, 8.9, 9.8 and 12.7 °C, and the thermal constants for development were 93.7, 129.8, 97.1 and 100.0 degree days (DD) for nymph 1, nymph 2, nymph 3 and male pupa stages, respectively. The developed phenology model predicted temperatures between 25 and 35 °C as the favourable range for P. solenopsis development, survival and reproduction. P. solenopsis population attained a maximum net reproductive rate (107–108 females/female/generation) and total fecundity (216.6–226.5 individuals/female/generation) at temperatures between 25 and 30 °C. Mean length of generations decreased from 75.6 days at 15 °C to 21 days at 40 °C. The maximum finite rate of increase (1.12–1.16 females/female/day) and shortest doubling time (4.3–6.1 days) were also observed at temperatures between 25 and 35 °C. The simulation of phenology model at fluctuating temperatures indicated that P. solenopsis populations might potentially increase with a finite rate of 1.06 females/female/day with an average generation time of 58.7 days and a doubling time of 12.1 days. The obtained life table parameters were reasonably similar when compared with literature data. The present model can be simulated spatially for estimating the pest risk and undertaking agro-ecoregion specific pest management strategies.     

Effect of climate change on Spodoptera litura Fab. on peanut: A life table approach

Investigations were conducted to understand the direct effects of rising temperature and the host-mediated effects of elevated CO₂ (eCO₂) on Spodoptera litura (Fabricius) (Noctuidae: Lepidoptera). This study involved i. the construction of life tables of S. litura at six constant temperatures viz., 20, 25, 27, 30, 33 and 35°C ± 0.5 °C reared on peanut (Arachis hypogaea L.) grown under eCO₂ (550 ppm) concentration in open top chambers ii. Estimation of threshold temperatures and thermal constants and iii. Prediction of the pest scenarios during near and distant future climate change periods. Significantly lower leaf nitrogen, higher carbon and a higher relative proportion of carbon to nitrogen (C:N) were observed in peanut foliage grown under eCO₂ over ambient CO₂ (aCO₂). The mean development time (days) of each stage, egg, larva, pupa, pre-oviposition and total life span decreased from 20 to 35 °C temperature on eCO₂ foliage. The thermal requirement of S. litura from egg to egg (within the range of 20 °C–35 °C) was 538.5 DD on eCO₂ as against 494.5 DD on aCO₂ foliage. Finite (λ) and intrinsic rates of increase (r_m), net reproductive rate (R_o), mean generation time (T) and doubling time (DT) of S. litura varied significantly with temperature and CO₂ and were found to have quadratic relationships with temperature. The present results on life table parameters estimated by the bootstrap technique showed that the ‘r_m’ values of S. litura on eCO₂ foliage were higher than those in the literature indicating a significant influence of eCO₂. The reduction of ‘T’ was noticed from a maximum of 50 days at 20 °C to minimum of 22 days at 35 °C and ‘λ’ which is the indicator of reproductive value of new eggs was highest at 35 °C and showed a negative relationship with temperature. The data on these life table parameters were plotted against temperature and two non-linear models developed for both CO₂ conditions and used for predicting the pest scenarios. Prediction of pest scenarios based on PRECIS A1B emission scenario data at eleven peanut growing locations of the country during near future (NF) and distant future (DF) climate change periods showed an increase of ‘r_m’ and ‘λ’ with varied ‘R_o’ and reduced ‘T’. The present results indicate that temperature and CO₂ are vital in influencing the growth and life table parameters of S. litura and that pest incidence is likely to be higher in the future.     

Pre-harvest glyphosate application effects on properties of β-glucan from oat groats

Pre-harvest glyphosate is applied to cereal grains to control weed growth. However, it has been claimed that oat (Avena sativa L.) composition is affected by pre-harvest glyphosate application. The research was conducted to evaluate differences in properties of β-glucan in grains of pre-harvest glyphosate treated versus untreated oat plants. Two oat cultivars (Rockford and Souris) were grown at Minot and Prosper, ND, in 2015, and glyphosate was sprayed during the soft dough stage, hard dough stage, or not applied. β-glucan viscosity was not significantly (p > 0.05) affected by treatment at soft dough (1082 cP) or mature (1166 cP) stages compared with untreated (1150 cP) controls. Applying glyphosate at the soft dough stage significantly (p < 0.05) reduced the content and solubility of the β-glucan versus untreated samples. β-glucan content and solubility in oat treated at soft dough were 4.35% and 52.1%, respectively, while in untreated samples were 4.65% and 60.6%, respectively. Treatment at soft dough and hard dough stages significantly (p < 0.05) increased weight average molecular weight (M_w) of the high molecular weight fraction of soluble β-glucan (4.4 × 10⁶ and 3.8 × 10⁶, respectively), compared with untreated controls (3.5 × 10⁶). The M_w of the low molecular weight fraction of soluble β-glucan fraction significantly (p < 0.05) increased at soft and hard dough treatments (5.5 × 10⁵ and 3.3 × 10⁵, respectively), versus untreated samples (3.0 × 10⁵). Therefore, glyphosate can be applied when the grain has reached physiological maturity or thereafter.     

Influence of high daytime temperature during the grain filling stage on fissure formation in rice

High daytime temperatures during the grain filling stage in rice have negative impacts on milling quality traits. In this study, we used growth chambers to evaluate the influence of high daytime temperature (33 °C) during grain filling, together with grain moisture content at harvest (26%, 18% and 15%), on grain fissure formation. Varietal susceptibility to fissure formation was also evaluated by exposing grains to high temperature at different grain filling stages (milky, dough, maturing). Two fissure resistant varieties: Cypress (long-grain) and Reiziq (medium-grain) and susceptible varieties: YC53-00-7 (long-grain) and Baru (medium-grain) were compared. The average head rice yield (HRY) of Cypress declined from 62.7% at 25 °C to 53.5% at 33 °C, while Reiziq declined from 56.2% (25 °C) to 47.4% (33 °C). Both were significantly higher than the HRY of YC53-00-7 (39.2% and 24.9%) and Baru (39.3% and 31.7%) at 25 °C and 33 °C, respectively. When grains were drier at harvest (15% cf. 26%) there was a greater reduction in HRY. When the four varieties were exposed to high temperature, the highest average reduction of HRY was recorded at 21 days after heading. It is important to choose an optimal sowing date to avoid coincidence of the final grainfilling stage with high temperatures, in order to minimize milling quality losses.     

Effect of temperature on the life history of Dysmicoccus neobrevipes (Hemiptera: Pseudoccocidae): An invasive species of gray pineapple mealybug in South China

The gray pineapple mealybug, Dysmicoccus neobrevipes Beardsley, is an invasive pest that during recent years has caused serious damage on Sisal (Agave sisalana Perrine) crops in South China. The biology of D. neobrevipes including its development, survivorship, longevity and reproduction was investigated at six constant temperatures (17, 20, 23, 26, 29 and 32 °C) under laboratory conditions. Results indicated that the developmental periods of D. neobrevipes females (from the first instar nymph to adult) shortened from 55.4 days at 17 °C to 16.9 days at 29 °C, while the males' decreased from 54.0 days at 17 °C to 15.8 days at 32 °C. The highest survivorship of D. neobrevipes from the first instar nymph to adult was recorded at 29 °C; 88.8% for females and 89.2% for males. The average longevity of females was 95.0 days at 17 °C, but decreased to 30.0 days at 26 °C. This was still significantly longer than those of males; 5.6 days at 17 °C and 2.3 days at 32 °C. The average number of nymphs laid per female increased with increasing temperature and reached a maximum of 409.4 nymphs at 23 °C. The intrinsic rates of increase (r_m) of D. neobrevipes at the range of temperatures between 17 and 32 °C were 0.0287, 0.0613, 0.0941, 0.1131, 0.1202 and 0.0485, respectively. The lower temperature thresholds for females and males of D. neobrevipes from the 1st instar nymph to adult estimated using the linear model were 8.7 and 10.3 °C, respectively. The thermal constants for females and males were 370.4 and 312.5DD, respectively. The results indicate that temperature has significant effects on the biology of D. neobrevipes and that the optimum temperature range for its population growth is 23–29 °C.     

Effect of temperature on the developmental time,survival of immatures and adult longevity of Aganaspis daci (Hymenoptera: Figitidae), a natural enemy of Ceratitis capitata (Diptera: Tephritidae)

Longevity, developmental time and offspring survival of parasitoid wasps are decisive in their effective performance as biocontrol agents. Optimum temperature range determines parasitoid survival, development and reproduction. Thus, controlling this abiotic factor is a key to the success of pest management programs. Adult longevity, developmental time from egg to adult and survival of immatures of Aganaspis daci were assessed in the laboratory under different constant temperatures; adult longevity without hosts, but with the provision of water and honey, and developmental time and survival of immatures from host pupae, whose larvae had been exposed to parasitoids. Results showed that longevity depended on temperature decreasing in the range 15–20 °C (36 – 25 days), but was lower in the range 25–35 °C (10 – 7 days). Regarding developmental time from egg to adult and survival of immatures, our results showed that 20 and 25 °C are the most suitable temperatures. At 15 and 30 °C mortality of the immature stages was very high (>90%) or developmental time to adult was very slow (>3 months). Immatures did not survive at 35 °C. We found no significant differences in developmental time to adult or survival of immatures between 20 and 25 °C. The sex ratio of parasitoid progeny was female biased at 25 °C; the proportion of females increased at all cases with temperature. The t_o and K for total development were 8.5 °C and 500 DD, respectively. Our findings provide some guidance for future inundative or inoculative field releases of this parasitoid for the management of Ceratitis capitata in Spain.     

Spring air temperature accounts for the bimodal temporal distribution of Septoria tritici epidemics in the winter wheat stands of Luxembourg

Septoria tritici is the causal agent of leaf blotch in wheat and among the most damaging fungal cereal pathogens in the humid regions of central Europe. The percentage of the leaf area colonized by S. tritici was recorded weekly between April and July every season between 2004 and 2010. A total of 11 cultivars with moderate susceptibility [ratings of 4–6 on a 1 (resistant) to 9 (susceptible) scale] were included. The disease level was assessed on the upper three leaf layers at 2 locations between 2004 and 2006 and at 3 locations between 2007 and 2010. The period between sowing and the point of time, when 50% of the leaf area was necrotized due to colonization by S. tritici (T₅₀) was estimated for each year, site, cultivar and leaf layer by non-linear regression. T₅₀ values followed a bimodal distribution with one maximum at 245 days after sowing (DAS; early epidemics) and one maximum at 270 DAS (late epidemics). Early epidemics were preceded by almost constant daily average temperatures of 13.2 ± 0.8 °C between 181 and 210 DAS. Late epidemics were preceded by an approximately linear increase in temperature from 8.7 ± 0.9 to 12.1 ± 0.9 °C during the same period of time. Based on these differences, it seems possible to predict whether an early or a late epidemic can be expected at least 35 days before the epidemic outbreak. Temperature sums calculated with a base temperature of 6.6 °C starting at sowing and ending when T₅₀ was reached were not significantly different between early and late epidemics (P = 0.73) and averaged 1721 ± 49°days. Fungicide applications, which resulted into a delay of the epidemic development similar to the difference between early and late epidemics, resulted in a yield increase between 11.7 and 12.6%.     

Effect of temperature on development,survival and reproduction of the mealybug,Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) on cotton

The effect of temperature on life cycle of the solenopsis mealybug, Phenacoccus solenopsis Tinsley, on cotton (Gossypium hirsutum L.) was assessed under laboratory conditions at ten constant temperatures (18–40 °C). The development duration of female and male nymphal instars linearly decreased with the increase in temperature from 18 to 32 °C. Cumulative developmental time of females ranged from 43.9 d (18 °C) to 15.0 d (32 °C). Survival of crawlers to adulthood was lowest (<53%) at 20 and 36 °C and highest (80%) at 32 °C. The solenopsis mealybug exhibited obligate sexual ovoviviparous reproduction and the pre-oviposition period in mated females showed a significant decreasing trend between 20 °C (23.0 d) and 30 °C (9.5 d). The oviposition period of 10.2–11.5 d at ≥25 °C was nearly half the duration than at 20 °C and the highest fecundity (245 eggs + crawlers) was observed at 30 °C. Longevity of mated females was significantly prolonged at 20 °C (46.0 d) compared to 30 °C (21.4 d). Proportion of females was highest (97.5%) at 25 °C. Males required higher degree-days (363.6) for their cumulative development compared to females (317.5). Lower temperature thresholds estimated from the linear model for cumulative female and male development were 11.7 and 10.1 °C, respectively. The estimated optimum temperature thresholds for nymphal instars (32–33.4 °C) from β type distribution function were closer to the observed maximum developmental rate compared to Lactin-2 model. The population trend index using survival, fecundity, and sex ratio of P. solenopsis with an initial population of 100 crawlers in the Morris-Watt life table model indicated a potential population increase of 170.3 and 97.6 times at 30 and 35 °C, respectively, in the next generation. The usefulness of the information on the temperature-dependent life cycle of P. solenopsis in understanding its field abundance and distribution on cotton and implications for management is discussed.     

Differential sensitivity to temperature of cuphea vegetative and reproductive growth

Cuphea (Cuphea viscosissima Jacq. x C. lanceolata W.T. Aiton; PSR23) is a new oilseed crop rich in medium-chain fatty acids similar to tropical palms. Agronomic studies suggest that temperature is a key determinant of cuphea seed yields. However, little is known about the growth and photosynthesis response of cuphea to temperature. The following study is the first of its kind to evaluate cuphea's growth and photosynthesis response to temperature. Cuphea was grown under day/night temperature regimes of 18/12, 24/18, and 30/24 °C and regression analysis was used to assess its responses of growth and photosynthesis and determine their optimum temperature range. Vegetative growth and leaf photosynthesis adapted well over the temperature range studied. However, reproductive growth was more sensitive showing a decline with increasing temperature. Reproductive growth rate was greatest under the lowest (18/12 °C) temperature treatment and declined by 43% at the highest growth temperatures. In contrast, vegetative growth, which was greatest under the 24/18 °C treatment, declined by just 25 and 10% at the lowest and highest temperatures, respectively. Photosynthesis acclimated to temperature by up-regulation of in vivo Rubisco activity with declining growth temperature. Maximum Rubisco activity (V_cmax) in leaves under the 18/12 °C treatment was 76% greater than that of leaves grown at 30/24 °C. Photosynthetic acclimation permitted cuphea to vegetatively grow well over a wide temperature range, but does not explain the sensitivity of reproductive growth to temperature, which will require further research to elucidate.     

Synergism between potassium sorbate dips and brief exposure to high CO2 or O2 at curing temperature for the control of citrus postharvest green and blue molds

Synergistic effects and very effective control of citrus postharvest green and blue molds, caused by Penicillium digitatum and Penicillium italicum, respectively, were observed on artificially inoculated ‘Valencia’ oranges and ‘Clemenules’ and ‘Ortanique’ mandarins after a potassium sorbate (PS) treatment was followed by 2 days of storage in atmospheres of elevated CO₂ or O₂ at a curing temperature. A combined treatment consisting of 60-s dips in aqueous solutions of 3% PS heated to 62 °C was followed by 48-h exposure to air, 15 kPa CO₂ or 30 kPa O₂ at 33 °C. Control treatment was a 60-s water dip at 20 °C followed by 24-h exposure to air at 20 °C. Synergism was observed on citrus fruit either incubated at 20 °C for up to 22 days, simulating direct commercialization, or stored at 5 °C for up to 45 days, simulating commercial cold storage. This research offers potential new tools to the citrus industry for implementation of nonpolluting integrated postharvest disease management programs, especially devoted to high added value organic markets or export markets with zero residue tolerance.     

Technological quality of field grown transgenic lines of commercial wheat cultivars expressing the 1Ax1 HMW glutenin subunit gene

Ten transgenic lines were studied which expressed a transgene encoding HMW subunit 1Ax1 in three elite spring wheat cultivars: Imp, Canon and Cadenza. These lines contained one to five copies of the transgene and the 1Ax1 subunit was expressed as 1–20% of the total glutenin protein. These lines were grown in field trials in a continental, arid climate (Martonvásár, Hungary) over two years (2004, 2005). The expression of the transgenes and their effects on the grain properties were stably inherited over the two years. Significant differences in yield were observed between three of the transgenic lines and the original genotypes, but no differences were found in their adaptiveness. Clear differences were found in the technological and rheological properties of four lines, with all the parameters characterising dough strength and extensibility (GI, W, G, Re, Ext, A) changing significantly. These differences were associated with increases in the ratio of HMW/LMW subunits and decreases in the ratios of 1Dx/1Dy and 1Bx/1By subunits. Two transgenic lines of cv Imp had high over-expression of the 1Ax1 subunit which in one line resulted in an overstrong type of dough, similar to that described previously for lines over-expressing HMW subunit 1Dx5. Transformation of cvs. Canon and Cadenza resulted in two lines with increased dough stability due to the significantly improved gluten quality. It is concluded that significant changes in the structure of the glutenin polymers caused by the altered ratio of x-type to y-type HMW subunits led to the changes in flour functional properties.