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Tsialtas J.T.,Greek National Agricultural Research Foundation | Soulioti E.,Aristotle University of Thessaloniki | Maslaris N.,Agronomic Research Service | Papakosta D.K.,Aristotle University of Thessaloniki
International Journal of Plant Production | Year: 2011

Water stress causes defoliation, which can reduce yield and root quality of sugar beets (Beta vulgaris L.) through altered gas exchange characteristics of the leaves. In a two-year experiment, three sugar beet cultivars (Europa, Rival and Corsica) were subjected to three defoliation levels (control-C, moderate-MD, severe-SD) and re-watering after their exposition to drought for a month. Leaf physiological traits including net photosynthesis (A), transpiration rate (E), stomatal conductance (gs), intracellular CO2 (Ci), water use efficiency (WUEL-A/E and WUEi-A/gs), leaf N concentration, petiole NO3-N concentration, specific leaf area (SLA), leaf water potential (WP) and leaf water content (LWC), were determined before defoliation and 15, 30 and 40 days after defoliation (DAD). On contrary to previous reports, water-stressed cultivars differed significantly in their leaf physiology; the late-season cultivar Corsica had the lowest E and gs values without any significant reduction in A. Thus, Corsica was the most water-conservative cultivar. Re-watering rapidly restored leaf physiology but a gradual decline, with the progress of DAD, was evident for A, E, gs and Ci. After re-growth, cultivars differed only in WP and LWC with Europa, the early-harvested cultivar, to have the highest values. Thus, the better response (higher yield increase and lower root quality degradation) of Corsica to re-watering and the subsequent re-growth, as reported by Tsialtas et al. (2009), could be ascribed to its better LAI maintenance compared to Europa and Rival rather than to a better leaf physiological response. The SD plants showed the highest leaf physiological activity since they had the highest A, E, gs and leaf N concentration. The high leaf activity and the low respiration rate are the means by which sugar beets tolerate foliage losses up to 75% and compensate yield losses after defoliation.


Tsialtas J.T.,Greek National Agricultural Research Foundation | Matsi T.,Aristotle University of Thessaloniki | Maslaris N.,Agronomic Research Service
International Journal of Plant Production | Year: 2010

In a three-year (2004-2006), field experiment, we aimed to study changes in leaf physiological traits (leaf water potential-Ψleaf, leaf water content-LWC, carbon isotope discrimination-Δ, specific leaf area-SLA, chlorophyll content as assessed by SPAD and modified SPAD-MSPAD) and elemental composition (K, Na, Ca, Mg, K/Na, Ca/Mg, total leaf salinity-TLS) of sugar beets (cv. Rizor) grown under Mediterranean, irrigated conditions. Each year, soil moisture content (SMC) and leaf parameters were determined 11 times from early June to the end of October. Growing seasons differed as regards water inputs with 2004 being the driest and 2006 being the wettest. Leaf physiology and chemistry showed plasticity to water availability and significant differences were found between years (except for Ca), sampling time and their interaction. Ψleaf, LWC, Δ, SLA, K/Na and Ca/Mg were positively affected by SMC while the adverse was evident for chlorophyll content (SPAD and MSPAD), Na, Ca, Mg and TLS. As a Chenopodiaceae, sugar beet used leaf succulence, lowering SLA, to cope with water shortage and maintain LWC ca 90%. Low SLA was related with low Ψleaf and Δ values. Succulent leaves were characterized by increased leaf salinity and chlorophyll accumulation, which was ascribed to increased Mg concentrations. Leaf salinity and mainly Na had a negative impact on Δ. Antagonistic effects of K on Na or Mg and synergistic effects of Na on Ca and Mg were recorded.


Maslaris N.,Agronomic Research Service | Tsialtas I.T.,Greek National Agricultural Research Foundation | Ouzounidis T.,Hellenic Sugar Industry
Communications in Soil Science and Plant Analysis | Year: 2010

For 7 years (1997-2003), five nitrogen (N) rates (0, 60, 120, 180, and 240 kg N ha-1) were applied to sugar beets arranged in randomized complete block (RCB) design experiments with six replications and grown on light soils (sand content >50 g kg-1) in northern Greece. The aim of this work was to identify soil characteristics that affect yield, quality, and sugar beet response to N fertilization. Before sowing, soil analyses were conducted in control plots (0 kg N ha-1) at two depths (0-30 and 30-60 cm). Soils differed in their physical and chemical properties and especially in sand content, which ranged from 500 to 732 g kg-1. Quantitative (root number, RN; root yield, RY; and sugar yield, SY) and qualitative (percentage sucrose content in fresh root weight, SC; potassium, K; sodium, Na; and α-amino N) traits of control plots were used as soil fertility index. The RN was positively affected by clay content, and RY and SY were positively related with sand and negatively with silt content. The SC was negatively affected by soil (NO3)-N and sodium (Na) concentrations. Also, soil (NO3)-N concentration was positively related with root impurities (K, Na, α-amino N). In combined data over years, N rates had a negative effect on the RN. The RY was the only trait affected by years, N rates, and their interaction. The SC and SY differed significantly between years, and N rates affected significantly the former but not the latter. In combined data over years, N rates were curvilinearly related with Na concentration in roots, whereas a strong, linear relationship was found between α-amino N concentration and N rates. To study the significant years × N rates interaction evidenced for the RY, the relative response (RR) of the RY to Nwas introduced. Actually, the RR expresses the increase or decrease of the RYfor a 150 kg N ha-1 rate compared to the control (0 kg N ha-1). The RR was strongly related with soil K concentration at the 0- to 30-cm depth (y = -0.00002x2 + 0.0082x + 0.5085, r2 = 0.92, P < 0.01, n = 7) and with total N concentration at the deeper layer (y = 1.8335x2 - 3.5312x + 2.6614, r2 = 0.88, P < 0.05, n = 6). Thus, the RY response to a rate of 150 kg N ha-1, which is the commonly applied to the sugar beet crop in Greece, can be predicted reliably by soil characteristics (K and total N concentration) determined before sowing. The strong relationship between soil K concentration and sugar beet response to N merits further research. © Taylor & Francis Group.


Tsialtas J.T.,Greek National Agricultural Research Foundation | Maslaris N.,Agronomic Research Service
Sugar Tech | Year: 2010

In a two-year (2002-2003) field study, six sugar beet cultivars were arranged in a Randomised Complete Block design with six replications. The aim of the work was to study the root shape variability using an image analysis system and to relate root shape parameters [area (A, cm2), maximum length (L, cm), maximum width (W, cm), average radial (AR, cm), radial variation (RV), circularity (Circ), elongation or the ratio W/L (El) and shape factor (SF)] with yield [fresh root weight (FRW), sugar yield (SY)] and quality [sucrose content % fresh root weight (SC), K, Na, α-amino N]. The main factors (year, site, cultivar) and their interaction had smaller effects on root shape parameters than on yield and its components. Cultivar affected only W but it had a significant impact on all quantitative and qualitative traits. No significant relationship between root W and yield or quality was found for cultivars. Significant, positive relationships between A and FRW or K in roots were found for the year × site × cultivar interaction. SC in roots was related with more rounded roots as revealed by the relationships between SC and Circ or El. Also, rounded roots were related with increased accumulation of K and decreased Na concentrations in sugar beets. © 2010 Society for Sugar Research & Promotion.


Tsialtas J.T.,Aristotle University of Thessaloniki | Maslaris N.,Agronomic Research Service
International Journal of Plant Production | Year: 2013

In a four-year experiment, five nitrogen rates (0, 60, 120, 180 and 240 kg N ha-1) were tested over irrigated sugar beets grown on clays, under Mediterranean conditions, in central Greece. There, sugar beets are commonly grown under water shortages, high temperatures and high soil Na concentrations. Contrary to previous reports, N rates did not affect significantly population density (as assessed by root number at harvest) and sucrose content in fresh and dry root weight (SC and SCD, respectively). Yield response to N was year dependent and only in one out of four seasons, was there a positive effect of N on sugar yield and white sugar yield. In that case, the estimated optimum N dose was high (220 kg N ha-1). Increasing N rates increased significantly N assimilation (as assessed by petiole NO3-N and root α-amino N) and water content in root (WCR) but decreased biomass partitioning to root (lower harvest index). Selective absorption (SA, the preferential uptake of K over Na in roots) decreased with increasing N rates and it was negatively correlated with sugar beet N nutrition indices (petiole NO3-N and root α-amino N). A negative correlation between SA and petiole NO3-N was also evident when data combined over years, indicating that strong Na exclusion was associated with poor N nutrition, a contradiction to previous reports. The higher the SA, the lower the WCR indicating less dilution of sucrose in root and thus, the higher the SC. Moreover, high SA evoked sucrose accumulation in roots as it was shown by its positive correlation with SCD.


Tsialtas J.T.,Aristotle University of Thessaloniki | Maslaris N.,Agronomic Research Service
International Journal of Plant Production | Year: 2012

The aim of this study was to identify leaf physiological traits, which could be used in selecting high yielding genotypes among 12 sugar beet cultivars grown in two contrasting pedo-climatic environments. In the stressful Site 1 (high temperatures, low rainfall, heavy-textured soil), high yielders had cooler leaves (lower ΔT) and thus, transpired (E) and photosynthesized (A) more. Also, these cultivars had higher chlorophyll content, as assessed by SPAD readings, supporting that staying green under stress conditions contributes to final yield. On the contrary, in the favorable Site 2 (mild temperatures, high rainfall, light-textured soil), high yielding cultivars had higher leaf area index (LAI > 3.5-4.0). In Site 2, a negative correlation between SPAD and yields (fresh root weight-FRW and sugar yield-SY) indicated that the investment in high leaf greenness under favorable conditions is a disadvantage for sugar beet productivity. Combining data of both sites, the optimum values of physiological traits related to yields (FRW and SY) were estimated, respectively, at -0.59 to -053 °C for ΔT, 20.37 to 19.26 μmol m -2 s -1 for A and 8.97 to 8.86 mmol m -2s -1 for E. It is proposed the use of SPAD as an easy, rapid and non-destructive screening for sugar beet high yielders under both stressful and favorable growing conditions.


Tsialtas J.T.,Aristotle University of Thessaloniki | Maslaris N.,Agronomic Research Service
Journal of Plant Nutrition | Year: 2012

This work aimed to study whether soil plant analysis development (SPAD) and its modifications (SPAD/SLA, SPAD/N) were sensitive indicators of intra-seasonal nitrogen (N) changes in the soil-root-petiole-leaf continuum in sugar beets. In a three-year, field experiment, 11 occasions of measurement per year took place. Significant intra-seasonal changes of soil [total N, nitrate (NO 3)-N], root (α-amino N), petiole (NO 3-N) and leaf [SPAD,%N, SLA, SPAD/N, SPAD/SLA, specific leaf nitrogen (SLN)] traits were found. SPAD readings failed to predict N status changes in soil and sugar beets. SPAD modifications (SPAD/SLA, SPAD/N) gave significant correlations with root α-amino N (r = -0.80, P < 0.001, n = 33) and petiole NO 3-N (r = -0.53, P < 0.01, n = 33) which are considered as sugar beet N status indicators. SPAD readings adjusted for intra-seasonal, leaf ontogenetic changes as they captured by SLA improved the correlations with the indicators of sugar beet N status and especially with root α-amino N. Also, SPAD/SLA gave a significantly correlation with leaf %N (r = -0.82, P < 0.001, n = 33). © 2012 Copyright Taylor and Francis Group, LLC.


Tsialtas J.T.,Aristotle University of Thessaloniki | Maslaris N.,Agronomic Research Service
Journal of Agricultural Science | Year: 2014

From 1999 to 2006, 36 field experiments were conducted in five sugar beet growing areas in Greece (Larissa, Plati, Serres, Xanthi and Orestiada) to monitor yield. Locations differed significantly regarding thermal variables during the growing season with Xanthi having the most favourable thermal conditions (Tmax, average daily maximum temperature; Tmean, average daily mean temperature; GDD, growing degree days) for sugar beet growth. From early June to the end of the harvesting campaign, successive harvests were conducted. Over the years, fresh root weight and sugar yield at the last harvest of the season (FRWLH, SYLH) did not differ significantly among locations. Also, there were no significant differences among locations regarding GDD for maximum FRW and SY (GDDMFRW, GDDMSY), with the means over location estimated at 2639·9 and 2792·5 °C, respectively. Days after seeding (DAS) necessary for maximum yield (DASMFRW, DASMSY, respectively) differed among locations, with the longest period (DASMFRW 206·4 days, DASMSY: 204·5 days) occurring in the northernmost location (Orestiada). Means for DASMFRW and DASMSY at the five locations were estimated at 190·4 and 188·9·days, respectively. Excluding Xanthi and combining the remaining locations, FRWLH and SYLH were negatively correlated with the average temperatures (Tmean, Tmax and Tmin, daily minimum temperature) over the growing season. The opposite was evident for Xanthi where sugar beet was grown under sub-optimal temperatures. The optimum mean Tmax of the five locations was estimated at 25·5 and 25·1 °C for FRWLH and SYLH, respectively. Elongation of the growing season, by means of early sowing, would increase yield by decreasing average temperatures (Tmean, Tmax) over the growing season in locations with the highest recorded temperatures (Larissa, Plati, Serres and Orestiada). In Xanthi, the projected temperature increase, as a result of climate change, is expected to have a positive effect on yields. Copyright © 2013 Cambridge University Press.


Tsialtas J.T.,Aristotle University of Thessaloniki | Baxevanos D.,Fodder and Pasture Plants Institute | Maslaris N.,Agronomic Research Service
Crop Science | Year: 2014

Across 2 yr and two locations in central Greece, 12 sugar beet (Beta vulgaris L.) cultivars were tested for yield (fresh root weight [FRW], sugar yield [SY], and white sugar yield [WSY]), sucrose content (SC) (% in fresh root weight), and their stability. Cultivar differences in photosynthetic machinery were nondestructively assessed by leaf chlorophyll (soil plant analysis development [SPAD] readings) and leaf area index (LAI) measurements on four occasions during the growing season, within the first week of June, July, August, and September 2004 and 2005. Values over the four measurements conducted during the growing season of the physiological parameters (SPAD value over the four measurements conducted during the growing season [SPADM] and LAI value over the four measurements conducted during the growing season [LAIM]) and measurements of SPAD in June (SPAD1) and LAI in July (LAI2) showed broad-sense heritability similar or even higher than those of yields. Both SPAD1 and LAI2 correlated positively with SPADM and LAIM, respectively, indicating that a single measurement, at a certain time point, might assess cultivar performance over the growing season. Three cultivars (Corsica, Palma, and Creta) performed best among the 12 genotypes, combining the highest WSY and stability as a genotype and genotype × environment biplot analysis depicted. Despite the fact that no relationship between SPAD and yields (FRW, SY, and WSY) or SC was found, cultivars instable in SPAD, as assessed by the Shukla stability variance (σ2 i) (σ2 i of SPAD1 and σ2 i of SPADM), were shown to be the high yielding ones. On the contrary, cultivars with high and stable LAIs (LAI2 and LAIM) had the highest and more stable yields. Under the Mediterranean conditions of this work, where sugar beets suffer successive defoliations and regrowths, cultivars to yield better are those that sustain high LAI canopies with adapting "greenness" to the prevailing environmental conditions. © Crop Science Society of America.

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