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Síndos, Greece

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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