White Sugar Yield Research Articles

Evaluation the effect of paclobutrazol on bolting, qualitative and quantitative performance in autumn sown-sugar beet genotypes in Moghan region

The response of sugar beet genotypes to different levels of paclobutrazol was studied during 2013-2014 as a split plot based on randomized complete block design with three replications. Treatments were paclobutrazol application at three levels (0, 150 ppm and 300 ppm) as main plots and sugar beet genotypes at six levels (Eudora, Giada, Jawaher, Levante, Vico and (FC607*474)*Pool-PC.F2-HSF60-P.3) as subplots. Bolting percentage, root yield, sugar content, root K and Na contents, amino nitrogen, molasses sugar percentage, gross sugar yield, extractable sugar yield, alkalinity factor, white sugar yield and extraction coefficient were estimated. Results indicated that bolting percentage, bolting height, sugar content, Na content, alkalinity factor, molasses sugar percentage, extractable sugar, white sugar yield and extraction coefficient were affected by the paclobutrazol levels. Overall, results highlighted the positive effects of paclobutrazol on bolting percentage reduction, content sugar and root quality improvement. A significant difference was found sugar beet genotypes in bolting percentage, root yield and sugar content.

Effect of methanol spraying and seed inoculation with Azospirillumlipoferum on sugar beet performance under deferent regimes of irrigation

The field study was carried out to evaluate the effects methanol concentrations and seed inoculation with Azospirillum in water stress conditions. Experiment was conducted using a randomized complete block design with a split-plot arrangement of treatments and four replications. The first treatment factor was two levels of water stress (based on 40 and 70% depletion of available soil moisture)as the main plots. The second treatment factor was methanol concentrations at three levels (0, 14 and 28 % (v/v) methanol) andthe third treatment factor was the absence and presence of seed inoculation with Azospirillumlipoferum Stain 21 bacteriaas subplots.RY(Root Yield), SC(Sugar content), SY(Sugar Yield), WSY(White Sugar Yield), Na, K and N contents,WSC, molasses sugar, alkalite were verified. Results showed a significant different between different concentrations of methanol on RY, SC, SY, WSY, and N contents. The greatest RY (60.01 ton ha -1 ) was observed in plots with 28 % (v/v) methanol spraying. The maximum WSY was found in 28 % (v/v) methanol treatment, followed by 14 % (v/v) methanol spraying (6.97 and 6.46 ton ha-1, respectively). Results also indicated that RY, SC, SY, WSY, Na, N contents, molasses sugar and alkalite were influenced by different levels of irrigation. Normal irrigation had a higher RY than deficit irrigation, 60.63 vs. 47.64 ton ha -1 . Furthermore, WSY was

Development of Sugar Beet Salt Tolerant Triploid Hybrids

Salinity is a major constraint on crop productivity in arid regions of Iran which decreases sugar beet yield. In order to identify and select salt tolerant triploid hybrids, 20 sugar beet three-way hybrids produced by crosses between 10 salinity improved pollinators and two cytoplasmic male sterile monogerm (231 × 261) and multigerm (MSC2 × A1) lines as seed parents. In 2007–2008 growing seasons, the 20 resulting hybrids along with five check varieties were evaluated in field study using a lattice square (5 × 5) design with three replications, and irrigated with 12 dS m−1 irrigation water. The combined analyses showed that the genotypes differed significantly (P < 0.01) for the most studied traits such as root yield; sugar yield; white sugar yield; sugar content; white sugar content; Na+ content; K+ content; extraction coefficient of sugar and molasses sugar indicating the presence of genetic variation and possibility of selection for sugar beet salinity tolerant lines under saline condition. The mean comparison for yield traits showed that monogerm triploid hybrids (261 × 231) × 19669-T and (261 × 231) × 13030 and multigerm triploid hybrids (MSC2 × A1) × JIT13, (MSC2 × A1) × C3.3, (MSC2 × A1) × 13030 and (MSC2 × A1) × 13022 produced 5.52 t/ha root yield and 1.38 t/ha sugar yield more than the mean of the checks under salinity stress across 2 years. Also, the means of five top hybrids showed 1.52 % sugar content, 1.77 % white sugar content and 3.19 % extraction coefficient of sugar more than the mean of the checks. These hybrids had 0.93 meq/100 gr K+ and 0.81 meq/100 gr Na+ less than the mean of the checks. These promising hybrids are currently being tested in Roudasht Agricultural Research Station as an important step towards development of sugar beet salt tolerant triploid hybrids.

Effect of Combined Application of Different Micronutrients on Productivity and Quality of Sugar Beet Plants (Beta vulgaris L.)

The experiments were conducted throughout two successive winter seasons 2010/2011 and 2011/2012 at Belquas, Dakahlia Governorate, Egypt. The aim of this work was to investigate the effect of foliar application with different micronutrients with excluding one element each treatment and its addition times on the productivity and quality of sugar beet plants. The treatments were six combinations of micronutrients, T0 (spraying with water),T1 (Fe+Zn+Mn+B), T2 (T1-Fe), T3 (T1-Zn), T4 (T1-Mn), T5 (T1-B) and two application times (once after 60 days from sowing or twice after 60 and 90 days from sowing) at 50ppm for each in the form of (Zinc sulphate, Manganese sulphate and Boric acid) and 100ppm in the form of Iron sulphate. Results indicated that, T1 recorded the highest values for yield characters i.e. root, top and sugar yields as well as root weight and dimensions as compared with other treatments followed by T2. Moreover, the results concluded that T1 treatment produced the maximum sucrose %, purity %, recoverable sugar % and white sugar yield followed by T2 in both seasons, this proving that Fe was the least effective microelement on productivity and quality traits of sugar beet. On the other hand, T3 and T4 recorded the lowest values of all yield and yield components and this may be due to the role of Zn and Mn in plant growth as well as their effect as metal components of some enzymes. Furthermore, Zn and B followed by Mn positively affected the impurities content i.e. K, Na and amino N % as well as sucrose loss to molasses, so

Chlorophyll Meter Readings, Leaf Area Index, and Their Stability as Assessments of Yield and Quality in Sugar Beet Cultivars Grown in Two Contrasting Environments

ABSTRACTAcross 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 (σ2i) (σ2i of SPAD1 and σ2i 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.

Assessment of breeding progress in sugar beet by testing old and new varieties under greenhouse and field conditions

Breeding has led to a continuous increase of the performance of sugar beet varieties and thereby contributes to meet the global needs for food and biomass. This study aimed to analyze the extent of the breeding progress in sugar beet and to determine which parameters and traits were modified by breeding. In 2007 and 2008 sugar beet varieties registered between 1964 and 2003 were cultivated in field trials and in greenhouse experiments to exclude effects from changes in agronomic operations and climatic conditions. Differences in white sugar yield related to the reference variety registered in 1964 were regarded as breeding progress. The results showed an increase in the white sugar yield of 0.6–0.9% a−1 from 1964 to 2003 due to breeding. This was achieved by an improved biomass partitioning (higher root to leaf ratio and higher sugar to marc ratio), better technical quality (decreased concentration of K, Na, and amino N combined as standard molasses loss) and enhanced assimilation (higher chlorophyll content, higher assimilation rates). No changes were observed in leaf development and cambium ring formation. A principle component analysis pointed out that breeding targets have shifted with time from “yield” to “biomass quality”. To continue the breeding progress in future it is essential to integrate multiple resistances and tolerances against biotic and abiotic stress.

Effects of Residual Wheat Straw and Nitrogen Fertilizer on Yield and Quality of Sugar Beet in a Semi-Arid Region

The effect of wheat residue and nitrogen fertilizer on the following sugar beet crop was investigated in two successive experiment years. Significant differences were observed in beet and sugar yield by elevating levels of nitrogen application in both experiment years. Different values of straw incorporation had no effect on beet and sugar yield compared to nitrogen-straw interaction treatments. Elevating nitrogen application resulted in significant white sugar yield in both the experiment years. The values of white sugar yields were greatly affected by nitrogen-straw interactions compared to corresponding pure straw treatments, while no significant differences were observed between nitrogen-straw interaction treatments and the corresponding nitrogen application treatments. The polarized sugar per cent and white sugar content were not significantly affected by different levels of straw incorporation, fertilizer N application and nitrogen-straw interaction treatments in both experiment years. The Elevating nitrogen applications resulted in significant increase of molasses sugar. The sugar losses in molasses were not compensated by straw-nitrogen interaction compared to corresponding pure nitrogen application treatments. The α-amino N values in beets were statistically increased by elevating levels of nitrogen fertilizer application, while no significant variations were observed between the straw-nitrogen interaction and the corresponding nitrogen application treatments. The values of Na and K impurities were not increased significantly by elevating applications of nitrogen fertilizer; also straw-nitrogen interaction did not greatly influence the Na and K values compared to corresponding nitrogen fertilizer application.

The soil Na concentration as a background of fertilizer Na recommendation: A case of sugar beet

Sugar beet accumulates a significant amount of Na, which affects both yield of storage root and its technical quality. So far there has not been developed a scientific basis of fertilizer Na recommendation. In order to solve this problem, in 2003 and 2004 series of field trials were carried in commercial farms out to determine the response of sugar beet to Na application. The experiments were established in 20 fields differing in soil Na concentration. Each trial consisted of control (NPK) and a plot with 50 kg Na ha−1 (NPK + Na). Soil samples were collected at two depths (0.0 – 0.3 m and 0.3 – 0.6 m) at spring, before the application of Na. The increase of beet yield (BY) varied from −0.8 to 15.1% compared with the control and averaged at 4.9%. The plants fertilized with Na showed lower sucrose concentration (ca−0.21% fresh matter) and higher root Na concentration (ca +0.65 mM kg−1 fresh matter) compared with the control. The relative increase of white sugar yield (WSY) varied from − 3.5 to 14.1% and was field specific. The effect of Na application on BY and quality depended on the level of plant-available Na. Its impact on WSY was modified by the content of exchangeable K. The highest WSY increase was observed both on Na-poor soils (<6 mg kg−1) and also on soils with K/Na ratio higher than 15–20:1. This study indicates that the diagnosis of plant-available Na content should include both the top- and subsoil. The highest WSY increase resulting from the plant's response to fertilizer Na should be expected on soils with ready-for-use Na content below 60 kg ha−1 within the layer 0.0–0.6 m. In addition, the rate of fertilizer Na for these soils should not exceed 90 kg ha−1.

Nitrogen effects on yield, quality and K/Na selectivity of sugar beets grown on clays under semi-arid, irrigated conditions

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.

Vertical Distribution of Heterodera schachtii under Susceptible, Resistant, or Tolerant Sugar Beet Cultivars.

Heterodera schachtii is managed by rotation with non-hosts, resistant cover crops, and resistant and tolerant sugar beet cultivars. Microplots 60 cm deep and 30 cm in diameter containing steamed field soil were (i) noninfested or infested with 550 H. schachtii eggs per 100 g at (ii) 0 to 60 cm, (iii) 0 to 30 cm or (iv) 30 to 60 cm in depth. Plots were planted to susceptible, resistant, and tolerant sugar beets. Five weeks later, the sugar beet canopy was largest in condition i, smallest in condition ii, and intermediate in conditions iii and iv. White sugar yield (WSY) was highest in condition i, second in condition iv, lowest in condition ii, and intermediate in condition iii. Cultivar-specific final nematode numbers were independent of the level of infestation. In two experiments utilizing 1-m2 microplots, naturally occurring H. schachtii populations were suppressed with fosthiazate at depth layers in reverse to those infested in the first experiment, and planted to susceptible, resistant, and tolerant sugar beets. In one experiment, WSY was highest in soil treated with fosthiazate at 0 to 60 cm in depth, lowest in nontreated, unaffected in soil treated at 30 to 60 cm in depth, and somewhat lower in soil treated at 0 to 30 cm in depth. In all cultivars, early root penetration predicted canopy diameter; only in the susceptible cultivar did the canopy diameter predict WSY. Deep-occurring H. schachtii can impact productivity in sugar beet cropping.

Yield of glyphosate-resistant sugar beets and efficiency of weed management systems with glyphosate and conventional herbicides under German and Polish crop production

In sugar beet production, weed control is one of the most important and most expensive practices to ensure yield. Since glyphosate-resistant sugar beets are not yet approved for cultivation in the EU, little commercial experience exists with these sugar beets in Europe. Experimental field trials were conducted at five environments (Germany, Poland, 2010, 2011) to compare the effects of glyphosate with the effects of conventional weed control programs on the development of weeds, weed control efficiency and yield. The results show that the glyphosate weed control programs compared to the conventional methods decreased not only the number of herbicide applications but equally in magnitude decreased the dosage of active ingredients. The results also showed effective weed control with glyphosate when the weed covering was greater and sugar beets had a later growth stage of four true leaves. Glyphosate-resistant sugar beets applied with the glyphosate herbicide two or three times had an increase in white sugar yield from 4 to 18% in comparison to the high dosage conventional herbicide systems. In summary, under glyphosate management sugar beets can positively contribute to the increasingly demanding requirements regarding efficient sugar beet cultivation and to the demands by society and politics to reduce the use of chemical plant protection products in the environment.

Sequential path analysis of some yield and quality components in sugar beet grown in normal and drought conditions

Through biometrical analyses of yield and its components selection indices can be generated and be used in future breeding programs. Sugar yield components were considered as the first order variables (FOV) in previous path analyses studies, while white sugar yield (WSY) and its related traits were the FOV here. Three lines of sugar beet (7219-P.69, BP-Karaj, 7112) were evaluated in drought and non-drought conditions. Two sequential path models were used for analysis of associations among WSY and its related traits by arraying the various variables in first-, second-, and third-order paths on the basis of their maximum direct effects and minimal collinearity. Four first-order variables, namely root diameter, sugar yield, molasses content and sugar content, revealed highest direct effects on WSY at normal condition, while root length, α-amino-N, root yield, crown dry weight, water use efficiency and Na+ were found to fit as second-order variables. Three first-order variables, namely sugar content, sugar yield and molasses content, revealed highest direct effects on white sugar yield at drought-stress condition. In this case, sugar yield had the highest direct effect on WSY. In general, the sequential path analysis was efficiently demonstrated the effects of predictor variables.

Susceptibility of intercrops to infection with Rhizoctonia solani AG 2‐2 IIIB and influence on subsequently cultivated sugar beet

The susceptibility of intercrop species (Raphanus sativus, Brassica juncea, B. rapa, Sinapis alba and Phacelia tanacetifolia) to the sugar beet pathogen Rhizoctonia solani was investigated in vitro, in the greenhouse and in the field with artificial inoculation. Disease severity in subsequently cultivated sugar beet was monitored in the field. Differences in susceptibility between species were found to be consistent in all experimental systems. All intercrop species were susceptible to R. solani. Brassica rapa and R. sativus were less susceptible than P. tanacetifolia. Compared to fallow, the cultivation of B. rapa and R. sativus reduced disease severity in subsequently grown sugar beet (median ratings of up to 3·0 and 3·5, respectively, depending on environmental conditions). This resulted in higher white sugar yield compared to fallow (up to 210% and 157% for B. rapa and R. sativus, respectively). This study demonstrates that in vitro and greenhouse resistance tests are suitable systems to predict the effects of intercrop species susceptibility in the field on disease severity and white sugar yield in subsequently grown sugar beet. Intercrop breeding programmes might profit from fast and efficient screening tests to provide Rhizoctonia‐resistant intercrops as an additional control measure against R. solani in sugar beet.

Effect of different drip irrigation regimes on sugar beet (Beta vulgaris L.) yield, quality and water use efficiency in Middle Anatolian, Turkey

Agricultural production has forced researchers to focus on increasing water use efficiency by improving either new drought-tolerant plant varieties or water management for arid and semi-arid areas under water shortage conditions. A field study was conducted to determine effects of seasonal deficit irrigation on plant root yield, quality and water use efficiency (WUE) of sugar beet for a 2-year period in the semi-arid region. Irrigations were applied when approximately 50–55% of the usable soil moisture was consumed in the effective rooting depth at the full irrigation (FI) treatment. In deficit irrigation treatments, irrigations were applied at the rates of 75, 50 and 25% of full irrigation treatment on the same day. Irrigation water was applied by a drip irrigation system. Increasing water deficits resulted in a relatively lower root and white sugar yields. The linear relationship between evapotranspiration and root yield was obtained. Similarly, WUE was the highest in DI25 irrigation conditions and the lowest in full irrigation conditions. According to the averaged values of 2 years, yield response factor (ky) was 0.93 for sugar beet. Sugar beet root quality parameters were influenced by drip irrigation levels in both years. The results revealed that irrigation of sugar beet with drip irrigation method at 75% level (DI25) had significant benefits in terms of saved irrigation water and large WUE, indicating a definitive advantage of deficit irrigation under limited water supply conditions. In an economic viewpoint, 25% saving of irrigation water (DI25) caused 6.1% reduction in the net income.

Effect of free air carbon dioxide enrichment combined with two nitrogen levels on growth, yield and yield quality of sugar beet: Evidence for a sink limitation of beet growth under elevated CO 2

The increase in atmospheric CO 2 concentration [CO 2] has been demonstrated to stimulate the growth of C 3 crops. However, little information exists about the effect of elevated [CO 2] on biomass production of sugar beet, and data from field experiments are lacking. In this study, sugar beet was grown within a crop rotation over two rotation cycles (2001, 2004) at present and elevated [CO 2] (375 μl l −1 and 550 μl l −1) in a free air CO 2 enrichment (FACE) system and at two levels of nitrogen supply [high (N2), and 50% of high (N1)], in Braunschweig, Germany. The objective of the present study was to determine the CO 2 effect on seasonal changes of leaf growth and on final biomass and sugar yield. Shading treatment was included to test whether sugar beet growth is sink limited under elevated [CO 2]. CO 2 elevation did not affect leaf number but increased individual leaf size in early summer resulting in a faster row closure under both N levels. In late summer CO 2 enrichment increased the fraction of senescent leaves under high but not low N supply, which contributed to a negative CO 2 effect on leaf area index and canopy chlorophyll content under high N at final harvest. Petioles contained up to 40% water-soluble carbohydrates, which were hardly affected by CO 2 but increased by N supply. More N increased biomass production by 21% and 12% in 2001 and 2004, respectively, while beet and sugar yield was not influenced. Concentration of α-amino N in the beet fresh weight was increased under low N and decreased under high N by CO 2 enrichment. The CO 2 response of total biomass, beet yield and white sugar yield was unaffected by N supply. Averaged over both N levels elevated [CO 2] increased total biomass by 7% and 12% in 2001 and 2004, respectively, and white sugar yield by 12% and 13%. The shading treatment in 2004 prevented the decrease in leaf area index under elevated [CO 2] and high N in September. Moreover, the CO 2 effect on total biomass (24%) and white sugar yield (28%) was doubled as compared to the unshaded conditions. It is concluded that the growth of the storage root of sugar beet is not source but sink limited under elevated [CO 2], which minimizes the potential CO 2 effect on photosynthesis and beet yield.

Maize genotype susceptibility to Rhizoctonia solani and its effect on sugar beet crop rotations

Root and crown rot is the major soil-borne fungal disease in sugar beet. In Europe, the disease is mainly caused by the anastomosis group (AG) 2-2IIIB of the basidiomycete Rhizoctonia solani (Kühn). No chemical fungicide to control the disease has been registered in Europe. Therefore, agronomic measures must be optimized to keep the disease severity below an economic damage threshold and to minimize white sugar yield losses. R. solani AG 2-2IIIB infects many other crops besides sugar beet, including maize, where it causes root rot. Sugar beet and maize are frequently grown in the same crop rotation. The proportion of cultivated maize in several European sugar beet growing areas is expected to rise due to a projected increase in demand for renewable resources over the next few years. Although the susceptibility to and tolerance of the disease varies among cultivars in both crops, little is known about the effects of cultivar susceptibility in the pre-crop on a subsequent susceptible crop. The cultivation of R. solani-resistant maize genotypes in rotation with resistant sugar beet might therefore be a useful tool in an integrated control strategy against R. solani, eliminating the need to restrict the desired crop rotation for phytosanitary reasons. A crop rotation experiment with artificially inoculated R. solani was conducted in the field to investigate the pre-crop effects of maize cultivars which differed in their susceptibility to R. solani on a susceptible sugar beet cultivar. We hypothesized that the maize genotype would influence the inoculum potential and performance of a susceptible sugar beet genotype grown after a maize pre-crop, and that this would correlate with the susceptibility of the maize genotype. The results demonstrate that the susceptibility of maize genotypes is consistent over a period of years and that cultivated maize genotypes influenced the inoculum potential measured as disease severity in sugar beet. However, disease severity in sugar beet did not correlate with the disease susceptibility of the genotype of the maize pre-crop. Possible reasons for this missing relationship might be differences in the quality of maize residues for the saprophytic survival of the pathogen or a genotype-specific alteration of the antagonistic microbial community. However, our findings showed that in the presence of maize- and sugar beet-pathogenic R. solani, the most favourable maize cultivar for a crop rotation cannot be determined solely on the basis of its resistance level against Rhizoctonia root rot.

Variety-specific Epidemiology ofCercospora beticolaSacc. and Consequences for Threshold-based Timing of Fungicide Application in Sugar Beet

In Central Europe, fungicides to control leaf spot disease in sugar beet caused by Cercospora beticola are applied based on thresholds of disease incidence (DI, per cent of infected plants). As variety-specific fungicide application was not analyzed to date, the epidemiology of C. beticola and its effect on white sugar yield (WSY) in varieties with different susceptibility were investigated at seven sites in Germany and Austria in 2004 and 2005. All varieties reached the summary thresholds 5 ⁄ 15 ⁄ 45% DI in all environments. Fitting a logistic growth curve to DI revealed significant differences among varieties. At high disease pressure, susceptible varieties reached a considerably higher disease severity (DS, per cent of infected leaf area) at harvest and a larger area under disease progress curve (AUDPC) than resistant varieties. Fitting a logistic growth curve to DS showed an increasing differentiation among varieties with time. The growth rate estimated based on the logistic growth curve was the only variable that performed equally well in differentiating varieties under low and high disease pressure. With increasing disease pressure, varieties differed considerably in WSY, but differences between susceptible and resistant varieties were significant only in some environments. The disease-loss relation between AUDPC and relative WSY was varietyspecific. Resistant varieties had an approximately identical WSY with and without infection and compensated for negative infection effects even at higher AUDPC. Therefore, at high disease pressure, resistant varieties had a higher relative yield compared to susceptible ones. However, our results indicate that there is no need to develop variety-specific thresholds, but resistant varieties reach the established thresholds later than susceptible ones. Consequently, the time of fungicide application can be delayed in resistant varieties. This will help to reduce the use of fungicides to the bare essentials as requested for the integrated crop protection management.

Soil properties effecting yield formation in sugar beet under ridge and flat cultivation

Field trials were conducted in 2006 and 2007 on a sandy soil (Uelzen county, Lower Saxony, Northern Germany) to examine the influence of soil properties as effected by ridge compared to flat cultivation on the growth of sugar beet. Mean daily soil temperature between sowing (mid-March to mid-April) and May (4–6-leaf-stage) was 7.0 °C in the ridge and 6.1 °C in the flat cultivated soil. In May, total plant dry matter yield (DMY) was 38.7% higher in ridge compared to flat cultivation. Correlation analysis revealed soil temperature as the most important factor effecting early growth. Between May and June (canopy closure), ridge cultivation significantly increased crop growth rate (CGR) like in the period before, but the influence of soil temperature on plant growth diminished and penetration resistance correlated most closely to CGR. In June, DMY increase due to ridge cultivation was 29.7%. During the second half of the growing season, no significant differences in CGR due to cultivation occurred. However, yield was higher in the ridge cultivation treatment until final harvest in October, when white sugar yield (WSY) was increased by 8.4% compared to flat cultivation. It was concluded that the basis of higher final WSY in ridge cultivation was established during early growth until June, primarily caused by warmer soil and growth stimulating soil structure.

Effects of limited irrigation on root yield and quality of sugar beet (Beta vulgaris L.)

This field study was conducted in order to investigate the yield and quality of sugar beet cv zargan in relation to different irrigation regimes during 2005 at Ardabil conditions. The experimental design was a randomized complete block design with four replicates. In this experiment irrigation regimes were I1 = Irrigation at 13.3 F.C (30% F.C), I2b= Irrigation at 15.5 F.C (50% F.C), I3 = Irrigation at 17.7 F.C (70% F.C) and I4 = Irrigation at 19.9 F.C (90% F.C). Parameters such as root yield (t/ha), leaf yield (t/ha), sugar content (%), Molasses (%), pure sugar content (%), white sugar yield (t/ha), Na (mmol/100 g root), K (mmol/100 g root) were evaluated. Irrigation treatments had a significant effect on sugar yield and its quality. Potassium concentration was not significantly affected by irrigation treatments. Results of irrigation treatments showed that the optimum soil water content for root yield is 70% of field capacity with 78.5 t/ha. The minimum root yield (52.5 t/ha) was observed at 90% of field capacity. Irrigation at 30, 50 and 70% of field capacity (I1, I2 and I3) had same effect on sugar content while sugar content decreased at 90% field capacity (I4). When the available soil water content was at 70% of field capacity, maximum root yield and quality was observed. Key word: Beta vulgaris, irrigation, root yield, sugar quality.

Development of a field biotest using artificial inoculation to evaluate resistance and yield effects in sugar beet cultivars against Cercospora beticola

Cercospora beticola resistance and disease yield loss relationships in sugar beet cultivars are best characterised under field conditions with heavy natural infection; this does not occur regularly under German climatic conditions. Since Cercospora resistance reduces the rate of pathogen development, high yield loss was observed in studies using artificial inoculation. Our study, therefore aimed to optimise inoculum density to obtain cultivar differentiation, which correlates to natural infection. In 2005 and 2006, field trials were carried out to determine the effect of different inoculum densities on Cercospora resistance of three sugar beet cultivars possessing variable resistance. The epidemic progress and white sugar yield loss (WSYloss) were determined and their relationship evaluated. An optimal inoculum concentration range (between 10,000–20,000 infectious Cercospora units ml−1 inoculum suspension) was determined which allowed maximum resistance parameter differentiation in terms of C. beticola disease severity (DS), area under the disease progress curve (AUDPC) and WSYloss. The correlation between AUDPC and WSYloss was identical for all cultivars independent of the resistance level, demonstrating that tolerant reactions of the cultivars under study were not detectable. This study provides evidence that even under optimal inoculum levels necessary to obtain maximum differentiation between cultivars, climatic conditions are important for disease management, but remain unpredictable, indicating that artificial inoculation needs to be optimised, but that single field locations are not sufficient and reliable to evaluate Cercospora resistance.