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This work aimed to study the intrinsic tolerance of Greek lentil accessions to imazamox herbicide by combining bioassays, pot and field experiments. Initially, 31 genotypes were evaluated in Petri dish bioassays for their tolerance to six concentrations of imazamox. The average root length of 10 lentil seedlings/dish at seven days after herbicide application was used for non-linear regression analysis and the GR50 values (the amount of the herbicide required for 50% root length reduction of the seedlings) were estimated to calculate the resistance ratio (R/S) of each cultivar. The results of the in vitro test clued the selection of nine accessions for further study in pot experiment, to assess their tolerance to four rates [0 (control), 20, 30, 40 g ai ha-1] of imazamox post-emergently applied at the seven true-leaf stage (V7 stage). Five weeks after treatment, the number of survived plants was recorded and the above-ground dry weight was determined in each pot. There was no direct correlation in the results of in vitro test and the pot experiment, suggesting no matching between the two methods. The evaluation of five accessions (cultivars with high commercial interest and accessions sporting tolerance in pot experiment) in field experiment demonstrated different but increased susceptibility to imazamox. Specifically, compared to the untreated control, the imazamox treatments reduced plant growth, delayed flowering and maturity and reduced yield, dry weight, 1000-seed weight and harvest index. Yet the protein concentration was increased in herbicide treatments. The findings of the study showed clearly that the evaluated lentil accessions lack genes with resistance to imazamox and different methods have to be used for assessing any potential tolerance. [ABSTRACT FROM AUTHOR]

Seven cotton ( Gossypium hirsutum L.) accessions were tested over 2 years under irrigated Mediterranean conditions on a loamy soil with nitrogen (N) as the only nutrient input. The study aimed to identify the critical nutritional and physiological factors determining seedcotton yield and fibre quality. A suite of leaf physiological traits [chlorophyll content (assessed by SPAD), carbon isotope discrimination (Δ), 15N natural abundance (δ15N), leaf water potential, N and C concentrations, C/N ratio, K, Na, Ca and Mg concentrations, their sum and ratios] was assessed, and their interrelationships then analysed. It was found that physiological indices such as SPAD, Δ and δ15N failed to discern genotypes for yield and did not relate with fibre quality traits. At the same time, leaf Ca concentration was the trait that showed the strongest correlation with both seedcotton ( SY) and lint yield ( LY). An increase of K/Na ratio up to 5.74 was beneficial for SY but higher ratios impacted yield adversely. In this line, exclusion of K in favour of Ca (lower K/Ca ratios) increased both SY and LY. The above results could be explained by Ca2+ control over activity of tonoplast and plasma membrane cation channels, resulting in redistribution of K+ between cell compartments. It is suggested that Ca2+-rich plants are more efficient in sequestering higher K+ quantities in leaf vacuoles, at the expense of cytosolic K+. Under K+-limiting conditions, such redistribution may trigger programmed cell death and enhance leaf senescence. This would remobilize and translocate nutrients (e.g. N) and organic substances to sinks (seedcotton), contributing to higher yields reported in the present work. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

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 I (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 Sfl were estimated, respectively, at -0.59 to -053 °C for ΔT, 20.37 to 19.26 μmol m-2S-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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

SUMMARY: Dry bean (Phaseolus vulgaris L.) is a traditional crop of north-western Macedonia, Greece, where two landraces (plaki Prespas and Chrisoupoli) in particular are grown. The aim of this study was to test whether the grain carbon isotope discrimination (Δ) and ash content (ASH) are related to grain yield (GY), protein content (PC) and mean grain weight (MGW) in dry bean. As a part of a honeycomb selection programme, 21 genotypes (19 lines derived via intra-landrace honeycomb selection for single plant yield at low density plus the two original populations) were grown at two densities, 1·2 and 4·8 plants/m2 under non-limiting water conditions in a glasshouse and in the field. Genotypes differed significantly for Δ, ASH and PC under the low density. In the dense stand, genotypes differed significantly only for ASH and PC. The environment (glasshouse or field conditions) affected all the traits significantly. Neither Δ nor ASH showed strong or consistent relationships with GY and thus, they cannot serve as reliable, indirect selection criteria for GY. Strong, negative relationships between Δ and PC were found especially in the dense stand, confirming analogous results in C3 cereals. Inconsistent genotypic ranking for grain physiological traits under the different densities and environments was indicative of large genotype×environment interaction. Genotypes performed consistently for GY and MGW under both densities, showing the strong stability of these traits. [ABSTRACT FROM AUTHOR]

In a 5-year study (2004–2008), the possibility of exploiting intra-cultivar variation in cotton (Gossypium hirsutum L.) was investigated. Honeycomb single-plant selection for seedcotton yield was employed within three cultivars at a low density of 1·15 plants/m2. First- and second-generation progeny lines (1GPLs and 2GPLs) were evaluated for seedcotton yield at low density at three sites, whereas third-generation progeny lines (3GPLs) were tested at the crop density of 10 plants/m2 across two sites and 2 years. Significant differentiation for seedcotton yield was discovered within cultivar (cvar) Christina and cvar Corona at both low and crop densities, and within cvar Flora at low density. In addition, significant intra-cultivar heterogeneity for fibre quality properties was found at crop density. The 1GPLs and 2GPLs grown at low density showed increases in seedcotton yield of 16 and 19%, respectively, in cvar Christina, and of 2·6 and 3·7%, respectively, in cvar Corona. In cvar Flora, the 1GPLs and 2GPLs yielded 10 and 3·3% lower than the mother cultivar, respectively. When grown at standard crop density, across sites and years, 12 and 5·2% higher yield was obtained by the Christina-derived 3GPLs and the Corona-derived 3GPLs, respectively, when compared with the original cultivars. These results provide evidence that elite cultivars are not homogeneous but rather heterogeneous material, within which selections can be made to maintain or improve uniformity and further improve desirable agronomic traits. [ABSTRACT FROM PUBLISHER]

In a three-year (2004-2006), field experiment, we aimed to study changes in leaf physiological traits (leaf water potential-Ѱleaf, 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. Ѱleaf, 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 Ѱleaf 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. [ABSTRACT FROM AUTHOR]

Six successive 15N treatments were applied during the growing season of 1997 to an upland Mediterranean grassland in order to measure the N2-fixation (%Ndfa, the percentage of nitrogen derived from atmosphere) by Trifolium repens. Nitrogen-15 (as (15NH4)2SO4, 12.5% enriched) was injected at two soil depths (5 and 15 cm), in three randomly selected 1m×1m squares for each treatment. %Ndfa was determined by 15N-enriched dilution method using the six most current non-legume species (Poa pratensis L., Lolium perenne L., Festuca valida (Uechtr.) Penzes, T. repens L., Taraxacum officinale Weber ex Wigg, Plantago lanceolata L., Achillea millefolium L.) as reference plants. %Ndfa and the absolute amount of fixed N (Symbiotic N2 Fixed, SNF) were influenced by the reference species, the depth of 15N application and the time of above-ground biomass harvest. Estimations of %Ndfa and SNF were higher when 15N was applied at 15 cm depth. T. officinale as a reference species gave the highest estimations for %Ndfa and SNF by T. repens. Estimations for the two parameters were lower when L. perenne was the reference plant. In general, dicots gave higher and independent from 15N application depth values of %Ndfa and SNF compared to grasses. Dicots seemed to be more suitable as reference species. An increase of %Ndfa with the progress of the growing season was attributed to the exhaustion of soil N with the progress of the growing season since a negative relation was found between the two parameters. %Ndfa was negatively but not significantly related to soil water content at the two soil depths (5 and 15 cm). SNF was mainly determined by the biomass production of T. repens and not by %Ndfa during the growing season and for this reason seasonal patterns of SNF were completely different compared to those of %Ndfa. [Copyright &y& Elsevier]