Hyperspectral remote sensing of yellow mosaic severity and associated pigment losses in Vigna mungo using multinomial logistic regression models

Yellow mosaic disease (YMD) has been a serious threat to blackgram cultivation especially during post-monsoon season. Visual assessment of disease severity is qualitative and time consuming. Rapid and non-destructive estimation of YMD by hyperspectral remote sensing has not been attempted so far on any of its hosts. Field studies were conducted for two seasons with eight blackgram genotypes having differential response to YMD. Comparison of mean reflectance spectra of the healthy and YMD infested leaves showed changes in all the broad band regions. However, reflectance sensitivity analysis of the narrow-band hyperspectral data revealed a sharp increase in reflectance from the diseased leaves compare to healthy at 669 (red), 505 and 510 nm (blue). ANOVA showed a significant decrease in leaf chlorophyll (p < 0.0001) with increase in disease severity, while no such relationship was observed for relative water content. By plotting coefficients of determination (R²) between leaf chlorophyll and percent reflectance at one nm wavelength interval, two individual bands (R₅₇₁; R₇₀₅) and two band ratios (R₅₇₁/R₇₂₁; R₇₀₅/R₅₉₃) with highest R² values were selected. These bands showed a significant linear relationship with SPAD chlorophyll readings (R² range 0.781–0.814) and spectrometric estimates of total chlorophyll content (R² range 0.477–0.565). Further, the relationship was stronger for band ratios compared to single bands. With optimal spectral reflectance ratios as inputs, disease prediction models were built using multinomial logistic regression (MLR) technique. Based on model fit statistics, reflectance ratios R₅₇₁/R₇₂₁ and R₇₀₅/R₅₉₃ were found better than the individual bands R₅₇₁ and R₇₀₅. Validation of MLR models using an independent test data set showed that the overall percentage of correct classification of the plant into one of the diseased categories was essentially same for both the ratios (68.75%). However, the MLR model using R₇₀₅/R₅₉₃ as dependent variable was of greater accuracy as it gave lower values of standard errors for slopes (β_G range 9.79–36.73) and highly significant estimates of intercept and slope (p < 0.05). Thus the models developed in this study have potential use for rapid and non-destructive estimation of leaf chlorophyll and yellow mosaic disease severity in blackgram.     

Elongation rate of sorghum leaves has a common response to meristem temperature in diverse African and European environmental conditions

We have tested whether thermal time can account for the effect of meristem temperature on leaf appearance rate (LAR) and leaf elongation rate (LER) of sorghum in a wide range of conditions without water or nutrient deficits. This requires that responses to temperature should be consistent in different locations and different seasons, and that responses of LER of different leaves of the plant should be similar. Sorghum plants (Sorghum bicolor (L.) Moench., cv. E-35-1) were sown in the field in Bamako (Mali) from October 1995 to August 1996, in Montpellier (France) in summers 1995 and 1997, and in a growth chamber. Irradiance, air and meristem temperatures (T_m) and air humidity were measured together with LER in all experiments. Unique and tight relationships were observed between T_m and LER of leaves located at different positions on the stem, for all experimental conditions when evaporative demand was low (meristem-to-air vapor pressure deficit, VPD_ma, lower than 2.5 kPa). Relationships remained linear over the whole studied range of T_m, i.e. 13–32°C (R², from 0.7 to 0.87). With high evaporative demand, LER was lower than the LER expected at the same temperature but with low VPD_ma (LER_reg); the normalized difference between LER measured on a given day (LER_a) and LER_reg was linearly related to VPD_ma (R²=0.52). A linear relationship was also observed between T_m and LAR measured before the beginning of stem elongation when T_m was lower than 27°C. The x-intercepts of relationships between T_m and LER or LAR did not differ in a covariance analysis, with a common value of 10.8°C. The use of thermal time without corrections for high temperature or photoperiod was the most appropriate way to account for the timing of leaf development. It allowed prediction of LER provided that the reduction in LER due to evaporative demand was taken into account.     

An acute case of intoxication with cyanobacteria and cyanotoxins in recreational water in Salto Grande Dam, Argentina

Cyanobacterial blooms and hepatotoxic microcystins (MCs) usually occur in summer, constituting a sanitary and environmental problem in Salto Grande Dam, Argentina. Water sports and recreational activities take place in summer in this lake. We reported an acute case of cyanobacterial poisoning in Salto Grande dam, Argentina, which occurred in January 2007. Accidentally, a young man was immersed in an intense bloom of Microcystis spp. A level of 48.6 μg·L(-1) of microcystin-LR was detected in water samples. Four hours after exposure, the patient showed nausea, abdominal pain and fever. Three days later, dyspnea and respiratory distress were reported. The patient was hospitalized in intensive care and diagnosed with an atypical pneumonia. Finally, a week after the exposure, the patient developed a hepatotoxicosis with a significant increase of hepatic damage biomarkers (ALT, AST and γGT). Complete recovery took place within 20 days. This is the first study to show an acute intoxication with microcystin-producing cyanobacteria blooms in recreational water.     

Determination of thermal and retrogradation properties of rice starch using near-infrared spectroscopy

Starch is a major component of rice grain and thus plays an important role in grain quality. For breeding rice with improved quality, the thermal and retrogradation properties of starch may be routinely measured. Since direct measurement is time-consuming and expensive, rapid predictive methods based on near-infrared spectroscopy (NIRS) can be applied to measure these quality parameters. In this study, calibration models for measurement of thermal and retrogradation properties were built from the spectra of grain and flour samples. The results indicated that both grain and flour spectra could give similar accuracy (r²=∼0.78) in determining the peak temperature (T_p) and conclusion temperature (T_c) of gelatinization. However, flour spectra (r²=0.80) were superior to the grain spectra (r²=0.73) in measuring onset temperature (T_o). Furthermore, the thermal properties of width at half peak height (ΔT_1/2) and enthalpy of gelatinization (ΔH_g), and retrogradation properties of enthalpy of retrogradation (ΔH_r) and retrogradation percentage (R%) could only be successfully modeled with the flour spectra. The models reported in the present study are usable for routine screening of a large number of samples in early generation of selection in breeding programs. For accurate assay of the thermal and retrogradation properties, however, direct instrumental measurement should be employed in later generations.     

Decadal and Monthly Change of an Empirical Coefficient in the Relation between Solar Radiation and the Daily Range of Temperature in Japan: Implications for the Estimation of Solar Radiation Based on Temperature

Abstract: The need for solar radiation (R_s, MJ m^–2 d^–1) estimation remains a common concern for agronomists. Evaluation of crop productivity is primarily based on R_s data, which are difficult to collect because of cost and calibration requirements. Generally, historical R_s data are more difficult to obtain. This study focused on an estimation model based on the daily range of temperature and evaluated its accuracy from the viewpoint of crop productivity analysis. The variability of an empirical coefficient in the model (K_rs), which was derived from the relation between R_s and daily range of temperature (T_max – T_min) was analyzed using climatic data observed in Japan considering data availability and quality. K_rs had significant monthly differences, and it significantly increased from 1981 – 1985 to 2003 – 2007 at all 10 locations. Period-month interactions were not significant, except for in Utsunomiya, suggesting that the seasonal pattern did not change during the period. Weather data indicated that the increase in K_rs was caused not only by increased solar radiation but also by a decrease in T_max – T_min. The substantial differences in K_rs produced considerable bias for the estimated R_s when the estimation was conducted with a constant K_rs (0.16). Despite the bias, the model is considered to perform well given the present availability of R_s data. The results of this study suggest that the evaluation of the seasonal pattern of K_rs greatly improves the model accuracy.     

Effects of Temperature,Solar Radiation,and Vapor-Pressure Deficit on Flower Opening Time in Rice

Abstract

Flower opening in the early morning helps to avoid sterility of rice (Oryza sativa L.) caused by heat stress at anthesis. Although flower opening time (FOT) is under genetic control, it is also affected by weather, particularly by air temperature (T_a). However, the effects of T_a, solar radiation (R_s), and vapor-pressure deficit (VPD) on rice FOT are unclear, making it difficult to predict FOT. Therefore, we investigated the correlation of FOT with T_a, R_s, and VPD during various periods before anthesis under field conditions. By photographing spikelets at 10-min intervals, we determined the FOT of five cultivars. To evaluate the individual effects of cultivar, T_a, R_s, and VPD on FOT, we constructed general linear models (GLMs) and calculated mean T_a, R _s, and VPD every 3 hr from 0000 to 1200. The GLMs revealed that the average T_a, R_s, and VPD between 0600 and 0900 significantly affected FOT (adjusted R ² =0.399; P <0.001). The standardized partial regression coefficients of T_a and R_s were negative and those of VPD were positive, indicating that higher T_a, higher R_s, and lower VPD in the early morning result in earlier FOT. Moreover, multiple-regression analysis showed that the period affecting FOT the most, and the relative contributions of T_a, R_s, and VPD to FOT differ with the cultivar.     

Early development and enlargement of wheat floret primordia suggest a role of partitioning within spike to grain set

Spike grain number, a major component in the yield of wheat, is suspected of being determined by the sudden death of most of the initiated floret primordia, which occurs at around booting. By counting twice weekly the number of floret primordia in the middle and top spikelets, the onset time for the death of floret primordia (T_d) was assessed in six genotypes of differing earliness and fertility subjected to three treatments that were applied during stem elongation. The variation in T_d was positively correlated with overall earliness, as well as with spike fertility. Ovary development and enlargement were quantified in eight specified positions within the spikes, but T_d could not be assigned to a developmental stage attained by any ovary. Development and enlargement were very strongly correlated with each other throughout the floret lifetime, yet with significant effects of genotype, treatment and position within spikes. In each position within a spike, the proportion of florets that set a grain correlated to the initial delay of development as compared to the most advanced floret (r² = 0.64), but this correlation was severely biased by genotype and the floret position effect. Better correlations were obtained with either the development or width of each ovary at T_d, thus highlighting the role of the preceding phase. The best prediction (r² = 0.93) was obtained from the ratio of ovary width to that of the most advanced floret at T_d. The importance of this width ratio emphasized the role of partitioning in grain set: only florets able to divert nutrients survived after T_d and eventually set a grain. This relationship was no longer biased by floret position, while some remaining variability due to genotype suggested potential for plant breeding: width ratios at T_d were generally related to the growth duration of various primordia, as well as to their relative growth rate.     

High Levels of Structural Diversity Observed in Microcystins from Microcystis CAWBG11 and Characterization of Six New Microcystin Congeners

Microcystins (MCs) are cyclic peptides produced by cyanobacteria, which can be harmful to humans and animals when ingested. Differences in the coding of the non-ribosomal peptide synthetase/polyketide synthase enzyme complex responsible for microcystin production have resulted in more than 100 microcystin variants being reported to date. The microcystin diversity of Microcystis CAWBG11 was investigated using matrix-assisted laser desorption/ionization-time of flight mass spectrometry and liquid chromatography-mass spectrometry. This revealed that CAWBG11 simultaneously produced 21 known microcystins and six new congeners: [Asp³] MC-RA, [Asp³] MC-RAba, [Asp³] MC-FA, [Asp³] MC-WA, MC-FAba and MC-FL. The new congeners were putatively characterized by tandem mass spectrometry and chemical derivatization. A survey of the microcystin congeners produced by 49 cyanobacterial strains documented in scientific literature showed that cyanobacteria generally produce four microcystin congeners, but strains which produce up to 47 microcystin congeners have been reported. Microcystis CAWBG11 (which produces at least 27 congeners) was positioned in the top ten percentile of the strains surveyed, and showed fluidity of the amino acids incorporated into both position two and position four.     

Molecular basis of the gelatinisation and swelling characteristics of waxy barley starches grown in the same location during the same season. Part II. Crystallinity and gelatinisation characteristics

Nine waxy barley samples (grown at the same site during the same season) were investigated to identify those molecular aspects of amylopectin structure and architecture which define the order and gelatinisation characteristics. Using ¹³C CP-MAS/NMR it was confirmed that the number of double helices within the starches were approximately constant although differences in crystallinity were identified by X-ray diffraction. These differences in terms of amount of crystalline order correlated well with gelatinisation temperatures. The onset (T_o), peak (T_p) and conclusion (T_c) gelatinisation temperatures were 53.4, 59.2 and 68.1 °C on average with the associated enthalpy (ΔH) of 11.0 and 13.5 J g⁻¹ on a starch and amylopectin basis. Annealing of the starches below T_o elevated T_o, T_p and T_c by +11.9, +8.2 and +5.1 °C on average and sharpened the gelatinisation range (T_c−T_o). Acid hydrolysis after annealing increased T_o, T_p and T_c (especially T_c) by +2.3, +17.4 and +34.7 °C on average. Annealing in the presence of α-amylase elevated similarly the gelatinisation parameters by +10.2, +7.1 and +2.8 °C for T_o, T_p and T_c, respectively. Crystalline lamellae lengths were found to be 5.2±0.7 and 6.2±0.4 nm using high sensitivity differential scanning micro-calorimetry and differential scanning calorimetry, respectively.     

Modelling density thresholds for managing mouse damage to maturing wheat

Predator-prey theory suggests that pest damage that occurs over a period of time is related to the initial pest density and their functional and numerical responses to the resource. Estimating the relationship between damage and initial density is therefore fundamental to determining the threshold density (D_T), above which the economic benefits of control exceed the economic costs of control. A manipulative experiment was conducted to parameterize a model of D_T for managing yield loss (YL) caused by mice (Mus domesticus L.) from the milky stage to harvest, by assessing the relationship between YL and initial mouse density at the milky stage (D_I). This relationship subsumed the functional and numerical response of mice to maturing wheat crops. The experiment was conducted in a typical wheat field and D_I was manipulated by releasing a known number of mice into an experimental crop enclosed by a mouse proofed fence. The estimated relationship was asymptotic exponential: YL increased almost linearly with D_I until apparent competition between mice occurred at densities in excess of about 500 mice ha⁻¹; and apparent competition limited further increases in YL at densities in excess of 2133 mice ha⁻¹. D_T varied depending on the effectiveness of the control method in reducing D_I and the cost of control as a percentage of the farm-gate value of wheat. D_T was 89 mice ha⁻¹ for triggering aerial baiting if this method was effective in reducing D_I by 41% and if the cost of baiting was 7.54% of farm-gate value of wheat. Grain growers will be able to use D_I immediately to make informed, timely decisions for managing mouse damage to wheat crops. Mouse densities should be monitored well before the milky stage so that D_I can be forecast by the trend of monitored densities. If the forecast D_I exceeds D_T, management should be implemented at least a week before the milky stage (allowing a week for control such as baiting to take effect). However, if the forecast D_I is much higher than D_T so that even after control the reduced D_I would still be higher than D_T, then additional control may be applied so that the final control applied a week before the milky stage would reduce D_I below D_T.     

Characterizing leaf gas exchange responses of cotton to full and limited irrigation conditions

Plant responses to water deficit need to be monitored for producing a profitable crop as water deficit is a major constraint on crop yield. The objective of this study was to evaluate physiological responses of cotton (Gossypium hirsutum) to various environmental conditions under limited water availability using commercially available varieties grown in South Texas. Soil moisture and variables of leaf gas exchange were measured to monitor water deficit for various varieties under different irrigation treatments. Lint yield and growth variables were also measured and correlations among growth parameters of interest were investigated. Significant differences were found in soil moisture, leaf net assimilation (A_n), stomatal conductance (g), transpiration rate (T_r), and instantaneous water use efficiency (WUE_i) among irrigation treatments in 2006 while no significant differences were found in these parameters in 2007. Some leaf gas exchange parameters, e.g., T_r, and leaf temperature (T_L) have strong correlations with A_n and g. A_n and WUE were increased by 30–35% and 30–40%, respectively, at 600 μmol (CO₂) m⁻² s⁻¹ in comparison with 400 μmol (CO₂) m⁻² s⁻¹. Lint yield was strongly correlated with g, T_r, WUE, and soil moisture at 60 cm depth. Relative A_n, T_r, and T_L started to decrease from FTSW 0.3 at 60 cm and FTSW 0.2 at 40 cm. The results demonstrate that plant water status under limited irrigation management can be qualitatively monitored using the measures of soil moisture as well as leaf gas exchange, which in turn can be useful for describing yield reduction due to water deficit. We found that using normalized A_n, T_r, and T_L is feasible to quantify plant water deficit.     

Influence of rate of development of water deficit on the expression of maximum osmotic adjustment and desiccation tolerance in three grain sorghum lines

An experiment was conducted to quantify the effect of rate of development of water deficit (R_ψ) on the expression of maximum osmotic adjustment (OA) and desiccation tolerance (DT) in three grain sorghum lines, TAM422, Tx2813 and QL27. DT was determined as the lethal relative water content (RWC^L) and lethal leaf water potential (ψ^L) of leaves, i.e. the value of these traits just prior to tissue death. Five rates of development of water deficit were generated by using different soil volumes in which the decrease in leaf water potential ranged from 0.093 MPa day⁻¹ to 0.153 MPa day⁻¹. The expression of maximum OA increased markedly with a reduced R_ψ, for all three lines. In contrast, DT decreased only slightly with a reduced R_ψ. The three lines differed for expression of maximum OA and DT. Both TAM422 and Tx2813 had higher maximum OA, higher RWC^L and lower ψ^L than QL27. There was a significant line-by-R_ψ interaction for the expression of OA and DT. The interaction was much smaller than the effect of lines for the expression of maximum OA. Therefore, the absolute level of OA for the three sorghum lines and the magnitude of the difference between them changed with the R_ψ without affecting their ranking. As with maximum OA, the interaction for RWC^L was smaller than the line effect. The RWC^L of TAM422 and QL27 was stable across rates of development of water deficit. The results indicated that low R_ψ increased the expression of OA and decreased ψ^L but had little effect on RWC^L. While line-by-soil-volume interactions were observed, these were largely explained by the increase in magnitude of the variation for the traits as R_ψ decreased and were not the result of changes in rank of the lines among soil volumes. Therefore, the current screening strategy is considered to be appropriate for examining genetic variation for OA and DT in grain sorghum. Opportunities exist for using smaller pots and soil volumes where large numbers of genotypes are examined.     

Foliar resistance to late blight in potato clones evaluated in national trials in 1997

Changes in the oomycetePhytophthora infestans in the United States and other parts of the world pose a significant threat to potato production. A continual evaluation of potato clones for resistance to late blight is necessary to identify clones with resistance and to monitor the stability of resistance in light of the emergence of new and more aggressive strains of this pathogen. Twentytwo potato clones (10 cultivars and 12 selections) were evaluated in 1997 for late blight resistance at seven U.S. locations. Seven late blight differentials (R₁R₂R₃R₄, R₁R₂R₄, R₁R₃R₄ R₃, R₈ R₁₀, and R_multi) were also included in the test at five of these locations. The US-8 strain of P.infestans was present at all locations. Percent infected foliage was recorded at approximately weekly intervals following the onset of disease. Area under the disease progress curve (AUDPC) was calculated. The nonparametric stability statistics mean absolute rank differences (S _i ⁽¹⁾ ) and variances of the ranks (S _i ⁽²⁾ ) were used to analyze phenotypic stability. Although neither of these statistics was significant for individual clones, both of these statistics were significant when summed over clones, indicating the importance of genotype × environment interactions on the rankings of these clones across locations. The most late blight-resistant and susceptible clones were the most stable; clones in the intermediate ranges were most subject to rank changes due to genotype × environment interactions. The most late blight-resistant clones were AWN86514-2, B0692-4, B0718-3, and B0767-2. The most susceptible clones were B0811-13, B1004-8, Nor-Donna, and Krantz. AUDPC was very low for the late blight differentials R₈ and R_multi, moderately low for R₁₀ and very high for the remaining differentials. This study is important in characterizing the reaction of potato clones to new strains of P.infestans.     

Assessing newly developed and published vegetation indices for estimating rice leaf nitrogen concentration with ground- and space-based hyperspectral reflectance

Non-destructive and quick assessment of leaf nitrogen (N) status is important for dynamic management of nitrogen nutrition and productivity forecast in crop production. This research was undertaken to make a systematic analysis on the quantitative relationship of leaf nitrogen concentrations (LNCs) to different hyperspectral vegetation indices with multiple field experiments under varied nitrogen rates and varied types in rice (Oryza sativa L.). The results showed that some published indices had good relations with LNC such as two-band indices, R₇₅₀/R₇₁₀ (ZM), Gitelson and Merzlyak index two (GM-2), R₇₃₅/R₇₂₀ (RI-1dB), R₇₃₈/R₇₂₀ (RI-2dB) and the normalized difference red edge index (NDRE), three-band indices, adjusted normalized index 705 (mND705), physiological reflectance index c (PRI_c), terrestrial chlorophyll index (MTCI), and red edge position derived with four point linear interpolation (REP_LI). Three-band indices performed better than two-band indices, with MTCI exhibiting the best logarithmic relation to LNC in rice. Then, hyper-spectral vegetation indices computed with random two bands (λ₁ and λ₂) from 400 to 2500 nm range were related to LNC of rice. The results indicated that two-band indices combined with bands of 550–600 nm and 500–550 nm in green region had good relationships with LNC, and simple ratio index SR(533,565) performed the best in all two-band indices, similar to the published three-band indices (mND705, PRI_c and MTCI). New three-band indices R₄₃₄/(R₄₉₆ + R₄₀₁) and R₇₀₅/(R₇₁₇ + R₄₉₁) were proposed for prediction of LNC with improved ability over the SR(533,565) and published spectral indices. Moreover, R₇₀₅/(R₇₁₇ + R₄₉₁) performed well in all the data from ground spectra, modeled AVIRIS and Hyperion spectra, and acquired Hyperion image hyperspectra. The R₄₃₄/(R₄₉₆ + R₄₀₁) also exhibited well in both ground and modeled AVIRIS and Hyperion image spectra, but could not be tested with the acquired Hyperion image because of the absence in radiometric calibration of the bands less than 416 nm. Overall, the newly developed three-band spectral index R₇₀₅/(R₇₁₇ + R₄₉₁) should be a good indicator of LNC at ground and space scales in rice. Yet, these new indices still need to be tested with more remote sensors based on ground, airborne and spaceborne, and verified widely in other ecological locations involving different cultivars and production systems.     

Effect of neemarin on life table indices of Plutella xylostella (L.)

The effects of neemarin at 5, 10, 15 and 20 mg l⁻¹ on the life table indices of Plutella xylostella (L.) were studied on cauliflower in the laboratory. Survivorship was increased with increasing concentrations. A total of 69% eggs hatched at 20 mg l⁻¹ compared 85% in the control. Mortality (d_x) of 1st instars was higher than the other instars in both exposed and unexposed individuals. Life expectancy (e_x) was high in the untreated control and reduced at 20 mg l⁻¹. Development times of immatures were prolonged to 32 days at 20 mg l⁻¹ as compared to 18.6 days in the untreated control. Neemarin significantly reduced the emergence of adults. Potential fecundity (P_f) was 34 females/female/generation at 20 mg l⁻¹ and 92 in the control. The net reproductive rate (R₀) was significantly reduced with the increase in concentration. The intrinsic rate of increase (r_m) and finite rate of increase (λ) were significantly decreased at 20 mg l⁻¹ as compared to other concentrations tested and in the control. Mean generation time (T_c) and corrected generation time (τ) were prolonged at 20 mg l⁻¹ and significantly differed to those of the untreated control. Doubling time (DT) was significantly extended to 28.4 days at 20 mg l⁻¹ as compared to 6.1 days in the control.     

Thermal requirements for barley maturation and leaf development in interior Alaska

Spring barley (Hordeum vulgare L.) is well adapted to the cool and short growing season of interior Alaska but little is known about thermal requirements for development and maturation of barley at such latitudes. Air temperature and barley development were monitored over the course of six growing seasons at Fairbanks (65°N) and Delta Junction (64°N), Alaska. These data were used to assess the base temperature (T_b) in the linear, thermal-unit model using the least variable, x-intercept, and regression coefficient methods. These methods indicated a range in T_b from 0°C to 1.5°C. At a T_b of 0°C, barley required nearly 1100°C d to mature. The phyllochron differed between early and late sowings and averaged 75°C d leaf⁻¹. Sowing date appeared to influence the phyllochron during early vegetative growth due to differences in daylength as well as temperature.     

Cyanobacterial Toxic and Bioactive Peptides in Freshwater Bodies of Greece: Concentrations,Occurrence Patterns,and Implications for Human Health

Cyanobacterial harmful algal blooms represent one of the most conspicuous waterborne microbial hazards in aquatic environments mostly due to the production of toxic secondary metabolites, mainly microcystins (MCs). Other bioactive peptides are frequently found in cyanobacterial blooms, yet their concentration and ecological relevance is still unknown. In this paper we studied the presence and concentration of cyanobacterial peptides (microcystins, anabaenopeptins, anabaenopeptilides) in 36 Greek freshwater bodies, using HPLC-DAD, ELISA, and PP1IA. Microcystins were found in more than 90% of the samples investigated, indicating that microcystin-producing strains seem to also occur in lakes without blooms. Microcystins MC-RR, MC-LR, and MC-YR were the main toxin constituents of the bloom samples. Anabaenopeptin A and B were predominant in some samples, whereas anabaenopeptolide 90A was the only peptide found in Lake Mikri Prespa. The intracellular concentrations of anabaenopeptins produced by cyanobacterial bloom populations are determined for the first time in this study; the high (>1000 µg·L⁻¹) anabaenopeptin concentration found indicates there may be some impacts, at least on the ecology and the food web structure of the aquatic ecosystems. The maximum intracellular MC values measured in Lakes Kastoria and Pamvotis, exceeding 10,000 µg·L⁻¹, are among the highest reported.     

Artificial Diet Influences Population Growth of the Root Maggot Bradysia impatiens (Diptera: Sciaridae)

In order to investigate the effects of artificial diets on the population growth of root maggot Bradysia impatiens, its population growth parameters were assayed on eight artificial diets (Diet 1, D2, D3, D4, D5, D6, D7, and D8). Results showed that developmental duration from egg to pupa was successfully completed on all eight artificial diets. However, the egg to pupal duration was shortest, while the survival rate of four insect stages was lowest when B. impatiens was reared on D1. When B. impatiens was reared on D7 and D8, the survival rate, female longevity, and female oviposition were higher than those reared on other diets. When B. impatiens was reared on D7, the intrinsic rate of increase (r_m = 0.19/d), net reproductive rate (R₀ = 39.88 offspring per individual), and finite rate of increase (λ = 1.21/d) were higher for its population growth with shorter generation time (T = 19.49 d) and doubling time (Dt = 3.67 d). The findings indicate that the D7 artificial diet is more appropriate for the biological parameters of B. impatiens and can be used an indoor breeding food for population expansion as well as further research. We propose that vitamin C supplement added to the D7 is critical for the improvement of the B. impatiens growth.     

Relationship between P and N concentrations in maize and wheat leaves

Simple plant-based diagnostic tools can be used to determine crop P status. Our objectives were to establish the relationships between P and N concentrations of the uppermost collared leaf (P_L and N_L) of spring wheat (Triticum aestivum L.) and maize (Zea mays L.) during the growing season and, in particular, to determine the critical leaf P concentrations required to diagnose P deficiencies. Various N applications were evaluated over six site-years for wheat and eight site-years for maize (2004-2006) with adequate soil P for growth. Phosphorus and N concentrations of the uppermost collared leaf were determined weekly and the relationships between leaf N and P concentrations were established using only the sampling dates from the stem elongation stage for wheat and from the V8 stage of development for maize. Leaf P concentration generally decreased with decreasing N fertilization. Relationships between P_L and N_L concentrations (mg g⁻¹ DM) using all site-years and sampling dates were described by significant linear-plateau functions in both maize (P_L = 0.82 + 0.089 N_L if N_L ≤ 32.1 and P_L = 3.7 if N_L > 32.1; R² = 0.41; P < 0.001) and wheat (P_L = 0.02 + 0.106 N_L if N_L ≤ 33.2 and P_L = 3.5 if N_L > 33.2; R² = 0.42; P < 0.001). Variation among sampling dates in the relationships were noted. By restricting the sampling dates [413-496 growing degree days (5 °C basis) in wheat (i.e., stem elongation) and 1494-1579 crop heat units in maize (i.e., silking), relationships for wheat (P_L = 0.29 + 0.073 N_L, R² = 0.66; P < 0.001) and maize (P_L = 1.04 + 0.084 N_L, R² = 0.66; P < 0.001) were improved. In maize, expressing P and N concentrations on a leaf area basis (P_LA and N_LA) at silking further improved the relationship (P_LA = 0.002 + 0.101 N_LA, R² = 0.80; P < 0.001). Predictive models of critical P concentration as a function of N concentration in the uppermost collared leaf of wheat and maize were established which could be used for diagnostic purposes.     

Influence of Crop Nutrition on Grain Yield, Seed Quality and Water Productivity under Two Rice Cultivation Systems

The system of rice intensification (SRI) is reported to have advantages like lower seed requirement,less pest attack,shorter crop duration,higher water use efficiency and the ability to withstand higher degree of moisture stress than traditional method of rice cultivation.With this background,SRI was compared with traditional transplanting technique at Indian Agricultural Research Institute,New Delhi,India during two wet seasons (2009-2011).In the experiment laid out in a factorial randomized block design,two methods of rice cultivation [conventional transplanting (CT) and SRI] and two rice varieties (Pusa Basmati 1 and Pusa 44) were used under seven crop nutrition treatments,viz.T 1,120 kg/hm2 N,26.2 kg/hm2 P and 33 kg/hm2 K;T 2,20 t/hm2 farmyard manure (FYM);T 3,10 t/hm2 FYM+ 60 kg/hm2 N;T 4,5 t/hm2 FYM+ 90 kg/hm2 N;T 5,5 t/hm2 FYM+ 60 kg/hm2 N+ 1.5 kg/hm2 blue green algae (BGA);T 6,5 t/hm2 FYM+ 60 kg/hm2 N+ 1.0 t/hm2 Azolla,and T 7,N 0 P 0 K 0 (control,no NPK application) to study the effect on seed quality,yield and water use.In SRI,soil was kept at saturated moisture condition throughout vegetative phase and thin layer of water (2-3 cm) was maintained during the reproductive phase of rice,however,in CT,standing water was maintained in crop growing season.Results revealed that CT and SRI gave statistically at par grain yield but straw yield was significantly higher in CT as compared to SRI.Seed quality was superior in SRI as compared to CT.Integrated nutrient management (INM) resulted in higher plant height with longer leaves than chemical fertilizer alone in both the rice varieties.Grain yield attributes such as number of effective tillers per hill,panicle length and panicle weight of rice in both the varieties were significantly higher in INM as compared to chemical fertilizer alone.Grain yields of both the varieties were the highest in INM followed by the recommended doses of chemical fertilizer.The grain yield and its attributes of Pusa 44 were significantly higher than those of Pusa Basmati 1.The seed quality parameters like germination rate and vigor index as well as N uptake and soil organic carbon content were higher in INM than those in chemical fertilizer alone.CT rice used higher amount of water than SRI,with water saving of 37.6% to 34.5% in SRI.Significantly higher water productivity was recorded in SRI as compared to CT rice.