Tolerance to excess moisture in maize (Zea mays L.): susceptible crop stages and identification of tolerant genotypes

Excess moisture (water-logging) during the summer–rainy season is one of the major production constraints for maize (Zea mays L.) in a large area of Southeast Asia. Identification and development of genotypes capable of withstanding the stress conditions could be an ideal and affordable approach suitable for resource poor maize-growing farmers of such areas. We attempted to identify the most susceptible/critical crop stage(s) of maize for excess moisture stress, and to develop a screening technique and selection strategies for identification of germplasm tolerant to excess moisture stress. Among the four crop stages, i.e. early seedling (V2), knee-high (V7), tasseling (VT) and milk stage (R1), V2 was found to be highly susceptible, followed by the V7 stage. A screening technique (cup method) was developed/standardized, and was found to be an efficient technique for large-scale screening of maize genotypes against excess soil moisture stress. Germplasm was screened using this technique followed by field evaluation at the V7 growth stage (seventh leaf visible). Excess soil moisture stress severely affected various growth and biochemical parameters, impaired anthesis and silking, and eventually resulted in poor kernel development and yield. However, remarkable variability was found among the genotypes studied. Genotypes with good carbohydrate accumulation in stem tissues, moderate stomatal conductance, <5 days ASI, high root porosity, and early brace root development ability have been found to have good tolerance against the hypoxia/anoxia caused by excess soil moisture conditions.     

BORON NUTRIPRIMING IMPROVES THE GERMINATION AND EARLY SEEDLING GROWTH OF RICE (ORYZA SATIVA L.)

Boron (B) is one of the important micronutrient required for rice in particular during reproductive growth. A laboratory study was conducted to explore the potential of boron nutripriming in improving the germination and early seedling growth of rice. Seeds of fine grain aromatic rice cultivar Super Basmati were primed in aerated B solution (0.001, 0.01, 0.1 and 0.5% w/v) while untreated dry seeds were taken as control. Seed priming in 0.001 and 0.1% B solutions improved the time to 50% germination, germination energy, final germination percentage, mean germination time, and germination index. Beyond this concentration either there was no effect or an adverse effect on rice seeds. In the cases of radicle length, plumule length and secondary roots priming more diluted B solution, i.e., 0.001% proved better than rest of the treatments as suppression in these three traits was observed by other B treatments than control. Seed priming in relatively concentrated B solution, i.e., 0.5% completely suppressed the germination and growth.     

Nutrients transport through variably structured soils

Abstract

Contribution of sesbania green manure, rice straw, and FYM (farm yard manure) was studied along with that of urea and A/SO₄ (ammonium sulphate) for the cultivation of lowland rice and for the residual soil fertility. The results revealed that A/SO₄ application resulted in a larger number of productive tillers, higher straw production, and higher grain yield compared to urea. Among the organic manures, sesbania green manure and FYM exerted almost similar effects on the number of productive tillers and paddy yield while the yield increase compared to the incorporation of rice straw. A similar affect of these organic manures on nitrogen uptake by rice straw, grain, and straw + grain was observed. Additional uptake of N due to the application of sesbania green manure, FYM and rice straw amounted to 15, 13, and 2.85 kg ha^?1, respectively. Residual N fertility was the highest when of sesbania green manure was applied followed by FYM and rice straw. Residual P fertility was higher in the case of FYM than other treatments whereas the residual K fertility was the highest in the case of rice straw incorporation.     

Boron Nutrition of Four Sweet Pepper Cultivars Grown in Boron-Deficient Soil

ABSTRACT

In a greenhouse study, boron (B) application significantly increased dry-matter yield of sweet pepper (Capsicum annum L.) cultivars (‘California Wonder,’ ‘Anahein,’ ‘Narwala,’ and ‘2573’) grown in a B-deficient (hot-water extractable, 0.28 B mg kg^?1), calcareous soil of the Shujabad series (Typic Ustochrepts). Five rates of B, ranging from 0 to 8 mg B kg^?1 soil, were applied as H₃BO₃ along with adequate basal fertilization of nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn). Four plants of sweet pepper were transplanted in each pot, two of which were harvested after three weeks of transplanting and the other two after six weeks. Maximum crop biomass was produced with ～1 mg B kg^?1, but application of higher rates proved toxic, resulting in dry-matter yield reductions. The four cultivars significantly differed in relative growth rate (RGR) and relative accumulation rate of B (RARB). Cultivar ‘2573’ showed the highest RGR while ‘Anahein’ showed the highest RARB. Relative accumulation rate was positively correlated (R² = 0.83) with dry-matter yield of four cultivars. Critical B concentration in sweet pepper whole shoots was 69 mg B kg^?1 for three-week-old plants and 49 mg B kg^?1 for six-week-old plants.     

Aflatoxins and ochratoxin A contamination in rice,corn and corn products from Punjab,Pakistan

In present study, a total of 275 retail cereal samples including rice, corn and corn products was analyzed for the presence of aflatoxins and ochratoxin A (OTA) using HPLC equipped with a fluorescence detector. The data has shown that 38 out of 68 samples of rice, 37/105 of corn and 43/102 samples of corn products have been found contaminated with AFs, average level of AFB₁ and total AFs, 8.23 and 19.54, 7.90 and 12.08, and 5.47 and 7.85 μg/kg, respectively. Furthermore, 34, 28 and 26 numbers of rice, corn and corn product samples were found to be contaminated with OTA with an average level of 12.94, 5.29 and 3.69 μg/kg, respectively. The samples of rice, corn and corn products found above the permissible European Union (EU) limit for AFB₁ and total AFs were 18, 13 and 14 and 28, 14 and 20%, respectively; however, the samples of rice, corn and corn products above the EU limit were 40, 14 and 15%, respectively.     

Changes in soil physicochemical and microbial properties along elevation gradients in two forest soils

The effects of the interaction between tree species composition and altitude on soil microbial properties are poorly understood. In this study, soil samples (0–20?cm) were collected in August 2011 from Betula platyphylla and Picea crassifolia forests along two different altitudinal gradients. Soil microbial activity and biomass were measured using Biolog-ECO plates and phospholipid fatty acid analysis. Both of the forest soils were characterized by a significantly lower soil pH (p?p?相似文献   

Contribution of Nitrogen Fixed by Mung Bean to the Following Wheat Crop

Crop rotation is a supportive management practice in which legumes greatly improve the growth and yield of subsequent cereal crops, particularly wheat. In this study, effects of mung bean (Vigna radiata)?? on the yield and quality of grains of following wheat crop were determined. An experiment was carried out with two sets of wheat (Triticum aestivum) crops: one grown following mung bean (Vigna radiata) crop and the other grown after a fallow period. Concentrations of macronutrients, sugar, protein, amino acids, and phytohormones of wheat were determined. The grain protein concentration of wheat was improved if cultivated after mung bean, and nitrogen and other macronutrients of wheat were increased significantly. In case of phytohormone contents in the wheat crop, abscisic acid concentration showed no change, but the concentrations of gibberellin increased significantly by 41% and indole acetic acid by 30% as a result of crop rotation. Sugar content in wheat cultivated after mung bean BRM-318 showed 10% increase and wheat protein content increased by 17% and 20%, respectively. The present study demonstrated that crop rotation simulated yield and improved the nutritional value of wheat grain compared to wheat which followed the fallow period.     

A comparative study to evaluate efficiency of EDTA and calcium in alleviating arsenic toxicity to germinating and young <Emphasis Type="Italic">Vicia faba</Emphasis> L. seedlings

Purpose

This study delineated the effect of calcium (Ca) and ethylenediaminetetraacetic acid (EDTA) addition on arsenic (As) accumulation and physiological attributes of Vicia faba L.

Materials and methods

Two separate experiments were performed. In the first experiment, V. faba seedlings, grown under hydroponic conditions, were exposed to three levels of As (25, 125 and 250 μM) in the presence and absence of three levels of EDTA (25, 125, 250 μM) and calcium (CaCl₂: 1, 5 and 10 mM). The effect of EDTA and Ca on As accumulation and physiological attributes of V. faba was assessed by determining As contents in roots and shoot, chlorophyll contents, H₂O₂ contents, and lipid peroxidation in young and old leaves. In the second experiment, V. faba seeds were grown in As-contaminated sand culture using the same treatment plan.

Results and discussion

The accumulation and toxicity of As to V. faba plants increased with increasing As levels in nutrient solution. Arsenic exposure enhanced the production of reactive oxygen species (ROS) in both roots and leaves, which resulted in lipid peroxidation and decreased chlorophyll contents. The presence of both EDTA and Ca, in general, significantly decreased As accumulation by V. faba seedlings, Ca being more effective than EDTA. Both the amendments decreased As-induced reactive oxygen species (ROS) production and lipid peroxidation. In the case of chlorophyll contents, EDTA significantly decreased chlorophyll contents, while Ca significantly increased chlorophyll contents compared to As. The effect of all the treatments was more pronounced in roots than leaves and in young leaves compared to old leaves.

Conclusions

It is proposed that EDTA and Ca greatly affect As accumulation and toxicity to V. faba, and the effect varies greatly with their applied levels as well as type and age of plant organs. The germinating seedlings of V. faba may be preferred for risk assessment studies, while transplanting 1-week-old V. faba seedlings to As-contaminated soils can decrease its toxicity.

     

应用聚合酶链反应检测鸡传染性贫血病毒

根据鸡传染性贫血病毒（CAV）Cux－1株的基因序列,设计了一对引物,用这对引物对三株CAV的核酸模板进行PCR扩增,结果均能特异性地扩增出420bp的片段,但对其它5种禽病病原体核酸模板的扩增,结果均为阴性,该PCR能检出10fg鸡传染性贫血病毒DNA模板。