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Agronomy, Volume 5, Issue 1 (March 2015) – 7 articles , Pages 1-106

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Article
Tools for Optimizing Management of a Spatially Variable Organic Field
Agronomy 2015, 5(1), 89-106; https://doi.org/10.3390/agronomy5010089 - 23 Mar 2015
Cited by 1 | Viewed by 3139
Abstract
Geostatistical tools were used to estimate spatial relations between wheat yield and soil parameters under organic farming field conditions. Thematic maps of each factor were created as raster images in R software using kriging. The Geographic Resources Analysis Support System (GRASS) calculated the [...] Read more.
Geostatistical tools were used to estimate spatial relations between wheat yield and soil parameters under organic farming field conditions. Thematic maps of each factor were created as raster images in R software using kriging. The Geographic Resources Analysis Support System (GRASS) calculated the principal component analysis raster images for soil parameters and yield. The correlation between the raster arising from the PC1 of soil and yield parameters showed high linear correlation (r = 0.75) and explained 48.50% of the data variance. The data show that durum wheat yield is strongly affected by soil parameter variability, and thus, the average production can be substantially lower than its potential. Soil water content was the limiting factor to grain yield and not nitrate as in other similar studies. The use of precision agriculture tools helped reduce the level of complexity between the measured parameters by the grouping of several parameters and demonstrating that precision agriculture tools can be applied in small organic fields, reducing costs and increasing wheat yield. Consequently, site-specific applications could be expected to improve the yield without increasing excessively the cost for farmers and enhance environmental and economic benefits. Full article
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Article
A Combined Field/Laboratory Method for Assessment of Frost Tolerance with Freezing Tests and Chlorophyll Fluorescence
Agronomy 2015, 5(1), 71-88; https://doi.org/10.3390/agronomy5010071 - 17 Mar 2015
Cited by 9 | Viewed by 3205
Abstract
Recent progress in genotyping allows for studies of the molecular genetic basis of cold resistance in cereals. However, as in many other fields of molecular genetic analysis, phenotyping for high numbers of genotypes is still a major bottleneck. The use of chlorophyll fluorescence [...] Read more.
Recent progress in genotyping allows for studies of the molecular genetic basis of cold resistance in cereals. However, as in many other fields of molecular genetic analysis, phenotyping for high numbers of genotypes is still a major bottleneck. The use of chlorophyll fluorescence measurements as an indicator for freezing stress is a well established and rapid method for evaluation of frost tolerance. In order to extend the applicability of this technique beyond plants grown under controlled conditions in growth chambers and sacrificed for the test, here we study its applicability for leaves harvested from field trials during winter and subjected to freezing tests. Such an approach allows for simultaneous studies of the advancement of cold hardening and other components of winter survival apart from frost tolerance. It is shown that cutting or senescence of cut leaves does not have adverse effects on the outcome of subsequent freezing stress tests. The time requirements for field sampling and laboratory testing on high numbers of genotypes allow for the application of the proposed approach for genotyping/phenotyping studies. Full article
(This article belongs to the Special Issue Field Phenotyping for Yield and Environmental Stress Tolerance Traits)
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Article
The Potential of Lr19 and Bdv2 Translocations to Improve Yield and Disease Resistance in the High Rainfall Wheat Zones of Australia
Agronomy 2015, 5(1), 55-70; https://doi.org/10.3390/agronomy5010055 - 16 Feb 2015
Cited by 3 | Viewed by 3067
Abstract
Chromosomal translocations in wheat derived from alien species are a valuable source of genetic diversity that have provided increases in resistance to various diseases and improved tolerance to abiotic stresses in wheat. These alien genomic segments can also affect multiple traits, with a [...] Read more.
Chromosomal translocations in wheat derived from alien species are a valuable source of genetic diversity that have provided increases in resistance to various diseases and improved tolerance to abiotic stresses in wheat. These alien genomic segments can also affect multiple traits, with a concomitant ability to alter yield potential in either a positive or negative fashion. The aim of this work was to characterize the effects on yield of two types of translocations, namely T4-derived translocations from Thinopyrum ponticum, carrying the leaf rust resistance gene Lr19, and the TC14 translocation from Th. intermedium, carrying the barley yellow dwarf virus resistance gene Bdv2, in Australian adapted genetic backgrounds and under Australian conditions. A large range of germplasm was developed by crossing donor sources of the translocations into 24 Australian adapted varieties producing 340 genotypes. Yield trials were conducted in 14 environments to identify effects on yield and yield components. The T4 translocations had a positive effect on yield in one high yielding environment, but negatively affected yield in low-yielding environments. The TC14 translocation was generally benign, however, it was associated with a negative impact on yield and reduced height in two genetic backgrounds. The translocation was also associated with a delayed maturity in several backgrounds. The T4 translocations results were consistent with previously published data, whilst this is the first time that such an investigation has been undertaken on the TC14 translocation. Our data suggests a limited role for each of these translocations in Australia. The T4 translocations may be useful in high yielding environments, such as under irrigation in NSW and in the more productive high rainfall regions of south-eastern Australia. Traits associated with the TC14 translocation, such as BYDV resistance and delayed maturity, would make this translocation useful in BYDV-prone areas that experience a less pronounced terminal drought (e.g., south-eastern Australia). Full article
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Article
Analysis of Temporal Variation of Soil Salinity during the Growing Season in a Flooded Rice Field of Thessaloniki Plain-Greece
Agronomy 2015, 5(1), 35-54; https://doi.org/10.3390/agronomy5010035 - 05 Feb 2015
Cited by 9 | Viewed by 3218
Abstract
The effects of regional water management practices (WMPs) on the soil salinity of a representative rice field under Mediterranean conditions (Thessaloniki plain, Greece) were investigated. The temporal variation of soil salinity parameters in the soil solution and in the exchangeable phase was monitored [...] Read more.
The effects of regional water management practices (WMPs) on the soil salinity of a representative rice field under Mediterranean conditions (Thessaloniki plain, Greece) were investigated. The temporal variation of soil salinity parameters in the soil solution and in the exchangeable phase was monitored at and below the root zone (15–20 and 35–40 cm) during the growing season. The comparative analysis (ANOVA for p = 0.05) of the measurements before and after the growing season showed that: (a) for the soil solution of the 15–20 cm layer, Ca2+, Mg2+, K+, HCO3 and EC were significantly reduced, Na+ remained constant and Cl increased, while in the 35–40 cm layer no significant differences were detected to all parameters except for Cl which was increased; (b) for the exchangeable cations Ca2+, Mg2+ and K+ no significant differences were found, while exchangeable Na+ and ESP were significantly increased in both soil layers during the short period of soil drying before harvest. The final values of Na+ and ESP were quite low to indicate soil degradation hazard. Overall the results showed adequate performance of WMPs to preserve a good soil salinity status but with the cost of high water consumption, exceeding 2000 mm. Full article
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Article
Benefits of Transgenic Insect Resistance in Brassica Hybrids under Selection
Agronomy 2015, 5(1), 21-34; https://doi.org/10.3390/agronomy5010021 - 08 Jan 2015
Cited by 5 | Viewed by 3019
Abstract
Field trials of transgenic crops may result in unintentional transgene flow to compatible crop, native, and weedy species. Hybridization outside crop fields may create novel forms with potential negative outcomes for wild and weedy plant populations. We report here the outcome of large [...] Read more.
Field trials of transgenic crops may result in unintentional transgene flow to compatible crop, native, and weedy species. Hybridization outside crop fields may create novel forms with potential negative outcomes for wild and weedy plant populations. We report here the outcome of large outdoor mesocosm studies with canola (Brassica napus), transgenic canola, a sexually compatible weed B. rapa, and their hybrids. Brassica rapa was hybridized with canola and canola carrying a transgene for herbivore resistance (Bt Cry1Ac) and grown in outdoor mesocosms under varying conditions of competition and insect herbivory. Treatment effects differed significantly among genotypes. Hybrids were larger than all other genotypes, and produced more seeds than the B. rapa parent. Under conditions of heavy herbivory, plants carrying the transgenic resistance were larger and produced more seeds than non-transgenic plants. Pollen derived gene flow from transgenic canola to B. rapa varied between years (5%–22%) and was not significantly impacted by herbivory. These results confirm that canola-weed hybrids benefit from transgenic resistance and are aggressive competitors with congeneric crops and ruderals. Because some crop and crop-weed hybrids may be competitively superior, escapees may alter the composition and ecological functions of plant communities near transgenic crop fields. Full article
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Editorial
Acknowledgement to Reviewers of Agronomy in 2014
Agronomy 2015, 5(1), 19-20; https://doi.org/10.3390/agronomy5010019 - 08 Jan 2015
Viewed by 2212
Abstract
The editors of Agronomy would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2014:[...] Full article
Article
Effect of Foliar Boron Fertilization of Fine Textured Soils on Corn Yields
Agronomy 2015, 5(1), 1-18; https://doi.org/10.3390/agronomy5010001 - 29 Dec 2014
Cited by 8 | Viewed by 3511
Abstract
Boron (B) is an essential micronutrient needed for normal plant growth and development. To evaluate the response of corn to foliar B applications at V4–V6 (4–6 leaves with visible collars) and VT (tasseling) growth stages on fine textured soils, a field experiment was [...] Read more.
Boron (B) is an essential micronutrient needed for normal plant growth and development. To evaluate the response of corn to foliar B applications at V4–V6 (4–6 leaves with visible collars) and VT (tasseling) growth stages on fine textured soils, a field experiment was conducted at four sites from 2008 to 2010 in Northeast Missouri. The treatments included a non-treated control; V4–V6 applied B at 0.56, 1.12 and 2.24 kg·ha−1; and VT applied B at 0.28, 0.56 and 1.12 kg·ha−1. Foliar B, applied at V4–V6 at 2.24 kg·ha−1, resulted in higher yields than VT applications. No significant differences in yield were found for B applications at different timings for concentrations of 0.56 and 1.12 kg·ha−1. Boron applied at V4–V6 and 2.24 kg·ha−1 increased yield 0.29 Mg·ha−1 compared to the non-treated control. The B applications at VT increased ear leaf tissue B concentration compared to V4–V6 applications and non-treated control, but it had no significant effect on corn yields. No significant difference between B treatments was observed for grain oil, protein, starch or extractable starch concentration; severity of anthracnose stalk rot or common rust; and ear tip fill. The B application of 2.24 kg·ha−1 at V4–V6 decreased the severity of gray leaf spot, but increased the severity of northern leaf blight compared to the non-treated control. Boron applied at V4–V6 at 2.24 kg·ha−1 was the most beneficial timing and concentration evaluated in these fine textured soils. Full article
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