Crop response of drought-tolerant and conventional maize hybrids in a semiarid environment

In the High Plains, corn (Zea mays L.) is an important commodity for livestock feed. However, limited water resources and drought conditions continue to hinder corn production. Drought-tolerant (DT) corn hybrids could help maintain high yields under water-limited conditions, though consistent response of such hybrids is unverified. In this two-year study, the effects of three irrigation treatments were investigated for a DT and conventional maize hybrid, Pioneer AQUAMax P0876HR and Pioneer 33Y75, respectively. In 2013, the drier of the 2 years, irrigation amounts and crop water use (ET_c) were greater for the conventional hybrid, but grain water use efficiency (WUE) and harvest index were significantly greater for the DT hybrid. In 2014, grain yields and WUE were not significantly different between hybrids. However, irrigation amounts, ET_c and biomass yields were greater for the conventional hybrid. Results from both years indicate that the DT hybrid required less water to maximize grain yield as compared to the conventional hybrid. Producing relatively high yields with reduced amounts of water may provide a means for producers to continue corn production in a semiarid environment with declining water supplies.     

Economics,adoption determinants,and impacts of micro-irrigation technologies: empirical results from India

Micro-irrigation technologies are promoted for various reasons in India. Despite the reported significant economic advantages, and the concerted support of the government and NGOs, the current micro-irrigation area in India remains an insignificant proportion of its potential. This paper analyzes: (1) the economics of alternative micro-irrigation technologies, (2) the determinants of adoption, (3) the poverty outreach of the different micro-irrigation systems, and (4) the sustainability implications of micro-irrigation adoption. In line with the findings of other studies, this study indicates that micro-irrigation technologies result in a significant productivity and economic gains. The most important determinants of micro-irrigation adoption include access to groundwater, cropping pattern, availability of cash, and level of education, the social status and poverty status of the farmer. Contrary to the expectations, the majority of the current adopters of low-cost micro-irrigation systems are the better-off farmers. The study indicates that the impact of micro-irrigation systems on the sustainability of groundwater resources depends upon the magnitude of the overall productivity gain following the shift from traditional irrigation method to micro-irrigation system, the pattern of use of the saved water, and the type and potential number of adopters. This study was supported by the Comprehensive Assessment of Water Management in Agriculture (CA) and IWMI-TATA Water Policy Program.

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A Comparison of the Effects of Two Prey Enrichment Media on Growth and Survival of Pacific Bluefin Tuna,Thunnus orientalis,Larvae

Three experiments were conducted to investigate the growth, survival, and standardized cohort biomass of Pacific bluefin tuna, Thunnus orientalis, larvae fed nutritionally enhanced prey during the first week of feeding using two commonly used, commercially available enrichment media, AlgaMac Enrich and Marine Glos. T. orientalis larvae exhibited exponential growth in standard length and dry weight. The daily specific growth rates in length and weight are the first reported for T. orientalis larvae and the averages ranged from 3.8 to 4.1% and 27.5%, respectively, for larvae in the AlgaMac treatment and from 4.1 to 6.1% and 31.5%, respectively, in the Marine Glos treatment. Average daily growth rates in length ranged from 0.16 to 0.23 mm/d for larvae in the AlgaMac treatment and from 0.17 to 0.27 mm/d for those in the Marine Glos treatment. Daily growth rates in length were similar to those reported for other tuna larvae reared in the laboratory but slower than most published estimates for larval tunas in situ at similar water temperatures. Mean prey number per gut was positively associated with mean prey level in the tank. Both enrichment media appear to be good sources of nutritional improvement of planktonic prey for T. orientalis larvae.     

Straw preservation reduced total N2O emissions from a sugarcane field

Post‐harvest biomass can be used as feedstock for energy production and alter N₂O emissions from the soil, which is among the main issues determining bioethanol sustainability. To assess the effects of sugarcane straw return on gas emissions, we established a field experiment in which 0, 50, 75 or 100% (0, 5.65, 8.47 and 11.30 Mg/ha dry biomass, respectively) of the crop residues (straw) was left in the field during the first two ratoon crops. As fertilizer is applied in bands to sugarcane, we also investigated the contribution of different positions to the N₂O emissions within the field. There was an interactive effect between straw and inorganic fertilizer, leading to a nonlinear effect of crop residues on the fertilizer emission factor (EF). However, straw consistently reduced N₂O emissions from the field, acting mainly in the unfertilized areas in the field (P < 0.05). We observed that considering the typical EF used in the literature, the N₂O‐N emissions attributed to fertilizer ranged from 0.19 to 0.79 kg/ha, while the total emissions ranged from 3.3 to 5.2 kg/ha, from the highest amount of straw to the lowest. We conclude that overall, the fertilizer EF is not as relevant as the total emissions, based on this and other studies. Consequently, management practices might be more effective in improving the GHG balance than changing inorganic fertilizer use. We conclude that keeping up to 11 Mg/ha of straw with a large C:N ratio (>100:1) on site might increase sugarcane production sustainability by reducing the greenhouse gas emissions from the field.     

Evaluation of different mulch materials for reducing soil surface evaporation in semi‐arid region

In recent years, the use of new mulches for soil water conservation in arid regions has been introduced as an alternative to conventional (plastic) mulches. However, systematic studies concerning the effects of different organic [pistachio shell mulch (PSM), wheat straw mulch, de‐oiled olive pomace mulch (DOM) or wood chips mulch], chemical [superabsorbent polymer (HM) or organic‐based emulsion polymer (PEM)] and mineral [gravel mulch (GM)] covers on soil and water conservation are scarce. Therefore, two experiments were carried out. Experiment 1 was aimed at evaluating the effects of mulches of different composition on soil surface evaporation, whereas in experiment 2 we investigated the effects of this decrease in soil evaporation due to different mulch materials on some olive tree physiological responses to soil drying. We analysed stem water potential, transpiration rate, stomatal conductance, leaf density and maximum efficiency of photosystem II photochemistry (Fv/Fm) of 2‐yr‐old plants of ‘Konservalia’ olive, grown in pots in open field. The results showed that different mulch materials had different efficiency on soil water conservation and DOM and pistachio shell mulch PSM – as new mulch materials – seems more favourable for conserving soil water. Water stress caused reductions in all parameters measured and increment in leaf density compared with unstressed treatment. Olive plants grown using different soil mulch presented higher values of stem water potential, transpiration rate, stomatal conductance and Fv/Fm ratio compared to control plants. Although all the mulch treatments improved the water content of soil, DOM and PSM were found to be superior in maintaining optimum soil water content for olive use.     

The use of digital image analysis and real‐time PCR fine‐tunes bioassays for quantification of Cercospora leaf spot disease in sugar beet breeding

Cercospora leaf spot, caused by the fungus Cercospora beticola, is a major fungal sugar beet disease worldwide and the cause of significant yield losses. The disease is most successfully countered by the introduction of genetic tolerance into elite sugar beet hybrids. To this end, breeding programmes require high quality biological assays allowing discrimination of minor differences between plants within a segregating population. This study describes the successful implementation of image analysis software in the bioassays for quantification of necrotic lesions at different stages of C. beticola infection, allowing selection on minor phenotypic differences during the sugar beet breeding process for C. beticola resistance. In addition, a real‐time PCR assay was developed for the quantification of C. beticola pathogen biomass in infected beet canopy. The use of both techniques, even in an early stage of infection, fine‐tunes current bioassays, allowing more accurate and efficient selection of resistant breeding material.     

Lignin als biologische Barriere gegen Schimmelpilze in Innenräumen

Many different fungi grow indoors as mold in the presence of moisture. Some of these fungi can cause allergic or toxic reactions, while a few may cause infections in susceptible individuals. A comprehensive treatment of this complex topic would take volumes. Therefore many groups search for alternative management strategies of these fungi. It has been tested if the growth of nine fungi (Alternaria alternata, Botrytis cinerea, Cladosporium herbarum, Fusarium culmorum, F. solani, F. verticillioides, Mucor sp., Penicillium sp. and Trichoderma sp.) which are common in interior buildings could be inhibited by mixing lignin into wall plaster. In maltextract agar lignin concentrations above 10 % inhibited mould growth except for Penicillium sp. However, none of the mould species showed and degradation of lignin. Further investigations on a lignin-plaster-agar, which contained only plaster as nutrient and had a high pH at 8, showed no inhibition on the tested fungi (Alternaria alternata, Fusarium verticillioides, Mucor sp., Trichoderma sp. and Penicillium sp.) at concentrations up to 5 %. Higher lignin concentrations lead to insufficient quality of building materials, e. g. cracking. Furthermore the color of the building materials turned from greyish-white in an exotherm reaction into brown, become not any more suitable for construction purposed.     

Biological control of the millet head miner Heliocheilus albipunctella in the Sahelian region by augmentative releases of the parasitoid wasp Habrobracon hebetor: effectiveness and farmers’ perceptions

On-farm augmentative releases of the parasitoid Habrobracon hebetor (Say) for controlling the millet head miner (MHM) Heliocheilus albipunctella (de Joannis) were tested in Burkina Faso, Mali and Niger from 2007 to 2009. In addition, a survey of farmers’ perceptions of insect pests, with particular focus on MHM, and the biological control program (BCP) was carried out. There was a significant increase of MHM parasitization rate after the releases, with up to 97% mortality. The survey on farmers’ perceptions revealed a fair knowledge of the MHM and the ability of farmers to describe the pest and the damage it caused. Farmers claimed that the biocontrol agent H. hebetor is effective and perceived a significant gain in grain yield due to this control strategy. Implications of these findings for a large extension of the MHM biocontrol program are discussed.     

Characterisation of a Quantitative Resistance to Vector Transmission of Tomato yellow leaf curl virus in Lycopersicon pimpinellifolium

Two wild genotypes from the same species Lycopersicon pimpinellifolium, WVA106 (susceptible) and INRA-Hirsute (so-called ‘resistant’), were compared with respect to their reaction to Tomato yellow leaf curl virus isolate Réunion (TYLCV-Mld[RE]), using both whitefly-mediated inoculation and graft inoculation. Disease incidence and symptom severity were scored. Presence and quantification of viral DNA were assessed by dot blot hybridisation. Upon insect inoculation, accession INRA-Hirsute showed a moderate resistance against TYLCV that was overcome by a high inoculation pressure obtained by increasing the cumulative number of inoculative whiteflies. Temporal analyses of the disease progress in relation to this criterion exhibited that the protection was quantitative, mainly reducing the TYLCV-Mld[RE] incidence by at maximum 50% at low inoculation pressure. When graft inoculated, the final TYLCV-Mld[RE] disease incidence was 100% in both susceptible and resistant genotypes with severe symptoms, suggesting a reduction of virus transmission by a vector resistance as a possible mechanism. Implications of using such type of resistance in breeding programmes are discussed.