Effect of different mulching materials on maize growth and yield in conservation agriculture systems of sub-humid Zimbabwe

Posted by gabrielamartinez on , in Journal Articles

The introduction of conservation agriculture (CA) for smallholders increased the competition for crop residues between crop and livestock enterprises of the mixed smallholder farming system. Smallholders practicing CA have resorted to using grass and leaf litter in addition to available crop residues. The effect of these different mulching materials on maize (Zea mays L.) growth and yield is not well documented in smallholder CA systems of southern Africa. A two-year experiment was run in 2012/13 and 2013/14 seasons to evaluate the effect of maize residues, grass (Hyparrhenia filipendula (L.) Stapf.) and leaf litter that farmers are currently using and residues from leguminous species, sunhemp (Crotolaria juncea L.) and Tephrosia (Tephrosia vogelii ((Hook) f.)) on maize nitrogen (N) uptake, growth and yield. Significant differences in soil water content across treatments were only observed during March in 2012/13 season. Maize residues retained more soil water and Tephrosia had the lowest soil water content when seasonal rainfall pattern was erratic. Grass and Tephrosia treatments had the lowest chlorophyll content. Conventional ploughing, maize residues and leaf litter had similar chlorophyll content which was significantly higher than grass and Tephrosia treatments. At a site with higher initial soil fertility conventional ploughing treatment out yielded the other treatments by 727–1265 kg ha−1. With more degraded sandy soil conventional practice had 119–430 kg ha−1 more maize grain than the CA treatments. With adequate fertilization, the mulching materials have a similar effect on maize growth in basins and direct seeding. Further studies on different application rates of mulching materials and mineral N fertilizer, and nutrient release patterns of these residues are critical in order to better understand soil fertility management under smallholder CA systems.

Source: Open Access Journals

Identification of Genomic Associations for Adult Plant Resistance in the Background of Popular South Asian Wheat Cultivar, PBW343

Posted by gabrielamartinez on , in Journal Articles

Rusts, a fungal disease as old as its host plant wheat, an enemy as old as wheat, has caused havoc for over 8,000 years. As the rust pathogens can evolve into new virulent races which quickly defeat to qualitative or vertical the resistance that primarily rely on race specificity over time, adult plant resistance (APR) has often been found to be race non-specific and hence is considered have been proven to be a more to be a more reliable and durable strategy to combat this malady. Over decades sets of donor lines have been identified at International Maize and Wheat Improvement Center (CIMMYT) representing a wide range of APR sources in wheat. In this study, using nine donors and a common parent ‘PBW343’, a popular Green Revolution variety at CIMMYT, the nested association mapping (NAM) population of 1122 lines was constructed to understand the APR genetics underlying these founder lines. Thirty-four QTL were associated with APR to rusts, and 20 of 34 QTL had pleiotropic effects on SR, YR and LR resistance. Three chromosomal regions, associated with known APR genes (Sr58/Yr29/Lr46, Sr2/Yr30/Lr27, and Sr57/Yr18/Lr34), were also identified, 13 previously reported QTL regions were validated. Of the 18 QTL first detected in this study, 7 were pleiotropic QTL, distributing on chromosomes 3A, 3B, 6B, 3D, and 6D. The present investigation revealed the genetic relationship of historical APR donor lines, the novel knowledge on APR, as well as the new analytical methodologies to facilitate the applications of NAM design in crop genetics. Results shown in this study will aid the parental selection for hybridization in wheat breeding, and envision the future rust management breeding for addressing potential threat to wheat production and food security.

Source: Frontiers | Identification of Genomic Associations for Adult Plant Resistance in the Background of Popular South Asian Wheat Cultivar, PBW343 | Plant Genetics and Genomics

Modelling and genetic dissection of staygreen under heat stress | SpringerLink

Posted by gabrielamartinez on , in Journal Articles

Plant chlorophyll retention—staygreen—is considered a valuable trait under heat stress. Five experiments with the Seri/Babax wheat mapping population were sown in Mexico under hot-irrigated environments. Normalized difference vegetation index (NDVI) during plant growth was measured regularly and modelled to capture the dynamics of plant greenness decay, including staygreen (Stg) at physiological maturity which was estimated by regression of NDVI during grainfilling. The rate of senescence, the percentage of plant greenness decay, and the area under the curve were also estimated based on NDVI measurements. While Stg and the best fitted curve were highly environment dependent, both traits showed strong (positive for Stg) correlations with yield, grainfilling rates, and extended grainfilling periods, while associations with kernel number and kernel weight were weak. Stg expression was largely dependent on rate of senescence which was related to the pattern of the greenness decay curve and the initial NDVI. QTL analyses revealed a total of 44 loci across environments linked to Stg and related traits, distributed across the genome, with the strongest and most repeatable effects detected on chromosomes 1B, 2A, 2B, 4A, 4B and 7D. Of these, some were common with regions controlling phenology but independent regions were also identified. The co-location of QTL for Stg and performance traits in this study confirms that the staygreen phenotype is a useful trait for productivity enhancement in hot-irrigated environments.

Source: Modelling and genetic dissection of staygreen under heat stress | SpringerLink

Resistance of Bt-maize (MON810) against the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) and its yield performance in Kenya

Posted by gabrielamartinez on , in Journal Articles

A study was conducted to assess the performance of maize hybrids with Bt event MON810 (Bt-hybrids) against the maize stem borer Busseola fusca (Fuller) in a biosafety greenhouse (BGH) and against the spotted stem borer Chilo partellus (Swinhoe) under confined field trials (CFT) in Kenya for three seasons during 2013e2014. The study comprised 14 non-commercialized hybrids (seven pairs of near-isogenic Bt and non-Bt hybrids) and four non-Bt commercial hybrids. Each plant was artificially infested twice with 10 first instar larvae. In CFT, plants were infested with C. partellus 14 and 24 days after planting; in BGH, plants were infested with B. fusca 21 and 31 days after planting. In CFT, the seven Bt hybrids significantly differed from their non-Bt counterparts for leaf damage, number of exit holes, percent tunnel length, and grain yield. When averaged over three seasons, Bt-hybrids gave the highest grain yield (9.7 t ha1), followed by non-Bt hybrids (6.9 t ha1) and commercial checks (6 t ha1). Bt-hybrids had the least number of exit holes and percent tunnel length in all the seasons as compared to the non-Bt hybrids and commercial checks. In BGH trials, Bt-hybrids consistently suffered less leaf damage than their non-Bt near isolines. The study demonstrated that MON810 was effective in controlling B. fusca and
C. partellus. Bt-maize, therefore, has great potential to reduce the risk of maize grain losses in Africa due to stem borers, and will enable the smallholder farmers to produce high-quality grain with increased
yield, reduced insecticide inputs, and improved food security.

Source: Resistance of Bt-maize (MON810) against the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) and its yield performance in Kenya

Variation in developmental patterns among elite wheat lines and relationships with yield, yield components and spike fertility

Posted by gabrielamartinez on , in Journal Articles

Developmental patterns strongly influence spike fertility and grain number, which are primarily deter-mined during the stem elongation period (i.e. time between terminal spikelet phase and anthesis). It has been proposed that the length of the stem elongation phase may, to an extent, affect grain number;thus it would be beneficial to identify genetic variation for the duration of this phase in elite germplasm. Variation in these developmental patterns was studied using 27 elite wheat lines in four experiments across three growing seasons. The results showed that the length of the stem elongation phase was (i)only slightly related to the period from seedling emergence to terminal spikelet, and (ii) more relevant than it for determining time to an thesis. Thus, phenological phases were largely independent and any particular time to an thesis may be reached with different combinations of component phases. Yield components were largely explained by fruiting efficiency of the elite lines used: the relationships were strongly positive and strongly negative with grain number and with grain weight, respectively. Although fruiting efficiency showed a positive trend with the duration of stem elongation that was not significant,a boundary function (which was highly significant) suggests that the length of this phase may impose an upper threshold for fruiting efficiency and grain number, and that maximum values of fruiting efficiency may require a relatively long stem elongation phase.

Source: Variation in developmental patterns among elite wheat lines and relationships with yield, yield components and spike fertility

Predicting wheat maturity and stay–green parameters by modeling spectral reflectance measurements and their contribution to grain yield under rainfed conditions

Posted by gabrielamartinez on , in Journal Articles

The normalized difference vegetation index (NDVI) continues to provide easy and fast methodologies to characterize wheat genetic resources in response to abiotic stresses. This study identifies ways to maximize green leaf area duration during grain filling and develops NDVI models to predict physiological maturity and different stay −green parameters to increase grain yield of rainfed winter wheat under terminal drought. Three wheat populations were evaluated: one containing 240 landraces from Afghanistan, the second with 250 modern lines and varieties, tested for two years under low rainfall conditions in Turkey, and the third with 291 landraces from Central and Western Asia (grown for one year in the same location). The onset of senescence, maximum “greenness”, rate of senescence and residual “greenness” at physiological maturity were estimated using sequential measurements of NDVI and have shown significant correlations with grain yield under low rainfall rainfed conditions. Trade-offs were identified among the different stay −green attributes, e.g. delayed onset of senescence and high maximum “greenness” resulted in accelerated rates of senescence and highest yields and were most evident in the landrace populations. It is concluded, that the use of rate of senescence to select for stay −green must be coupled with other stay −green components, e.g. onset of senescence or maximum “greenness” to avoid the effects of the trade-offs on final grain yield. The NDVI decay curves (using the last three NDVI measurements up to maturity) were used to estimate days to maturity using the NDVI decay during the senescence period and days to heading. A training and testing set (20 and 80% of each population, respectively) were used for calibrations allowing for correlations between predicted and observed maturity of up to r = +0.85 (P < 0.0001). This procedure will facilitate large −scale wheat phenotyping in the future.

Source: Predicting wheat maturity and stay–green parameters by modeling spectral reflectance measurements and their contribution to grain yield under rainfed conditions

Long term effect of conservation agriculture in maize rotations on total organic carbon, physical and biological properties of a sandy loam soil in north-western Indo-Gangetic Plains

Posted by gabrielamartinez on , in Journal Articles

Maize-based crop rotations are advocated as alternate to rice-based systems in South Asia due to better suitability for diverse ecologies, higher yields with less water use and more palatable maize fodder compared to rice, and increased demand of maize from piggery and poultry industries. Alternate tillage and crop establishment practices are important management strategies for tackling the issues of soil health deterioration and over exploitation of underground water resources, particularly in rice based intensive crop rotations. The conservation agriculture (CA) based tillage and crop establishment practices such as zero tillage (ZT) and permanent raised beds (PB) hold potential to enhance soil organic carbon (SOC), physical and biological properties for sustainability of soil health. Therefore, a long term study was conducted to evaluate the twelve combinations of tillage practices (03) and irrigated intensive maize based crop rotations (04) on organic carbon, physical properties and microbial biomass and enzymatic activities of a sandy loam (Typic Haplustept) soil in north-western India. The tillage practices consisted of ZT, PB and conventional tillage (CT) in main plots and four diversified intensive maize based crop rotations (MWMb: Maize-Wheat-Mungbean, MCS: Maize-Chickpea-Sesbaina, MMuMb: Maize-Mustard-Mungbean, MMS: Maize-Maize-Sesbania) in sub plots. In this study we analysed the SOC, physical and biological properties of soil at various depths after 7 years of continuous ZT, PB and CT in diversified maize rotations. Compared to CT plots, the soil physical properties like water stable aggregates (WSA) > 250 μm were 16.1-32.5% higher, and bulk density (BD) and penetration resistance (PR) showed significant (P < 0.05) decline (11.0–14.3 and 11.2–12.0%) in ZT and PB plots at 0–15 and 15–30 cm soil layers. The soil organic carbon (SOC) increased by 34.6-35.3% at 0–15 cm, and 23.6-26.5% at 15–30 cm soil depths with conservation agriculture (ZT and PB) based crop establishment techniques over CT. Similarly, the soil microbial biomass carbon (MBC) under CA based systems increased by 45–48.9% in 0–30 cm profile depth of a sandy loam (Typic Haplustept) soil. Significant (P < 0.05) improvement in soil enzymatic activities i.e., Fluorescein diacetate, dehydrogenase, β Glucosidase and Alkaline phosphatase was also recorded in the CA based treatments. Significant (P < 0.05) synergistic effects of summer legumes (mungbean and Sesbania) with winter legume/cereal in crop rotations were observed on SOC,WSA, BD, PR and Ksat at 0–15 and 15–30 cm depths. Interaction between tillage and crop rotations were significant (P < 0.05) for soil organic carbon, physical properties and enzymatic activities. Thus our long-term study suggests that CA based crop management with selected diversified maize based rotations (MCS and MWMb) can be advocated as sustainable intensification strategy in light textured soils of north-western India and other similar agro-ecologies of South Asia.

Source: Long term effect of conservation agriculture in maize rotations on total organic carbon, physical and biological properties of a sandy loam soil in north-western Indo-Gangetic Plains

Bio-energy, water-use efficiency and economics of maize-wheat-mungbean system under precision-conservation agriculture in semi-arid agro-ecosystem

Posted by gabrielamartinez on , in Journal Articles

The maize-wheat-mungbean (MWMb) cropping system is being advocated as an alternative to the traditional rice-based cropping systems of north-western Indo-Gangetic Plains (IGP) to address the issues of energy and nutritional scarcity, residue burning, decline in biomass productivity and water tables. In semi-arid regions, the climate-change-induced variability in rainfall and temperature may have an impact on phenological responses of cereals and pulses which in turn would affect biomass production, economic yield and energy and water-use efficiency (WUE) of the crops. Henceforth, quantification of bioequivalent yields, energy requirement, economics and WUE of MWMb system is essentially required owing to have better understanding of this cropping system. Following a 4-year study was conducted under different tillage and nutrient management. ZT and PB plots had significantly higher pooled average (17.2–20.3%) biomass productivity, (34.4–39.8%) net returns and (49.8–66.2%) biomass water-use efficiency with lesser (8.5–16.1%) water-use than the CT plots. Significantly higher pooled bioenergetic yields (21.7–35.2%), net returns (31.4–37.8%) and biomass water-use efficiency (30.1–35.2%) was observed in SSNM/Ad-hoc plots compared with FFP plots. The total pooled energy input in ZT/PB and SSNM/Ad-hoc plots was significant (P < 0.05) higher than CT and FFP plots, respectively, with greater net energy output, energy productivity and energy efficiency. The interactions between tillage and nutrient management practices on pooled input energy and energy productivity of MWMb system was significant (P < 0.05). Thus, adoption of conservation tillage (ZT/PB) practices with improved nutrient management (SSNM/Ad-hoc) could be a viable option for achieving higher biomass productivity, water and energy-use efficiency and profitability in MWMb system.

Source: Bio-energy, water-use efficiency and economics of maize-wheat-mungbean system under precision-conservation agriculture in semi-arid agro-ecosystem

Spot Spraying Reduces Herbicide Concentrations in Runoff 

Posted by gabrielamartinez on , in Journal Articles

Rainfall simulator trials were conducted on sugar cane paddocks across dry-tropical and subtropical Queensland, Australia, to examine the potential for spot spraying to reduce herbicide losses in runoff. Recommended rates of the herbicides glyphosate, 2,4-D, fluoroxypyr, atrazine, and diuron were sprayed onto 0, 20, 40, 50, 70, or 100% of the area of runoff plots.
Simulated rainfall was applied 2 days after spraying to induce runoff at one plant cane and three ratoon crop sites. Over 50% of all herbicides were transported in the dissolved phase of runoff, regardless of the herbicide’s sediment−water partition coefficient.
For most sites and herbicides, runoff herbicide concentrations decreased with decreasing spray coverage and with decreasing herbicide load in the soil and cane residues. Importantly, sites with higher infiltration prior to runoff and lower total runoff had lower runoff herbicide concentrations.

Source: Spot Spraying Reduces Herbicide Concentrations in Runoff – Journal of Agricultural and Food Chemistry (ACS Publications)

Genomic prediction models for grain yield of spring bread wheat in diverse agro-ecological zones : Scientific Reports

Posted by gabrielamartinez on , in Journal Articles

Genomic and pedigree predictions for grain yield and agronomic traits were carried out using high density molecular data on a set of 803 spring wheat lines that were evaluated in 5 sites characterized by several environmental co-variables. Seven statistical models were tested using two random cross-validations schemes. Two other prediction problems were studied, namely predicting the lines’ performance at one site with another (pairwise-site) and at untested sites (leave-one-site-out). Grain yield ranged from 3.7 to 9.0 t ha−1across sites. The best predictability was observed when genotypic and pedigree data were included in the models and their interaction with sites and the environmental co-variables. The leave-one-site-out increased average prediction accuracy over pairwise-site for all the traits, specifically from 0.27 to 0.36 for grain yield. Days to anthesis, maturity, and plant height predictions had high heritability and gave the highest accuracy for prediction models. Genomic and pedigree models coupled with environmental co-variables gave high prediction accuracy due to high genetic correlation between sites. This study provides an example of model prediction considering climate data along-with genomic and pedigree information. Such comprehensive models can be used to achieve rapid enhancement of wheat yield enhancement in current and future climate change scenario.

Source: Genomic prediction models for grain yield of spring bread wheat in diverse agro-ecological zones : Scientific Reports