Ivan Ortiz-Monasterio

Nutritious subsistence food systems

The major subsistence food systems of the world that feed resource‐poor populations are identified and their capacity to supply essential nutrients in reasonable balance to the people dependent on them has been considered for some of these with a view to overcoming their nutrient limitations in sound agronomic and sustainable ways. The approach discusses possible cropping system improvements and alternatives in terms of crop combinations, external mineral supply, additional crops, and the potential for breeding staples in order to enhance their nutritional balance while maintaining or improving the sustainability and dietary, agronomic, and societal acceptability of the system. The conceptual framework calls for attention first to balancing crop nutrition that in nearly every case will also increase crop productivity, allowing sufficient staple to be produced on less land so that the remaining land can be devoted to more nutrient‐dense and nutrient‐balancing crops. Once this is achieved, the additional requirements of humans and animals (vitamins, selenium, and iodine) can be addressed. Case studies illustrate principles and strategies. This chapter is a proposal to widen the range of tools and strategies that could be adopted in the HarvestPlus Challenge Program to achieve its goals of eliminating micronutrient deficiencies in the food systems of resource‐poor countries.

Identifying the agricultural imprint on the global N2O budget using stable isotopes

Agricultural soils are the most important anthropogenic source of nitrous oxide to the atmosphere. We observed large shifts with time in the emission rate (from 170 to 16 ng N cm−2 h−1) and in δ15N of N2O emitted (from −46‰ to +5‰ relative to atmospheric N2) from a urea-fertilized and irrigated agricultural field in Mexico. We calculated overall instantaneous enrichment factors for the sampling period, which suggest that the microbial N2O production shifts from nitrification (week 1) to denitrification (week 2). Isotopic signatures of N2O emissions were not always in accord with other proxies (such as NO/N2O emission ratio or water-filled pore space) used to estimate the relative importance of nitrification and denitrification as N2O sources. These observations strongly suggest that the soil surface emissions integrate processes occurring at different depths in the soil and a decoupling of NO and N2O production in this system. Further clues as to the source of N2O come from the positional dependence of 15N in the emitted N2O, reported here for the first time in soil emissions. Enrichment at the central N position increased relative to the terminal N position by 9.3‰ during the first 4 days after irrigation, implying that nitrification preferentially enriches the central N position compared to denitrification. The overall δ15N signature we measured for N2O emitted from N-fertilized agricultural systems is more depleted than observed δ15N values for N2O emitted from more N-limited forest soils. Assuming that one half of the total agricultural N2O emissions associated with the global increase in soil nitrogen fertilizer use have an isotopic composition comparable to those of the agricultural fields reported here, we predict a decline in the isotopic signature of tropospheric N2O during this century of as much as 3‰ for 15N. Although many uncertainties remain, we suggest that measurements of δ15N-N2O in firn air will provide constraints on how the N2O budget has changed during the past century.

Selenium concentration in wheat grain: Is there sufficient genotypic variation to use in breeding?

Selenium (Se) is an essential micronutrient for humans and animals, with antioxidant, anti-cancer and anti-viral effects, and wheat is an important dietary source of this element. In this study, surveys of Se concentration in grain of ancestral and wild relatives of wheat, wheat landrace accessions, populations, and commercial cultivars grown in Mexico and Australia were conducted. Cultivars were also grown under the same conditions to assess genotypic variation in Se density. Eleven data sets were reviewed with the aim of assessing the comparative worth of breeding compared with fertilising as a strategy to improve Se intake in human populations. Surveys and field trials that included diverse wheat germplasm as well as other cereals found grain Se concentrations in the range 5–720μgkg−1, but much of this variation was associated with spatial variation in soil selenium. This study detected no significant genotypic variation in grain Se density among modern commercial bread or durum wheat, triticale or barley varieties. However, the diploid wheat, Aegilops tauschii and rye were 42% and 35% higher, respectively, in grain Se concentration than other cereals in separate field trials, and, in a hydroponic trial, rye was 40% higher in foliar Se content than two wheat landraces. While genotypic differences may exist in modern wheat varieties, they are likely to be small in comparison with background soil variation, at least in Australia and Mexico. Field sites that are spatially very uniform in available soil Se would be needed to allow comparison of grain Se concentration and content in order to assess genotypic variation.

Nitrogen leaching and soil nitrate, nitrite, and ammonium levels under irrigated wheat in Northern Mexico

Nitrate (NO−13) leaching from agricultural soils can represent a substantial loss of fertilizer nitrogen (N), but a large variation in losses has been reported. We report N leaching losses under four N fertilizer treatments and two farmers fields in the Yaqui Valley, Mexico. In these irrigated wheat systems, farmers typically apply 250 kg N ha−1 as anhydrous ammonia (knifed in) or urea(broadcast), with 75% applied directly before planting and 25% at the time of the first post-planting irrigation. Over two wheat seasons, we compared typical farmers practices to alternatives that applied less N and more closely timed fertilizer application to plant demand. Field lysimeter measurements and predictions from a water transport simulation model (called NLOSS) were used to estimate the amount of N leached over the season. Approximately 5 and 2% of the applied N leached below the root zone with the typical farmers practice in 1995–96 and 1997–98,respectively. The alternative treatments reduced N leaching losses by 60 to95% while producing comparable economic returns to the farmer. Leaching losses from the two farmers fields were substantially higher (about 14and26% of the applied N). Our results indicate that the typical farmers practice leads to relatively high N leaching losses, and that alternative practices synchronizing fertilizer application with crop demand can substantially reduce these losses.

A strategy for breeding staple-food crops with high micronutrient density

Food-based approaches to addressing micronutrient malnutrition in much of the human population have hitherto been based mainly on balancing cereal-based diets with vegetables, and to a lesser extent, animal products. Although high in micronutrients, these commodities are more expensive foods than staples, and also more seasonal, subject to spoilage, and difficult to store and transport. Moreover, their availability in some countries is only 10–15% of what is required to meet the needs of the people (Ali et al., 1994). Because of the wide availability of staples, their high proportion in the diet of the most malnourished, because field fortification has several advantages over fortification during processing, and because staples are known for their low content of these essentials, we have studied the possibility of breeding to improve plant staples as sources of micronutrients for humans. This is in response to the WHO/FAO call for a food-based solution to micronutrient malnutrition which is considered now to affect more than 2 billion people world-wide (WHO, 1992).

Are synthetic hexaploids a means of increasing grain element concentrations in wheat

Element concentration in wheat grains is an important objective of plant breeding programs. For this purpose, synthetic hexaploid lines (Triticum durum ×Aegilops tauschii) have been identified as potential sources of high element concentration in grains. However, it is not known if these lines reach higher element concentrations in grains as the consequence of a dilution effect due to lower grain yield. In addition, most of the studies carried out with these lines did not evaluate above-ground element uptake. The objective of this study was to improve understanding of grain element concentrations as a function of grain yield, element uptake and biomass and element partitioning to grains in synthetic and conventional cultivars of wheat. One experiment with two standard sowing dates was carried out under field conditions. Biomass, grain yield, and macronutrient(Ca, Mg, K, P and S) and micronutrient (Cu,Fe, Mn and Zn) concentrations in grains and vegetative tissues were measured in two cultivars and one synthetic (chosen from ten lines). The synthetic showed higher element concentration in grains, e.g. between 25 and 30% for Fe, Mn and Zn across sowing dates, than cultivars while grain yield was similar or lower, depending on the sowing date. On the contrary, the synthetic showed lower concentration of Cain grains. This line showed also higher uptake of Fe, Mn, K and P than cultivars. The superior grain element concentration of the synthetic line was not only due to a dilution effect but also to a higher uptake efficiency. Therefore, synthetics would bea valuable source of germplasm for increasing element grain concentration, at least in this case for Fe, Mn, K and P.

A study of allelic diversity underlying flowering-time adaptation in maize landraces

Landraces (traditional varieties) of domesticated species preserve useful genetic variation, yet they remain untapped due to the genetic linkage between the few useful alleles and hundreds of undesirable alleles. We integrated two approaches to characterize the diversity of 4,471 maize landraces. First, we mapped genomic regions controlling latitudinal and altitudinal adaptation and identified 1,498 genes. Second, we used F-one association mapping (FOAM) to map the genes that control flowering time, across 22 environments, and identified 1,005 genes. In total, we found that 61.4% of the single-nucleotide polymorphisms (SNPs) associated with altitude were also associated with flowering time. More than half of the SNPs associated with altitude were within large structural variants (inversions, centromeres and pericentromeric regions). The combined mapping results indicate that although floral regulatory network genes contribute substantially to field variation, over 90% of the contributing genes probably have indirect effects. Our dual strategy can be used to harness the landrace diversity of plants and animals.

Methodology for Selecting Segregating Populations for Improved N-Use Efficiency in Bread Wheat

While new lines developed by CIMMYT under intermediate levels of nitrogen are more nitrogen efficient than older lines, it is not known whether this method of selection is the most efficient. Two lines with high N up-take efficiency (UPE) were crossed to two lines with high N utilization efficiency (UTE). Their progenies were visually selected for superior agronomic type from the F2 till the F6 under each of five selection regimes. These were: always under low N (0 added) (LN), always under medium N (150 kg N ha−1 added) (MN), always under high N (300 kg N ha−1 added) (HN), alternating between low and high N starting with low N in the F2 (ALN) and alternating between high and low N starting with high N in the F2 (AHN). The resulting advanced lines (F8) were tested in replicated yield trials under low, medium, and high levels of added N on an N deficient soil. The AHN selection regime resulted in the highest yields at intermediate and high N levels. The lowest yields occurred for ALN. Harvest Index (HI) did not change. Hence all effects on yield were the result of changes in biomass. Under low N all selection regimes showed progress in yield due to an improved biomass and HI, but with no differences among regimes. UPE expressed a higher correlation with yield and biomass than UTE under all levels of N.

Evaluation of a Reduced Cost Active NDVI Sensor for Crop Nutrient Management

There are methods to increase fertilizer nitrogen use efficiency through optical sensor-based nitrogen application; however, the sensors are expensive and cost prohibitive to farmers in the developing world. This study evaluated a novel, reduced cost, prototype, and optical sensor to determine if it could be used with the same level of accuracy as a commercial sensor. The stability of the prototype sensor (pocket sensor) to maintain an accurate calibration over time, the effect of operator on sensor readings, and sensor performance in maize and wheat were assessed. Evaluation of the sensor performance was conducted in existing wheat and maize trials, as well as turf grass canopies at the International Maize and Wheat Improvement Center, Ciudad Obregon, Mexico.The prototype sensors were highly correlated to the commercial GreenSeeker NDVI sensor in turf grass, wheat, and maize canopies (, , and , resp.). The Pocket Sensors lacked some precision in comparison to the commercial sensor; however, even with the reduced precision, the cost of the sensor and robustness of N fertilizer algorithms compensate for this apparent weakness. The pocket sensor is a new and viable tool to assess wheat and maize nitrogen status and make nitrogen recommendations based upon the data collected with this sensor.

Looking for Win-Wins in Intensive Agriculture

Agricultural intensification through the use of high-yielding crop varieties, chemical fertilizers and pesticides, irrigation, and mechanization— known as the green revolution— has been responsible for dramatic increases in grain production in developing countries over the past four decades. Expansion of food production into previously nonagricultural lands has likewise increased, but was responsible for only around 10 percent of the overall increased production in the three decades following the beginning of the green revolution (table 3.1; Naylor 1996). Most analysts estimate that close to a doubling of food production will be required in the coming several decades to meet the needs of a growing population and improve food quality and quantity for all, and these increases will most likely take place through continued intensification (FAO 2006a; Bruinsma 2009).