Globally, rainfed crop yields are about 50% lower than yields obtained under irrigated conditions. The low productivity of rainfed agricultural systems is the main factor that accentuates hunger, ...poverty, unemployment, and illegal migration in Central America and other regions in Latin America. Because of rainfall dependence, farmers can cultivate their crops during only one growing season per year, with high vulnerability to periodic droughts and flooding. To face the challenge of a sustainable food supply in the context of increasing food demand, since the mid-2000s, FLAR (Latin American Fund for Irrigated Rice), a public-private alliance of organizations from 17 Latin American countries CFC (Common Fund for Commodities), and CIAT (International Center for Tropical Agriculture) have been investing resources and efforts to sustainably intensify and diversify high-risk rainfed production systems through capturing runoff rainwater in reservoirs to transform those systems into highly profitable irrigated systems. This article summarizes concepts, results, and experiences from pilot farms using water harvesting in Nicaragua and Mexico, where irrigation combined with smart crop management practices allowed small-/medium-scale farmers to increase their yields of rice, maize, beans, and high-value crops by two to four times in comparison with historical yields obtained under rainfed conditions.
Rice (Oryza sativa L.)grain quality is a set of complex interrelated traits that include grain milling, appearance, cooking, and edible properties. As consumer preferences in Latin America and the ...Caribbean evolve, determining what traits best capture regional grain quality preferences is fundamental for breeding and cultivar release. In this study, a genome‐wide association study (GWAS), marker‐assisted selection (MAS), and genomic selection (GS) were evaluated to help guide the development of new breeding strategies for rice grain quality improvement. For this purpose, 284 rice lines representing over 20 yr of breeding in Latin America and the Caribbean were genotyped and phenotyped for 10 different traits including grain milling, appearance, cooking, and edible quality traits. Genetic correlations among the 10 traits ranged from −0.83 to 0.85. A GWAS identified 19 significant marker/trait combinations associated with eight grain quality traits. Four functional markers, three located in the Waxy and one in the starch synthase IIa genes, were significantly associated with six grain‐quality traits. These markers individually explained 51–75% of the phenotypic variance depending on the trait, clearly indicating their potential utility for MAS. Cross‐validation studies to evaluate predictive abilities of four different GS models for each of the 10 quality traits were conducted and predictive abilities ranged from 0.3 to 0.72. Overall, the machine learning model random forest had the highest predictive abilities and was especially effective for traits where large effect quantitative trait loci were identified. This study provides the foundation for deploying effective molecular breeding strategies for grain quality in Latin American rice breeding programs.
Core Ideas
Latin America rice germplasm exhibit complex genetic correlations among grain quality traits relevant for breeding.
Amylose‐content, gelatinization temperature, and setback are ideal targets for marker‐assisted selection in Latin America indica germplasm.
Random forest models displayed higher prediction abilities for oligogenic grain quality traits.
In irrigated rice fields, plant-mediated transfer of CH
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from submerged soils to the atmosphere raise the possibility of genotypic differences in CH
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emissions. Previous research has been ...contradictory, and varietal differences in rice CH
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emissions in Latin America have not been examined. A field experiment in Colombia tested whether irrigated rice emissions might be reduced using a breeding line, an inbred variety, and two rice hybrids. Data was collected on CH
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emissions, phenotypic, root, and grain yield parameters. Variations observed in CH
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emissions, grain yield, root length, and root surface area were in the order Hybrid 2 > Hybrid 1 > breeding line > inbred variety. CH
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emissions per unit area were between 29% and 62% greater for the hybrids than the inbred variety and breeding line, and CH
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emissions per unit grain yield were comparable across genotypes. Our findings suggest that differences in root characteristics and aboveground biomass explain genetic influences on CH
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emissions. The transition to low-emission rice production systems can be accelerated by using differences in productivity and root qualities among cultivars.
CH
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emission intensities were comparable among the breeding line, inbred variety and hybrids.
Breeding for shorter roots, lower root volume, and surface area without compromising yields may be beneficial in reducing rice-based methane emissions.
High-yielding, low-CH
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emission rice should be classified as a clean development technology that qualifies for carbon credits.
Rice is a crucial contributor to global food security and is an important staple for over half the world's population. Irrigated paddy rice is a water-intensive crop, and an important contributor to ...greenhouse gas emissions. Thus, improving the efficiency of using rice as food rather than non-food uses is paramount to sustainably feeding a growing global population. One source of inefficiency in the rice market is using broken rice for non-food purposes. This study focuses on consumer preferences for rice with different broken percentages in Colombia. We used a mixed-method approach to ascertain the stated (experimental setting) and revealed (using samples that consumers independently purchased in a market) willingness to pay for broken rice to assess whether the rice market in Colombia efficiently prices rice quality. The findings highlight that consumers are aware of quality differences and are willing to pay a premium for rice with a low broken percentage, but also point to potential inefficiencies given that the willingness to pay estimates from both the two methods are statistically different. We find that the discount revealed in the market is significantly higher than that stated experimentally, which can have implications for pricing rice based on quality. Both methods found consumers were willing to pay a premium for rice under 10% broken, but beyond that threshold, there were no differences in willingness to pay. The Colombian rice industry and policymakers can use these findings to make the domestic rice market more responsive to the revealed preferences of consumers, which could have significant consequences for food security and sustainability.
Display omitted
•Colombian consumers prefer milled rice with low percentage of broken.•The relationship between milled rice price and broken percentage is not linear.•Information on the percentage of broken in milled rice affects consumers' preferences.•From a consumer point of view, the rice market prices broken rice inefficiently.•The findings have relevant commercial and policy implications.
Integrated research efforts are needed to provide insights for simultaneously achieving food production and environmental goals in rice production systems. In this study we evaluated eight ...Sustainable Rice Platform performance indicators (net profit, labor productivity, grain yield, water use efficiency, nitrogen use efficiency, phosphorus use efficiency, pesticide use efficiency, and greenhouse gas emissions) for 65 rice farmers in Peru. The aim was to (1) identify the major management factors influencing profitability, (2) evaluate potential tradeoffs between economic and environmental sustainability, and (3) understand farmer perceptions and decision-making processes related to profitability. For data analysis, farmers were grouped into profitability categories based on net profit: top (top 20%), middle (middle 60%), and bottom (bottom 20%). Our results indicate that rice yields, grain sale price, and total spending drive profitability in this region of Peru. An important finding is that the top profitability group achieved higher yields while using lower inputs of labor, pesticides, elemental P, and irrigation hours, resulting in improved environmental performance (e.g., higher nutrient and water use efficiency and lower greenhouse gas emissions). Results from focus group discussions highlighted that rice production has changed in recent decades, and there is a need for improved extension support to cope with increasing pests, disease, and water scarcity. Moreover, farmers indicated they are vulnerable to exploitation from vendors along the rice supply chain, with limited access to credit facilities and market channels and little negotiating power over the cost of inputs and rice sale price. Our results suggest that rice productivity and profitability can be improved in this region without negatively influencing environmental footprint per unit production, yet this is unlikely to occur unless key agronomic and socio-economic challenges are addressed, such as improved access to crop management recommendations, alternative financing and credit options, and technologies that decrease the costs of production.
It is internationally accepted that malnutrition and chronic diseases in developing countries are key limitations to achieving the Millennium Development Goals. In many developing countries, rice is ...the primary source of nutrition. In those countries, the major forms of malnutrition are Fe-induced anaemia, Zn deficiency and Vitamin A deficiency, whereas the major chronic disease challenges are Type II diabetes, cardiovascular disease and some cancers. There is a growing corpus of evidence regarding both limitations and opportunities as to how rice could be an effective vehicle by which to tackle key nutrition and health related problems in countries with limited resources. Rice breeding programs are able to focus on developing new varieties carrying enhanced amounts of either Fe, Zn or beta-carotene because of large public investment, and the intuitive link between providing a mineral/vitamin to cure a deficiency in that mineral/vitamin. By contrast, there has been little investment in progressing the development of particular varieties for potential impact on chronic diseases. In this review article we focus on the broad battery of evidence linking rice-related nutritional limitations to their impact on a variety of human health issues. We discuss how rice might offer sometimes even simple solutions to rectifying key problems through targeted biofortification strategies and finally, we draw attention to how recent technological (−omics) developments may facilitate untold new opportunities for more rapidly generating improved rice varieties specifically designed to meet the current and future nutritional needs of a rapidly expanding global population.
The burgeoning demand for rice in Latin America and Caribbean (LAC) exceeds supply, resulting in a rice deficit. To overcome this challenge, rice production should be increased, albeit sustainably. ...However, since rice production is associated with increases in the atmospheric concentration of two greenhouse gases (GHGs), namely methane (CH4) and nitrous oxide (N2O), the challenge is on ensuring that production increases are not associated with an increase in GHG emissions and thus do not cause an increase in GHG emission intensities. Based on current understanding of drivers of CH4 and N2O production, we provide here insights on the potential climate change mitigation benefits of management and technological options (i.e., seeding, tillage, irrigation, residue management) pursued in the LAC region. Studies conducted in the LAC region show intermittent irrigation or alternate wetting and drying of rice fields to reduce CH4 emissions by 25–70% without increasing N2O emissions. Results on yield changes associated with intermittent irrigation remain inconclusive. Compared to conventional tillage, no-tillage and anticipated tillage (i.e., fall tillage) cause a 21% and 25% reduction in CH4 emissions, respectively. From existing literature, it was unambiguous that the mitigation potential of most management strategies pursued in the LAC region need to be quantified while acknowledging country-specific conditions. While breeding high yielding and low emitting rice varieties may represent the most promising and possibly sustainable approach for achieving GHG emission reductions without demanding major changes in on-farm management practices, this is rather idealistic. We contend that a more realistic approach for realizing low GHG emitting rice production systems is to focus on increasing rice yields, for obvious food security reasons, which, while not reducing absolute emissions, should translate to a reduction in GHG emission intensities. Moreover, there is need to explore creative ways of incentivizing the adoption of promising combinations of management and technological options.
Rice (
L.) is one of the most important cereals, which provides 20% of the world's food energy. However, its productivity is poorly assessed especially in the global South. Here, we provide a first ...study to perform a deep-learning-based approach for instantaneously estimating rice yield using red-green-blue images. During ripening stage and at harvest, over 22,000 digital images were captured vertically downward over the rice canopy from a distance of 0.8 to 0.9 m at 4,820 harvesting plots having the yield of 0.1 to 16.1 t·ha
across 6 countries in Africa and Japan. A convolutional neural network applied to these data at harvest predicted 68% variation in yield with a relative root mean square error of 0.22. The developed model successfully detected genotypic difference and impact of agronomic interventions on yield in the independent dataset. The model also demonstrated robustness against the images acquired at different shooting angles up to 30° from right angle, diverse light environments, and shooting date during late ripening stage. Even when the resolution of images was reduced (from 0.2 to 3.2 cm·pixel
of ground sampling distance), the model could predict 57% variation in yield, implying that this approach can be scaled by the use of unmanned aerial vehicles. Our work offers low-cost, hands-on, and rapid approach for high-throughput phenotyping and can lead to impact assessment of productivity-enhancing interventions, detection of fields where these are needed to sustainably increase crop production, and yield forecast at several weeks before harvesting.
Abstract
Rice hoja blanca (RHB) is one of the most serious diseases in rice-growing areas in tropical Americas. Its causal agent is RHB virus (RHBV), transmitted by the planthopper Tagosodes ...orizicolus Müir. Genetic resistance is the most effective and environment-friendly way of controlling the disease. So far, only 1 major quantitative trait locus (QTL) of Oryza sativa ssp. japonica origin, qHBV4.1, that alters the incidence of the virus symptoms in 2 Colombian cultivars has been reported. This resistance has already started to be broken, stressing the urgent need for diversifying the resistance sources. In the present study, we performed a search for new QTLs of O. sativa indica origin associated with RHB resistance. We used 4 F2:3-segregating populations derived from indica-resistant varieties crossed with a highly susceptible japonica pivot parent. Besides the standard method for measuring disease incidence, we developed a new method based on computer-assisted image processing to determine the affected leaf area (ALA) as a measure of symptom severity. Based on the disease severity and incidence scores in the F3 families under greenhouse conditions and SNP genotyping of the F2 individuals, we identified 4 new indica QTLs for RHB resistance on rice chromosomes 4, 6, and 11, namely, qHBV4.2WAS208, qHBV6.1PTB25, qHBV11.1, and qHBV11.2, respectively. We also confirmed the wide-range action of qHBV4.1. Among the 5 QTLs, qHBV4.1 and qHBV11.1 had the largest effects on incidence and severity, respectively. These results provide a more complete understanding of the genetic bases of RHBV resistance in the cultivated rice gene pool and can be used to develop marker-aided breeding strategies to improve RHB resistance. The power of joint- and meta-analyses allowed precise mapping and candidate gene identification, providing the basis for positional cloning of the 2 major QTLs qHBV4.1 and qHBV11.1.
El arroz (Oryza sativa L.) en Venezuela, es afectado por el añublo de la vaina causado por Rhizoctonia solani (Teleomorfo = Thanatephorus cucumeris). No existe resistencia completa ante esta ...enfermedad. Por ello, los programás de mejoramiento genético deben evaluar un alto numero de cultivares para seleccionar aquellos cuantitativamente mejores en resistencia. Los objetivos fueron comparar métodos de evaluación de resistencia y la reacción de cultivares para resistencia al añublo de la vaina del arroz causado por R. solani AG-1 IA. Los métodos de evaluación usados fueron microcámaras y bola de micelio en umbráculo, la prueba de cinetina en laboratorio y la infestación con arroz colonizado bajo condiciones de campo. Se evaluaron 23 genotipos de arroz, incluyendo variedades testigo. Tres haplotipos de R. solani, previamente caracterizados, fueron utilizados para las inoculaciones. Los ensayos fueron de bloques completos al azar con tres repeticiones. La efectividad de los ensayos se determinó con base a la discriminación de los testigos de reacción conocida y a la mejor correlación de los métodos de laboratorio y umbraculo con los resultados de campo. El método de microcámaras, combinado con el aislado de R. solani A5B4 (64), presento la mejor correlación con los resultados de campo (r = 0,50 en promedio), seguido por el método de bola de micelio (r = 0,49, promedio). Los cultivares testigo 'Tetep' (resistente) y 'Lemont' (susceptible) fueron consistentes en los ensayos. El análisis de componentes principales identificó los genotipos CT15150-M-11-4-3-2-M (derivado de un cruce con O. glaberrima), 'SD20A' y 'D-Sativa' con los mejores niveles de resistencia. Estos resultados indican la existencia de métodos confiables para evaluar el añublo de la vaina y de cultivares adaptados con resistencia a la enfermedad. Palabras clave adicionales: Oryza sativa, Thanatephorus cucumeris, inoculación, métodos. The rice (Oryza sativa L.), in Venezuela, is affected by sheath blight caused by Rhizoctonia solani (teleomorph = Thanatephorus cucumeris). No complete resistance has been found in the world. In consequence, breeding programs should evaluate many cultivars for selecting those with the best quantitative level of resistance. The objectives were to compare methods of evaluation and cultivars reaction for resistance to the sheath blight caused by R. solani AG-1 IA. The evaluation methods were microchamber and mycelium ball in greenhouse conditions, kinetin test in laboratory and colonized rice infestation under field conditions. The cultivars were 23 genotypes of rice, including control varieties. Three haplotypes of R. solani, previously characterized, were used for the inoculations. The experimental designs were randomized complete block with three replications. The effectiveness of the trials was determined based on the discrimination of controls with well-known reaction and the best correlation of the laboratory and greenhouse methods with the field results. The method of microchamber using the isolate A5B4 (64) had the best correlation with field results (r = 0.50 on average), followed by the method of ball mycelium (r = 0.49, on average). The control cultivars 'Tetep' (resistant) and 'Lemont' (susceptible) were consistent across the experiments. The principal component analysis identified the genotypes CT15150-M-11-4-3-2-M (derived from a cross with O. glaberrima), 'SD20A' and 'D-Sativa' with the best levels of resistance. These results indicate the existence of reliable methods to evaluate this disease and adapted cultivars with resistance to rice sheath blight. Additional key words: Oryza sativa, Thanatephorus cucumeris, inoculation, methods
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