Jaumer Ricaurte

Adaptive attributes of tropical forage species to acid soils. III. Differences in phosphorus acquisition and utilization as influenced by varying phosphorus supply and soil type

Abstract Low phosphorus (P) supply is a major limitation of forage production in acid soils of the tropics. A glasshouse experiment was conducted to determine the differences in P acquisition and utilization among three legumes (Arachis pintoi, Stylosanthes capitata and Centrosema acutifolium) and one grass (Brachiaria dictyoneura). The plants were grown under monoculture or in grass + legume associations in two acid Oxisols of contrasting texture (sandy loam or clay loam). The soils were amended with soluble phosphate at rates ranging from 0 to 50 kg‐ha‐1. After 80 days of growth, total P and nitrogen (N) content in different plant parts, inorganic P content and acid phosphatase activity in roots and leaves, vesicular‐arbuscular mycorrhizal root infection, total P acquisition from soil, P acquisition efficiency, P transport index, and P use efficiency were determined. Total P acquisition (per unit soil surface) of A. pintoi was higher than that of the other two legumes at 50 kg‐ha‐l of P supply. Phosphor...

Adaptive attributes of tropical forage species to acid soils II. Differences in shoot and root growth responses to varying phosphorus supply and soil type

Abstract Identification of plant attributes that improve the performance of tropical forage ecotypes when grown as monocultures or as grass+legume associations in low fertility acid soils will assist the development of improved forage plants and pasture management technology. The present work compared the shoot and root growth responses of four tropical forages: one grass and three legumes. The forages were grown in monoculture or in grass+legume associations at different levels of soil phosphate. Two infertile acid soils, both Oxisols, were used: one sandy loam and one clay loam. They were amended with soluble phosphate at rates ranging from 0 to 50 kg ha‐1. The forages, Brachiaria dictyoneura (grass), Arachis pintoi, Stylosanthes capitata and Centrosema acutifolium (legumes), were grown in large plastic containers (40 kg of soil per container) in the glasshouse. After 80 days of growth, shoot and root biomass production, dry matter partitioning, leaf area production, total chlorophyll content in leaves,...

Simulating phosphorus responses in annual crops using APSIM: model evaluation on contrasting soil types

Crop simulation models have been used successfully to evaluate many systems and the impact of change on these systems, e.g. for climatic risk and the use of alternative management options, including the use of nitrogen fertilisers. However, for low input systems in tropical and subtropical regions where organic inputs rather than fertilisers are the predominant nutrient management option and other nutrients besides nitrogen (particular phosphorus) constrain crop growth, these models are not up to the task. This paper describes progress towards developing a capability to simulate response to phosphorus (P) within the APSIM (Agricultural Production Systems Simulator) framework. It reports the development of the P routines based on maize crops grown in semi-arid eastern Kenya, and validation in contrasting soils in western Kenya and South-western Colombia to demonstrate the robustness of the routines. The creation of this capability required: (1) a new module (APSIM SoilP) that simulates the dynamics of P in soil and is able to account for effectiveness of alternative fertiliser management (i.e. water-soluble versus rock phosphate sources, placement effects); (2) a link to the modules simulating the dynamics of carbon and nitrogen in soil organic matter, crop residues, etc., in order that the P present in such materials can be accounted for; and (3) modification to crop modules to represent the P uptake process, estimation of the P stress in the crop, and consequent restrictions to the plant growth processes of photosynthesis, leaf expansion, phenology and grain filling. Modelling results show that the P routines in APSIM can be specified to produce output that matches multi-season rotations of different crops, on a contrasting soil type to previous evaluations, with very few changes to the parameterization files. Model performance in predicting the growth of maize and bean crops grown in rotation on an Andisol with different sources and rates of P was good (75–87% of variance could be explained). This is the first published example of extending APSIM P routines to another crop (beans) from maize.

Detecting bacterial endophytes in tropical grasses of the Brachiaria genus and determining their role in improving plant growth

Sorghum is a staple food grain in many semi-arid and tropic areas of the world, notably in Sub-Saharan Africa because of its good adaptation to hard environments and its good yield of production. Among important biochemical components for sorghum processing are levels of starch (amylose and amylopectin) and starch depolymerizing enzymes. Current research focus on identifying varieties meeting specific agricultural and food requirements from the great biodiversity of sorghums to insure food security. Results show that some sorghums are rich sources of micronutrients (minerals and vitamins) and macronutrients (carbohydrates, proteins and fat). Sorghum has a resistant starch, which makes it interesting for obese and diabetic people. In addition, sorghum may be an alternative food for people who are allergic to gluten. Malts of some sorghum varieties display

Adaptive attributes of tropical forage species to acid soils. IV. Differences in shoot and root growth responses to inorganic and organic phosphorus sources

Abstract In highly weathered acid soils, low supply of phosphorus (P), a major plant nutrient, severely limits pasture establishment and production. Previous research indicated that inherent differences in efficiencies of P acquisition and use exist between tropical forage grasses and legumes when grown in acid soils. These differences in P acquisition between grasses and legumes may result from their ability to use sources of less available P from infertile acid soils. We tested this hypothesis by conducting a greenhouse study. The main objective was to determine differences in shoot and root growth responses between the grass Brachiaria dictyoneura CIAT 6133 and the legume Arachis pintoi CIAT 17434 when grown under monoculture or in grass+legume association with different sources of inorganic and organic P. Two acid soils of contrasting texture (sandy or clay loam) were amended with different sources of P: di‐calcium phosphate (Ca‐P), aluminum phosphate (Al‐P),phyticacid(organic‐P), and cow manure (dung...

Root Distribution and Nutrient Uptake in Crop-Forage Systems on Andean Hillsides

ABSTRACT Root growth and distribution of crop and forage components of production systems on hillsides could have important effects on nutrient acquisition and plant growth, as well as on soil loss. A long-term field experiment was established in 1994 in the Andean hillsides region of Cauca, Colombia. Soil at the site is medium- to fine-textured Andisol derived from volcanic-ash deposits. Four treatments–cassava monocrop, cassava + cover legumes intercrop, elephant grass forage, and imperial grass forage-were selected to determine differences in dry matter partitioning, leaf area index, nutrient composition, root distribution (0–80 cm soil depth), nutrient acquisition and soil loss. Root biomass of the cassava + cover legumes intercrop was 44% greater than that of the cassava monocrop. The presence of cover legumes not only reduced soil loss but also improved potassium acquisition by cassava. Among the two forage systems, elephant grass had greater root biomass (9.3 t/ha) than the imperial grass (4.2 t/ha). The greater root length density (per unit soil volume) of the former contributed to superior acquisition of nitrogen, phosphorus, potassium and calcium from soil. In addition, the abundance of very fine roots in the elephant grass forage system in the topsoil layers reduced the loss of soil from the steep slopes. These results indicate that (i) the presence of cover legumes can improve potassium acquisition by cassava; and (ii) the use of elephant grass as a forage grass can reduce soil loss in Andean hillsides.

Development of a QTL-environment-based predictive model for node addition rate in common bean

Key messageThis work reports the effects of the genetic makeup, the environment and the genotype by environment interactions for node addition rate in an RIL population of common bean. This information was used to build a predictive model for node addition rate.AbstractTo select a plant genotype that will thrive in targeted environments it is critical to understand the genotype by environment interaction (GEI). In this study, multi-environment QTL analysis was used to characterize node addition rate (NAR, node day− 1) on the main stem of the common bean (Phaseolus vulgaris L). This analysis was carried out with field data of 171 recombinant inbred lines that were grown at five sites (Florida, Puerto Rico, 2 sites in Colombia, and North Dakota). Four QTLs (Nar1, Nar2, Nar3 and Nar4) were identified, one of which had significant QTL by environment interactions (QEI), that is, Nar2 with temperature. Temperature was identified as the main environmental factor affecting NAR while day length and solar radiation played a minor role. Integration of sites as covariates into a QTL mixed site-effect model, and further replacing the site component with explanatory environmental covariates (i.e., temperature, day length and solar radiation) yielded a model that explained 73% of the phenotypic variation for NAR with root mean square error of 16.25% of the mean. The QTL consistency and stability was examined through a tenfold cross validation with different sets of genotypes and these four QTLs were always detected with 50–90% probability. The final model was evaluated using leave-one-site-out method to assess the influence of site on node addition rate. These analyses provided a quantitative measure of the effects on NAR of common beans exerted by the genetic makeup, the environment and their interactions.

A Predictive Model for Time-to-Flowering in the Common Bean Based on QTL and Environmental Variables

The common bean is a tropical facultative short-day legume that is now grown in tropical and temperate zones. This observation underscores how domestication and modern breeding can change the adaptive phenology of a species. A key adaptive trait is the optimal timing of the transition from the vegetative to the reproductive stage. This trait is responsive to genetically controlled signal transduction pathways and local climatic cues. A comprehensive characterization of this trait can be started by assessing the quantitative contribution of the genetic and environmental factors, and their interactions. This study aimed to locate significant QTL (G) and environmental (E) factors controlling time-to-flower in the common bean, and to identify and measure G × E interactions. Phenotypic data were collected from a biparental [Andean × Mesoamerican] recombinant inbred population (F11:14, 188 genotypes) grown at five environmentally distinct sites. QTL analysis using a dense linkage map revealed 12 QTL, five of which showed significant interactions with the environment. Dissection of G × E interactions using a linear mixed-effect model revealed that temperature, solar radiation, and photoperiod play major roles in controlling common bean flowering time directly, and indirectly by modifying the effect of certain QTL. The model predicts flowering time across five sites with an adjusted r-square of 0.89 and root-mean square error of 2.52 d. The model provides the means to disentangle the environmental dependencies of complex traits, and presents an opportunity to identify in silico QTL allele combinations that could yield desired phenotypes under different climatic conditions.

QTL analyses for tolerance to abiotic stresses in a common bean (Phaseolus vulgaris L.) population

Common bean productivity is reduced by several abiotic stress factors like drought and low soil fertility, leading to yield losses particularly in low input smallholder farming systems in the tropics. To understand the genetics of stress tolerance, and to improve adaptation of common bean to adverse environments, the BAT 881 x G21212 population of 95 recombinant inbred lines (RILs) was evaluated under different abiotic stress conditions in 15 trials across four locations in Colombia, representing two higher altitude (Darién, Popayán) and two lower altitude (Palmira, Quilichao) locations. Stress vs non-stress treatments showed that yields were reduced in drought trials in Palmira by 13 and 31%, respectively, and observed yield reductions in low phosphorus stress were 39% in Quilichao, 16% in Popayán, and 71% in Darién, respectively. Yield components and biomass traits were also reduced. Traits linked to dry matter redistribution from stems, leaves and pods to seed, such as pod harvest index and total non-structural carbohydrates, were found to be important factors contributing to yield in all conditions. In contrast, early maturity was correlated with improved yield only in lower altitude locations, whereas in higher altitudes delayed maturity promoted yield. Superior RILs that combine stress tolerance and high cross-location productivity were identified. Lines that showed good yield under strong stress conditions also performed well under non-stress conditions, indicating that breeder’s selection can be applied for both conditions at the same time. Quantitative trait loci (QTL) analyses revealed a stable yield QTL on chromosome Pv04, detected individually in all locations, several stress treatments and in best linear unbiased predictions (BLUPs) across all trials. Furthermore, two QTL hotspots for maturity traits were identified on Pv01 and Pv08, which are the most stable QTL. The constitutive yield QTL could serve as a good candidate for marker development and could be used in marker assisted selection. Increased understanding of the physiology of abiotic stress tolerance, combined with the availability of superior germplasm and molecular tools, will aid breeding efforts for further improvement of these plant traits.