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Although social learning (SL) conceptualization and implementation are flourishing in sustainability sciences, and its non-rigid conceptual fluidity is regarded as an advantage, research must advance the understanding of SL phenomenon patterns based on empirical data, thus contributing to the identification of its forms and triggering mechanisms, particularly those that can address urgent Anthropocene socio-ecological problems. This study aims to discover fundamental patterns along which SL in natural resources management differs by identifying SL archetypes and establishing correlations between the SL process and overall geopolitical conditions. Using a systematic literature review comprising 137 case studies in the five continents, content analysis, and correlations were performed. Results show two main archetypes of social learning (endogenous and exogenous). Their occurrence was linked, to where social learning occurs and how venues/preconditions for social learning are placed. In the Global South, endogenous SL should be better potentialized as a catalyzer of deliberative processes for sustainable natural resources management.

Improving crop water use efficiency, the amount of carbon assimilated as biomass per unit of water used by a plant, is of major importance as water for agriculture becomes scarcer. In rice, the genetic bases of transpiration efficiency, the derivation of water use efficiency at the whole-plant scale, and its putative component trait transpiration restriction under high evaporative demand remain unknown. These traits were measured in 2019 in a panel of 147 African rice (Oryza glaberrima) genotypes known to be potential sources of tolerance genes to biotic and abiotic stresses. Our results reveal that higher transpiration efficiency is associated with transpiration restriction in African rice. Detailed measurements in a subset of highly contrasted genotypes in terms of biomass accumulation and transpiration confirmed these associations and suggested that root to shoot ratio played an important role in transpiration restriction. Genome wide association studies identified marker-trait associations for transpiration response to evaporative demand, transpiration efficiency, and its residuals, with links to genes involved in water transport and cell wall patterning. Our data suggest that root-shoot partitioning is an important component of transpiration restriction that has a positive effect on transpiration efficiency in African rice. Both traits are heritable and define targets for breeding rice with improved water use strategies.

A deep understanding of the genetic control of drought tolerance and iron deficiency tolerance is essential to hasten the process of developing improved varieties with higher tolerance through genomics-assisted breeding. In this context, an improved genetic map with 1205 loci was developed spanning 2598.3 cM with an average 2.2 cM distance between loci in the recombinant inbred line (TAG 24 × ICGV 86031) population using high-density 58K single nucleotide polymorphism (SNP) “Axiom_Arachis” array. Quantitative trait locus (QTL) analysis was performed using extensive phenotyping data generated for 20 drought tolerance- and two iron deficiency tolerance-related traits from eight seasons (2004–2015) at two locations in India, one in Niger, and one in Senegal. The genome-wide QTL discovery analysis identified 19 major main-effect QTLs with 10.0–33.9% phenotypic variation explained (PVE) for drought tolerance- and iron deficiency tolerance- related traits. Major main-effect QTLs were detected for haulm weight (20.1% PVE), SCMR (soil plant analytical development (SPAD) chlorophyll meter reading, 22.4% PVE), and visual chlorosis rate (33.9% PVE). Several important candidate genes encoding glycosyl hydrolases; malate dehydrogenases; microtubule-associated proteins; and transcription factors such as MADS-box, basic helix-loop-helix (bHLH), NAM, ATAF, and CUC (NAC), and myeloblastosis (MYB) were identified underlying these QTL regions. The putative function of these genes indicated their possible involvement in plant growth, development of seed and pod, and photosynthesis under drought or iron deficiency conditions in groundnut. These genomic regions and candidate genes, after validation, may be useful to develop molecular markers for deploying genomics-assisted breeding for enhancing groundnut yield under drought stress and iron-deficient soil conditions.

Crop growth is a dynamic process whereby the sorghum plant germinates, emerges and begins to capture solar radiation and, via photosynthesis, accumulate biomass. Interacting with its surrounding environment, the sorghum plant adapts to the various biotic and abiotic challenges on its journey towards flowering and, ultimately, seed production. We will explain the physiology of growth and yield in sorghum using a framework based on crop growth and development. The process of evolution has enabled plants to utilise a variety of timing mechanisms that regulate development, improving the chance that germination and reproduction are aligned with favourable periods of growth. Crop development is predominantly affected by photoperiod and temperature. In contrast, crop growth, which represents the biomass produced, is predominantly affected by incoming radiation. Grain yield can be defined as the product of resource capture (light, water and nitrogen), resource use efficiency and partitioning of that resource into grain. Since water limitation is the key constraint to sorghum yield globally, crop growth will be considered in the context of water-limiting and non-limiting scenarios. In the absence of water limitation, the sorghum crop is largely limited by radiation, and in this scenario, biomass accumulation is the product of intercepted radiation and its conversion efficiency, the radiation use efficiency (RUE, biomass produced per unit of radiation intercepted). When water is a limitation, biomass accumulation under drought stress becomes a function of the total amount of water used by a crop (transpiration, T) and the transpiration efficiency (TE, biomass produced per unit of water transpired). For the first time in history, we now have the tools to measure physiological traits, such as dynamic biomass growth or canopy radiation use efficiency at a high-throughput scale that can match the genomic data. These new tools will allow us to phenotype thousands of lines that bre

Pearl millet (Pennisetum glaucum L.) is the sixth most important cereal crop globally, predominantly grown for food and forage in arid and semi-arid tropical regions. Under climate change, pearl millet will face more adverse climatic conditions, particularly due to drought and heat stress and newly emerging disease, blast. Crop wild relatives (CWR) are the reservoir of valuable genes for tolerance/resistance to various abiotic/biotic stresses. Primary genepool species Pennisetum glaucum subsp. violaceum evolved in hot and dry conditions of Sahel region in Africa, grows in even more arid regions than the cultigen, and thus possess higher levels of drought and heat tolerance. Four pre-breeding populations were developed using wild Pennisetum violaceum accessions and cultivated pearl millet genotypes following advanced backcross approach. These populations were evaluated for flowering-stage heat stress during 2018 summer season across three locations, Agra in Uttar Pradesh, and SK Nagar and Tharad in Gujarat in India. These populations were also evaluated for terminal drought during 2018 rainy season at two locations, Hisar and Bawal. Promising ILs having improved heat and drought tolerance were identified. These populations were also evaluated under LeasyScan for the canopy-related parameters, as well as at LysiField facility for the traits related to water-use and water- use efficiency under well-watered and water-stress conditions. Further, screening of promising drought and/or heat tolerant ILs for five diverse pathotypes, Pg 45, Pg 138, Pg 186, Pg 204 and Pg 232 of blast resulted in the identification of resistant ILs. Preliminary screening of three populations for Striga hermonthica in Niger resulted in the identification of several ILs having improved Striga resistance. Re-screening of the material will be done during 2019 rainy season to confirm the results. Utilization of these promising ILs in breeding programs will assist in developing new varieties/hybrids

The mandate grain legumes of ICRISAT include chickpea, pigeonpea and groundnut which are important crops of Asia and Africa. The grain legumes improvement program of ICRISAT has access to the largest collection of germplasm of these crops (20,602 accessions of chickpea, 13,771 accessions of pigeonpea, and 15,446 accessions of groundnut) available in ICRISAT genebank, state-of-the art genomics lab, Platform for Translational Research on Transgenic Crops (PTTC), precision phenotyping facilities for abiotic and biotic stresses, controlled environment facilities and a global network of research partners. The major objectives of grain legumes improvement include high yield, early maturity, resistance/tolerance to key abiotic and biotic stresses, and market preferred grain traits (size, shape and color). The crop-specific breeding objectives include suitability to machine harvesting and herbicide tolerance in chickpea, development of hybrids in pigeonpea, and enhanced oil yield and quality (high oleic content) and tolerance to aflatoxin contamination in groundnut. The crop breeding programs have been making extensive use of the germplasm, including wild species. The advances in genomics include availability of draft genome sequences, large number of molecular markers, high density genetic maps, transcriptomic resources, physical maps and molecular markers linked to genes/quantitative trait loci for key traits. There are successful examples of introgression of traits through marker-assisted backcrossing in chickpea and groundnut. Transgenics events are available for pod borer resistance in chickpea and pigeonpea and drought tolerance in groundnut. Advances have also been made in use of secondary metabolites for promotion of plant growth, control of insect pests and plant pathogens, and biofortification. The breeding materials and germplasm supplied by ICRISAT have led to release of 160 varieties of chickpea in 26 countries, 91 varieties/hybrids of pigeonpea in 19 countries

Grain legumes form an important component of the human diet, provide feed for livestock, and replenish soil fertility through biological nitrogen fixation. Globally, the demand for food legumes is increasing as they complement cereals in protein requirements and possess a high percentage of digestible protein. Climate change has enhanced the frequency and intensity of drought stress, posing serious production constraints, especially in rainfed regions where most legumes are produced. Genetic improvement of legumes, like other crops, is mostly based on pedigree and performance-based selection over the past half century. To achieve faster genetic gains in legumes in rainfed conditions, this review proposes the integration of modern genomics approaches, high throughput phenomics, and simulation modelling in support of crop improvement that leads to improved varieties that perform with appropriate agronomy. Selection intensity, generation interval, and improved operational efficiencies in breeding are expected to further enhance the genetic gain in experimental plots. Improved seed access to farmers, combined with appropriate agronomic packages in farmers’ fields, will deliver higher genetic gains. Enhanced genetic gains, including not only productivity but also nutritional and market traits, will increase the profitability of farming and the availability of affordable nutritious food especially in developing countries.

Background Terminal drought stress leads to substantial annual yield losses in chickpea (Cicer arietinum L.). Adaptation to water limitation is a matter of matching water supply to water demand by the crop. Therefore, harnessing the genetics of traits contributing to plant water use, i.e. transpiration rate and canopy development dynamics, is important to design crop ideotypes suited to a varying range of water limited environments. With an aim of identifying genomic regions for plant vigour (growth and canopy size) and canopy conductance traits, 232 recombinant inbred lines derived from a cross between ICC 4958 and ICC 1882, were phenotyped at vegetative stage under well-watered conditions using a high throughput phenotyping platform (LeasyScan). Results Twenty one major quantitative trait loci (M-QTLs) were identified for plant vigour and canopy conductance traits using an ultra-high density bin map. Plant vigour traits had 13 M-QTLs on CaLG04, with favourable alleles from high vigour parent ICC 4958. Most of them co-mapped with a previously fine mapped major drought tolerance “QTL-hotspot” region on CaLG04. One M-QTL was found for canopy conductance on CaLG03 with the ultra-high density bin map. Comparative analysis of the QTLs found across different density genetic maps revealed that QTL size reduced considerably and % of phenotypic variation increased as marker density increased. Conclusion Earlier reported drought tolerance hotspot is a vigour locus. The fact that canopy conductance traits, i.e. the other important determinant of plant water use, mapped on CaLG03 provides an opportunity to manipulate these loci to tailor recombinants having low/high transpiration rate and plant vigour, fitted to specific drought stress scenarios in chickpea.

Chickpea, the second most important legume crop, suffers major yield losses by terminal drought stress (DS). Stronger root system is known to enhance drought yields but this understanding remains controversial. To understand precisely the root traits contribution towards yield, 12 chickpea genotypes with well-known drought response were field evaluated under drought and optimal irrigation. Root traits, such as root length density (RLD), total root dry weight (RDW), deep root dry weight (deep RDW) and root:shoot ratio (RSR), were measured periodically by soil coring up to 1.2 m soil depth across drought treatments. Large variations were observed for RLD, RDW, deep RDW and RSR in both the drought treatments. DS increased RLD below 30 cm soil depth, deep RDW, RSR but decreased the root diameter. DS increased the genetic variation in RDW more at the penultimate soil depths. Genetic variation under drought was the widest for RLD ∼50 DAS, for deep RDW ∼50–75 DAS and for RSR at 35 DAS. Genotypes ICC 4958, ICC 8261, Annigeri, ICC 14799, ICC 283 and ICC 867 at vegetative stage and genotypes ICC 14778, ICCV 10, ICC 3325, ICC 14799 and ICC 1882 at the reproductive phase produced greater RLD. Path- and correlation coefficients revealed strong positive contributions of RLD after 45 DAS, deep RDW at vicinity of maturity and RSR at early podfill stages to yield under drought. Breeding for the best combination of profuse RLD at surface soil depths, and RDW at deeper soil layers, was proposed to be the best selection strategy, for an efficient water use and an enhanced terminal drought tolerance in chickpea.

Chickpeas are often grown under receding soil moisture and suffer ~50% yield losses due to drought stress. The timing of soil water use is considered critical for the efficient use of water under drought and to reduce yield losses. Therefore the root growth and the soil water uptake of 12 chickpea genotypes known for contrasts in drought and rooting response were monitored throughout the growth period both under drought and optimal irrigation. Root distribution reduced in the surface and increased in the deep soil layers below 30 cm in response to drought. Soil water uptake was the maximum at 45–60 cm soil depth under drought whereas it was the maximum at shallower (15–30 and 30–45 cm) soil depths when irrigated. The total water uptake under drought was 1-fold less than optimal irrigation. The amount of water left unused remained the same across watering regimes. All the drought sensitive chickpea genotypes were inferior in root distribution and soil water uptake but the timing of water uptake varied among drought tolerant genotypes. Superiority in water uptake in most stages and the total water use determined the best adaptation. The water use at 15–30 cm soil depth ensured greater uptake from lower depths and the soil water use from 90–120 cm soil was critical for best drought adaptation. Root length density and the soil water uptake across soil depths were closely associated except at the surface or the ultimate soil depths of root presence.

Terminal drought stress leads to substantial yield losses in chickpea (Cicer arietinum L.). Water conservation at vegetative growth (canopy conductivity and canopy size and development) allow plants to increase soil water extraction during grain filling and are hypothesised to help chickpea adaptation to water limited environments. Plant vigour and water saving traits were phenotyped in 232 recombinant inbred lines (RILs), derived from a cross between ICC4958 and ICC1882, at 28 days after sowing under well water conditions using a high throughput phenotyping platform. Different density genetic maps (241-SSRLow density, 1007-SSR+SNPs-High density and 1557-SNPs-Ultra high density) were used for QTLs identification. Several major QTLs (M-QTLs) for plant vigour traits (3D-leaf area, shoot biomass, plant height and growth related traits) were identified on CaLG04, and co-mapped with previously identified and fine mapped major drought tolerance QTL-hotspot region on CaLG04 (~300Kb).The canopy conductance trait (e.g Transpiration rate) had a M-QTL mapped on CaLG03 using ultra-high density bin markers. Plant vigour traits on CaLG04 and canopy conductance related traits on CaLG03 provide opportunity to manipulate these loci to tailor recombinants having lower transpiration rate and high plant vigour. This ideotype might be enhancing the water stress adaptation in chickpea. To test this hypothesis, a subset of 40 RILs contrasting for vigour and water use traits was tested in lysimeters and field under different water stress treatments. High vigour low water use lines had higher seed yield under severe water stress treatments than high vigour and high water use lines, validating the hypothesis.

Transpiration efficiency (TE) has been considered as an important component for water use efficiency (WUE) and to screen yield variation under drought stress in peanut. A Recombinant Inbred Lines (RIL’s) for Valencia breeding were developed for high WUE from two contrasting parents differed in their drought tolerance. A set of 112 RILs derived from drought tolerant ICGV7243 and drought susceptible Valencia-C were used along with parents to evaluate TE and pod yield. A lysimetric system was used to grow the plants and to screen the RILs for their water use, dry weight, TE, pod yield and haulm weight. One experiment was conducted during December, 2015 to March 2016 using randomized complete block design with 4 replications. Plants were subjected to drought stress treatment, imposed from 30 days after sowing in the form of an intermittent stress, i.e. the plant were subjected to cycles of drying and re-watering similar to treatments applied under field conditions. A 2 fold variation for TE was observed among 112 RILs derived from drought tolerant and susceptible parents. Other parameters pod yield, water use and haulm weight showed significant variation among the RILs. A significant association was observed between TE and seed yield in this study, although the coefficient of variation was relatively weak (R2 = 0.14), which was also quite typical of mild vapor pressure deficit environment. The distribution of TE among the 112 RILs indicates polygenic character of TE controlled by dominant and additive genes. This study further requires quantitative trait loci (QTL) analysis for marker assisted selection to select and breed efficient genotypes for improved TE.

Chickpea is the second most important legume crop largely grown under semi-arid tropics where terminal drought is one of the major constraints for its productivity. A trait-based selection had been considered more beneficial in drought tolerance breeding to overcome the environmental influence on drought yields. Large number of traits had been suggested in literature, with less indication on their importance and priority, for use in such breeding programs resulting in poor utilization of critical traits in drought tolerance breeding. To identify the most critical traits that contribute to grain yield under drought, 12 chickpea genotypes, with well-defined drought response, were field evaluated by sampling at regular intervals during the cropping period. Large range of variation was observed for shoot biomass productivity, specific leaf area (SLA) and leaf area index (LAI) at different days after sowings (DAS), canopy temperature depression (CTD) at mid-reproductive stages, growth duration and both morphological and analytical yield components. Grain yield under drought was closely associated with the rate of partitioning (p), crop growth rate (C), CTD, phenology, LAI at mid-pod fill stage, pod number m−2 at maturity, shoot biomass at reproductive growth stages and SLA at physiological maturity. The shoot trait(s) were prioritized based on their significance and contribution to drought tolerance. The trait(s) that conferred tolerance varied across genotypes. The order of traits/plant functions identified as important and critical for the drought tolerance were p, C, CTD, growth duration and other related traits. Relatively less important traits were LAI, SLA at the mid reproductive stage and pod number per unit area at maturity. The traits Dr, seeds pod−1 and 100-seed weight were found to be least important. Breeding for the best combination of p and C with the right phenology was proposed to be the best selection strategy to enhance terminal drought tolerance in chi

Genetics and genomics will have the potential to enhance sustainable peanut production. The major contribution of these technologies for peanut will likely be improved disease resistance, oil quality, and enhanced productivity. Those attributes may be achieved more effectively through genomic biotechnology to utilize the genetic resources preserved in germplasm collections for maximizing the genetic potential in breeding. Superior cultivars will maximize desirable genetic traits and provide growers with cultivars that are locally adapted and highly productive. Genomics involves the study of the complete genetic makeup, through mapping, sequencing, and functional studies to identify genes that regulate, control or modify trait expression. With the development in sequencing technologies, next-generation sequencing (NGS) has opened the gateway to sequence the genomes in a fast, reliable, and cost-effective manner. The international peanut genome sequencing project was discussed in 2010 and launched in 2012 after much deliberation and strategic planning. The exciting news is that the Peanut Genome Consortium, representing a coalition of international scientists and stakeholders engaged in the International Peanut Genome Initiative, announced the public release of the first chromosomal-scale draft sequences of two peanut species (Arachis duranensis and Arachis ipaënsis) on April 2, 2014 (http://www.peanutbioscience.com/images/4-2-14_News_Release_Notice.pdf). In this chapter, we update the information on the molecular markers, genetic linkage maps, and quantitative trait loci (QTLs) of traits mapped to date. Information of the preview of genome sequences, which would be available in peanut populations for high resolution genetic and trait mapping such as multiparent advanced generation intercross and nested association mapping, is also discussed. Furthermore, an innovative method to identify a causal mutant single nucleotide polymorphism or major allele for QTLs through N

Background Although chickpea (Cicer arietinum L.), an important food legume crop, is sensitive to salinity, considerable variation for salinity tolerance exists in the germplasm. To improve any existing cultivar, it is important to understand the genetic and physiological mechanisms underlying this tolerance. Results In the present study, 188 recombinant inbred lines (RILs) derived from the cross ICCV 2 × JG 11 were used to assess yield and related traits in a soil with 0 mM NaCl (control) and 80 mM NaCl (salinity) over two consecutive years. Salinity significantly (P < 0.05) affected almost all traits across years and yield reduction was in large part related to a reduction in seed number but also a reduction in above ground biomass. A genetic map was constructed using 56 polymorphic markers (28 simple sequence repeats; SSRs and 28 single nucleotide polymorphisms; SNPs). The QTL analysis revealed two key genomic regions on CaLG05 (28.6 cM) and on CaLG07 (19.4 cM), that harboured QTLs for six and five different salinity tolerance associated traits, respectively, and imparting either higher plant vigour (on CaLG05) or higher reproductive success (on CaLG07). Two major QTLs for yield in the salinity treatment (explaining 12 and 17% of the phenotypic variation) were identified within the two key genomic regions. Comparison with already published chickpea genetic maps showed that these regions conferred salinity tolerance across two other populations and the markers can be deployed for enhancing salinity tolerance in chickpea. Based on the gene ontology annotation, forty eight putative candidate genes responsive to salinity stress were found on CaLG05 (31 genes) and CaLG07 (17 genes) in a distance of 11.1 Mb and 8.2 Mb on chickpea reference genome. Most of the genes were known to be involved in achieving osmoregulation under stress conditions. Conclusion Identification of putative candidate genes further strengthens the idea of using CaLG05 and CaLG07 genomic regions fo