Root Senescence in Red Clover (\u3cem\u3eTrifolium Pratense\u3c/em\u3e L.)

Legume root systems form a mosaic of living, ageing and dead roots and nodules. The balance between these stages alters during plant development. Stressful events (drought, temperature change, reduced carbon supply, etc.) disturb the balance (Butler et al., 1959). Effects of root and nodule death on soil structure, composition and leaching and on plant persistency are understood poorly. Plants with differing senescence patterns are useful tools to study these effects. Molecular studies of root senescence need detailed knowledge of the process and timing of root senescence and death. Biochemical and histochemical markers of senescence were used to generate preliminary results of the effects of reduced carbon input, temporary (by defoliation, D) or permanent (by defoliation and shading, DS) on red clover shoot survival and root death

Evaluation of a White Clover Variety With Increased Resistance to Stem Nematode (\u3cem\u3eDitylenchus Dipsaci\u3c/em\u3e) Under Sheep Grazing and Cutting

Stem nematode (Ditylenchus dipsaci (Kühn) Filipjev) is a major pest of white clover (Trifolium repens L.) in UK pastures (Cook et al., 1992a) and in other parts of the world. In a previous trial, resistant and susceptible selections yielded the same in three years in the absence of the nematode but, on infested plots, the susceptible yielded the same as the resistant selection in year 1 but only 68 and 58% in years 2 and 3, as the nematode infestation increased (Cook et al., 1992b). We have now developed varieties with enhanced resistance to this pest by screening under controlled conditions (Plowright et al., 2002). We describe an experiment to test the hypothesis that stress imposed on the plant by grazing as opposed to cutting management would exacerbate the effects of nematode infestation and accentuate the advantages of resistance through longer survival of clover plants

Leaf and roots yields responses of three improved cassava (Manihot esculenta Crantz) varieties to organo-mineral fertilizers and leaf harvest in the South-West Nigeria

Open Access Article; Published online: 17 Aug 2020L’étude a été menée dans l’objectif d’évaluer la production de trois variétés améliorées de manioc en réponse à la récolte des feuilles et aux fertilisants NPK, compost et Compost-NPK. L’essai a été fait selon le dispositif en split-split plot, à blocs aléatoires complets à trois facteurs et trois réplications. Les récoltes ont été réalisées à 3 mois et 5 mois après la plantation. La récolte finale a été faite à 12 Mois Après la Plantation (MAP). Le résultat montre qu’une différence non significative (p>0,05) a été observée entre les variétés et entre les traitements fertilisants du rendement en feuilles sèches total. La moyenne totale du rendement en feuilles sèches s'élève à 1454,19 kg/ha au niveau du contrôle. Et ce rendement augmente en moyenne de 10,42% en présence du compost, 39,91% quand le mélange Compost-NPK a été appliqué et de 34, 19% en présence de NPK. Le rendement racinaire varie significativement (p˂0,05) en fonction des variétés et traitement de récolte des feuilles. La perte moyenne de rendement sec due à la récolte des feuilles est de 3,86 t/ha soit 45,77%. La perte du rendement racinaire sec a été compensée en moyenne de 35,59% soit 1,64 t/ha par le mélange Compost-NPK, et 24,05% soit 1,11 t/ha quand le NPK a été appliquée. Parmi les variétés, deux répondent aux fertilisants et sont capables de compenser les pertes. L’IITA-TMS-IBA071393 serait un bon candidat pour les petits exploitants dépourvus de moyen d’intrant. This study was carried out to investigate the leaf and root yield response to leaf harvest and the application of NPK fertilizer, compost and the combination of NPK plus compost of three improved cassava varieties. The experiment was a complete randomised split-split plot design with three factors and three replications. Leaf harvest was at 3 months and 5 months after planting (MAP). The final root harvest was at 12 MAP. The leaf dry matter yield was not significantly (p> 0.05) different between varieties and fertilizer treatments. The average leaf yield was 1454.19 kg/ha DM in control. Leaf yield increased by 10.42% when compost was applied, by 39.91% when compost plus NPK was applied and by 34.19% when only NPK was applied. Root yield was significantly (p˂0.05) affected by cassava variety and leaf harvest. Average root DM yield losses were 3.86 t/ha (45.77%) when leaves were harvested. Root DM yield loss was compensated to 35.59% (1.64 t/ha) when compost plus NPK fertilizer was applied and 24.05% (1.11 t/ha) when NPK was applied. Two varieties responded positively to fertilisers and were able to compensate for root yield losses. IITA-TMS-IBA071393 appears a suitable candidate for cassava farmers with small income because it did not require inputs

Quantitative Trait Locus Analysis of Morphogenetic and Developmental Traits in an SSR and AFLP-Based Genetic Map of White Clover (\u3cem\u3eTrifolium Repens\u3c/em\u3e L.)

Molecular marker-assisted plant breeding is a key target for the temperate legume pasture crop white clover (Trifolium repens L.). The first genetic linkage map of white clover has been constructed using self-fertile mutants to derive an intercross based fourth and fifth generation inbred parental genotypes (F2[I.4R x I.5J]). The framework map was constructed using simple sequence repeat (TRSSR) and amplified fragment length polymorphism (AFLP) markers. Eighteen linkage groups (LG) corresponding to the anticipated 16 chromosomes of white clover (2n = 4x = 32), with a total map length of 825 cM were derived from a total of 135 markers (78 TRSSR loci and 57 AFLP loci). The F2(I.4R x I.5J) family has been subjected to intensive phenotypic analysis for a range of morphogenetic and developmental traits over several years at IGER, Aberystwyth, Wales and East Craigs, near Edinburgh, Scotland. The resulting phenotypic data were analysed independently to identify QTL (quantitative trait loci) for the various traits, using single marker regression (SMR), interval mapping (IM) and composite interval mapping (CIM) techniques. Multiple coincident QTL regions were identified from the different years and different sites for the same or related traits. The data were reanalysed using a meta-analysis across years and sites and Best Linear Unbiased Estimates (BLUEs) were derived for the plant spread, petiole length, leaf width, leaf length, leaf area, internode length, plant height and flowering date traits. A total of 24 QTLs were identified on 10 of the linkage groups. Three regions on LGs 2, 7 and 12 all demonstrated overlapping QTLs for multiple traits (Figure 1). A meta-analysis approach can quickly identify regions of the genome that control the trait in a robust predictable manner across multiple spatial and temporal replication for rapid targeted genetic enhancement via marker-assisted breeding. This first genetic dissection of agronomic traits in white clover provides the basis for comparative trait-mapping studies and the enhanced development and implementation of marker-assisted breeding strategies

Application of genomicsassisted breeding for generation of climate resilient crops: progress and prospects

CCAFS Climat

Global agricultural intensification during climate change: A role for genomics

Summary: Agriculture is now facing the 'perfect storm' of climate change, increasing costs of fertilizer and rising food demands from a larger and wealthier human population. These factors point to a global food deficit unless the efficiency and resilience of crop production is increased. The intensification of agriculture has focused on improving production under optimized conditions, with significant agronomic inputs. Furthermore, the intensive cultivation of a limited number of crops has drastically narrowed the number of plant species humans rely on. A new agricultural paradigm is required, reducing dependence on high inputs and increasing crop diversity, yield stability and environmental resilience. Genomics offers unprecedented opportunities to increase crop yield, quality and stability of production through advanced breeding strategies, enhancing the resilience of major crops to climate variability, and increasing the productivity and range of minor crops to diversify the food supply. Here we review the state of the art of genomic-assisted breeding for the most important staples that feed the world, and how to use and adapt such genomic tools to accelerate development of both major and minor crops with desired traits that enhance adaptation to, or mitigate the effects of climate change. &gt

Mobilizing Crop Biodiversity

Over the past 70 years, the world has witnessed extraordinary growth in crop productivity, 1 enabled by a suite of technological advances, including higher yielding crop varieties, improved farm management, synthetic agrochemicals, and agricultural mechanization. While this “Green Revolution” intensified crop production, and is credited with reducing famine and malnutrition, its benefits were accompanied by several undesirable collateral effects (Pingali, 2012). These include a narrowing of agricultural biodiversity, stemming from increased monoculture and greater reliance on a smaller number of crops and crop varieties for the majority of our calories. This reduction in diversity has created vulnerabilities to pest and disease epidemics, climate variation, and ultimately to human health (Harlan, 1972). The value of crop diversity has long been recognized (Vavilov, 1992). A global system of genebanks (e.g.www.genebanks.org/genebanks/) was established in the 1970s to preserve the abundant genetic variation found in traditional “landrace” varieties of crops and in crop wild relatives (Harlan, 1972). While preserving crop variation is a critical first step, the time has come to make use of this variation to breed more resilient crops. The DivSeek International Network (https://divseekintl.org/) is a scientific, not-for profit organization that aims to accelerate such effort

Triterpene Saponins from the Aerial Parts of Trifolium medium L. var. sarosiense

Seven previously unreported triterpene glycosides (1−7) were isolated from methanol extract of the aerial parts of Trifolium medium var. sarosiense (zigzag clover). Their structures were established by the extensive use of 1D and 2D NMR experiments along with ESI-MS and HRMS analyses. Compounds 1−7 are oleanane derivatives characterized by the presence of a keto group at C-22 of an aglycone and a primary alcoholic function at C-24 and differing functions at C-30. Among these, compounds 1−3 and 6 showed a secondary alcoholic function at C-11, which is methoxylated in compounds 4 and 7. Compound 5 was shown to possess a known aglycone, wistariasapogenol A; however, it is described here for the first time as a saponin constituent of the Trifolium genus. Some aspects of taxonomic classification of zigzag clover are also discussed

Collection, genotyping and virus elimination of cassava landraces from Tanzania and documentation of farmer knowledge

Open Access Journal; Published online: 17 Aug 2021Cassava (Manihot esculenta Crantz.) has been a vital staple and food security crop in Tanzania for several centuries, and it is likely that its resilience will play a key role in mitigating livelihood insecurities arising from climate change. The sector is dominated by smallholder farmers growing traditional landrace varieties. A recent surge in virus diseases and awareness in the commercial potential of cassava has prompted a drive to disseminate improved varieties in the country. These factors however also threaten the existence of landraces and associated farmer knowledge. It is important that the landraces are conserved and utilized as the adaptive gene complexes they harbor can drive breeding for improved varieties that meet agro-ecological adaptation as well as farmer and consumer needs, thereby improving adoption rates. Here we report on cassava germplasm collection missions and documentation of farmer knowledge in seven zones of Tanzania. A total of 277 unique landraces are identified through high-density genotyping. The large number of landraces is attributable to a mixed clonal/sexual reproductive system in which the soil seed bank and incorporation of seedlings plays an important role. A striking divergence in genetic relationships between the coastal regions and western regions is evident and explained by (i) independent introductions of cassava into the country, (ii) adaptation to prevailing agro-ecological conditions and (iii) farmer selections according to the intended use or market demands. The main uses of cassava with different product profiles are evident, including fresh consumption, flour production, dual purpose incorporating both these uses and longer-term food security. Each of these products have different trait requirements. Individual landraces were not widely distributed across the country with limited farmer-to-farmer diffusion with implications for seed systems

Adapting legume crops to climate change using genomic approaches

Our agricultural system and hence food security is threatened by combination of events, such as increasing population, the impacts of climate change, and the need to a more sustainable development. Evolutionary adaptation may help some species to overcome environmental changes through new selection pressures driven by climate change. However, success of evolutionary adaptation is dependent on various factors, one of which is the extent of genetic variation available within species. Genomic approaches provide an exceptional opportunity to identify genetic variation that can be employed in crop improvement programs. In this review, we illustrate some of the routinely used genomics‐based methods as well as recent breakthroughs, which facilitate assessment of genetic variation and discovery of adaptive genes in legumes. Although additional information is needed, the current utility of selection tools indicate a robust ability to utilize existing variation among legumes to address the challenges of climate uncertainty