Genotypic Variation for Root Development, Water Extraction and Yield Components in Groundnut Under Low Phosphorus and Drought Stresses

[Context] Unpredictable water deficit (drought) and low soil phosphorus (LP) are major interacting constraints to groundnut growth and grain yield in Sahelian zones of West Africa. Combining breeding efforts for drought tolerance and P efficiency could lead to improve tolerance and grains yield in these zones. [Objectives] This study assessed six groundnut genotypes under lysimetric system to better understand the relative importance of P deficiency, water stress, and their interaction; investigate the water extraction pattern of genotypes under these constraints and identify tolerance related traits to accelerate development of more resilient varieties. [Methods] Thus, in experiment 1 (Exp.1) roots traits were investigated at 50% flowering, pod filling stage (60 days after sowing) and maturity stage (90 days after sowing) under high phosphorus (HP) and LP treatments. In experiment 2 (Exp.2), two water regimes (WW=well water, and WS = water stress) were imposed to HP and LP plants and parameters like total transpired water (TTW), transpiration efficiency (TE), water extraction (Wex), pods and haulm weights were investigated. [Results] Roots traits showed significant decrease due to LP stress, pod and haulm weights correlated significantly to roots length density (RLD) and roots dry matter (RDM). Genotypes 12CS-116 and ICGV 12991 revealed tolerant to LP stress while RLD and RDM revealed LP tolerance related traits in groundnut. Interacting effect of LP and drought stress (LPWS) was higher than separate effect of LP and WS. Under LPWS, Wex, TTW, TE, pod and haulm yields decreased significantly. This study suggests that RLD and RDM contributed to Wex in 12CS-116 and ICG 12991 under LPWS. 55-437 and JL-24 with highest TTW showed drought tolerance strategy while drought avoidance strategy could explain 12CS-116, 12CS-79, ICG 12991 and ICGV 97183 response to WS. Pod weight showed tight correlation (R2 =0.7) to TE only under LPWS suggesting that TE explains a large part of pod yield variation under LPWS conditions. TE revealed WS and LPWS tolerance related trait. The genotypic variation observed on Wex and TTW under LPWS suggests different patterns of water extraction and use among the groundnut genotypes

Tolerant pearl millet (Pennisetum glaucum (L.) R. Br.) varieties to low soil P have higher transpiration efficiency and lower flowering delay than sensitive ones

Abstract Background and aim In the West African Sahel low soil phosphorus (P) and unpredictable rainfall are major interacting constraints to growth and grain yield of pearl millet. Investigating the relationship between transpiration and final yield under the combined effect of water and P stress is fundamental to understand the underlying mechanisms of tolerance and improve breeding programs. Methods We conducted two lysimeter trials using 1 m long PVC tubes (35 cm diameter) filled with a P poor Sahelian soil mimicking soil profiles to assess grain and stover yield, and water use of 15 pearl millet genotypes grown under different P (no P supply or addition of 1.5 g P tube−1) and water (well watered or terminal water stress) regimes. In experiment 2 transpiration was measured twice a week from tube weight differences, and transpiration efficiency (TE) was calculated as dry matter (DM) produced per kg of water transpired. Results Low soil P delayed flowering, and more so in sensitive genotypes. Later flowering of genotypes sensitive to low P made them more sensitive to terminal water stress. Under P limiting soil, genotypes tolerant and sensitive to low P used similar amounts of water (19.8 and 21.7 kg water plant−1, respectively). However, tolerant lines transpired less water prior to anthesis (8.8 kg water plant−1) leaving more water available for grain filling (11 kg water plant−1) while sensitive lines used 14.4 kg water plant−1 pre-anthesis, leaving only 7.2 kg water plant−1 for grain filling. Low soil P decreased grain yield by affecting seed size at harvest and its damage during seed filling overrode the effect of seed size at sowing. Grain yield was positively correlated with water extracted after anthesis. TE was enhanced by P supply, especially in sensitive lines, and TE was higher in tolerant than in sensitive genotypes under low soil P. Conclusions Pearl millet plants tolerant to low P were more resistant to the delay of flowering caused by low P soil and they presented higher transpiration efficiency. The pattern of transpiration was important to cope with terminal water stress under different levels of P availability. Higher transpiration after anthesis, resulting from conservative water mechanism pre-anthesis (higher TE) and possibly by a shorter delay in flowering under low soil P, enhanced grain yield

Abiotic Stresses Tolerance and Nutrients Contents in Groundnut, Pearl Millet and Sorghum Mini Core Germplasm for Food and Nutrition Security

Groundnut, pearl millet and sorghum germplasm were investigated to identify new sources of tolerance to low phosphorus (LP) and/or drought stress (WS) and to assess genotypic variation for iron (Fe) and zinc (Zn) contents. Experiments were conducted in lysimetre conditions in a randomized completely block design with 5 replications, 2 water and 2 phosphorus treatments. Genotypic variability was observed for morphoagronomic and nutrients traits investigated. Groundnut accessions ICG 3312, ICG 11855, ICG 10053, ICG 15232 and ICG 11088 revealed drought tolerant. The combined WS-LP effect (73%) was higher than individual WS (68%) and LP (49%) effects. LP signifi cantly delayed heading and fl owering dates, accessions IP1060, IP11405 and IP9000 (millet), and ISS1412, ISS2167, ISS376 and ISS738 (sorghum) showed less delay and LP tolerance. Fe and Zn contents under LP showed that accessions IP17775, IP5581, IP5153, IP1060, IP6517 and IP5438 of millet; ISS376, ISS1412, ISS2167, ISS242, ISS311 and ISS2151 of sorghum revealed high Fe and/or Zn concentrations

Effect of water deficit at different stages of development on the yield components of cowpea (Vigna unguiculata L. Walp) genotypes

Cowpea cultivation is widespread in West Africa where it is an important source of protein. This study is aimed at determining the effects of water deficit applied at different stages of cowpea development on yield and its components (pod number, seed number, seed yield, aerial biomass yield, harvest index and root biomass of the plant). The experiments were carried out in pots during the rainy season of 2016 under natural conditions of illumination, temperature and relative humidity. Three water regimes were applied to plants at different stages of cowpea development: total suspension of watering at flowering phase (43 days after sowing) (S1); suspension of watering at the beginning of pod formation on the 46th day after sowing (S2); and normal watering as control until harvest (S0). At the water regime level, yield components had higher values in S0 followed by S2. The lowest values were obtained at S1 level. The root to aerial biomass ratios was higher under water deficit than in the control. In conditions of water deficiency, Suvita2, IT96D-610, and ISV128 genotypes gave the highest seed yields and Tiligré the lowest yield. The harvest index showed a genotypic variation according to the water regime. Suvita2 and ISV128 gave the best harvest index in all water regimes. This study may have contributed to the selection of genotypes adapted to drought

Seed coat mediated resistance against Aspergillus flavus infection in peanut

Toxic metabolites known as aflatoxins are produced via certain species of the Aspergillus genus, specifically A. flavus, A. parasiticus, A. nomius, and A. tamarie. Although various pre- and post-harvest strategies have been employed, aflatoxin contamination remains a major problem within peanut crop, especially in subtropical environments. Aflatoxins are the most well-known and researched mycotoxins produced within the Aspergillus genus (namely Aspergillus flavus) and are classified as group 1 carcinogens. Their effects and etiology have been extensively researched and aflatoxins are commonly linked to growth defects and liver diseases in humans and livestock. Despite the known importance of seed coats in plant defense against pathogens, peanut seed coat mediated defenses against Aspergillus flavus resistance, have not received considerable attention. The peanut seed coat (testa) is primarily composed of a complex cell wall matrix consisting of cellulose, lignin, hemicellulose, phenolic compounds, and structural proteins. Due to cell wall desiccation during seed coat maturation, postharvest A. flavus infection occurs without the pathogen encountering any active genetic resistance from the live cell(s) and the testa acts as a physical and biochemical barrier only against infection. The structure of peanut seed coat cell walls and the presence of polyphenolic compounds have been reported to inhibit the growth of A. flavus and aflatoxin contamination; however, there is no comprehensive information available on peanut seed coat mediated resistance. We have recently reviewed various plant breeding, genomic, and molecular mechanisms, and management practices for reducing A. flavus infection and aflatoxin contamination. Further, we have also proved that seed coat acts as a physical and biochemical barrier against A. flavus infection. The current review focuses specifically on the peanut seed coat cell wall-mediated disease resistance, which will enable researchers to understand the mechanism and design efficient strategies for seed coat cell wall-mediated resistance against A. flavus infection and aflatoxin contamination

Agronomic performance of pearl millet genotypes under variable phosphorus, water, and environmental regimes

Water and P deficiency can significantly limit pearl millet [Pennisetum glaucum (L.) R. Br.] productivity and response to N application in the arid and semi-arid regions of Africa. The objectives of this research were to quantify the responses of improved pearl millet genotypes and a landrace to contrasting rainfall gradient and P deficient soil conditions across different locations in Niger. The study was conducted at four locations: (a) Tara, (b) the Inter national Crop Research Institute for the Semi-Arid Tropics (ICRISAT) research station at Sadoré, (c) Maradi, and (d) Araourayé, Niger, during 2015 and 2016 rainy seasons. Results of the study indicated that the effect of P fertilizer application on shoot weight, panicle weight, grain yield, and harvest index was different by environment (year × location). As high as 113% straw yield, 72% panicle weight, and 100% grain yield advantage was obtained with P application over low P in favorable environments. Across all genotypes and in both P treatments, irrigation had a consistent effect on the agronomic performance. On average, there was s ignificantly greater straw yield (629 vs. 492 g m –2 ), panicle weight (472 vs. 229 g m –2 ), grain yield (257 vs. 122 g m –2 ), and harvest index (0.25 vs. 0.15) in the irrigated site compared with rainfed sites. Among the tested genotypes, Mil de Siaka showed relatively consistent performance in irrigated, water deficit, and P deficient conditions, emerging as an ideal candidate for inclusion into pearl millet breeding programs, aimed toward developing multi-stress tolerant pearl millet varieties

Genetic structure and diversity in Sorghum bicolor (L.) Moench landraces from marginal sorghum production lands in Senegal, based on SSR markers

Data on sorghum genetic diversity in Senegal are missing despite its importance in the food and feed in the country. In order to contribute to the sustainable in situ management of sorghum germplasm, we investigated its genetic diversity and structure in its marginal production areas. Investigations were focused on Thiès, Diourbel and Kédougou regions where sorghum landraces have been less investigated and genetic information on landraces is unknown. A total of 148 sorghum accessions representative of landraces used in production systems have been sampled and analyzed with 30 microsatellite markers. A total of 138 alleles have been recorded. The number of alleles per locus varied from 3 (7 loci) to 8 (3 loci). The observed heterozygosity varied from 0 to 0.62. The low genetic distance (0.12) was recorded between Thiès and Diourbel populations and the highest distance (0.22) between Thiès and Kédougou populations. Dendrogram obtained according to Neighbour joining classification model allowed the classification of sorghum accessions into three main groups. The Genetic structure is not function to the regions indicating that landraces are not specific to a region. The results are a first step toward the sustainable in situ management of genetic resources. Data on the whole range of existing diversity of sorghum in Senegal is an important key for its germplasm management; so, the genotyping must be extended to accessions from the whole country

Mitigating aflatoxin contamination in groundnut through a combination of genetic resistance and post-harvest management practices

Aflatoxin is considered a “hidden poison” due to its slow and adverse effect on various biological pathways in humans, particularly among children, in whom it leads to delayed development, stunted growth, liver damage, and liver cancer. Unfortunately, the unpredictable behavior of the fungus as well as climatic conditions pose serious challenges in precise phenotyping, genetic prediction and genetic improvement, leaving the complete onus of preventing aflatoxin contamination in crops on post-harvest management. Equipping popular crop varieties with genetic resistance to aflatoxin is key to effective lowering of infection in farmer’s fields. A combination of genetic resistance for in vitro seed colonization (IVSC), pre-harvest aflatoxin contamination (PAC) and aflatoxin production together with pre- and post-harvest management may provide a sustainable solution to aflatoxin contamination. In this context, modern “omics” approaches, including next-generation genomics technologies, can provide improved and decisive information and genetic solutions. Preventing contamination will not only drastically boost the consumption and trade of the crops and products across nations/regions, but more importantly, stave off deleterious health problems among consumers across the globe

Pearl millet genome sequence provides a resource to improve agronomic traits in arid environments

Pearl millet [Pennisetum glaucum (L.) R. Br., syn. Cenchrus americanus (L.) Morrone], is a staple food for over 90 million poor farmers in arid and semi-arid regions of sub-Saharan Africa and South Asia. We report the ~1.79 Gb genome sequence of reference genotype Tift 23D2B1-P1-P5, which contains an estimated 38,579 genes. Resequencing analysis of 994 (963 inbreds of the highly cross-pollinated cultigen, and 31 wild accessions) provides insights into population structure, genetic diversity, evolution and domestication history. In addition we demonstrated the use of re-sequence data for establishing marker trait associations, genomic selection and prediction of hybrid performance and defining heterotic pools. The genome wide variations and abiotic stress proteome data are useful resources for pearl millet improvement through deploying modern breeding tools for accelerating genetic gains in pearl millet.publishersversionPeer reviewe