Shoot water content and reference evapotranspiration for determination of crop evapotranspiration

Determination of water requirement for crops in resource limited areas is challenging, yet worsened by the common assumption that all crop varieties within a species have similar water requirements. The objective of the study was to indirectly determine crop evapotranspiration of soybean varieties, using reference evapotranspiration and shoot water content under tillage and no tillage cultivation. The treatments were no tillage and conventional tillage as main plots, and soybean varieties Nyala, SB19, and SB20 as sub-plots, replicated three times. Crop evapotranspiration (ETC) and crop coefficient (KC) were different among varieties, and increased during growth period. SB20 had the highest KC (0.8437 at 87 days after planting - DAP); followed by SB19 (0.7888 at 70 DAP), and Nyala (0.7026 at 66 DAP). Conversely,water use efficiency (WUE) was 0.58 in SB19, 0.52 in Nyala, and 0.47 in SB20.Validation of the calculated ETC using a crop production function showed a correlation of r = 0.97 between the observed and predicted yields of the three varieties. Furthermore, the normalised root mean square error (NRMSE) and the index of agreement (d) were 0.14 and 0.87, respectively indicating accurate fit. Calculated crop coefficient strongly correlated with observed shoot water content of Nyala (R2 = 1), SB19 (R2 = 1), and SB20 (R2 = 1).La d\ue9termination du besoin en eau de la plante dans des milieux \ue0 ressources limit\ue9es est un d\ue9fi, encore aggrav\ue9 par l\u2019hypoth\ue8se commune qui stipule que toutes les vari\ue9t\ue9s d\u2019une esp\ue8ce ont les m\ueames besoins en eau. L\u2019objectif de cette \ue9tude \ue9tait de d\ue9terminer indirectement l\u2019\ue9vapotranspiration de la culture des vari\ue9t\ue9s de soja, en utilisant l\u2019\ue9vapotranspiration de r\ue9f\ue9rence et la teneur en eau de la pousse sous labour et sans labour. Les traitements \ue9taient sans labour et avec labour conventionnel comme parcelles principales, et les vari\ue9t\ue9s de soja Nyala, SB19, et SB20 comme sous parcelles, r\ue9pliqu\ue9es trois fois. L\u2019\ue9vapotranspiration des cultures (ETc) et le coefficient de culture (Kc) \ue9taient diff\ue9rents entre les vari\ue9t\ue9s, et augmentaient durant la p\ue9riode de croissance. SB20 avait la valeur la plus \ue9lev\ue9e de Kc (0,8437 \ue0 87 jours apr\ue8s plantation - DAP)\ua0; suivie de SB19 (0,7888 \ue0 70 DAP), et Nyala (0,7026 \ue0 66 DAP). Inversement, l\u2019efficience d\u2019utilisation de l\u2019eau (WUE) \ue9tait 0,58 dans SB19, 0,52 dans Nyala, et 0,47 dans SB20. La validation de l\u2019ETc calcul\ue9e en utilisant la fonction de production de la culture a montr\ue9 une corr\ue9lation r= 0.97 entre les rendements observ\ue9s et pr\ue9dits des trois vari\ue9t\ue9s. De plus, la racine des carr\ue9es moyens normalis\ue9s de l\u2019erreur (NRMSE) et l\u2019index d\u2019accord (d) \ue9taient 0,14 et 087, respectivement indiquant une concordance pr\ue9cise. La valeur calcul\ue9e du coefficient de culture \ue9tait fortement corr\ue9l\ue9e avec la valeur observ\ue9e de la teneur en eau de la pousse de Nyala (R2 = 1), SB19 (R2 = 1), et SB20 (R2= 1)

Morphological, physiological and molecular markers for salt-stressed plants

Open Access Journal; Published online: 27 Jan 2021Plant growth and development is adversely affected by different kind of stresses. One of the major abiotic stresses, salinity, causes complex changes in plants by influencing the interactions of genes. The modulated genetic regulation perturbs metabolic balance, which may alter plant’s physiology and eventually causing yield losses. To improve agricultural output, researchers have concentrated on identification, characterization and selection of salt tolerant varieties and genotypes, although, most of these varieties are less adopted for commercial production. Nowadays, phenotyping plants through Machine learning (deep learning) approaches that analyze the images of plant leaves to predict biotic and abiotic damage on plant leaves have increased. Here, we review salinity stress related markers on molecular, physiological and morphological levels for crops such as maize, rice, ryegrass, tomato, salicornia, wheat and model plant, Arabidopsis. The combined analysis of data from stress markers on different levels together with image data are important for understanding the impact of salt stress on plants

Shoot water content and reference evapotranspiration for determination of crop evapotranspiration

Determination of water requirement for crops in resource limited areas is challenging, yet worsened by the common assumption that all crop varieties within a species have similar water requirements. The objective of the study was to indirectly determine crop evapotranspiration of soybean varieties, using reference evapotranspiration and shoot water content under tillage and no tillage cultivation. The treatments were no tillage and conventional tillage as main plots, and soybean varieties Nyala, SB19, and SB20 as sub-plots, replicated three times. Crop evapotranspiration (ETC) and crop coefficient (KC) were different among varieties, and increased during growth period. SB20 had the highest KC (0.8437 at 87 days after planting - DAP); followed by SB19 (0.7888 at 70 DAP), and Nyala (0.7026 at 66 DAP). Conversely,water use efficiency (WUE) was 0.58 in SB19, 0.52 in Nyala, and 0.47 in SB20.Validation of the calculated ETC using a crop production function showed a correlation of r = 0.97 between the observed and predicted yields of the three varieties. Furthermore, the normalised root mean square error (NRMSE) and the index of agreement (d) were 0.14 and 0.87, respectively indicating accurate fit. Calculated crop coefficient strongly correlated with observed shoot water content of Nyala (R2 = 1), SB19 (R2 = 1), and SB20 (R2 = 1)

Receptor-like Kinases (LRR-RLKs) in response of plants to biotic and abiotic stresses

Open Access Journal; Published online: 10 Oct 2022Plants live under different biotic and abiotic stress conditions, and, to cope with the adversity and severity, plants have well-developed resistance mechanisms. The mechanism starts with perception of the stimuli followed by molecular, biochemical, and physiological adaptive measures. The family of LRR-RLKs (leucine-rich repeat receptor-like kinases) is one such group that perceives biotic and abiotic stimuli and also plays important roles in different biological processes of development. This has been mostly studied in the model plant, Arabidopsis thaliana, and to some extent in other plants, such as Solanum lycopersicum, Nicotiana benthamiana, Brassica napus, Oryza sativa, Triticum aestivum, Hordeum vulgare, Brachypodium distachyon, Medicago truncatula, Gossypium barbadense, Phaseolus vulgaris, Solanum tuberosum, and Malus robusta. Most LRR-RLKs tend to form different combinations of LRR-RLKs-complexes (dimer, trimer, and tetramers), and some of them were observed as important receptors in immune responses, cell death, and plant development processes. However, less is known about the function(s) of LRR-RLKs in response to abiotic and biotic stresses. Here, we give recent updates about LRR-RLK receptors, specifically focusing on their involvement in biotic and abiotic stresses in the model plant, A. thaliana. Furthermore, the recent studies on LRR-RLKs that are homologous in other plants is also reviewed in relation to their role in triggering stress response processes against biotic and abiotic stimuli and/or in exploring their additional function(s). Furthermore, we present the interactions and combinations among LRR-RLK receptors that have been confirmed through experiments. Moreover, based on GENEINVESTIGATOR microarray database analysis, we predict some potential LRR-RLK genes involved in certain biotic and abiotic stresses whose function and mechanism may be explored

Closing the yield gap of soybean (Glycine max (L.) Merril) in southern Africa: a case of Malawi, Zambia, and Mozambique.

Open Access JournalIntroduction: Smallholder farmers in Sub-Saharan Africa (SSA) are increasingly producing soybean for food, feed, cash, and soil fertility improvement. Yet, the difference between the smallholder farmers’ yield and either the attainable in research fields or the potential from crop models is wide. Reasons for the yield gap include low to nonapplication of appropriate fertilizers and inoculants, late planting, low plant populations, recycling seeds, etc. Methods: Here, we reviewed the literature on the yield gap and the technologies for narrowing it and modelled yields through the right sowing dates and suitable high-yielding varieties in APSIM. Results and Discussion: Results highlighted that between 2010 and 2020 in SSA, soybean production increased; however, it was through an expansion in the cropped area rather than a yield increase per hectare. Also, the actual smallholder farmers’ yield was 3.8, 2.2, and 2.3 times lower than the attainable yield in Malawi, Zambia, and Mozambique, respectively. Through inoculants, soybean yield increased by 23.8%. Coupling this with either 40 kg ha−1 of P or 60 kg ha−1 of K boosted the yields by 89.1% and 26.0%, respectively. Overall, application of 21–30 kg ha-1 of P to soybean in SSA could increase yields by about 48.2%. Furthermore, sowing at the right time increased soybean yield by 300%. Although these technologies enhance soybean yields, they are not fully embraced by smallholder farmers. Hence, refining and bundling them in a digital advisory tool will enhance the availability of the correct information to smallholder farmers at the right time and improve soybean yields per unit area

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Inoculant, nitrogen and phosphorus improves photosynthesis and water-use efficiency in soybean production

Open Access Article; Published online: 07 Sep 2021Soybean yield within the Southern Africa falls below its potential despite similar climatic conditions across some agroecologies, replicable agronomic management practices and introduced improved varieties. Understanding physiological processes and water-use efficiency (WUE) of soybean offer information on bridging this yield gap. A field study was conducted in 2017 and 2018 seasons in two agroecologies (Angonia and Ruace) in Mozambique to evaluate the effects of Bradyrhizobium diazoefficiens strain USDA110 formerly known as Bradyrhizobium japonicum inoculant, nitrogen and phosphorus on nodulation, physiology and yield of non-promiscuous (Safari) and promiscuous (TGx 1740-2F) soybean varieties. Data on transpiration, photosynthesis, leaf area index, radiation interception and WUE from the beginning of flowering to maturity were collected. Transpiration rate varied considerably with interaction between locations, growth stages, varieties and treatments. At podding, phosphorus-treated soybean at Angonia transpired less (6.3 mmol/m2/s) than check plants (6.6 mmol/m2/s). Photosynthesis rate and WUE were distinct with variety, growth stages and inputs within agroecologies. For instance, in Angonia 2018 season, phosphorus fertilized TGx 1740-2F photosynthesized more at flowering (25.3 μmol/m2/s) while the lowest was phosphorus-treated Safari at podding with 17.2 μmol/m2/s. At the same site in 2017, inoculated soybean photosynthesized more at 22.8 μmol/m2/s leading to better WUE of 3.6 that corresponded to 2894 kg/ha yield. Overall, soybean WUE was higher when inoculated than N-treated, while P application yielded better. Results from this study will complement breeders’ effort in developing phosphorus efficient varieties suited for a wide range of changing climatical conditions

Evaluation of wheat genotypes for heat stress tolerance and identification of early stress indicators

Heat stress is an abiotic factor that reduces wheat yields. This study assessed the morphological and physiological traits essential for early detection of heat tolerance in wheat and identified suitable genotypes for specific agro-ecologies prone to heat stress in Zambia. Twelve wheat genotypes were evaluated in a heat-stress environment (Chakanka) and a non-stress heat environment (UNZA). Early heat stress indicators like leaf thickness and chlorophyll content had a 92% and 90% relationship with the yields of heat-tolerant genotypes, respectively. An increase in either or both parameters improved the yields of heat-tolerant genotypes relative to the susceptible ones. Among the heat-tolerant genotypes, Entry 48 had the highest yield (5866.5 kg ha−1) at the heat-stress site; this yield was 51.2% higher than that of the most susceptible genotype, Kwale (2864.0 kg ha−1). Entry 48 was more adapted to heat stress and yielded better than others due to early flowering (53.8 days to 50% flowering) and longer grain-filling duration (40.3 days). Entry 48 possessed traits of a climate-smart variety and could be a candidate for breeding future heat-tolerant and high-yielding wheat varieties

Optimizing root yield of cassava under fertigation and the masked effect of atmospheric temperature

Published online: 17 May 2020BACKGROUND Fertigation is a rare and an expensive method of fertilizer application to cassava, and hence there is a need to optimize its efficiency for profitability. This study's objective was to optimize root yield of cassava through fertigation using a logistic model. RESULTS The field treatments were six fertigation concentrations against three cassava varieties, selected according to their maturity period. The logistic model predicted 52%, 116% and 281% benefit of fertigation for the varieties Mweru, Kampolombo and Nalumino, respectively. Furthermore, only half of the amount of fertilizer applied for Mweru was required to achieve twice the root yield of Kampolombo. During the experiment, an unknown importance of atmospheric temperature to cassava and its relationship to fertigation was observed. An elevation of 3.7 °C in atmospheric temperature led to 226%, 364% and 265% increase in root yield of Mweru, Kampolombo and Nalumino, respectively. Conversely, shoot biomass and root yield declined when the average atmospheric temperatures dropped by 3.6 °C. However, the cold temperatures affected the short‐growth‐duration (Mweru) and medium‐growth‐duration (Kampolombo) varieties earlier, 22 days after the drop, than the long‐growth‐duration variety (Nalumino) – 50 days after the drop. CONCLUSION Fertigation induced resilience of the shoot biomass production to cold which was most pronounced in the root yield of Mweru in response to the highest fertigation concentration. Thus, while fertigation improved cassava's resilience to cold, it only did so effectively for short‐growth‐duration variety, Mweru. Also, enhanced performance of cassava under increased atmospheric temperature indicated its importance as a climate‐smart crop