Crops, Volume 2, Issue 4 (December 2022) – 11 articles

The low agricultural productivity of key crops and food insecurity continue to be a problem in sub-Saharan Africa (SSA), and Tanzania in particular. The growing population and climate change further increase the food shortage. Irrigation has been strategized to reduce poverty and food insecurity, and improve the livelihoods of communities in African countries, and in particular Tanzania. Transformational leadership for small-scale irrigation is urgently needed to attain the planned agenda for irrigation schemes. This study assessed the challenges of leadership in leading and transforming small-scale irrigation schemes. The questionnaires were distributed to leaders of the agriculture sector in four strata (agriculture extension officer (25), AMCOS leaders (6), agriculture engineers (2), irrigation committee (9)) with a total of 42 leaders as participants. A total of 118 farmers were interviewed from four irrigation canals (Ngollo (32), Ngarasero I (32), Ngarasero II (33), and Abisinia (21)) in the Usa River ward. The study found that the challenges of leaders in leading the transformation of small-scale farming for success were commitment of leaders, market chain, pest control mechanisms, irrigation extension service, planning, technological transformation and adoption, mobilization of farmers and professionals, monitoring and evaluation, knowledge of irrigation, and agro-input supply. This study shows that leaders’ transformation skills can play a great role in poverty reduction in small-scale irrigation in the Usa River ward. Therefore, leaders in the study area should play the role of transformational leadership effectively in managing small-scale irrigation by practicing a participatory approach to farmers problem-solving. Full article

The non-turning or only superficial turning of soil is considered to be a gentle tillage method. Nevertheless, conventional ploughs are widely used in organic farming for crop production reasons. For the further development of reduced tillage, and up to no tillage, the effects of three cover crop species and their incorporation with different tillage intensities on nitrogen (N) dynamics, weed emergence and the yield of the subsequent main crop, oats, were examined in a repeated organic one-year trial. Sinapis alba, Trifolium resupinatum, Vicia sativa and bare fallow were tested and incorporated using (1) a plough (PL), (2) reduced tillage (RT), (3) mulching + drilling (MD) and (4) direct drilling (DD). V. sativa was the most promising cover crop in combination with RT, MD and DD. In Trial 1, the soil mineral N content and oat yields after the introduction of V. sativa were on a similar level as those in the PL treatments, and weeds were not yield-limiting there. In Trial 2, the biomass production of V. sativa was only about half of that of Trial 1 and did not offer sufficient weed control, but V. sativa was still successful in the RT treatments. In both trials, the yield differences were more pronounced between the cover crop treatments after RT than after PL. RT, therefore, was more dependent on an adequate cover crop species than PL. The no-till method was not only dependent on an adequate cover crop species but also on its proper biomass production for sufficient weed control. Full article

Plants have developed mechanisms to cope with stresses in their environments as they grow in diverse settings. Such means include releasing plant defense compounds upon attacks by pests or other stressors. Plants with these characteristics are essential as a plant germplasm source for breeding resistance against herbivores and insect pests. Therefore, this study aimed to screen germplasms for whitefly resistance and characterize the secondary metabolites responsible for this. Thirty local tomato accessions were screened for resistance against whiteflies (Bemisia tabaci Gennadius) in the screen house located at Tanzania Plant Health and Pesticides Authority (PTHPA) between January and April 2021. From this screening, seven local tomato cultivars: TZA3729, TZA5554, TZA5545, TZA5562, TZA5552, TZA3177 and TZA5157, showed resistance, and one accession (TZA5496) that showed susceptibility to whiteflies (negative control) and accession V1030462 that was a standard (positive control) were selected for the subsequent experiments. The experiment was conducted in July–October 2021 in the screen house at TPHPA and repeated in January–April 2022 using a completely randomized block design with three replications. From this experiment, three accessions: TZA3729, TZA5562 and TZA5157, showed resistance against whiteflies. However, accession TZA3729 was more resistant than TZA5562 and TZA5157 when compared to the resistant accession V1030462. Therefore, these accessions were further screened for secondary metabolites responsible for resistance against herbivores and insect pests—in this case, whiteflies. The GS-MS methanol extract results showed accession TZA3729 to possess a wide array of secondary plant metabolites responsible for plant self-defenses, such as diterpenes, Tetraterpenes, alkaloids, carotenoids and fatty acid esters. Therefore, the study recommends accession TZA3729 as a source of tomato plant germplasm for breeding tomatoes resistant to whiteflies. Full article

Rice is an important food crop, and its production is significantly affected by salt stress under the changing climate. Soil-inhabiting microbial inoculants as well as efficient nitrogen (N) nutrition may have ameliorative effects on rice growth and yield under salt stress. However, the effects of the interaction between N application and microbial inoculants on the growth and grain yield of rice under salt stress is not yet fully understood. This study aimed to clarify whether the use of the Bacillus pumilus strain TUAT-1 biofertilizer, along with the right amount of N fertilizer, would alleviate salt stress in lowland rice production. We applied the Bacillus pumilus strain TUAT-1 as a biofertilizer in combination with different rates of N fertilizer: control (0% N), 2.64 g (NH₄)₂SO₄ per nursery tray (100% N: the farmer-recommended amount), and 3.96 g (NH₄)₂SO₄ per nursery tray (150% N). Salinity (100 mM of NaCl) was applied at the heading stage of rice plants in pot culture in the greenhouse, and the growth and yield components were accessed at harvest. In the nursery phase, the application of the biofertilizer TUAT-1 significantly increased seedling vigor and the root development of 21-day-old seedlings. Salinity stress at the heading stage significantly reduced chlorophyll content, panicle number, straw biomass, and grain yield; however, either the application of N alone or in combination with TUAT-1 ameliorated the salinity-related reduction in grain yield and yield component parameters. Plants receiving a high amount of N fertilizer (150% N) showed similar straw biomass and grain yield with or without TUAT-1 inoculation, regardless of saline or non-saline conditions. In both saline and control conditions, straw biomass and grain yield were higher in the plants inoculated with TUAT-1 than in those without TUAT-1. Specifically, the combined application of TUAT-1 and the farmer-recommended N level (100% N) led to an increase of 8% in straw biomass and 15% in grain yield under saline stress when compared with their respective plants without TUAT-1. Straw biomass and grain yield were similar in the (un-inoculated) plants grown under normal conditions and TUAT-1 + 100% N under salinity treatments, because TUAT-1 enhanced root development, which may promote soil nutrient uptake. Our results indicated that combined nursery application of TUAT-1 biofertilizer and 100% N fertilizer rate has the potential to boost the capacity of this bacteria to increase seedling vigor, which subsequently ameliorated the salt-induced reduction in the grain and straw yield. Full article

Coriander (Coriandrum sativum L.) is an aromatic member of the Apiaceae with a wide diversity of uses. Its rapid life cycle allows it to fit into different growing seasons, making it possible to grow the crop under a wide range of conditions. Even though extensive demand for this herb exists among ethnic communities, its’ production in the eastern USA is essentially non-existent. We are interested in facilitation of commercial production of this herb and to characterize its’ composition. We have previously observed that coriander can be commercially produced in Virginia but composition of coriander seed produced in Virginia (Mid-Atlantic region of the United States of America) is unknown. To remedy this situation, we conducted two experiments during 2015 and 2016 with three cultivars (‘Santo’, ‘Santo Monogerm’, and ‘Marino-Organic’). Coriander seed in this study had 7.6 and 8.7 percent oil and 17 and 15 percent protein in winter (planted in December 2015 and harvested in July, 2016) or summer crop (planted in May, 2016 and harvested), respectively whereas mean concentrations (g per 100 g) of P, K, S, Mg, Ca, and Na were 501, 830, 140, 332, 620, 10, respectively. Concentrations of B, Zn, Mn, Fe, and Cu (mg per 100 g) were 1.10, 2.71, 2.81, 8.96, and 1.29, respectively. Coriander seed in this study contained approximately 19, 63, and 17 percent total saturated, MUFA, and PUFA fatty acids, respectively. Coriander seed contained 0.179, 0.877, and 0.219 percent fructose, glucose, and sucrose, respectively. Our results indicated that coriander seed produced in Virginia has seed composition, generally, similar to that produced elsewhere. Full article

Industrial hemp (Cannabis sativa L.) as a grain and fiber crop is experiencing a resurgence in North America. Due to governmental prohibition, there has been limited information on regional agronomic production systems including basic information on seed germination. This study was initiated to provide basic information on the relationship between temperature and germination in hemp seed. Germination was measured at constant temperatures ranging from 3 to 42 °C. Cardinal temperatures were determined for two industrial oil crop hemp cultivars (‘Georgina’ and ‘Victoria’). The optimal germination temperature indicated by a high mean germination percentage and rate was between 19 and 30 °C. Optimal (29.6 °C), base (3.4 °C) and ceiling (42.6 °C) temperatures were calculated from a linear regression of the germination rates to reach 50% germination for each temperature. The thermal time for ‘Georgina’ and ‘Victoria’ to reach 50% germination at suboptimal temperatures was 694 and 714 °C h, respectively. The osmotic and solid matrix-primed hemp seeds germinated faster than the untreated seeds, but the final germination percentages were not different. The primed seeds germinated faster at supraoptimal temperatures but did not impact final germination percentages in the thermally inhibited seeds. Full article

Industrial hemp (Cannabis sativa L.) is experiencing a resurgence in North America as an agricultural commodity. Germplasm improvement for locally adapted and stable cannabinoid production is an industry priority. This study used seed priming and pericarp removal to recover seedlings in low-germinating seed lots that could prove important for plant breeding and germplasm conservation. Both seed priming and pericarp removal improved early seed germination, but pericarp removal was more effective in improving overall final germination percentages. On average, pericarp removal improved final germination in low-germinating seed lots by approximately 38% compared to intact seed germination. In seeds with the pericarp removed, the initial germination substrate had an impact on normal seedling development following transplanting: those germinated for 2 to 3 days on rolled towels produced more normal seedlings compared to those started in Petri dishes. There was a dramatic increase in abnormal seedlings produced in the low-germinating seed lot initially germinated in a Petri dish wetted with 6 mL water where nearly 80% never transitioned to normal actively growing seedlings. Full article

Drought stress negatively affects plant growth and development, thus reducing plant productivity. Therefore, understanding the molecular mechanisms underlying drought stress responses is essential for crop improvement. The plant-specific NAM/ATAF1,2/CUC2 (NAC) transcription factors play important roles in the drought stress response. Here, we show that rice (Oryza sativa) ONAC054, a membrane-bound NAC transcription factor, is involved in the drought stress response. We found that onac054 mutants were sensitive, whereas ONAC054-overexpressing (ONAC054-OX) plants were tolerant to drought stress. Under drought stress conditions, several genes associated with abscisic acid (ABA) synthesis and signaling were downregulated in onac054 mutants but upregulated in ONAC054-OX plants. Among these genes, the TRANSCRIPTION FACTOR RESPONSIBLE FOR ABA REGULATION 1 (TRAB1), which encodes an ABA-inducible bZIP transcription factor, was directly activated by ONAC054. On the other hand, the expression of ONAC054 was directly activated by several ABA-responsive elements (ABRE)-binding factors (ABFs) in an ABA-dependent manner, indicating that ONAC054 acts as an enhancer of ABA-induced drought stress tolerance. Additionally, the overexpression of ONAC054 in rice greatly improved grain yield under drought stress conditions, indicating that the overexpression of ONAC054 could facilitate the improvement of drought stress tolerance in rice and other crops. Full article

Potato leaves are ice-tolerant but are frost-damaged at −3 °C. Freezing occurs in two steps, a first non-destructive freezing event and a second independent lethal event. Localization of ice, and whether cells freeze-dehydrate after the first freezing event remains unknown. The cause of frost damage during the second freezing event lacks experimental evidence. Cytological responses of mesophyll cells were examined during ice formation using cryo-microscopic techniques after high-pressure freeze-fixation and freeze-substitution. CO₂ gas exchange on frozen leaves revealed functional responses, but also frost damage. After the first freezing event, gas exchange was uninterrupted. Consequently, intercellular spaces are free of ice, and ice may be restricted to xylem vessels. The cellular shape of the mesophyll cells was unchanged, cells did not freeze-dehydrate but were supercooled. When thawed after the first freezing event, leaves were initially photoinhibited but regained photosynthesis. During the second freezing event, cells froze intracellularly, and some palisade parenchyma cells remained intact for a prolonged time. Intracellular ice caused complete destruction of cells, and chloroplasts became invisible at the light microscopic level. When thawed after the second freezing, leaves were unable to regain photosynthesis. Consequently, freezing avoidance is the only viable strategy for potatoes to survive frost. Full article

Globalization propelled human migration and commercial exchanges at the global level, but woefully led to the introduction of non-indigenous organisms into several agroecological systems. These include pathogenic bacteria with devastating consequences for numerous crops of agronomical importance for food production worldwide. In the last decade, research efforts have focused on these noxious organisms, aiming to understand their evolutionary processes, degree of pathogenicity, and mitigation strategies, which have allowed stakeholders and policymakers to develop evidence-based regulatory norms to improve management practices and minimize production losses. One of these cases is the bacterium Pseudomonas syringae pv. actinidiae (Psa), the causal agent of the kiwifruit bacterial canker, which has been causing drastic production losses and added costs related to orchard management in the kiwifruit industry. Although Psa is presently considered a pandemic pathogen and far from being eradicated, the implementation of strict regulatory norms and the efforts employed by the scientific community allowed the mitigation, to some extent, of its negative impacts through an integrated pest management approach. This included implementing directive guidelines, modifying cultural practices, and searching for sources of plant resistance. However, bacterial pathogens often have high spatial and temporal variability, with new strains constantly arising through mutation, recombination, and gene flow, posing constant pressure to agroecosystems. This review aims to critically appraise the efforts developed to mitigate bacterial pathogens of agronomical impact, from orchard management to genome analysis, using Psa as a case study, which could allow a prompter response against emerging pathogens in agroecosystems worldwide. Full article

Protected cropping produces more food per land area than field-grown crops. Protected cropping includes low-tech polytunnels utilizing protective coverings, medium-tech facilities with some environmental control, and high-tech facilities such as fully automated glasshouses and indoor vertical farms. High crop productivity and quality are maintained by using environmental control systems and advanced precision phenotyping sensor technologies that were first developed for broadacre agricultural and can now be utilized for protected-cropping applications. This paper reviews the state of the global protected-cropping industry and current precision phenotyping methodology and technology that is used or can be used to advance crop productivity and quality in a protected growth environment. This review assesses various sensor technologies that can monitor and maintain microclimate parameters, as well as be used to assess plant productivity and produce quality. The adoption of precision phenotyping technologies is required for sustaining future food security and enhancing nutritional quality. Full article