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The formation and development of storage roots is the most important physiological process in sweetpotato production. Sucrose transporters (SUTs) regulate sucrose transport from source to sink organs and play important roles in growth and development of plants. However, whether SUTs involved in sweetpotato storage roots formation is so far unknown. In this study, we show that IbSUT1, a SUT, is localized to the plasma membrane. Overexpression of IbSUT1 in sweetpotato promotes the sucrose efflux rate from leaves, leading to increased sucrose levels in roots, thus induces lignin deposition in the stele, which inhibits the storage roots formation and compromises the yield. Heterologous expression of IbSUT1 in Arabidopsis significantly increases the sucrose accumulation and promotes lignification in the inflorescence stems. RNA-seq and biochemical analysis further demonstrated that IbMYB1 negatively regulates the expression of IbSUT1. Overexpression of IbMYB1 in Arabidopsis reduces the sucrose accumulation and lignification degree in the inflorescence stems. Moreover, co-overexpression of IbMYB1 and IbSUT1 restores the phenotype of lignin over-deposition in Arabidopsis. Collectively, our results reveal that IbSUT1 regulates source-sink sucrose transport and participates in the formation of sweetpotato storage roots and highlight the potential application of IbSUT1 in improving sweetpotato yield in the future.

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(1) The development of sweet potato storage roots is impacted by nitrogen (N) levels, with excessive nitrogen often impeding development. Starch synthesis enzymes such as sucrose synthase (SUS) and ADP-glucose pyrophosphorylase (AGPase) are pivotal in this context. Although the effects of excessive nitrogen on the formation of sweet potato storage roots are well documented, the specific responses of IbSUSs and IbAGPases have not been extensively reported on. (2) Pot experiments were conducted using the sweet potato cultivar "Pushu 32" at moderate (MN, 120 kg N ha-1) and excessive nitrogen levels (EN, 240 kg N ha-1). (3) Nine IbSUS and nine IbAGPase genes were categorized into three and two distinct subgroups based on phylogenetic analysis. Excessive nitrogen significantly (p < 0.05) suppressed the expression of IbAGPL1, IbAGPL2, IbAGPL4, IbAGPL5, IbAGPL6, IbAGPS1, and IbAGPS2 in fibrous roots and IbSUS2, IbSUS6, IbSUS7, IbSUS8, IbSUS9, IbAGPL2, and IbAGPL4 in storage roots, and then significantly (p < 0.05) decreased the SUS and AGPase activities and starch content of fibrous root and storage root, ultimately reducing the storage root formation of sweet potato. Excessive nitrogen extremely significantly (p < 0.01) enhanced the expression of IbAGPL3, which was strongly negatively correlated with the number and weight of storage roots per plant. (4) IbAGPL3 may be a key gene in the response to excessive nitrogen stress and modifying starch synthesis in sweet potato.

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Early cassava storage root formation and bulking is a medium of escape that farmers and processors tend to adopt in cases of abiotic and biotic stresses like drought, flood, and destruction by domestic animals. In this study, 220 cassava genotypes from the International Institute of Tropical Agriculture (IITA), National Root Crops Research Institute (NRCRI), International Center for Tropical Agriculture (CIAT), local farmers (from farmer's field), and NextGen project were evaluated in three locations (Umudike, Benue, and Ikenne). The trials were laid out using a split plot in a randomized incomplete block design (alpha lattice) with two replications in 2 years. The storage roots for each plant genotype were sampled or harvested at 3, 6, 9, and 12 month after planting (MAP). All data collected were analyzed using the R-statistical package. The result showed moderate to high heritability among the traits, and there were significant differences (p< 0.05) among the performances of the genotypes. The genome-wide association mapping using the BLINK model detected 45 single-nucleotide polymorphism (SNP) markers significantly associated with the four early storage root bulking and formation traits on Chromosomes 1, 2, 3, 4, 5, 6, 8, 9, 10, 13, 14, 17, and 18. A total of 199 putative candidate genes were found to be directly linked to early storage root bulking and formation. The functions of these candidate genes were further characterized to regulate i) phytohormone biosynthesis, ii) cellular growth and development, and iii) biosynthesis of secondary metabolites for accumulation of starch and defense. Genome-wide association study (GWAS) also revealed the presence of four pleiotropic SNPs, which control starch content, dry matter content, dry yield, and bulking and formation index. The information on the GWAS could be used to develop improved cassava cultivars by breeders. Five genotypes (W940006, NR090146, TMS982123, TMS13F1060P0014, and NR010161) were selected as the best early storage root bulking and formation genotypes across the plant age. These selected cultivars should be used as sources of early storage root bulking and formation in future breeding programs.

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[This corrects the article DOI: 10.3389/fpls.2022.1042379.].

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This study investigates the impact of sweet potato plant sanitation on the yield and external and internal quality root storage exploring the nutritional content affected by various cooking methods (raw, boiled, and oven-cooked). The presence of viruses, and concretely of the sweet potato leaf curl virus (SPLCV), in sweet potato propagation material is shown to significantly reduce yield and modify storage root quality. Notably, the research reveals a substantial improvement in crop yield and external quality, reinforcing the efficacy of plant sanitation methods, specifically apical meristem culture, in preserving the overall productivity of sweet potato crops. Furthermore, the investigation identifies a noteworthy decrease in starch content, suggesting a dynamic interaction between plant sanitation and starch metabolism in response to viral diseases. The study also delves into the alteration of mineral absorption patterns, shedding light on how plant sanitation influences the uptake of essential minerals in sweet potato storage roots. While the health status of the plants only slightly affected magnesium (Mg) and manganese (Mn) accumulation, indicating a potential resilience of mineral balance under virus-infected conditions. Moreover, the research identifies significant modifications in antioxidant levels, emphasizing the role of plant sanitation in enhancing the nutritional quality of sweet potatoes. Heat-treated storage roots, subjected to various cooking methods such as boiling and oven-cooking, exhibit notable differences in internal quality parameters. These differences include increased concentrations of total soluble solids (SS) and heightened levels of antioxidant compounds, particularly phenolic and flavonoid compounds. The observed increase in antioxidant capacity underscores the potential health-promoting benefits associated with plant sanitation practices. Overall, the study underscores the critical importance of plant sanitation in enhancing sweet potato production sustainability, contributing to food security, and supporting local agricultural economies. The results emphasize the need for further research to optimize plant sanitation methods and promote their widespread adoption globally, providing valuable insights into the complex relationships in food quality.

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This article presents data of the effects of fly ash on growth and yield of radish plant under two types of soil (delta clay rich soil and coastal sandy soil). The experiment was conducted under semi-controlled conditions in a greenhouse at the Faculty of Agronomy, Vietnam National University of Agriculture (latitude 21°0'01N, longitude 105° 9'32″ W). The experiment has been conducted with the Randomized Complete Block Design (RCBD), each experimental formula was repeated 5 times. A total of 10 experimental formulas were performed including 100% delta clay rich soil, 95% delta clay rich soil+5% FA, 90% delta clay rich soil+10% FA, 85% delta clay rich soil+15% FA, 80% delta clay rich soil+20% FA, 100% coastal sandy soil, 95% coastal sandy soil+5%FA, 90% coastal sandy soil +10%FA, 85% coastal sandy soil+15%FA, and 80% coastal sandy soil+20%FA. Data on germination rate, plant height, number of leaves, SPAD values, leaf area, shoot fresh and dry weight, storage-root traits, storage-root fresh and dry weight were collected to assess the effects of fly ash on growth and yield of radish plant under delta clay rich soil and coastal sandy soil. This data could help develop a strategy fly ash application for crop cultivation.

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As a major worldwide root crop, the mechanism underlying storage root yield formation has always been a hot topic in sweet potato [Ipomoea batatas (L.) Lam.]. Previously, we conducted the transcriptome database of differentially expressed genes between the cultivated sweet potato cultivar "Xushu18," its diploid wild relative Ipomoea triloba without storage root, and their interspecific somatic hybrid XT1 with medium-sized storage root. We selected one of these candidate genes, IbNF-YA1, for subsequent analysis. IbNF-YA1 encodes a nuclear transcription factor Y subunit alpha (NF-YA) gene, which is significantly induced by the natural auxin indole-3-acetic acid (IAA). The storage root yield of the IbNF-YA1 overexpression (OE) plant decreased by 29.15-40.22% compared with the wild type, while that of the RNAi plant increased by 10.16-21.58%. Additionally, IAA content increased significantly in OE plants. Conversely, the content of IAA decreased significantly in RNAi plants. Furthermore, real-time quantitative reverse transcription-PCR (qRT-PCR) analysis demonstrated that the expressions of the key genes IbYUCCA2, IbYUCCA4, and IbYUCCA8 in the IAA biosynthetic pathway were significantly changed in transgenic plants. The results indicated that IbNF-YA1 could directly target IbYUCCA4 and activate IbYUCCA4 transcription. The IAA content of IbYUCCA4 OE plants increased by 71.77-98.31%. Correspondingly, the storage root yield of the IbYUCCA4 OE plant decreased by 77.91-80.52%. These findings indicate that downregulating the IbNF-YA1 gene could improve the storage root yield in sweet potato.

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Background: Panax ginseng, one of the valuable perennial medicinal plants, stores numerous pharmacological substrates in its storage roots. Given its perennial growth habit, organ regeneration occurs each year, and cambium stem cell activity is necessary for secondary growth and storage root formation. Cytokinin (CK) is a phytohormone involved in the maintenance of meristematic cells for the development of storage organs; however, its physiological role in storage-root secondary growth remains unknown. Methods: Exogenous CK was repeatedly applied to P. ginseng, and morphological and histological changes were observed. RNA-seq analysis was used to elucidate the transcriptional network of CK that regulates P. ginseng growth and development. The HISTIDINE KINASE 3 (PgHK3) and RESPONSE REGULATOR 2 (PgRR2) genes were cloned in P. ginseng and functionally analyzed in Arabidopsis as a two-component system involved in CK signaling. Results: Phenotypic and histological analyses showed that CK increased cambium activity and dormant axillary bud formation in P. ginseng, thus promoting storage-root secondary growth and bud formation. The evolutionarily conserved two-component signaling pathways in P. ginseng were sufficient to restore CK signaling in the Arabidopsis ahk2/3 double mutant and rescue its growth defects. Finally, RNA-seq analysis of CK-treated P. ginseng roots revealed that plant-type cell wall biogenesis-related genes are tightly connected with mitotic cell division, cytokinesis, and auxin signaling to regulate CK-mediated P. ginseng development. Conclusion: Overall, we identified the CK signaling-related two-component systems and their physiological role in P. ginseng. This scientific information has the potential to significantly improve the field-cultivation and biotechnology-based breeding of ginseng.

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An appropriate planting density could realize the maximum yield potential of crops, but the mechanism of sweet potato storage root formation in response to planting density is still rarely investigated. Four planting densities, namely D15, D20, D25, and D30, were set for 2-year and two-site field experiments to investigate the carbohydrate and lignin metabolism in potential storage roots and its relationship with the storage root number, yield, and commercial characteristics at the harvest period. The results showed that an appropriate planting density (D20 treatment) stimulated cambium cell differentiation, which increased carbohydrate accumulation and inhibited lignin biosynthesis in potential storage roots. At canopy closure, the D20 treatment produced more storage roots, particularly developing ones. It increased the yield by 10.18-19.73% compared with the control D25 treatment and improved the commercial features by decreasing the storage root length/diameter ratio and increasing the storage root weight uniformity. This study provides a theoretical basis for the high-value production of sweet potato.

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Sucrose synthases (SUS; EC 2.4.1.13) encoded by a small multigene family are the central system of sucrose metabolism and have important implications for carbon allocation and energy conservation in nonphotosynthetic cells of plants. Though the SUS family genes (SUSs) have been identified in several plants, they have not been explored in sweet potato. In this research, nine, seven and seven SUSs were identified in the cultivated sweet potato (Ipomoea batatas, 2n = 6x = 90) as well as its two diploid wild relatives I. trifida (2n = 2x = 30) and I. triloba (2n = 2x = 30), respectively, and divided into three subgroups according to their phylogenetic relationships. Their protein physicochemical properties, chromosomal localization, phylogenetic relationship, gene structure, promoter cis-elements, protein interaction network and expression patterns were systematically analyzed. The results indicated that the SUS gene family underwent segmental and tandem duplications during its evolution. The SUSs were highly expressed in sink organs. The IbSUSs especially IbSUS2, IbSUS5 and IbSUS7 might play vital roles in storage root development and starch biosynthesis. The SUSs could also respond to drought and salt stress responses and take part in hormone crosstalk. This work provides new insights for further understanding the functions of SUSs and candidate genes for improving yield, starch content, and abiotic stress tolerance in sweet potatoes.

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Sweet potato is in its introductory phase as a food-based approach to alleviate malnutrition in the Afar region, where, due to climate change, agricultural drought impedes crop production. This study assesses the impact of climate change on orange-fleshed sweet potato (OFSP) fresh storage root yield production over the Afar region using the Aqua Crop model. This model was fed with daily rainfall and minimum and maximum temperature datasets, for the baseline climate (1980-2009) as well as future (2010-2099) climate projections under two representative concentration pathways: RCP 4.5 and RCP 8.5. These datasets were statistically downscaled from twenty (20) general circulation models that are used in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The impact of climate change on sweet potatoes was assessed by comparing the change in average sweet potato yields in the baseline climate condition against the average of simulated sweet potato yields in the Near-term (NT) (2010-2039), Mid-term (MT) (2040-2069), and End-term (ET) (2070-2099) under RCP 8.5 and RCP 4.5. Simulation shows increased future storage root yield production for NT (3.23%), MT (3.90%), and ET (7.25%) under RCP 4.5 and MT (5.88%) and NT (6.71%) from the observed yield data (32.0 t/ha) except for Near-term (-9.59%) under RCP 8.5. Similarly, projected climate shows increase in temperature Tmax (0.93-4.10 °C), Tmin (0.88-4.54 °C) and precipitation (28.9-37.8%) under both RCPs which will favor sweet potato yield production increase in near-term, mid-term reaching climax in end-term. Simulation with planting dates shows that normal planting date (July 01), gives better yields than early (April 22) or late planting (01 August). This finding may perhaps be used as preliminary data in adoption and upscaling of orange-fleshed sweet potato in Afar region.

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Sweet potato is a widely cultivated crop with storage roots. Although many studies have been conducted on the mechanism of its storage root formation, the details have not been fully elucidated. We screened mutant lines with inhibition of storage root formation to clarify parts of the mechanism. In this study, the process of storage root formation in one of the mutant lines, C20-8-1, was investigated. The inhibition of storage root formation was observed during the early stages of growth. The roots in C20-8-1 did not show histological differences compared to those in wild type. The transition from fibrous roots to pencil roots, which are the developmental stages prior to mature storage root formation, was delayed or inhibited in C20-8-1. The upregulation of starch biosynthesis-related genes and downregulation of lignin biosynthesis genes with storage root swelling were not confirmed in the root of C20-8-1 during the developmental transition stage, suggesting that most of the roots in C20-8-1 are in the pre-transition state toward the storage root swelling. C20-8-1 showed a mutant phenotype during the critical period of storage root swelling initiation, and further clarification of this mutation is expected to provide new insights into storage root formation.

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A study was carried out in five sweet potato growing regions of Bangladesh, each characterized by suitable agro-ecologies, in order to demonstrate the most favorable varietal performance and trait correlations. A completely randomized block design with three replications was used to compare the varietal performance of BARI (Bangladesh Agricultural Research Institute) released sweet potato varieties (viz. BARI Mistialu-9, BARI Mistialu-10, BARI Mistialu-12, BARI Mistialu-15 and BARI Mistialu-17). During the 2021-22 cropping season, sweet potato varieties were tested in five districts of Bangladesh, namely Gazipur, Bogura, Jamalpur, Jashore, and Chattogram. The findings revealed that the BARI Mistialu-12 variety exhibited remarkable attributes, including a high marketable storage root yield of 39.88 t/ha. Additionally, it demonstrated exceptional performance in various yield components such as vine length, average storage root weight, and dry weight of the root. Furthermore, a positive correlation was observed between several traits and yield, as well as yield-attributing characteristics. This correlation suggests that enhancing these traits could potentially contribute to an overall increase in the storage root yield of sweet potatoes.

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Sweet potato (Ipomoea batatas (L.) Lam.) is one of the most important crops with high storage roots yield. The formation and expansion rate of storage root (SR) plays a crucial role in the production of sweet potato. Lignin affects the SR formation; however, the molecular mechanisms of lignin in SR development have been lacking. To reveal the problem, we performed transcriptome sequencing of SR harvested at 32, 46, and 67 days after planting (DAP) to analyze two sweet potato lines, Jishu25 and Jishu29, in which SR expansion of Jishu29 was early and had a higher yield. A total of 52,137 transcripts and 21,148 unigenes were obtained after corrected with Hiseq2500 sequencing. Through the comparative analysis, 9577 unigenes were found to be differently expressed in the different stages in two cultivars. In addition, phenotypic analysis of two cultivars, combined with analysis of GO, KEGG, and WGCNA showed the regulation of lignin synthesis and related transcription factors play a crucial role in the early expansion of SR. The four key genes swbp1, swpa7, IbERF061, and IbERF109 were proved as potential candidates for regulating lignin synthesis and SR expansion in sweet potato. The data from this study provides new insights into the molecular mechanisms underlying the impact of lignin synthesis on the formation and expansion of SR in sweet potatoes and proposes several candidate genes that may affect sweet potato yield.

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BACKGROUND: Variability in sugar content between raw and cooked sweetpotato storage roots impact nutritional and dietary importance with implications for consumer preference. High-throughput phenotyping is required to breed varieties that satisfy consumer preferences. RESULTS: Near-infrared reflectance spectroscopy (NIRS) calibration curves were developed for analysing sugars in baked storage roots using 147 genotypes from a population segregating for sugar content and other traits. The NIRS prediction curves had high coefficients of determination in calibration (R2 c ) of 0.96 (glucose), 0.93 (fructose), 0.96 (sucrose), and 0.96 (maltose). The corresponding coefficients of determination for cross-validation (R2 cv ) were 0.92 (glucose), 0.89 (fructose), 0.96 (sucrose) and 0.93 (maltose) and were similar to the R2 c for all sugars measured. The ratios of the standard deviation of the reference set to the standard error of cross-validation were greater than three for all sugars. These results confirm the applicability of the NIRS curves in efficiently determining sugar content in baked sweetpotato storage roots. External validation was performed on an additional 70 genotypes. Coefficients of determination (r2 ) were 0.88 (glucose), 0.88 (fructose), 0.86 (sucrose) and 0.49 (maltose). The results were comparable to those found for the calibration and cross-validation in fructose, glucose, and sucrose, but were moderate for maltose due to the low variability of maltose content in the population. CONCLUSIONS: NIRS can be used for screening sugar content in baked sweetpotato storage roots in breeding programs and can be used to assist with the development of improved sweetpotato varieties that better meet consumer preferences. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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The development of storage roots is a key factor determining the yields of crop plants, including sweet potato. Here, using combined bioinformatic and genomic approaches, we identified a sweet potato yield-related gene, ADP-glucose pyrophosphorylase (AGP) small subunit (IbAPS). We found that IbAPS positively affects AGP activity, transitory starch biosynthesis, leaf development, chlorophyll metabolism, and photosynthesis, ultimately affecting the source strength. IbAPS overexpression in sweet potato led to increased vegetative biomass and storage root yield. RNAi of IbAPS resulted in reduced vegetative biomass, accompanied with a slender stature and stunted root development. In addition to the effects on root starch metabolism, we found that IbAPS affects other storage root development-associated events, including lignification, cell expansion, transcriptional regulation, and production of the storage protein sporamins. A combinatorial analysis based on transcriptomes, as well as morphological and physiological data, revealed that IbAPS affects several pathways that determine development of vegetative tissues and storage roots. Our work establishes an important role of IbAPS in concurrent control of carbohydrate metabolism, plant growth, and storage root yield. We showed that upregulation of IbAPS results in superior sweet potato with increased green biomass, starch content, and storage root yield. The findings expand our understanding of the functions of AGP enzymes and advances our ability to increase the yield of sweet potato and, perhaps, other crop plants.

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Drought is the major abiotic stress limiting crop production worldwide, with drought events being expected to be harsher and more frequent due to the global warming. In this context, the development of strategies to mitigate the deleterious effects of drought, such as the use of biostimulants, is imperative. Radish is a globally cultivated root vegetable, with high nutritional and phytochemical value. Thus, this study aimed to evaluate the potential of exogenous carnitine application in the mitigation of drought stress on radish morphophysiology. For this, radish plants were grown for 30 days, being irrigated with 80% (well-watered) or 15% (drought stress) of water holding capacity and sprayed with carnitine (5, 50, and 500 µM) or water (0 µM-no carnitine). The experimental design was completely randomized, in a 4 × 2 factorial scheme (carnitine concentrations × water conditions) with six replicates, and each experimental unit consisted of one plant. The gas exchanges, chlorophyll a fluorescence, photosynthetic pigments, electrolyte leakage, relative water content, and biomass production and allocation were evaluated. Drought reduced the photosynthetic capacity of plants by impairing water balance and membrane integrity, decreasing biomass accumulation, mainly in globular roots. The application of low carnitine (5 µM) mitigated these negative effects caused by drought, increasing membrane integrity and water balance of plants, while higher carnitine concentration (50 and 500 µM) aggravated drought stress. This study highlights the potential of carnitine in the mitigation of drought stress on radish plants, supporting its role as a biostimulant. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01308-6.

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Increasing storage root number is a pivotal approach to enhance both storage root (SR) yield and appearance quality of sweet potato. Here, 2-year field experiments were conducted to investigate the effect of 0 (K0), 120 (K1), 240 (K2), and 360 (K3) kg ha-1 potassium fertilizer (K2O) on lignin metabolism, root growth, storage root yield, and uniformity. The results demonstrated that potassium (K) application led to a decrease in the activities of key enzymes involved in lignin biosynthesis, including phenylalanine deaminase (PAL), 4-coumarate coenzyme A ligase (4-CL), cinnamic acid dehydrogenase (CAD), polyphenol oxidase (PPO), and peroxidase (POD). This resulted in a significant reduction in lignin and G-type lignin contents in potential SRs compared to K0 treatment within 10-30 days after planting (DAP). BJ553 exhibited a significant decrease in PAL activity, as well as lignin and G-type contents at 10 DAP, whereas YS25 showed delayed effects until 20 DAP. However, the number and distribution of secondary xylem conduits as well as the mid-column diameter area in roots were increased in K2 treatment. Interestingly, K2 treatment exhibited significantly larger potential SR diameter than other treatments at 15, 20, and 25 DAP. At harvest, K2 treatment increased the SR number, the single SR weight, and overall yield greatly compared with K0 treatment, with an average increase of 19.12%, 16.54%, and 16.92% respectively. The increase of SR number in BJ553 was higher than that of YS25. Furthermore, K2 treatment exhibited the lowest coefficient of variation for both SR length and diameter, indicating a higher yield of middle-sized SRs. In general, appropriate potassium application could effectively suppress lignin biosynthesis, leading to a reduction in the degree of pericycle lignification in potential SRs. This promotes an increase in the number of storage roots and ultimately enhances both yield and appearance quality of sweet potato. The effect of potassium fertilizer on lignin metabolism in BJ553 roots was earlier and resulted in a greater increase in the SR number compared to YS25.

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Sweet potato is a significant root crop that can be used for both food and feed. Bench-Sheko zone mid-altitudes, in general, are among the most important sweet potato growing regions in southwest Ethiopia. During the 2017 and 2018 growing seasons, a study was carried out in the Semen-Bench district of the Bench-sheko zone, southwestern Ethiopia, to investigate the adaptability and performance of improved sweet potato varieties and to identify the best performer variety. A randomized complete block design with three replications was used to compare the performance of five improved (viz., Awassa-83, Beletch, Berkume, Kulfo, Tula) and one Local sweet potato variety. The results of both years and over year combined statistical analysis indicated that the varieties significantly varied in terms of all yield and yield-related traits. As a result, the Awassa-83 variety acquired the greatest values of average root diameter in both the 2017 (11.9 cm) and 2018 (10.1 cm) growing seasons, followed by the Berkume variety. In both 2017 and 2018 growing seasons and over year combined analysis, the highest average storage root length (21.5 cm), marketable storage root yield (29.06 ton/ha), total storage root yield (43.22 ton/ha), and storage root dry weight (42%) was recorded from variety Awassa-83. Variety Beletech and Berkume were found to be statistically similar and the next highest in terms of marketable storage root yield, and total storage root yield; moreover, variety Berkume was found to be the next highest in terms of storage root dry weight in two years combined result. On the other hand, the variety Beletech, which was closely followed by Awassa-83, had the highest average number of roots per plant (8.28) and the greatest number of marketable roots per plant (7.04). Therefore, considering overall traits Awassa-83 was found to be superior in overall performance and can be recommended for production in the study area and related agro-ecologies.

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MAIN CONCLUSION: The efficiency of suberized plant/environment interfaces as transpiration barriers is not established by the suberin polymer but by the wax molecules sorbed to the suberin polymer. Suberized cell walls formed as barriers at the plant/soil or plant/atmosphere interface in various plant organs (soil-grown roots, aerial roots, tubers, and bark) were enzymatically isolated from five different plant species (Clivia miniata, Monstera deliciosa, Solanum tuberosum, Manihot esculenta, and Malus domestica). Anatomy, chemical composition and efficiency as transpiration barriers (water loss in m s-1) of the different suberized cell wall samples were quantified. Results clearly indicated that there was no correlation between barrier properties of the suberized interfaces and the number of suberized cell layers, the amount of soluble wax and the amounts of suberin. Suberized interfaces of C. miniata roots, M. esculenta roots, and M. domestica bark periderms formed poor or hardly any transpiration barrier. Permeances varying between 1.1 and 5.1 × 10-8 m s-1 were very close to the permeance of water (7.4 × 10-8 m s-1) evaporating from a water/atmosphere interface. Suberized interfaces of aerial roots of M. deliciosa and tubers of S. tuberosum formed reasonable transpiration barriers with permeances varying between 7.4 × 10-10 and 4.2 × 10-9 m s-1, which were similar to the upper range of permeances measured with isolated cuticles (about 10-9 m s-1). Upon wax extraction, permeances of M. deliciosa and S. tuberosum increased nearly tenfold, which proves the importance of wax establishing a transpiration barrier. Finally, highly opposite results obtained with M. esculenta and S. tuberosum periderms are discussed in relation to their agronomical importance for postharvest losses and tuber storage.

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