Effect of Mechanical Properties of Sweet Potato Seedlings on Quality of Mechanized Processing and Recycling Work

Sweet potato symptomless virus 1 (SPSMV-1) is a member of genus Mastrevirus, in the family Geminiviridae. SPSMV-1 was detected from sweet potato (Ipomoea batatas) seedlings by small-RNA deep-sequencing. PCR analysis indicated that SPSMV-1 was detected in 12 out of 114 individual sweet potato seedlings from seeds collected from a SPSMV-1-infected sweet potato plant, and additionally, detected in whole seeds, seed coats attached with endosperm, and in embryos. The complete genome of the virus was subsequently cloned by using a polymerase chain reaction (PCR) method with back-to-back (full) primer pairs from sweet potato seedlings and seeds. In summary, the results suggest that SPSMV-1 may be a seed-borne virus and a seed transmissible virus in sweet potato. To our knowledge, this is the first evidence for seed transmission of SPSMV-1, and seed transmission under natural conditions for any mastrevirus as well.

Whether the stems and leaves of leaf-vegetable sweet potatoes can be listed ahead of schedule is related to the improvement in economic benefits for farmers, and the key to all of this is to implement the safe overwintering of potato seedlings under the premise of saving production costs. Only in this way can we truly seize the “market opportunity” and achieve the goals of cost saving and increasing economic benefit. In this study, the main leaf-vegetable sweet potato variety Fucai 18 was used as the material, and the L9(34) orthogonal experiment was carried out in a simple solar greenhouse environment for two consecutive years from 2021 to 2022 and from 2022 to 2023, respectively. The effects of nine different combinations of factors on the above-ground and underground agronomic traits of overwintering sweet potato seedlings were studied under the conditions of four factors and three levels: planting density (a); different cutting seedlings (b); rooting agent concentration (c); and transplanting time (d). The methods of principal component analysis, membership function method, cluster analysis, grey correlation degree and stepwise regression analysis were used to evaluate the growth of overwintering seedlings, and try to screen out the key indicators that can be used to identify and evaluate the growth of overwintering sweet potato seedlings. Through range analysis, identify the optimal combination of four factors and three levels, and explore the main factors that have a significant impact on the key indicators for evaluating the growth of overwintering potato seedlings. The results indicate the following: (1) The use of simple sunlight greenhouse in Changsha area can achieve the safe overwintering of vegetable sweet potato seedlings. (2) Stem thickness, root length, and root diameter can be used as three key indicators for identifying and evaluating the growth potential of vegetable sweet potato overwintering seedlings. (3) Under four factors and three levels, the best combination was A3B3C1D1 (planting density of 250,000 plants/ha, stem tip core-plucking seedlings, rooting agent concentration of 50 mg/L, the first batch of transplanting time). (4) The transplanting time (D) is the main factor for the two key evaluation indicators of stem diameter and root diameter, while there is no significant difference in the three other factors. (5) Different cutting seedlings (B) are the main influencing factors for the key evaluation index of root length, while the other three factors have the following impact on root length: transplanting time (D) > rooting agent concentration (C) > planting density (A). The results of this study not only contribute to the construction of a safe overwintering cultivation technology system for vegetable sweet potato seedlings, but also provide a certain theoretical basis for the breeding of new cold-leaf-vegetable sweet potato varieties in the future.

Design and control of a side dense transplanting machine for sweet potato seedlings on mulch film

Abstract. Sweet potato seedlings are soft, thin and tangled, which restrict the development of mechanical sorting and transplanting technology. Sweet potato planting depends extensively on manual labor with low production efficiency. But if sweet potato seedlings were planted mechanically, some physical damages might happen easily such as missing leaves, damaged leaves and broken seedlings. Till now, it is not clear to what extent these physical damages will affect the growth of sweet potato seedlings and yield of sweet potato. In this study, sweet potato seedlings named Longshu 9 were planted in small raised bed using three-leaf planting method, and sweet potato growth and yield were analyzed by field testing. The results showed that survival rate of seedlings with damaged leaves, seedlings with damaged stems, normal seedlings were 94%, 85% and 100%, respectively. Number of young roots was almost same and irregular, but total length of young roots varied greatly between different treatments. Total length of young roots for damaged seedling was shorter than that of normal seedlings. Tubers, stems and leaves grew early and quickly for normal seedlings, and total weight increase of stems, leaves and tubers were 4.45g, 3.88g, 5.18g for damaged leaves, damaged stems and normal seedlings, respectively. Between three treatments, tubers yield differed significantly and had regularity. Compared with normal seedlings, yield of seedlings with damaged leaves was reduced about 11.3%, and yield of seedlings with damaged stems was reduced about 22.8%. In conclusion, damaged sweet potato seedlings have little or no effect on number of young roots and tubers, but damaged leaves and stems have a significant effect on survival rate, root burgeon, leaves and stems growth, and tubers yield. The more serious the damage is, the more severe the impact is. This research provides a theoretical and experimental basis for mechanical sorting and transplanting of sweet potato seedlings.

Sweet potato is an increasingly significant crop and its effective and sustainable cultivation has become important in temperate countries. The purpose of this pilot study was to investigate the effects of a mycorrhizal inoculum, Symbivit, and whether it could establish a symbiotic relationship with the seedlings of two sweet potato varieties (orange and purple). The effectiveness of the mycorrhizal inoculation with a sterilized substrate on the mycorrhizal parameters (F%, M%, m%, a%, A%) and physical parameters “[length of roots and shoots (cm), the fresh weight of shoots and roots (g) as well as the length of stem (cm)]” on the sweet potato seedlings has also been studied. Results show that the sterilization treatment with Symbivit in both varieties increased the frequency of mycorrhiza in the root system. For the intensity of the mycorrhizal colonization in the root fragments and the arbuscular abundance, there was a difference between the mycorrhizal inoculum and the sterilization treatment among the varieties. Overall, the preliminary results provided remarkable information about mycorrhizal inoculation, substrate sterilization on mycorrhizal development, as well as changes in the physical parameters between sweet potato seedlings. Our results could serve as a practical strategy for further research into adding significance to the effect of the beneficial soil microbes on sweet potatoes.

Viral diseases caused severe yield losses and quality decline of sweet potato. To identify viruses that are infecting sweet potato in fields in Beijing, we used small RNA deep sequencing and PCR or RT-PCR and found seven RNA viruses and four DNA viruses, including an unrecorded virus, broad bean wilt virus 2. Sweet potato leaf curl virus and sweet potato feathery mottle virus had the highest incidence (88% of tested samples). Coinfection with sweet potato viruses was common in Beijing, and most samples were simultaneously infected by four or more virus species with different genomic types. These results indicated that potyviruses and DNA viruses were prevalent in sweet potato in Beijing, which will be useful for detection and control of viral diseases. This is the first comprehensive report of sweet potato viruses in Beijing. We expected that targeted detection of viruses in sweet potato seedlings will increase the number detected and thus inform management decisions of sweet potato seedlings.

Sweet potato leaf curl virus (SPLCV) threatens global sweet potato production. SPLCV is transmitted by Bemisia tabaci or via infected vegetative planting materials; however, SPLCV was suggested to be seed transmissible, which is a characteristic that is disputed for geminiviruses. The objective of this study was to revisit the validity of seed transmission of SPLCV in sweet potato. Using large-scale grow-out of sweet potato seedlings from SPLCV-contaminated seeds over 4 consecutive years, approximately 23,034 sweet potato seedlings of 118 genotype entries were evaluated. All seedlings germinating in a greenhouse under insect-proof conditions or in a growth chamber were free of SPLCV; however, a few seedlings grown in an open bench greenhouse lacking insect exclusion tested positive for SPLCV. Inspection of these seedlings revealed that B. tabaci had infiltrated the greenhouse. Therefore, transmission experiments were conducted using B. tabaci MEAM1, demonstrating successful vector transmission of SPLCV to sweet potato. Additionally, tests on contaminated seed coats and germinating cotyledons demonstrated that SPLCV contaminated a high percentage of seed coats collected from infected maternal plants, but SPLCV was never detected in emerging cotyledons. Based on the results of grow-out experiments, seed coat and cotyledon tests, and vector transmission experiments, we conclude that SPLCV is not seed transmitted in sweet potato.

Sufficient soil moisture is required to ensure the successful transplantation of sweet potato seedlings. Thus, reasonable water management is essential for achieving high quality and yield in sweet potato production. We conducted field experiments in northern China, planted on 18 May and harvested on 18 October 2021, at the Nancun Experimental Base of Qingdao Agricultural University. Three water management treatments were tested for sweet potato seedlings after transplanting: hole irrigation (W1), optimized drip irrigation (W2), and traditional drip irrigation (W3). The variation characteristics of soil volumetric water content, soil temperature, and soil CO2 concentration in the root zone were monitored in situ for 0-50 days. The agronomy, root morphology, photosynthetic parameters, 13C accumulation, yield, and yield components of sweet potato were determined. The results showed that soil VWC was maintained at 22-25% and 27-32% in the hole irrigation and combined drip irrigation treatments, respectively, from 0 to 30 days after transplanting. However, there was no significant difference between the traditional (W3) and optimized (W2) drip irrigation systems. From 30 to 50 days after transplanting, the VWC decreased significantly in all treatments, with significant differences among all treatments. Soil CO2 concentrations were positively correlated with VWC from 0 to 30 days after transplanting but gradually increased from 30 to 50 days, with significant differences among treatments. Soil temperature varied with fluctuations in air temperature, with no significant differences among treatments. Sweet potato survival rates were significantly lower in the hole irrigation treatments than in the drip irrigation treatments, with no significant difference between W2 and W3. The aboveground biomass, photosynthetic parameters, and leaf area index were significantly higher under drip irrigation than under hole irrigation, and values were higher in W3 than in W2. However, the total root length, root volume, and 13C partitioning rate were higher in W2 than in W3. These findings suggest that excessive drip irrigation can lead to an imbalance in sweet potato reservoir sources. Compared with W1, the W2 and W3 treatments exhibited significant yield increases of 42.98% and 36.49%, respectively. The W2 treatment had the lowest sweet potato deformity rate.

Melatonin (MT) is a multifunctional molecule in animals and plants and is involved in defense against salinity stress in various plant species. In this study, MT pretreatment was simultaneously applied to the roots and leaves of sweet potato seedlings [Ipomoea batatas (L.) Lam.], which is an important food and industry crop worldwide, followed by treatment of 150 mM NaCl. The roles of MT in mediating K+/Na+ homeostasis and lipid metabolism in salinized sweet potato were investigated. Exogenous MT enhanced the resistance to NaCl and improved K+/Na+ homeostasis in sweet potato seedlings as indicated by the low reduced K+ content in tissues and low accumulation of Na+ content in the shoot. Electrophysiological experiments revealed that exogenous MT significantly suppressed NaCl-induced K+ efflux in sweet potato roots and mesophyll tissues. Further experiments showed that MT enhanced the plasma membrane (PM) H+–ATPase activity and intracellular adenosine triphosphate (ATP) level in the roots and leaves of salinized sweet potato. Lipidomic profiling revealed that exogenous MT completely prevented salt-induced triacylglycerol (TAG) accumulation in the leaves. In addition, MT upregulated the expression of genes related to TAG breakdown, fatty acid (FA) β-oxidation, and energy turnover. Chemical inhibition of the β-oxidation pathway led to drastic accumulation of lipid droplets in the vegetative tissues of NaCl-stressed sweet potato and simultaneously disrupted the MT-stimulated energy state, PM H+–ATPase activity, and K+/Na+ homeostasis. Results revealed that exogenous MT stimulated TAG breakdown, FA β-oxidation, and energy turnover under salinity conditions, thereby contributing to the maintenance of PM H+–ATPase activity and K+/Na+ homeostasis in sweet potato.

The mechanized transplanting of sweet potato slips onto mulched raised beds in China’s Huang-Huai-Hai region faces significant challenges due to fragmented smallholder farms and the specific agronomic requirement of “boat-shaped” horizontal planting. To address this gap, this study aimed to develop a compact, cost-effective transplanter that meets the “boat-shaped” planting agronomy and adapts to small plots. We designed the 2CGX-1 mini wheel-driven transplanter coupled with a tractor. This machine features a compact chassis (<1.5 m length) for enhanced maneuverability on small plots, a novel five-bar taking-planting mechanism optimized for boat-shaped placement (achieving a stem-soil angle of 56.2° and planting depth of 110 mm), and an integrated spring buffer system. Transmission design ensures precise synchronization between the dual-chain seedling feeding mechanism and planting actions, allowing plant spacing adjustment from 18 to 30 cm. Coupled Adams–EDEM simulations demonstrated that the buffer system reduces maximum resistance on the clip fingers by 37.8% when encountering obstacles. Field validation under optimal parameters (0.55 km/h operating speed, 30 plants/min transplanting frequency) showed high consistency: average planting depth 101.3 mm (SD 1.38), plant spacing 330.3 mm (SD 11.24), seedling length under the film 185 mm (SD 3.65), and stem-soil angle 47.9° (SD 3.41), with qualification rates exceeding 91.9% for all key parameters except submerged length (82.5%). Compared with manual planting (≤0.1 ha/day per person, labor cost > ¥800/ha), this transplanter achieves a daily operational efficiency of ~0.35 ha/day (calculated by 0.55 km/h speed × 0.8 m working width × 8 h daily working time). Meanwhile, the consistency of its key planting indicators and the planting qualification rate are significantly superior to those of manual planting, while improving operational quality and significantly reducing labor cost input. Deviations in individual indicators mainly stem from planting positioning deviations induced by terrain undulations in hilly test areas, and sweet potato seedlings’ tendency to fall off during clamping due to mechanical vibration. However, these errors are within the acceptable agricultural operation range and do not compromise the machine’s overall compliance with agronomic requirements. The transplanter effectively meets agronomic requirements while offering a cost-effective, adapted solution for small-scale sweet potato production systems, significantly advancing mechanization capabilities for mulched cultivation.

To develop a way to mass-produce sweet potatoes (Ipomoea batatas (L.) Lam.) as an energy crop to replace fossil fuels, the effects of using a sewage supply as a fertilizer and heat source were investigated. When 25 pots planted with sweet potato vine seedlings were arranged in three layers and cultivated for 160 days from June to November by supplying treated sewage to the root zone, the yield of tuberous roots reached 19.5 kg m−2 due to the massive growth of leaves. In addition, when sweet potato seedlings were replanted in December and treated sewage was supplied to maintain the irrigation water temperature above 15 °C even in winter, overwintering cultivation was successful and 8.4 kg m−2 of tuberous roots were harvested in July. As a result, the annual production rate for 12 months increased to 25.3 kg m−2, about 10 times the national average of 2.4 kg m−2 for open-field cultivation. The results far exceed previously reported maximum production of resource crops, such as sugarcane and eucalyptus, suggesting that the mass production of sweet potatoes by supplying treated sewage could provide an alternative to fossil fuels on a large scale.

Abstract. The morphological and mechanical characteristics of sweet potato seedlings in suitable transplanting period have great impact on the structure and design parameters of sweet potato transplanting machinery. In order to study its morphological and mechanical characteristics, sweet potato seedlings named Longshu 9 were in nurture 35 days and cut as test materials, and then seedlings were measured and tested with a universal material testing machine. The results showed sweet potato seedlings varied in length from 19cm to 35cm, and the moisture content averaged 90.96%. The diameter varied in across the length of seedlings, and average diameters measured in three locations (root, middle and bottom) were 4.16mm, 3.84mm and 1.49mm, respectively. AS a result of different internal fibers, seedlings near the bottom were broken easily in tension test, and breaking force averaged 1.37N. Most of seedlings were shear off with the load more than 0.96N, and the crushing force averaged 8.07N when seedlings near the root were completely crushed. In conclude, the research on morphological and mechanical characteristics of sweet potato seedlings provides useful guidance for the design and optimization of sweep potato transplanter.

Soilless culture systems, which promote plant growth and enable the precise control of the root-zone environment, have yet to be fully established for sweet potatoes. In this study, we developed a soilless culture system and examined the effects of soil covering and light exposure on the storage roots of sweet potatoes. Sweet potato seedlings with induced storage roots were transplanted into five systems: a previously developed pot-based hydroponics system (Pot), an improved version with storage roots enclosed in a plastic box and covered with a soil sheet (SS), the SS system without the soil sheet (SD), the SD system with light exposure to storage roots after 54 days (SL), and a deep flow technique (DFT) hydroponics system. Our study enabled the time-course observation of storage root enlargement in the SS, SD, and SL systems. In the SL system, light exposure suppressed the storage root enlargement and reduced epidermal redness. No storage root enlargement was observed in the DFT system, even at 151 days after transplantation. Light exposure in the SL system increased the chlorophyll and total phenolic contents in the cortex beneath the epidermis, while the starch content was the lowest in this system. These findings indicate that the developed system can induce normal storage root enlargement without soil. Additionally, the observed changes in growth and composition due to light exposure suggest that this system is effective for controlling the root-zone environment of sweet potatoes.

Sweet potato virus disease (SPVD) occurs in sweet potato at all localities on the perimeter of Lake Victoria areas surveyed in Uganda and Tanzania, and was particularly common in Kagera District in Tanzania and in Rukungiri District in Uganda. All fields were planted with landraces and the most important control practices, as perceived by farmers, were the planting of cuttings derived from only symptomless parents and destroying diseased plants. Although SPVD‐resistant landraces were available, they were perceived by most farmers to have poor and late yields. Most farmers considered that their greatest need was new, more acceptable, SPVD‐resistant genotypes. Few farmers had seen either sweet potato seeds (15%) or sweet potato seedlings (11%) and, of those that had, most had ignored them. The lack of seedlings and their neglect by farmers is likely to be hindering the evolution of more acceptable, SPVD‐resistant landraces, and is probably responsible for SPVD being a long‐term disease problem.

The use of branches from selected plants may favor the productivity of the sweet potato crop, which makes necessary high production of branches per unit of mother plant. Thus, this study aimed to evaluate the branches production of sweet potato plants grown in suspended pots containing substrate fertilized with different doses of nitrogen. For this study, the experiment was installed in randomized blocks with time split plot, with 10 repetitions. It was used a factorial 5 x 2, being five doses of N (0; 0.24; 0.48; 0.72 and 0.96 g per pot) and two the amount of plants per pot (one or two plants). The sweet potato seedlings were produced in trays and planted in pots. The fertilization of the substrate with urea occurred every 30 days. The branches of the plants were collected at 60, 105, 150 and 195 days after transplantation, keeping the potted plants with branches of 0.30 m. It were evaluated length and dry mass of the branches of sweet potato produced in pots. As a result, it was found that the use of nitrogen in doses of 0.72 and 0.96 g per pot and the cultivation of only one plant per pot favored greater growth of sweet potato plant branches. Therefore, the addition of nitrogen to the substrate where sweet potato plants are cultured is feasible to obtain greater amount of plant material in order to produce new plants. Additional keywords: cutting; Ipomoea batatas (L.) Lam; mother plant; multiplication; substrate; vegetative propagation.