Mycorrhizal Inoculation Effect on Sweet Potato (Ipomoea batatas (L.) Lam) 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.

The Effect of Low Temperature Stress on the Leaves and MicroRNA Expression of Potato Seedlings

In recent years, with the wanton destruction of the ecological environment by humans and the frequent occurrence of extreme bad weather, many places that should have been warm and blooming in spring have instead experienced the phenomenon of the “April blizzard,” which has seriously affected China's crops, especially spring potato production in most areas. Potato cultivars, especially potato seedlings, are sensitive to frost, and low temperature frost has become one of the most important abiotic stresses affecting potato production. Potato cold tolerance is regulated by a complex gene network. Although some low temperature resistant microRNAs have been identified, little is known about the role of miRNAs in response to low temperature stress in potato. Therefore, the objective of this study is to clarify the influence of low temperature stress on the miRNA expression of potato by comparing the expression differences of miRNA in potato which was treated with different low temperatures. For the study, 307 known miRNAs belonging to 73 small RNA families and 211 novel miRNAs were obtained. When the temperature decreased, the number of both known and novel miRNA decreased, and the minimum temperature was −2°C. Most of the miRNAs respond to low temperature, drought, and disease stress; some conserved miRNAs were first found to respond to low temperature stress in potato, such as stu-miR530, stu-miR156d, and stu-miR167b. The Gene Ontology, Kyoto Encyclopedia of Genes, and Genomes pathway enrichment analysis of 442 different expression miRNAs target genes indicated that there existed diversified low temperature responsive pathways, but Abscisic Acid was found likely to play a central coordinating role in response to low temperature stress in many metabolism pathways. Quantitative real-time PCR assays indicated that the related targets were negatively regulated by the tested different expression miRNAs during low temperature stress. The results indicated that miRNAs may play an important coordination role in response to low temperature stress in many metabolic pathways by regulating abscisic acid and gibberellin, which provided insight into the roles of miRNAs during low temperature stress and would be helpful for alleviating low temperature stress and promoting low temperature resistant breeding in potatoes.

A rapid and efficient method to evaluate the infection of major DNA viruses in sweet potato seedlings and tubers

Background Sweet potato is an important food crop in China which is the fifth largest staple crop next to rice, wheat, maize, and soybean. Recent years the destroy infecting by DNA viruses in sweet potato was more and more serious. Three DNA viruses (sweepoviruses, Badnavirus and Mastrevirus) are major agents in viral diseases of sweet potato in China. It is necessary to establish a rapid and efficient method to evaluate the health of sweet potato seedlings and tubers,which will greatly affect the yield, quality of tubers and seeding circulation of sweet potatoes. Sweepoviruses were a group phylogenetically distinct from other begomoviruses that infects plants of the family Convolvulaceae including sweet potato. Sweet potato symptomless virus 1 (SPSMV-1) is the only species of Mastrevirus which can infected sweet potato. Sweet potato Badnavirus B (SPBV-B) are non-enveloped bacilliform DNA viruses with a monopartite genome which belonged to the genus Badnavirus of the family Caulimoviridae and was first found in sweet potato in 2009. As the mixed infection of these viruses is very common, rapid detection is required for etiologic diagnosis. Results In this study, a rapid and efficient method to evaluate the infection of major DNA viruses (sweepoviruses, Badnavirus and Mastrevirus) in sweet potato seedlings and tubers was developed and applied. A mixture of three pairs of primers was used for amplification of viral nucleic acids, yielding three different amplicons with sizes of 750 bp, 147 bp and 396 bp for sweepoviruses, Badnavirus and Mastrevirus respectively. The specificity and sensitivity of multiplex PCR were also evaluated. A total of 65 sweet potato samples with virus-like symptoms cuttings and storage roots from Henan province in China were collected between June 2019 and July 2021. They were tested for the presence of three DNA viruses by multiplex PCR which showed sweepoviruses, Badnavirus and Mastrevirus infections were 60.0%, 36.7%, and 43.3% respectively. Co-infections with three viruses, sweepoviruses and Badnavirus, sweepoviruses and Mastrevirus, Badnavirus and Mastrevirus were identified in different samples (the detection ratio of co-infections was 13.3%, 20.0%, 13.3%, and 10.0% respectively). Conclusions In the current situation of frequent virus mixed infection in sweet potatoes, this method is the first report on a simple assay and may be a potentially useful for apid and efficient method to evaluate the infection of major DNA viruses in sweet potato seedlings and tubers in China.

RNA-Seq Transcriptome Analysis of Potato with Differential Tolerance to Bentazone Herbicide

Potato (Solanum tuberosum), an important food crop worldwide, is threatened by broadleaf weeds. Bentazone is an effective herbicide for controlling weeds; however, as a photosynthesis inhibitor, it can also affect potato plants. Therefore, screening potato seedlings for bentazone resistance and determining the genes involved is essential. Herein, we selected potato varieties with tolerance and sensitivity to bentazone. The photosynthetic rate of sensitive plants was notably affected by bentazone application, whereas the tolerant plants showed a significantly higher photosynthetic rate. We observed 95.7% bentazone degradation within 24 d after application in the tolerant plants. Transcriptome sequencing revealed that the numbers of differentially expressed genes (DEGs) between the tolerant and sensitive potato seedlings were 2703 and 11,024 before and after bentazone application, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that the majority of DEGs were enriched in metabolic pathways, biosynthesis of secondary metals, carbon metabolism, glutathione metabolism, and photosynthesis. Polyphenol oxidase (PPO), flavonoid 3’,5’-methyltransferase-like (AOMT3), ribulose bisphosphate carboxylase small chain C (RBCS-C), and chalcone synthase 2 (CHS2) were identified as candidates contributing to bentazone tolerance. These results provide a theoretical basis for selecting potato stress-resistant resources in the future.

Antioxidant Activity of Potato Seedlings at Different Storage Temperatures

In order to promote the storage and growth of potato seedlings, the antioxidant activities of potato seedlings at different storage temperatures were analyzed. The antioxidant activities of potato seedlings at two different temperatures were compared. In addition, the effects of high temperature and normal temperature on the growth phenotype and antioxidant system physiological indexes of potato seedlings were analyzed by high temperature treatment. According to the significant change characteristics of SOD activity of antioxidant index at different temperatures, the SOD genes of potato were screened and bioinformatics analysis and gene expression analysis were carried out. The results showed that high temperature inhibited the antioxidant activity of potato seedlings and affected the growth of potato seedlings. The growth of potato seedlings can be promoted in medium and low temperature environment. In the future research, the experimental results can be used as the theoretical basis for potato planting.

Large-Scale Seedling Grow-Out Experiments Do Not Support Seed Transmission of Sweet Potato Leaf Curl Virus in Sweet Potato

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.

Design Optimization and Experiment of Four-Row Potato Seedling-Cutting Machine

HighlightsBased on the innovative analysis of the seedling-cutting operation mechanism, five shapes of seedling-cutting blades were designed, and a four-row potato seedling-cutting machine was developed.The kinematics and mechanics of seedling-cutting blades were analyzed, which can provide a theoretical basis for the selection of experimental factors.A regression orthogonal experiment and variance analysis were carried out to verify the performance of the four-row potato seedling-cutting machine. Finally, the main and secondary factors affecting the seedling-cutting performance and the optimal parameter combination were obtained.Compared with other studies, the structure of the seedling-cutting blades are more complete in this study. The test results show that the qualified rate of the broken length of the potato seedlings is significantly improved, the missed cutting rate of the potato seedlings is reduced, and the length of the stubble is more uniform, which greatly improves the quality of seedling-cutting.Abstract. A four-row potato seedling-cutting machine was designed to address the problems associated with potato seedling-cutting machines with low qualified rates of broken length and stubble length and high missed cutting rates. Based on the analysis of the seedling-cutting operation mechanism, key components were designed, and the kinematics and mechanics were analyzed. A regression orthogonal experiment was carried out, taking the rotation speed of the seedling-cutting blade shaft, forward speed of the seedling-cutting machine, and height of the short blade of the ridge top from the ridge platform as the experimental factors and the qualified rate of the broken length of the potato seedlings, missed cutting rate of the potato seedlings, rate of carrying potatoes, and length of the stubble as experimental indexes. The results showed that the prioritized impact of various factors on the qualified rate of the broken length of the potato seedlings ranked as follows: the rotation speed of the seedling-cutting blade shaft > the height of the short blade of the ridge top from the ridge platform > the forward speed of the seedling-cutting machine. The prioritized impact of various factors on the missed cutting rate of the potato seedlings ranked as follows: the forward speed of the seedling-cutting machine > the rotation speed of the seedling-cutting blade shaft > the height of the short blade of the ridge top from the ridge platform. The prioritized impact of various factors on the rate of carrying potatoes and the length of the stubble ranked as follows: the height of the short blade of the ridge top from the ridge platform > the rotation speed of the seedling-cutting blade shaft > the forward speed of the seedling-cutting machine. The optimal parameter combination was a rotation speed of the seedling-cutting blade shaft of 1400 r/min, forward speed of the seedling-cutting machine of 4.22 km/h, height of the short blade of the ridge top from the ridge platform of 62 mm. Based on this combination, the qualified rate of the broken length of potato seedlings was 94.1%, the missed cutting rate of the potato seedlings was 0.30%, the rate of carrying potatoes was 0.49%, and the length of the stubble was 54 mm. The index values of the verification experiments were 94.6%, 0.38%, 0.53%, and 56 mm, which were better than the standard values, indicating that this machine meets the basic operation requirements. The test results can provide theoretical support and technical reference for improving the parameter and structural design of a potato seedling-cutting machine. Keywords: Field experiment, Flail blade, Potato, Seedling-cutting machine.