Tuber Maturation Research Articles

Reduced Late-Season Irrigation Improves Potato Quality, Often at the Expense of Yield and Economic Return

With a rising global population and looming water shortages in the U.S., there is a pressing need for water-efficient farming methods. The water needs of potato plants decrease in the late season due to foliage aging and tuber maturation. Therefore, proper late-season irrigation is vital in preventing water waste and maximizing potato profits. This study assessed the feasibility of reducing late-season irrigation to improve crop water productivity (WPc), tuber quality, and economic return. Field trials were planted near Othello, WA, across three years (2018–20). Treatments included five irrigation levels (ILs), 40%, 60%, 80%, 100%, and 120% of modeled evapotranspiration (ET), and five potato cultivars: Alturas, Clearwater Russet, Ranger Russet, Russet Burbank, and Umatilla Russet. Treatments started 100 to 105 days after planting (DAP), approximately 1500 day degrees (at or near peak canopy growth), and ended at vine kill, 150 to 155 DAP. Water from reduced ILs of 40% to 80% ET was more efficiently converted into yield (WPc) for Alturas than higher ILs; however, economic return for all cultivars typically peaked when irrigation was supplied at or above 80% ET. Tuber quality generally improved with a reduction in irrigation level, occasionally at the expense of yield and economic value.

Influence of Harvesting Stages on Phytonutrients and Antioxidant Properties of Leaves of Five Purple-Fleshed Sweet Potato (Ipomoea batatas) Genotypes.

Sweet potatoes (Ipomoea batatas) are highly profitable, contribute to food security, and their leaves rich in phytonutrients. This study examined the optimal leaf harvesting stage by harvesting newly formed leaves (leaves 1 to 5) to achieve the highest concentration of carotenoids, phenolic compounds, antioxidant properties and mineral content. Leaves of five purple-fleshed sweet potato genotypes '2019-11-2' and '2019-1-1', 'Purple-purple', and from the USA '08-21P' and '16-283P' were harvested based on tuber life cycle [vegetative 8 weeks after planting (VS-8WAP), tuber initiation (TIS-12WAP), and tuber maturation phases (TMS-16WAP)]. At the 8WAP stage, leaves of genotype '2019-11-2' had the highest concentrations of cyanidin-caffeoyl-sophoroside-glucoside (17.64 mg/kg), cyanidin-caffeoyl-feruloyl-sophoroside-glucoside (41.51 mg/kg), peonidin-caffeoyl-hydroxybenzoyl-sophoriside-glucoside (45.25 mg/kg), and peonidin caffeoyl-feruloyl-sophoriside-glucoside (24.47 mg/kg), as well as antioxidant scavenging activity. In contrast, 'Purple-purple' harvested at TIS-12WAP showed the highest concentration of caffeoylquinic acid derivatives. Zeaxanthin, lutein, all trans-β-carotene, and cis-β-carotene are the most abundant carotenoids in genotype '08-21P' at VS-8WAP. As a result, local genotypes '2019-11-2' harvested at 8WAP and 'Purple-purple' harvested at 12WAP are potential sources of anthocyanins and caffeoylquinic acid derivatives. Conversely, USA's genotype '08-21P' at the VS-8WAP stage is an excellent source of carotenoids. The leaves of USA's '08-21P' genotype and the local '2019-11-2' genotype at TMS-16WAP exhibited the highest content of Fe and Mn, respectively. The study identified the optimal leaf stage for consumption of leaves and for use as a functional ingredient.

Biomass partitioning reveals the adaptability of tiger nut (Cyperus esculentus L.) in an arid ecosystem in Inner Mongolia, China

AbstractTiger nuts (Cyperus esculentus L.) have been widely cultivated as a bioenergy crop in northern China. The value of tubers is receiving special attention, but the lack of information on how organs of tiger nuts coordinate resources to adapt to arid environments has limited the potential tuber production and diverse use. To address this knowledge gap, we experimented in the Ulan Buh Desert, Inner Mongolia (106° 33′ 28″ E, 40° 27′ 32″ N). Three fertilizer treatments were applied: zero fertilizer (N:P = 0:0), traditional fertilizer (N:P = 15:15), and additional nitrogen fertilizer (N:P = 60:15). Investigations were conducted at seedling, rhizome production, tuber formation, and tuber maturation stages. The results showed that under zero fertilizer, tiger nuts allocated biomass predominantly to propagative organs, namely rhizomes and tubers. However, an increase in leaf area or root surface area would necessitate more investment in leaf or root dry mass, resulting in diminishing returns. For biomass allocation, tiger nut responded the same way to traditional fertilizer treatment and zero fertilizer treatment, but the tuber number and yield increase under traditional fertilizer application. Additional nitrogen fertilizer stimulated shoot production through accelerated rhizome production aided by leaf area increasing. Fertilizer application can significantly increase both the number of tiger nuts and tuber yield. Nitrogen addition positively influenced aboveground biomass and enhanced rhizome tillering. Strong adaptability of tiger nuts makes the plant a suitable pioneer crop for developing marginal lands. The robust aboveground growth after nitrogen application enhances suitability for pasture utilization.

Visible and near-infrared spectroscopy predicted leaf nitrogen contents of potato varieties under different growth and management conditions

Visible-Near Infrared (vis-NIR) spectroscopy can provide a faster, cost-effective, and user-friendly solution to monitor leaf N status, potentially overcoming the limitations of current techniques. The objectives of the study were to develop and validate partial least square regression (PLSR) to estimate the total N contents of fresh and removed leaves of potatoes using the vis-NIR spectral range (350–2500 nm) generated from a handheld proximal sensor. The model was built using data collected from Hancock Agricultural Research Station, WI, USA in 2020 and was validated using samples collected in 2021 for four different conditions. The conditions included two sites (Coloma and Hancock), four potato varieties (Burbank, Norkotah, Goldrush, and Silverton), two N rates (unfertilized and 308 kg N ha−1), and four growth stages (vegetative, tuber initiation, tuber bulking, and tuber maturation). The calibration and validation models had high predictive performance for leaf total N with R2 > 0.8 and RPD > 2. The model accuracy was affected by the total N contents in the leaf samples where the model underpredicted the samples with total leaf N contents greater than 6%.

N-Linked Glycoproteome Analysis of Diosorea alata Tuber Shows Atypical Glycosylation and Indicates Central Role of Glycosylated Proteins in Tuber Maturation.

Glycosylation is an important post translational modification in plants. First analysis of N-linked glycosylated proteins of Dioscorea alata using Concanavalin A lectin affinity chromatography enrichment coupled with label free quantification is presented. In total, 114 enriched glycoproteins were detected. Signal P and sub-cellular localization showed 42.2% of proteins to be secretory. These included peroxidases, endochitinases, calreticulin, calnexin, thaumatins and lipid transfer proteins. Gene Ontology and MapMan analysis predicted the enriched glycoproteins to be involved in processes essential for tuber maturation namely: signal transduction, lignification, protein trafficking, endoplasmic reticulum quality control and cell wall remodeling. This was supported by biochemical validation of the essential glycoproteins. Interestingly, out of the two dioscorin isoforms, Dio B was the only N-glycosylated form. In silico analysis showed O-glycosylation sites in the other form, Dio A suggesting its similarity with sporamin, the storage protein of sweet potato. Absence of signal peptide in Dio B and the presence of non-canonical motif hints towards its atypical glycosylation. The analysis revealed that N-glycosylation of Dio B isoform maintains the activities associated with Dioscorin at maturity and provides an overview of protein N-glycosylation, enriching the glycoproteome database of plants especially tubers.

Effect of Water Deficiency in Different Stages of Potato (Solanum tuberosum L.) Growth

The experiment was conducted to assess the sensitivity of potato yield to different irrigation levels at different growth stages. Irrigation levels were determined as percentages (WI 100% as readily available water to the crop (RAW)), and for the rest of the treatments (WII 75%, WIII 50%), as they were applied separately to all four stages of crop growth i.e., vegetative (SI), tuber initiation (SII), tuber bulking SIII, and tuber maturation (SIV). The design of complete random sectors was adopted to perform the experiments. The results revealed that all the studied parameters: plant height (cm), vegetation plant weight (g), number of tubers per plant, tuber weight (g), tuber yield (ton/ha), and crop water productivity (kg/m3) varied among irrigation water levels at different stages of growth. It was found that the two stages, SII and SIII in potato crops, were more sensitive to deficit irrigation compared to other stages. According to the obtained results, in the case of water abundance conditions, the treatment WII SI can be applied to obtain the highest water crop productivity. In conditions of water scarcity, it becomes necessary to apply the treatment WIII SIII to obtain the highest crop water productivity.

Analysis of Cyperus esculentus SMP family genes reveals lineage-specific evolution and seed desiccation-like transcript accumulation during tuber maturation

Seed maturation proteins (SMPs) represent a class of late embryogenesis-abundant proteins that are highly hydrophilic and abundant in mature seeds. Although it has been proven that SMPs are indispensable for the desiccation resistance of orthodox seeds , information on their putative roles in the desiccation resistance of non-seed storage organs is still scarce. This study presents a first transcriptome-based characterization of SMP family genes in tigernut ( Cyperus esculentus L., Cyperaceae), whose underground tubers represent a unique system that contains a considerably low moisture content of less than 10% without affecting the sprouting capability. Five family members identified from the full-length tigernut transcriptome are relatively more than four found in the genome of Carex littledalei , another Cyperaceae plant. Moreover, 69 family genes were also identified from 15 representative plant species and comparative genomics analysis supports the monogenic origin of this special family as well as lineage-specific evolution after monocot-eudicot split. In the Cyperaceae lineage, four clades present in the last common ancestor of tigernut and C. littledalei , which represent four out of 11 orthogroups proposed in this study, are more likely to result from transposed and dispersed duplications. In contrast to seed- or embryo-preferential expression of SMP genes in seed-bearing plants (e.g. rice and maize), transcriptional profiling and qRT-PCR analysis showed that most CeSMP genes are predominantly expressed in late stages of developmental tigernut tubers, negatively correlating with the moisture content. This seed desiccation-like accumulation of CeSMP transcripts during tuber maturation implies their putatively important roles in the desiccation resistance of tigernut tubers as observed in orthodox seeds. These findings not only improve the knowledge on lineage-specific evolution of the SMP gene family, but also provide valuable information for further functional analysis and genetic improvement in tigernut. • This is a first transcriptome-based analysis of SMP family genes in tigernut. • Comparative genomics analysis reveals the monogenic origin of the SMP family. • Lineage-specific family evolution was observed after monocot-eudicot split. • CeSMP transcripts are negatively correlating the moisture content of tubers. • Accumulation of CeSMPs in mature tubers implies a role in desiccation resistance.

Identification and Expression Analysis of the Solanum tuberosum StATG8 Family Associated with the WRKY Transcription Factor

Autophagy is an evolutionarily well-conserved cellular catabolic pathway in eukaryotic cells and plays an important role in cellular processes. Autophagy is regulated by autophagy-associated (ATG) proteins. Among these ATG proteins, the ubiquitin-like protein ATG8/LC3 is essential for autophagosome formation and function. In this study, the potato StATG8 family showed clade I and clade II with significantly different sequences. Expression of the StATG8 family was also increased in senescence. Interestingly, the expression of the StATG8 and other core StATG genes decreased in potato tubers as the tubers matured. The StATG8 family also responded to a variety of stresses such as heat, wounding, salicylic acid, and salt stress. We also found that some Arabidopsis WRKY transcription factors interacted with the StATG8 protein in planta. Based on group II-a WRKY, StATG8-WRKY interaction is independent of the ATG8 interacting motif (AIM) or LC3 interacting region (LIR) motif. This study showed that the StATG8 family had diverse functions in tuber maturation and multiple stress responses in potatoes. Additionally, StATG8 may have an unrelated autophagy function in the nucleus with the WRKY transcription factor.

Potato Periderm Development and Tuber Skin Quality.

The periderm is a corky tissue that replaces the epidermis when the latter is damaged, and is critical for preventing pathogen invasion and water loss. The periderm is formed through the meristematic activity of phellogen cells (cork cambium). The potato skin (phellem cells) composes the outer layers of the tuber periderm and is a model for studying cork development. Early in tuber development and following tuber expansion, the phellogen becomes active and produces the skin. New skin layers are continuously added by division of the phellogen cells until tuber maturation. Some physiological disorders of the potato tuber are related to abnormal development of the skin, including skinning injuries and russeting of smooth-skinned potatoes. Thus, characterizing the potato periderm contributes to modeling cork development in plants and helps to resolve critical agricultural problems. Here, we summarize the data available on potato periderm formation, highlighting tissue characteristics rather than the suberization processes.

Critical dilution curves for calcium, magnesium, and sulfur in potato (Solanum tuberosum L. Group Andigenum) cultivars Diacol Capiro and Pastusa Suprema

Diagnostic tools must be developed to optimize the management of calcium (Ca), magnesium (Mg), and sulfur (S) in potato crops. This research aimed to develop the critical dilution curves for Ca, Mg, and S in potato (Solanum tuberosum L. Group Andigenum), establishing harvest indices and characterizing the nutrient relationships. Four field experiments were established in two growth cycles in the localities of Facatativá (high fertility soils) and Chocontá (low fertility soils) in Colombia. Two cultivars (Diacol Capiro and Pastusa Suprema) and two levels of fertilization (0 and 100% of macro and micronutrients) were evaluated. The dry biomass and Ca, Mg, and S concentration in tubers and aerial parts were measured from the formation of main stems until tuber maturation; this information was used to calculate the critical concentrations (Cac, Mgc, Sc), harvest indices, and nutrient correlations. The critical curves established were for Capiro: Cac = 1.7326W-0.2956, Mgc = 0.7191W-0.2803, Sc = 0.6461W-0.3904 and for Suprema: Cac = 1.523W-0.2559, Mgc = 0.6507W-0.236, Sc = 0.7669W-0.3932. Critical levels were established for five phenological stages. Capiro had a higher accumulation of Ca, Mg, and S in the tubers independently of locality, while Suprema had better performance in Chocontá. The accumulation of mineral nutrients in the tubers followed the order Ca<Mg<S. Capiro was a genotype with greater Ca-Mg-S uptake and better adaptation to locations. The Cac, Mgc and Sc curves provided a tool to carry out the nutritional diagnoses at critical stages of development and they are the first ones reported for potato of Group Andigenum.

Genome-Wide Identification and Analysis of the NF-Y Gene Family in Potato (Solanum tuberosum L.).

Nuclear factor Y (NF-Y) is a ubiquitous transcription factor in eukaryotes, which is composed of three subunits (NF-YA, NF-YB, and NF-YC). NF-Y has been identified as a key regulator of multiple pathways in plants. Although the NF-Y gene family has been identified in many plants, it has not been reported in potato (Solanum tuberosum). In the present study, a total of 41 NF-Y proteins in potato (StNF-Ys) were identified, including 10 StNF-YA, 22 StNF-YB, and nine StNF-YC subunits, and their distribution on chromosomes, gene structure, and conserved motif was analyzed. A synteny analysis indicated that 14 and 38 pairs of StNF-Y genes were orthologous to Arabidopsis and tomato (Solanum lycopersicum), respectively, and these gene pairs evolved under strong purifying selection. In addition, we analyzed the expression profiles of NF-Y genes in different tissues of double haploid (DM) potato, as well as under abiotic stresses and hormone treatments by RNA-seq downloaded from the Potato Genome Sequencing Consortium (PGSC) database. Furthermore, we performed RNA-seq on white, red, and purple tuber skin and flesh of three potato cultivars at the tuber maturation stage to identify genes that might be involved in anthocyanin biosynthesis. These results provide valuable information for improved understanding of StNF-Y gene family and further functional analysis of StNF-Y genes in fruit development, abiotic stress tolerance, and anthocyanin biosynthesis in potato.

Effects of Different Irrigation Management Practices on Potato (Solanum tuberosum L.)

Decisions in irrigation management can greatly impact the overall sustainability of potato production. A field study was conducted in 2018 and 2019 to evaluate the impacts of different irrigation regimes on yield and quality of three russet potato varieties. For Russet Burbank, fry quality at harvest and at 4 and 8 months after harvest was assessed. During early growth stages, the standard practice of irrigating to maintain 60–80% soil moisture was employed. The irrigation treatments were applied during the late tuber bulking and maturation growth stages, and consisted of irrigation at 125%, 100%, 75%, and 50% of daily evapotranspiration (ET). We found that 125%ET provided no increase in total yield and marketable yield compared to other treatments in 2018, and it produced similar marketable yield to 100%ET in 2019. Total yield, but not marketable yield, of 125%ET and 100%ET was significantly higher than the number under 50%ET in 2019. In both years, increasing irrigation rate led to a decrease in irrigation efficiency and water-use efficiency. Irrigation rate had no significant effects on tuber quality at harvest and during storage. This study indicated that over-irrigation at 125%ET was not beneficial to profitable potato production in the Upper Midwest of the US, and deficit irrigation at 75%ET during late tuber bulking and tuber maturation could potentially result in more sustainable water use while not jeopardizing tuber growth. The results support the possibility of adopting late-season deficit irrigation for growing potatoes in the region, though more years of research would allow for a better understanding of the impacts of this practice.

Improving Potato Yield Prediction by Combining Cultivar Information and UAV Remote Sensing Data Using Machine Learning

Accurate high-resolution yield maps are essential for identifying spatial yield variability patterns, determining key factors influencing yield variability, and providing site-specific management insights in precision agriculture. Cultivar differences can significantly influence potato (Solanum tuberosum L.) tuber yield prediction using remote sensing technologies. The objective of this study was to improve potato yield prediction using unmanned aerial vehicle (UAV) remote sensing by incorporating cultivar information with machine learning methods. Small plot experiments involving different cultivars and nitrogen (N) rates were conducted in 2018 and 2019. UAV-based multi-spectral images were collected throughout the growing season. Machine learning models, i.e., random forest regression (RFR) and support vector regression (SVR), were used to combine different vegetation indices with cultivar information. It was found that UAV-based spectral data from the early growing season at the tuber initiation stage (late June) were more correlated with potato marketable yield than the spectral data from the later growing season at the tuber maturation stage. However, the best performing vegetation indices and the best timing for potato yield prediction varied with cultivars. The performance of the RFR and SVR models using only remote sensing data was unsatisfactory (R2 = 0.48–0.51 for validation) but was significantly improved when cultivar information was incorporated (R2 = 0.75–0.79 for validation). It is concluded that combining high spatial-resolution UAV images and cultivar information using machine learning algorithms can significantly improve potato yield prediction than methods without using cultivar information. More studies are needed to improve potato yield prediction using more detailed cultivar information, soil and landscape variables, and management information, as well as more advanced machine learning models.

Effects of Irrigation Management on Chipping Potato (Solanum tuberosum L.) Production in the Upper Midwest of the U.S.

Irrigation is required for profitable commercial potato (Solanum tuberosum L.) production. Excessive or deficit soil water availability during the growing season can have adverse effects on tuber yield, quality, and storability. A field study was conducted during the 2018 and 2019 field and storage seasons in Central Wisconsin, a region in the U.S. with a high volume of potato production, to evaluate the impacts of different irrigation rates on three chipping potato varieties, Hodag, Lamoka, and Snowden. The treatments were implemented during the late-tuber bulking and tuber maturation growth stages, and consisted of irrigation at 125%, 100%, 75%, and 50% of crop evapotranspiration (ET). Irrigation before the treatment period was at 100%ET for all plots. With the industry standard irrigation practice being at 100%ET, other treatments were designated as over-irrigation or deficit irrigation. The impact of these watering rates on tuber yield and quality was evaluated at harvest, and tuber storage quality was assessed by measuring chip fry color and sugar concentrations at 0, 4, and 8 months of storage. It was found that compared to the standard practice, the over-irrigation treatment at 125%ET when tubers reached late bulking resulted in no significant increase in total yield, marketable yield, tuber quality at harvest and during storage, as well as reduced irrigation efficiency (IE) and water-use efficiency (WUE). This treatment also increased nitrate leaching potential in both years. In comparison, deficit irrigation at 75%ET or even 50%ET during the late season had no impact on tuber growth, could increase IE and WUE in one of the two years, and showed reduced drainage. In both years, irrigation rate had no significant effects on hollow heart incidence, tuber specific gravity at harvest, and fry quality during the 8-month storage period. This study suggested that over-irrigation was not beneficial for potato production in Central Wisconsin of the U.S., and deficit irrigation during late tuber bulking and tuber maturation stages could potentially result in more sustainable water use while not penalizing tuber yield, quality and storability of chipping potatoes.

Changes in Carotenoid Profile during Potato (Solanum tuberosum L.) Tuber Maturation

Potato tubers are an important agricultural crop containing carotenoids, an important group of secondary plant metabolites showing positive health benefits. This paper examines nine carotenoids at weekly intervals in three cultivars with different flesh color during the tuber maturation process, as analyzed by HPLC-DAD. Total carotenoids showed a bell-shaped distribution with maximum values in the middle of the tuber maturation process rather than in ready-to-harvest tubers. Xanthophylls (viola-, anthera-, neoxanthin and lutein) were the predominant carotenoid forms found in the cultivars. Red and purple-fleshed cultivars contained only a quarter of the total carotenoids of a commercial cultivar with yellow flesh. Weather conditions moderately influenced the carotenoids of the xanthophyll cycle. In red or purple-fleshed tubers no relationship was found between total carotenoids and total anthocyanidins.

Hormonal and transcriptional analyses provides new insights into the molecular mechanisms underlying root thickening and isoflavonoid biosynthesis in Callerya speciosa (Champ. ex Benth.)\xa0Schot

Callerya speciosa (Champ. ex Benth.) Schot is a traditional Chinese medicine characterized by tuberous roots as the main organ of isoflavonoid accumulation. Root thickening and isoflavonoid accumulation are two major factors for yield and quality of C. speciosa. However, the underlying mechanisms of root thickening and isoflavonoid biosynthesis have not yet been elucidated. Here, integrated morphological, hormonal and transcriptomic analyses of C. speciosa tuberous roots at four different ages (6, 12, 18, 30 months after germination) were performed. The growth cycle of C. speciosa could be divided into three stages: initiation, rapid-thickening and stable-thickening stage, which cued by the activity of vascular cambia. Endogenous changes in phytohormones were associated with developmental changes during root thickening. Jasmonic acid might be linked to the initial development of tuberous roots. Abscisic acid seemed to be essential for tuber maturation, whereas IAA, cis-zeatin and gibberellin 3 were considered essential for rapid thickening of tuberous roots. A total of 4337 differentially expressed genes (DEGs) were identified during root thickening, including 15 DEGs participated in isoflavonoid biosynthesis, and 153 DEGs involved in starch/sucrose metabolism, hormonal signaling, transcriptional regulation and cell wall metabolism. A hypothetical model of genetic regulation associated with root thickening and isoflavonoid biosynthesis in C. speciosa is proposed, which will help in understanding the underlying mechanisms of tuberous root formation and isoflavonoid biosynthesis.

Dioscorea Alata Tuber Proteome Analysis Uncovers Differentially Regulated Growth-associated Pathways of Tuber Development.

During its life cycle, the Dioscorea tuber undergoes multiple morphological and biochemical changes. To gain a better understanding of the metabolic changes associated with tuber growth, a stage-specific gel-free proteome analysis of four distinct morphological stages namely germinating tuber (S1), degrading tuber (S2), new tuber formation (S3) and tuber maturation (S4) was done and validated by principal component analysis. A comprehensive data set identifying 78.2% of the total 3,681 proteins was generated. PANTHER and KEGG MAPPER revealed both expected (carbohydrate metabolism and redox regulation) and novel biological processes (transcription factors and hormonal regulation) characteristic for each developmental stage. Higher abundance of the enzymes of ascorbate-glutathione cycle and carbohydrate metabolism was detected during tuber germination (S1) and tuber formation stages (S3) in comparison with the mature tuber. The presence of ethylene biosynthesis components during tuber formation hints toward its probable role in postharvest shelf life. The data set comprehensively describes the proteome of Dioscorea tuber and provides growth-specific markers for tuber germination (ascorbate peroxidase, monodehydroascorbate reductase, invertase) and tuber formation (sucrose synthase), which were validated by enzyme activity assays and Western blotting. The study provides information that may influence the direction of research for improving the productivity of this under-utilized and largely neglected crop.

Impact of the length of the storage period on physiological age and crop performance of four contrasting potato varieties (Solanum tuberosum L.) grown in a Mediterranean environment

Physiological age of seed potato tubers could limit crop productivity. In this research, physiological and biochemical methods were used to assess the impact of seed age on crop performance of cvs Liseta, Spunta, Bellini and Mondial. Physiological age impact was assessed at different growth stages, namely: tuber initiation, tuber bulking and tuber maturation. Results suggest that yield decrease due to seed ageing was significantly correlated with the decline of sprouts characters of mother tubers resulting in decrease in the number of stems. Seed age also influenced chlorophyll fluorescence of photosynthetic leaves. The Fv/Fm (maximum quantum yield of Photosystem II), was lower during tuber induction and tuber initiation in plants from young seed tubers and decreased with the achievement of the tuberization process. Our study clearly indicated that starch accumulation decreased with the seed age which result in a reduced plant productivity.

Growth Stages Classification of Potato Crop Based on Analysis of Spectral Response and Variables Optimization.

Potato is the world’s fourth-largest food crop, following rice, wheat, and maize. Unlike other crops, it is a typical root crop with a special growth cycle pattern and underground tubers, which makes it harder to track the progress of potatoes and to provide automated crop management. The classification of growth stages has great significance for right time management in the potato field. This paper aims to study how to classify the growth stage of potato crops accurately on the basis of spectroscopy technology. To develop a classification model that monitors the growth stage of potato crops, the field experiments were conducted at the tillering stage (S1), tuber formation stage (S2), tuber bulking stage (S3), and tuber maturation stage (S4), respectively. After spectral data pre-processing, the dynamic changes in chlorophyll content and spectral response during growth were analyzed. A classification model was then established using the support vector machine (SVM) algorithm based on spectral bands and the wavelet coefficients obtained from the continuous wavelet transform (CWT) of reflectance spectra. The spectral variables, which include sensitive spectral bands and feature wavelet coefficients, were optimized using three selection algorithms to improve the classification performance of the model. The selection algorithms include correlation analysis (CA), the successive projection algorithm (SPA), and the random frog (RF) algorithm. The model results were used to compare the performance of various methods. The CWT-SPA-SVM model exhibited excellent performance. The classification accuracies on the training set (Atrain) and the test set (Atest) were respectively 100% and 97.37%, demonstrating the good classification capability of the model. The difference between the Atrain and accuracy of cross-validation (Acv) was 1%, which showed that the model has good stability. Therefore, the CWT-SPA-SVM model can be used to classify the growth stages of potato crops accurately. This study provides an important support method for the classification of growth stages in the potato field.

Quantifying Control Efficacy of Fungicides Commonly Applied for Potato Early Blight Management

Early blight is an economically important foliar disease of potato in the United States. Because of the lack of resistant potato cultivars, fungicides are applied extensively to obtain adequate control. To manage early blight, standard protectant fungicides and single-site mode-of-action "specialty" fungicides are applied either alone or incorporated into a fungicide rotation program. Control efficacy at two crop growth stages (tuber initiation/early bulking and late bulking/tuber maturation) and the overall tuber yield response to standard and specialty fungicides were assessed using network metaanalytic models. Control efficacy of fungicides ranged from moderate to very high (>30 to 75%) compared with the nontreated control. For both potato growth stages, specialty fungicides performed better than standard protectant fungicides. Furthermore, control efficacy of both fungicides was higher (3 to 9%) at late bulking and tuber maturation when compared with early bulking crop growth stage. Specialty fungicide programs increased overall tuber yields by 4 and 9% over standard fungicides and nontreated control, respectively. Based on the results, more precise fungicide use recommendations and fungicide programs can be developed for early blight management.