Commercial Potato Varieties Research Articles

Exploration of resistance level against Black Scurf caused by Rhizoctonia solani in different cultivars of potato

Black Scurf is one of the destructive fungal diseases of potato crops caused by fungus Rhizoctonia solani. Cultural practices and fungicide applications are insufficient in effectively combating the pathogen, while utilizing resistant cultivars has become one of the most economical and effective way to control disease. About ten commercial potato varieties were screened out against the disease by artificially inoculating the plants with R. solani and these potato varieties were grouped based on disease incidence and disease severity. Four varieties (Ronoldo, Rubi, Challenge, and Sadaf) were grouped as resistant, three varieties (SH-5, Sante and Astrex) as moderately susceptible and three varieties (Karoda, Mosica and Simply red) as susceptible with significantly highest disease incidence (P ≤ 0.05). Disease also reduced number and size of tubers, while the disease incidence showed negative (P < 0.001) correlation with chlorophyll and protein contents, and activities of catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO) enzymes. It was concluded that a combination of phenotypic and physiological indices could be used to identify black scurf resistance in potatoes.

Characterization of traditional small potato (Solanum tuberosum L.) cultivars for nutritional, quality traits and ploidy level

Traditional small potato cultivars of North Eastern region of India are an important food source, but no documentation is availableregarding their ploidy level and nutritional worth. The study was undertaken to explore these cultivars to determine their ploidy levelby flow cytometry method. Fluorescence-activated cell sorter (FACS) based method was used for the analysis of ploidy level and theknown diploid potato clone Solanum chacoense was used as the reference clone. The ploidy level of these cultivars was determined bycomparing the value of mean peak position of G1 of reference diploid clone with mean peak position of G1 of small potato cultivars.Results indicated that all the 11 small potato cultivars collected from the Northeastern region were tetraploid with an average genomesize of 837.38 Mb although they were suspected to be diploid based on the tuber characters and overall plant morphology. Thesecultivars were characterized by having anthocyanin pigmentation of newly emerged sprouts and eye on tuber, small and narrow leaf,long stolon length (average 7.38 cm) and high number (average 33.90/plant) of very small (average 7.41 g) tubers compared to thecommercial potato varieties. However, these cultivars surpassed India’s commercial tetraploid potato varieties for dry matter, starch,ascorbic acid, β-carotene and total phenol contents. Appreciably rich nutritional profile coupled with matching levels of ploidy not onlyenhanced the biodiversity of cultivated potato but also suggested the possibility of utilizing these cultivars in the breeding programmeto enhance nutrient and antioxidant contents.

ОЦІНЮВАННЯ СТІЙКОСТІ СОРТІВ КАРТОПЛІ, ПОШИРЕНИХ НА ТЕРИТОРІЇ УКРАЇНИ,ДО ЗБУДНИКА М'ЯКОЇ ГНИЛІ ТА ЧОРНОЇ НІЖКИ

B a c k g r o u n d . The potato crop is affected by various diseases, including blackleg and soft rot caused by Pectobacterium atrosepticum. One of the reasons for the rapid spread of these bacterial pathogens is the absence of commercial potato varieties with natural immunity to blackleg and soft rot. While some potato varieties may exhibit partial resistance, the lack of complete resistance contributes to the widespread occurrence of these diseases. The study aimed to evaluate the resistance of potato varieties most common in Ukraine to blackleg and soft rot pathogens. M e t h o d s . Potato varieties from different region of Ukraine were used in the study. 24 h culture of Pectobacterium atrosepticum B-1084T was used for assessing potato sensitivity to soft rot and blackleg. Potato susceptibility to soft rot pathogen was evaluated by two criteria: disease incidence (%) and disease severity (weight and area of macerated tissue). R e s u l t s . Potato tubers of different varieties, as well as of the same varieties, but grown in different regions of Ukraine, showed different levels of resistance to the museum strain of soft rot and blackleg pathogen. The disease incidence – the proportion of tubers with symptoms of rotting for all analyzed potato varieties reached 100 %.Tubers of the Riviera variety obtained from the Odesa region were significantly more affected by the pectolytic enzymes of P. atrosepticum B-1084T as compared to tubers of other cultivars: macerated area in tubers of this variety was 1.5 times higher than those in Queen Anne, Riviera (Chernihiv) and Bellarosa (Odesa) varieties. The median of maceration area of Picasso and Bellarosa (Chernihiv) tubers were 2.5 times smaller than that in the Riviera variety. These patterns of sensitivity to soft rot and blackleg pathogen were also confirmed by the results of comparative assessment of the weight of. C o n c l u s I o n s . Thus, Riviera potato variety was most susceptible to the infection with soft rot and blackleg pathogen. Potato cultivar Picasso was the least sensitive to P. atrosepticum B-1084T. Potato tubers of the same variety grown in different regions of the country had different susceptibility rates to the soft rot and blackleg pathogen, indicating that the field effect outweighs the influence of genotype.

Comparative Proteomics of Potato Cultivars with a Variable Dormancy Period.

The control of the duration of the dormancy phase is a significant challenge in the potato industry and for seed producers. However, the proteome landscape involved in the regulation of the length of the dormancy period over potato cultivars remains largely unexplored. In this study, we performed for the first time a comparative proteome profiling of potato cultivars with differential duration of tuber dormancy. More specifically, the proteome profiling of Agata, Kennebec and Agria commercial potato varieties with short, medium and medium-long dormancy, respectively, was assessed at the endodormancy stage using high-resolution two-dimensional electrophoresis (2-DE) coupled to reversed-phase liquid chromatography–tandem mass spectrometry (LC-TripleTOF MS/MS). A total of 11 proteins/isoforms with statistically significant differential abundance among cultivars were detected on 2-DE gels and confidently identified by LC-TripleTOF MS/MS. Identified proteins have known functions related to tuber development, sprouting and the oxylipins biosynthesis pathway. Fructokinase, a mitochondrial ADP/ATP carrier, catalase isozyme 2 and heat shock 70 kDa were the proteins with the strongest response to dormancy variations. To the best of our knowledge, this study reports the first candidate proteins underlying variable dormancy length in potato cultivars.

Identification of diseases and physiological disorders in potato via multispectral drone imagery using machine learning tools

The rapid and precise detection of diseases and plant disorders is the basis for the adequate and timely design of management strategies. Currently, there are several non-destructive alternatives that allow early detection, highlighting the use of spectral cameras attached to unmanned aerial vehicles (UAVs). The objective of this research was to evaluate the use of multispectral cameras on UAVs to discriminate vascular wilt caused by Verticillium spp., (VW), waterlogging stress (WL), and an unknown alteration (UA) in commercial potato (Solanum tuberosum) variety “Diacol Capiro” crops. Plots were monitored during the crop cycle, performing the visual characterization of the diseases and disorders present. Five spectral band images were acquired using a MicaSense RedEdge spectral camera attached to a Map-T680 hexacopter drone to extract the bands and calculate the vegetation indices that were calibrated and evaluated to determine their ability to discriminate between diseased and healthy plants based on a generalized linear model (GLM) and Kappa index. Additionally, the supervised random forest classification method was implemented, optimized, and evaluated using the accuracy, area under receiver operating characteristic curve (ROC-AUC), kappa index, and inference error based on k-fold cross-validation. After algorithms optimization our results show a classifier accuracy, kappa and ROC-AUC values to VW, WL and UA between 73.5–82.5%, 0.56–0.71, 0.97–0.98, and 35 37.5–51.9%, 0.07–0.06, and 0.88–0.94 for plots 1 and 2, respectively. This study reports an approach to the use of multispectral cameras attached to UAVs as a tool with potential for the detection of diseases and physiological disorders in commercial potato crops.

Techniques to Develop Genetically Improved Potato with Increased Resistance to Potato Late Blight (Phythophthora Infestans) A Review

Infestation of potatoes with phythophthora infestans ,also known as ‘’potato late blight ‘’ is the most devastating potato disease world wide. Its occurrence often results in huge economic losses for potato producers. Current control measures involving extensive use of fungicides come with environmental costs. Efforts have been made to develop commercial potato varieties with increased resistance to p.infesting (the causal agent of late blight )using a variety of approaches .Due to the remarkable ability of p.infesting to over come resistance ,potato breeders have not yet succeeded in developing commercial potato varieties with resistance that is lasting. One approach where genetic engineering is used to ‘stack’ genes with broad spectrum resistance to p.infesting in commercial potato varieties ,has been recently been employed as a means to create genetically improved potato varieties with more durable resistance. DOI: 10.7176/JNSR/12-18-01 Publication date: September 30 th 2021

TUBER SIZE EFFECTS ON YIELD AND NUMBER OF POTATO MINITUBERS OF COMMERCIAL VARIETIES IN A GREENHOUSE PRODUCTION SYSTEM

The aim of this study was to determine the effects of three different minituber (Mt) sizes (large, cutting and small) on the number and yield of minitubers (Mts) in 6 commercial potato varieties. The research was carried out according to the split plot design of greenhouse conditions in the 30x30cm plant density in 2017 and 2018. From potato varieties, Soylu were given the highest values in large and small Mt sizes, the number of Mt per plant and per hectare. Mt weight per plant, average Mt weight and Mt yield per hectare Cevher variety showed better performance than other varieties. Approximately 48-50 % of the Mts obtained in terms of Mt size were determined as Mts of 45-60 mm. The size of the cutting Mt was given a higher yield per hectare and the number of Mts than the others. According to the results of the study, Mts of commercial varieties in greenhouse conditions were planted in 30x30 cm plant density and 90% of them were planted directly in the field (≥ 25mm), firstly. Approximately 700000 Mts can be produced from one hectare greenhouse in the greenhouse production system in narrow plant density.

Heat and drought stress and their implications on potato production under dry African tropics

The two most important abiotic factors affecting potato productivity in many areas of the world and especially in the dry African tropics are drought and high temperature. The situation is worsened by global warming. High temperature and drought reduce not only yields but also quality of potatoes. The effects of drought depend on the genotype, timing, duration and severity of the stress; plant emergence and tuberization are two critical periods when water stress most affects the final tuber yield. The susceptibility of potato crops to high temperature largely depends on genotype, development stage and stress duration; tuber initiation and bulking are critical stages. High temperature, particularly high night temperature, is reported to delay tuber induction, prolong tuber setting, and delay the onset of rapid tuber growth. The optimum soil temperature range for tuber initiation and tuber growth is 15–20 0C, and the colder the soil temperature, the more rapid the initiation of tubers and the greater the number of tubers formed. At high temperature more photoassimilates are partitioned to the vegetative parts than tubers resulting in acceleration of haulm growth and inhibition of tuber initiation and growth. In tropical Africa, potato production is moving to the dry mid and low altitudes due to high population pressure in the moist highlands. In these dry areas, potato production is facing the double tragedy of high temperature and water stress. This has led to low yields and poor quality since there is no available commercial potato variety which is tolerant to high temperature and water stress. Breeding for heat and drought tolerance in potatoes is hard because in most cases, especially in dry tropics, these two conditions occur concurrently. In addition, the two traits are polygenic with low inheritance making conventional breeding difficult; more progress could be achieved through molecular breeding and/or genetic engineering.

Exploring the relationship between potato components and Maillard reaction derivative harmful products using multivariate statistical analysis

The correlation between potato components and Maillard reaction derivative harmful products (MRDHPs) formation during heat-processing was assessed in nine commercial potato varieties in China. Principal component analysis (PCA) combined with canonical correlation analysis (CCA) approach was performed to explore their relationships. The variables contributing most to the PCA results were extracted for CCA, and the results indicated that several amino acids, including lysine, tryptophan, alanine, phenylalanine, aspartate, and glutamate, have significant impacts on acrylamide and β-carboline heterocyclic amine formation. Moreover, 5-O-caffeoylquinic acid, 3-O-caffeoylquinic acid, α-solanine, and α-chaconine were also important factors associated with acrylamide and β-carboline heterocyclic amine formation. Optimally using raw potato varieties based on the impacts of these factors can help control MRDHP formation during thermal processing. For the first time, such approach was applied, which may be a useful tool for discovering the correlation of food components and MRDHPs.

Glycoalkaloids in commercial potato varieties traded in Nairobi, Kenya

Background: Glycoalkaloids are naturally occurring toxins in potatoes which, at high levels, pose food safety concerns to consumers. Their concentrations in potatoes are dependent on postharvest handling, variety and stress factors tubers are exposed to. Limited information, however, exists on levels of glycoalkaloids in commercially traded potato tubers in Kenya. The current study sought to determine the glycoalkaloid levels in potatoes traded in Nairobi, Kenya. Methods: Three potato varieties, Shangi, Dutch Robjin and Royal sold in open-air markets and supermarkets were randomly sampled and their glycoalkaloid levels determined by high-performance liquid chromatography. Results: The levels varied significantly (p&lt;0.05). The Shangi variety had the highest glycoalkaloids with a mean of 410.35 mg kg-1 dry weight with samples from supermarkets having the highest levels (550.8 mg kg-1). The same variety from open air markets averaged 382.26 mg kg-1 dry weight compared to the Dutch Robjin (129.2 mg kg-1 dry weight) and Royal variety (98.2 mg kg-1 dry weight) which had the least levels of glycoalkaloids. Conclusions: The levels in sampled tubers did not exceed the recommended levels of 1000 mg/kg on dry weight basis and, therefore, consumption of these potatoes would not raise safety concerns. There is, however, a need to ensure that marketing of tubers is carried out under conditions that minimize occurrence of glycoalkaloids, especially for the Shangi variety, which is the most common in the markets but had relatively high levels of these toxins. There is also a need to educate marketers on the need for proper storage and handling of potatoes during marketing to avoid risk of accumulation of glycoalkaloids.

Glycoalkaloids in commercial potato varieties traded in Nairobi, Kenya

Background: Glycoalkaloids are naturally occurring toxins in potatoes which, at high levels, pose food safety concerns to consumers. Their concentrations in potatoes are dependent on postharvest handling, variety and stress factors tubers are exposed to. Limited information, however, exists on levels of glycoalkaloids in commercially traded potato tubers in Kenya. The current study sought to determine the glycoalkaloid levels in potatoes traded in Nairobi, Kenya. Methods: Three potato varieties, Shangi, Dutch Robjin and Royal sold in open-air markets and supermarkets were randomly sampled and their glycoalkaloid levels determined by high-performance liquid chromatography. Results: The levels varied significantly (p&lt;0.05). The Shangi variety had the highest glycoalkaloids with a mean of 410.35 mg kg-1 dry weight with samples from supermarkets having the highest levels (550.8 mg kg-1). The same variety from open air markets averaged 382.26 mg kg-1 dry weight compared to the Dutch Robjin (129.2 mg kg-1 dry weight) and Royal variety (98.2 mg kg-1 dry weight) which had the least levels of glycoalkaloids. Conclusions: The levels in sampled tubers did not exceed the recommended levels of 1000 mg/kg on dry weight basis and, therefore, consumption of these potatoes would not raise safety concerns. There is, however, a need to ensure that marketing of tubers is carried out under conditions that minimize occurrence of glycoalkaloids, especially for the Shangi variety, which is the most common in the markets but had relatively high levels of these toxins. There is also a need to educate marketers on the need for proper storage and handling of potatoes during marketing to avoid risk of accumulation of glycoalkaloids.

Potato Psyllid (Hemiptera: Triozidae) Behavior on Three Potato Genotypes With Tolerance to 'Candidatus Liberibacter solanacearum'.

The potato/tomato psyllid Bactericera cockerelli (Šulc) transmits ‘Candidatus Liberibacter solanacearum’ (Lso) (also known as ‘Candidatus Liberibacter psyllaurous’), the bacterium associated with zebra chip disease (ZC) in potato. When disease incidence is high, ZC causes large economic losses through reductions in potato yield and tuber quality. No commercial potato variety has been found totally resistant to the pathogen. We evaluated host acceptance behaviors using no-choice assays on three breeding clones derived from Solanum chacoense Bitter with putative tolerance to Lso and/or ZC as part of an effort to determine whether the disease tolerance observed in those breeding clones was related to effects on psyllid settling behavior. We also counted the number of eggs laid and nymphs hatched on the different genotypes to observe any differences in reproduction. The potato variety ‘Russet Burbank’ was used as a susceptible control. Probing frequency and female walking duration were greater on Russet Burbank than the other genotypes. Oviposition did not differ among genotypes. However, female psyllids on two of the Lso-tolerant genotypes displayed reduced fertility 18–24 d after confinement with a male, relative to females on Russet Burbank. These results suggest that although the germplasms display minor abiotic activity on psyllid fertility, tolerance to Lso may be more strongly linked with plant tolerance to the pathogen rather than effects on host acceptance behaviors.

Distribution of P1(D1) wart disease resistance in potato germplasm and GWAS identification of haplotype-specific SNP markers

Key messageA Genome-Wide Association Study using 330 commercial potato varieties identified haplotype specific SNPmarkers associated with pathotype 1(D1) wart disease resistance.Synchytrium endobioticum is a soilborne obligate biotrophic fungus responsible for wart disease. Growing resistant varieties is the most effective way to manage the disease. This paper addresses the challenge to apply molecular markers in potato breeding. Although markers linked to Sen1 were published before, the identification of haplotype-specific single-nucleotide polymorphisms may result in marker assays with high diagnostic value. To identify hs-SNP markers, we performed a genome-wide association study (GWAS) in a panel of 330 potato varieties representative of the commercial potato gene pool. SNP markers significantly associated with pathotype 1 resistance were identified on chromosome 11, at the position of the previously identified Sen1 locus. Haplotype specificity of the SNP markers was examined through the analysis of false positives and false negatives and validated in two independent full-sib populations. This paper illustrates why it is not always feasible to design markers without false positives and false negatives for marker-assisted selection. In the case of Sen1, founders could not be traced because of a lack of identity by descent and because of the decay of linkage disequilibrium between Sen1 and flanking SNP markers. Sen1 appeared to be the main source of pathotype 1 resistance in potato varieties, but it does not explain all the resistance observed. Recombination and introgression breeding may have introduced new, albeit rare haplotypes involved in pathotype 1 resistance. The GWAS approach, in such case, is instrumental to identify SNPs with the best possible diagnostic value for marker-assisted breeding.

Transcriptome profiling of resistance response to Meloidogyne chitwoodi introgressed from wild species Solanum bulbocastanum into cultivated potato

BackgroundMeloidogyne chitwoodi commonly known as Columbia root-knot nematode or CRKN is one of the most devastating pests of potato in the Pacific Northwest of the United States of America. In addition to the roots, it infects potato tubers causing internal as well as external defects, thereby reducing the market value of the crop. Commercial potato varieties with CRKN resistance are currently unavailable. Race specific resistance to CRKN has been introgressed from the wild, diploid potato species Solanum bulbocastanum into the tetraploid advanced selection PA99N82–4 but there is limited knowledge about the nature of its resistance mechanism. In the present study, we performed histological and differential gene expression profiling to understand the mode of action of introgressed CRKN resistance in PA99N82–4 in comparison to the CRKN susceptible variety Russet Burbank.ResultsHistological studies revealed that the nematode juveniles successfully infect both resistant and susceptible root tissue by 48 h post inoculation, but the host resistance response restricts nematode feeding site formation in PA99N82–4. Differential gene expression analysis shows that 1268, 1261, 1102 and 2753 genes were up-regulated in PA99N82–4 at 48 h, 7 days, 14 days and 21 days post inoculation respectively, of which 61 genes were common across all the time points. These genes mapped to plant-pathogen interaction, plant hormonal signaling, antioxidant activity and cell wall re-enforcement pathways annotated for potato.ConclusionThe introgressed nematode resistance in PA99N82–4 is in the form of both pattern-triggered immune response and effector-triggered immune response, which is mediated by accumulation of reactive oxygen species and hypersensitive response (HR). Salicylic acid is playing a major role in the HR. Polyamines and suberin (a component of the Casperian strip in roots) also play an important role in mediating the resistance response. The present study provides the first ever comprehensive insights into transcriptional changes among M. chitwoodi resistant and susceptible potato genotypes after nematode inoculation. The knowledge generated in the present study has implications in breeding for CRKN resistance in potato.

Omics analyses of potato plant materials using an improved one-class classification tool to identify aberrant compositional profiles in risk assessment procedures

The objective of this study was to quantitatively assess potato omics profiles of new varieties for meaningful differences from analogous profiles of commercial varieties through the SIMCA one-class classification model. Analytical profiles of nine commercial potato varieties, eleven experimental potato varieties, one GM potato variety that had acquired Phytophtora resistance based on a single insert with potato-derived DNA sequences, and its non-GM commercial counterpart were generated. The ten conventional varieties were used to construct the one-class model. Omics profiles from experimental non-GM and GM varieties were assessed using the one-class SIMCA models. No potential unintended effects were identified in the case of the GM variety. The model showed that varieties that were genetically more distant from the commercial varieties were recognized as aberrant, highlighting its potential in determining whether additional evaluation is required for the risk assessment of materials produced from any breeding technique, including genetic modification.

Dietary Supplementation of Potato Peel Powders Prepared from Conventional and Organic Russet and Non-organic Gold and Red Potatoes Reduces Weight Gain in Mice on a High-Fat Diet.

The present study investigated the potential of potato peel powders, high in bioactive phenolic compounds and glycoalkaloids, to reduce weight gain in mice consuming a high-fat diet. Potato peel powders were prepared from the following fresh commercial potato varieties by hand-peeling and then freeze-drying and grinding the peels into powder: non-organic (conventionally grown) gold, red, and Russet and organically grown Russet. Mice diets (25% fat by weight) were supplemented with either 10 or 20% potato peel powders for 3 weeks. In comparison to the control diet, the isocaloric and isonitrogenous peel-containing diets induced a reduction in weight gain that ranged from 17-45% (10% peel diets) to 46-73% (20% peel diets), suggesting that differences in weight gain are associated with the potato peel source and peel concentration of the diet. Weight reductions were accompanied by reduced epididymal white adipose tissue ranging from 22 to 80% as well as changes in the microbiota analyzed using next-generation sequencing and in obesity-associated genetic biomarkers determined by the quantitative real-time polymerase chain reaction. Safety aspects and possible mechanisms of the antiobesity effects are discussed in terms of the composition of the bioactive potato peel compounds, which were determined using high-performance liquid chromatography. The results suggest that potato peels, a major peeling byproduct of potato processing used to prepare fries, chips, and potato flour, that showed exceptionally high antiobesity properties in fat mice, have the potential to serve as an antiobesity functional food.

QTL Analysis of Tuber Dormancy and Sprouting in Potato

Tuber dormancy and sprouting are important traits in commercial potato varieties. Since wild Solanum species can contribute new alleles in breeding, we combined Solanum chacoense and S. berthaultii species in a mapping population to develop a linkage map with genome wide markers and identify quantitative trait loci (QTL) for tuber dormancy and sprouting. There was genetic variation for the evaluated traits and high correlation (0.80) between dormancy and apical dominance release. QTL for tuber dormancy and sprouting traits were mapped to the same or similar positions on chromosomes 2, 3, 5, and 7, explaining from 9.5% to 16.3% of the phenotypic variance. We identified candidate genes associated with all major phytohormone regulation in close linkage with the QTL. The QTL on chromosomes 2, 3 and 7 are good candidates for marker assisted breeding, since they were associated with dormancy and apical dominance release and should be useful to delay or accelerate tuber sprouting.

Molecular structure of Maori potato starch

New Zealand Maori potatoes (Taewa) represent unique genetic resources for potato quality, though they are much underutilized. In this report, the composition and molecular structure of starches from 5 Maori potato varieties were studied. In particular, the internal unit chain composition of the amylopectins in the form of β-limit dextrins was highlighted. Starches from a commercial modern potato variety and a maize variety with normal amylose contents were employed for comparison. Genetic diversity in the amylose (e.g., 22.6% in Moemoe to 28.6% in Turaekuri) and phosphorus (5.4 mg/100 g in Turaekuri to 7.0 mg/100 g in Kowiniwini) contents as well as the molecule structure of the starches (e.g., external chain length of amylopectin ranged from 13.0 glucosyl residues in Turaekuri to 15.8 glucosyl residues in Karuparera) has been revealed. Maori potato amylopectins have the highest amount of long unit and internal chains and the lowest amount of these chains among amylopectins from different sources. Overall, Maori potato starch appeared to be structurally and compositionally similar to modern potato starch.

Organic production of native potato landrace “pintaboca” (Solanum stenotomum Juz. &amp; Bukasov) in Bolivia: experimenting planting times and cultivation strategies

In the municipality of Colomi, in the highlands of Bolivia, market pressure leads small scale farmers to substitute their native landraces with commercial potato varieties. Organic cultivation might offer a channel for selling native potatoes to an emerging industry of coloured native potato crisps. Nevertheless, as the area is endemic for late blight (Phytophthora infestans), adequate cultivation practices that allow organic production must be defined. The present experiment compared four cultivation strategies (two organic, which included the use of beneficial microoorganisms applied in the soil and through foliar spray, one conventional, which included cymoxanil and mancozeb based fungicides and a control with the same soil treatment as the organic strategies but no foliar spray) and two planting dates (early and main season planting) on a native potato landrace locally known as ‘pintabocaʼ (Solanum stenotomum). Our results showed that early planting resulted in significantly higher yields, although the area under disease progress curve (AUDPC) of late blight did not differ significantly between planting dates. The lower yields in the plot planted during the main season were mainly due to the combined incidence of early and late blight. There was no significant difference in yields and quality of the tubers cultivated with conventional, organic or control treatment, with the exception that the largest tuber size category was produced only in the conventional treatment. We conclude that farmers in Colomi who want to shift to organic cultivation of the landrace ʻpintabocaʼ at altitudes around 3,300 m a.s.l. could benefit from practicing early planting, although additional trials covering several seasons are needed to confirm our results.

Costs and Tradeoffs of Resistance and Tolerance to Belowground Herbivory in Potato

The success of sustainable crop production depends on our ability to select or create varieties that can allocate resources to both growth and defence. However, breeding efforts have emphasized increases in yields but have partially neglected defence traits against pests. Estimating the costs of multiple defences against tuber herbivores and the tradeoffs among them, as well as understanding the relationship between yield and multiple defences is still unknown but relevant to both basic and applied ecology. Using twenty commercial potato varieties available in Colombia and the tuber herbivore Tecia solanivora, we tested whether high yielding varieties show a reduction in three types of defence: constitutive and induced resistance, as well as tolerance. Specifically, we determined (1) the costs in terms of yield of all three defences, (2) the possible tradeoffs among them, and (3) if oviposition preference was related to the expression of these defences. We detected no costs in terms of yield of constitutive and induced resistance to tuber damage. We did, however, find evidence of costs of being able to tolerate tuber herbivory. While we found no tradeoffs among any of the estimated defences, there was a positive correlation between aboveground compensatory growth and tolerance in terms of tuber production, suggesting that after damage there are no shifts in the allocation of resources from aboveground to belowground biomass. Finally, we found that females laid more eggs on those varieties with the lowest level of constitutive resistance. In conclusion our findings suggest that in potatoes, breeding for higher yields has not caused any reduction in constitutive or induced resistance to tuber damage. This is not the case for tolerance where those varieties with higher yields are also less likely to tolerate tuber damage. Given the high incidence of tuber pests in Colombia, selecting for higher tolerance could allow for high productivity in the presence of herbivores. Finding mechanisms to decouple the tolerance response from yield should be a new priority in potato breeding in Colombia to guarantee a higher yield in both the presence and absence of herbivores.