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Macronutrient contents of 94 genotypes from the Colombian Central Collection (CCC) and 13 genotypes from the Native Collection (NC) of diploid potatoes (Solanum tuberosum Group Phureja) were evaluated, considering six genotypes, four diploid and two tetraploid potato commercial cultivars, as control. Dry matter, protein, soluble dietary fibre (SDF) and insoluble dietary fibre (IDF), fat, and ash contents were determined in entire boiled tubers. Macronutrient contents varied widely among the 113 genotypes. Protein contents found in CCC and NC (1.8–17.2 g/100 g dry weight, DW) were greater than those in commercial cultivars (3.1–9.5 g/100 g DW). Total dietary fibre (TDF), SDF, and IDF were greater in CCC and NC (9.4–27.1 g/100 g DW, 1.6–6.6 g/100 g DW, and 6.4–20.9 g/100 g DW, respectively) than in the commercial cultivars (9.0–15.3 g/100 g DW, 2.7–4.4 g/100 g DW, and 6.4–12.3 g/100 g DW, respectively). Several genotypes from CCC and NC are good candidates as parental materials for developing new cultivars, with the highest protein content in CCC-76 (17.2 ± 0.3 g/100 g DW) and NC-8 (16.7 ± 0.7 g/100 g DW) and the highest TDF in CCC-110 (27.1 ± 4.0 g/100 g DW).

Fusarium head blight (FHB) is a destructive disease affecting cereal crops globally due to mycotoxin contamination of grains that reduce yield and quality. Among hundreds of QTLs identified for resistance, the QTL-Fhb1 is of significant interest even today, for its major contribution to FHB resistance. Previously, QTL-Fhb1 dissection based on a combined metabolo-genomics approach, identified a few potential resistance genes, including a NAC like transcription factor for FHB resistance. Sequencing and phylogenetic analysis confirmed NAC to be the wheat TaNAC032. Also, the quantitative RT-PCR studies revealed a greater induced expression of TaNAC032 in resistant NIL in comparison to susceptible NIL upon Fusarium graminearum (Fg) infection. The virus-induced gene silencing (VIGS) based functional validation of TaNAC032 in resistant NIL confirmed increased disease severity and fungal biomass. Metabolic profiling revealed low abundances of resistance-related (RR) metabolites in TaNAC032 silenced NIL-R compared to non-silenced. Silenced plants showed decreased transcript abundances of RR metabolite biosynthetic genes associated with a reduction in total lignin content in rachis, confirming the regulatory role of TaNAC032 in wheat in response to Fg infection. If TaNA032 is mutated in an FHB susceptible cultivar, it can be edited to enhance FHB resistance.

Fusarium head blight (FHB) caused by Fusarium graminearum is one of the devastating diseases of small grain crops, including barley and wheat. Breeding for resistance is one of the best and ecofriendly strategies to manage the FHB. However, the existing methods used for screening genotypes, both under field and greenhouse conditions, often resulted in high experimental error, leading to inconsistent ranking of genotypes over years. In the postgenomic era, precise assessment of resistance is crucial to identify candidate genes. Here, we report a pathogen inoculation procedure and a real-time quantitative polymerase chain reaction (qPCR) based protocol for the quantification and discrimination of quantitative resistance among barley and wheat genotypes to FHB. Using Fusarium specific primer pair Tri6_10, for the trichothecene biosynthetic cluster (Tri6) gene, we successfully quantified the relative fungal biomass in both spikelets and rachis. A qPCR of spikelets and rachis collected on 6 dpi, from inoculated three alternate spikelet regions, discriminated resistance with less experimental error than those based on the proportion of spikelets diseased (PSD) at 9 dpi. This method can be applied for medium to high-throughput barley and wheat breeding programmes to discriminate quantitative resistance among genotypes against FHB.

This project was supported by the International Development Research Center and Department of Foreign Affairs, Trade and Development Canada (Project number 106926, “Improving Potato Production for Increasing Food Security of Indigenous Communities in Colombia”). The authors are grateful with Ministry of Environment and Sustainable Development for the granted access to S. tuberosum group Phureja genetic resources through the Contract No. 53.

A High Performance Liquid Chromatography (HPLC) method was developed and validated to quantify sucrose (non-reducing sugar), glucose, and fructose (reducing sugars) in raw tubers of Solanum tuberosum Group Phureja. Chromatographic analysis was performed using an AMINEX HPX 87H column, at 18 °C, linked to a refraction index detector, at 35 °C. The eluent was 10 mM sulfuric acid. The conditions established for the method provided an optimum separation of sugars, citric acid, and malic acid, with resolution values higher or equal to one. Among the four sugar extraction methods tested, the double 50% (v/v) aqueous methanol extraction gave the highest level of analytes. Recovery of this extraction method ranged between 94.14 and 99.77%. The HPLC method was validated for repeatability, reproducibility, linearity, and limits of detection, and quantification. Relative standard deviation was found to be lower than five, when testing repeatability and reproducibility, which is suitable considering a range of acceptability from 5.3 to 7.3. Additionally, the regression analyses supported the method linearity in a range of quantification from 3 to 100 mg/L with regression coefficients values greater than 0.998 for the three analytes. Limits of detection were 3.0 mg/L for the three sugars and limits of quantification were 2.0 mg/L for sucrose and 3.0 mg/L for glucose and fructose. Four Colombian commercial cultivars (Criolla Guanena, Criolla Paisa, Criolla Galeras, and Criolla Colombia) and five landrace accessions from the Colombian Core Collection of Group Phureja were grown in the district of Usme (Bogota) fields to analyze their sugar contents. Sucrose, glucose, and fructose contents were found ranging from 0.93 to 3.11 g/100 g tuber dried weight (DW), from 0.25 to 4.53 g/100 g tuber DW, and from 0.10 to 1.49 g/100 g tuber DW, respectively. Therefore, a high range in the variability of sugar contents was found among genotypes. However, the variability was low among technical replicates of the same genotype, revealing an accurate quantification of sugars in Group Phureja. This method can be used to assess the amount of reducing and non-reducing sugars accumulation in potato germplasm.

Plants continuously encounter various environmental stresses and use qualitative and quantitative measures to resist pathogen attack. Qualitative stress responses, based on monogenic inheritance, have been elucidated and successfully used in plant improvement. By contrast, quantitative stress responses remain largely unexplored in plant breeding, due to complex polygenic inheritance, although hundreds of quantitative trait loci for resistance have been identified. Recent advances in metabolomic and proteomic technologies now offer opportunities to overcome the hurdle of polygenic inheritance and identify candidate genes for use in plant breeding, thus improving the global food security. In this review, we describe a conceptual background to the plant-pathogen relationship and propose ten heuristic steps streamlining the application of metabolo-proteomics to improve plant resistance to biotic stress.

Volatile organic compounds collected from the headspace of mango cv. Keitt inoculated with Lasiodiplodia theobromae (stem-end rot), Colletotrichum gloeosporioides (anthracnose), mock (as the first control) and non-wounded-non-inoculated mango (as the second control) were analyzed using GC/MS to investigate the feasibility of automatic detection and diagnosis of diseases of mango in stores. A total of 37 metabolites, relatively consistent in 8 replicates, were identified based on mass spectral match using NIST library. Several of these were specific to a disease/inoculation or when common to all treatments, they varied in their abundances. 1-Pentanol was specific to Lasiodiplodia-inoculated mangoes while thujol was detected only in Colletotrichum-inoculated mangoes. Discriminant analysis models based on normalized abundances of 35 consistent metabolites and normalized abundances of 150 mass ions correctly classified 67 and 75% of the observations, respectively, based on cross-validation. The study has shown for the first time that it is possible to detect and differentiate between anthracnose and stem-end rot diseases of mangoes (cv. Keitt) based on their volatile production patterns using GC/MS. The methods developed here have the potential applications to mango industry to detect and diagnose diseases of mango fruits, at relatively early stages of the disease progress, after validation under commercial conditions.

This study was carried out to evaluate the effect of pectin-based edible emulsion coating on activity and disease severity of Lasiodiplodia theobromae in avocados, and their subsequent influence on the fruit quality. In order to assess the influence of coating and disease, avocados were sorted and devided into four equal lots and all were incubated at 20 °C for up to 4 days. The first and second lots constituted samples which were stored as coated and uncoated, respectively, without fungal inoculation. The third and fourth lots were coated and un-coated fruits inoculated with the fungal disease. For coating, a previously standardized pectin-based emulsion was used. The incubated fruits were examined for the spread of disease, respiration rate and quality parameters, color and texture. As the incubation time increased, the volume of disease (VDS) increased, which in turn influenced the respiration rate (RR) in both coated and uncoated fruits. However, the coated fruits sustained a significantly slower rate of disease spread and RR. Similarly, the associated quality changes (texture and color) were much lower in coated fruits as compared with the control. Thus, the pectin based coating was effective in controlling the spread and severity of stem end rot in avocados. Changes in physical and physiological parameters of coated and uncoated fruits were well described by some form of semi-logarithmic models and were related to the VDS as well as case dependent incubation time.

Metabolic profiles of spikelets of wheat cultivars, Roblin and Sumai3, respectively, susceptible and resistant to fusarium head blight (FHB) were analyzed using GC/MS to develop a technology to discriminate resistance. More than 700 peaks were detected and a total of 55 compounds were tentatively identified, of which 49 were induced/up-regulated following pathogen inoculation, including 23 in Roblin and 26 in Sumai3. However, only five metabolites were significantly different both between cultivars and inoculations. Metahydroxycinnamic acid, though was detected in all four treatments, exhibited a six-fold increase in abundance in Sumai3 following pathogen inoculation, with no corresponding change in Roblin. The abundance of myo-inositol in Sumai3 was higher than that in Roblin, and in both the abundance increased following pathogen inoculation. The compounds common to all treatments were subjected to factor analysis to identify groups of compounds, based on significant factor-loadings, associated with susceptibility or resistance against FHB. The treatment involving pathogen-inoculation of the resistant cv. Sumai3 was associated with the highest scores for the first and second factors that can be used for the discrimination of resistance against FHB. The first factor was associated with higher abundances of several fatty acids and aromatic compounds, while the second factor was associated with metabolites such as p- and m-coumaric acids, myo-inositol and other sugars, and malonic acid. The treatments involving pathogen-inoculation had higher factor scores for the third factor than the water inoculated, the highest being for the susceptible cultivar Roblin, and may be useful in explaining susceptibility/pathogenesis. The third factor had positive correlation with metabolites from different groups, mostly amino acids, fatty acids, and aromatics. The various compounds detected in this study are discussed, in terms of their possible roles in plant defense against pathogen-stress, their metabolic pathways of synthesis, and their potential application for screening cultivars of wheat for resistance to FHB.

Kinetics changes in cooking quality (texture and color) of potatoes stored at different temperatures (4–20 °C) were evaluated in this study. At selected time intervals, potatoes were removed from storage and their cooking quality evaluated. Cylindrical test samples (20 mm diameter and 20 mm length cut beneath the skin) of potatoes were cooked in boiling water for 10 min, quickly water cooled and kept in a plastic bag (to prevent moisture loss). Texture was evaluated using a single-cycle compression test in a universal testing machine and color was evaluated using a tristimulus colorimeter. Progressive softening of texture was evident in cooked potatoes with the passage of storage time. As expected, the most and the least changes were observed at the two extreme storage conditions, 20 and 4 °C, respectively. Brightness color parameter, L value, of cooked potatoes decreased and the total color difference (Δ E ) increased with time, but no major changes were observed in a and b values. Changes in texture loss were modeled based on the conventional first-order rate model, while a modified first-order model was used to characterize the color change kinetics of cooked potatoes. Temperature sensitivity of rate constants was described by the Arrhenius model for both color and texture. Kinetic data indicated that quality attributes of cooked potatoes could be related to those of raw potatoes.

Models were developed to predict the potential of leak development from factors influencing infection and lesion expansion. Such models could be used as a tool to manage leak in potato after harvest. Potato tubers, cv. Russet Burbank were wounded, inoculated with 20 μl of 104 sporangia per ml suspension of Pythium ultimum and incubated in mist chambers placed in growth chambers. Inoculated tubers were kept at 4, 8, 12, 16 and 20 °C. After 3, 6, 12, 24 and 48 h of incubation samples of five tubers were removed, stored at 12 °C and 95% RH. After 30 days of storage the disease severity was assessed to determine infection potential. Tubers were inoculated, incubated in mist chambers for 24 h, at 16 °C, to establish initial infections, and stored at 4, 8, 12, and 16 °C, for 15, 30, 45, 60, 75 and 90 days, at 95% RH to quantify lesion expansion potential. At the end of storage time, tubers were sliced, disease severity was assessed as volume diseased and the data were transformed into proportion of maximum volume diseased (PVD). The PVD was the least at the lowest temperature level tested and at the end of 12 h wet period at 12 °C, but it increased with increase in wetness duration and temperature. The maximum PVD was observed at 20 °C and 48 h wetness duration. Very little lesion expansion occurred at 4 °C, however, the lesions expanded rapidly with increase in temperature. A cubic model to predict infection potential from incubation temperature and duration of wetness explained 96.75% of the variation in PVD. A cubic model to predict lesion expansion potential as a function of storage temperature and duration explained of 99.2% of the variation in PVD. The potential application of these models to manage leak is discussed.

Undesirable storage conditions lead to physical and chemical quality loss in stored potatoes, which affect their consumer acceptability. Studies aimed at quantifying the extent of those changes under different storage conditions are valuable for minimizing the deleterious effect on product quality. The objective of this study was to evaluate the quality change in stored potatoes and quantify the associated kinetic parameters (rate constants) and activation energy to help model the changes in potato quality as function of storage temperature and time. Potatoes were stored at five temperatures (4°C, 8°C, 12°C, 16°C and 20°C) and, at different storage times (at least 5 time intervals) samples were removed and evaluated for different quality parameters (physical: texture and color; chemical: ascorbic acid (AA), reducing sugars (RS), starch (S), total sugars (TS), total soluble solids, pH and titrable acidity (TA) and physiological: respiration rate). The results revealed that potatoes became softer and darker by passage of time, and higher temperature resulted in more rapid changes in the different quality parameters. Chemical changes during the storage were decreased AA, pH and S, and increased TA, RS and TS. Only small changes were observed with peroxidase and polyphenoloxidase activity. Respiration rate increased with temperature and duration of storage. In general, most changes were well described by some form of first-order rate. Temperature sensitivity of rate constants was adequately described by the Arrhenius model.

Sprouting of tubers and spoilage due to invasion by bacterial and fungal pathogens are problems of potato storage that are usually dealt with by specialized chemicals. This study was aimed at determining whether both problems could rather be solved by a single thermal treatment without affecting the quality. The applicability to short-term storage conditions in cool climates and tropical climates was investigated. This study demonstrates that potato tubers can be safely stored for 12 weeks at either 8 or 18°C without sprouting, if dipped in a 57.5°C hot water bath for 20–30 min. Neither electron microscopy of starch granules, puncture tests nor chromacity analysis provided evidence of damage due to the thermal treatment.