Postharvest Physiological Deterioration Research Articles

Physiological Deterioration of Cassava Tuber

The present study was carried out to evaluate cassava genotypes for Postharvest Physiological Deterioration (PPD). Tubers from different genotypes were evaluated at 1,2,3,4 and 5 days after harvest for PPD. Two genotypes viz., CI 850 and YTP 1 showed their supremacy in recording low levels of PPD (9.81 and 11.76 % respectively) even five days after harvest. This could be the result of lower cyanide (HCN) content. Starch content was decreased at storage. This study can be used to understand the mechanisms of PPD in cassava tubers.

Influence of Harvest Periods on Cassava (<i>Manihot esculenta</i> Crantz) Agronomic Traits and Physiological Response to Post-Harvest Physiological Deterioration

Cassava (Manihot esculenta Crantz) is the third largest source of calories in tropical countries and the sixth most important food crop in the World. However, the short shelf life of its storage roots after harvest due to a rapid post-harvest physiological deterioration (PPD) makes the roots to be considered as a risky product to market. The objectives of this work were to investigate the influence of two harvest periods on cassava agronomic parameters and their physiological response to PPD. Three cassava cultivars 96/1414, I070593 and LMR were selected for the experiment and harvested at 10 and 12 months after planting (MAP). The response to PPD was assessed during storage at 0, 3, 8 and 15 days after harvest (DAH). Total proteins content, soluble sugars and starch, total polyphenols compounds, polyphenoloxidase and peroxidase activities were recorded during storage. Results showed large variation among the parameters at the two harvest periods across the cultivars. High number of tubers was recorded in all the cultivars at 12 MAP and a significant increase in storage roots length was observed in 96/1414 and LMR from 10 MAP to 12 MAP (25 ± 5.1 to 41.3 ± 5.9 and 22.6 ± 3.3 to 27.9 ± 4.8) respectively. A reduction of about 49% of tubers weight was observed in I070593 from 10 to 12 MAP while an increase of about 36% and 11% were recorded in LMR and 96/1414 respectively. Tubers from I070593 showed less susceptibility to PPD when harvested at 10 MAP compared to those from LMR and 96/1414 where less susceptibility to PPD were recorded at 12 MAP. An increase in soluble sugars content, total proteins content and peroxidase activity subsequently to a decrease in starch content were recorded during storage from 8 to 15 days after harvest especially at 10 MAP in I070593 and at 12 MAP in LMR and 96/1414. High content of total phenolic compounds and less activity of polyphenol oxidase were correlated to PPD susceptibility. This work opens a new insight issue of the consideration of the appropriate harvest time of the cultivars as a tool to better control the onset of postharvest physiological deterioration.

Comparative Transcriptome Profiling of Cassava Tuberous Roots in Response to Postharvest Physiological Deterioration.

Cassava is one of the most versatile tuberous-root crops on Earth. However, the postharvest storage properties of cassava tuberous root mean that it is perishable through a process known as postharvest physiological deterioration (PPD), which seriously affects its starch quality. Therefore, a comprehensive understanding of the transcriptional regulatory activity of cassava against the PPD response is necessary in order to extract key molecular mechanisms related to PPD tolerance. In this study, we found that RYG1 tuberous roots showed delayed PPD compared to those of SC8. In addition, RYG1 roots maintained a more stable cell wall structure after storage than those of SC8. The transcriptome changes in tuberous roots were analyzed for both RYG1 and SC8 after 21 days of storage (SR and SS) compared to fresh (FR and FS) by the RNA-Seq method. The total number of differentially expressed genes (DEGs) in the various comparisons of these four samples ranged from 68 to 3847. Of these, a total of 2008 co-DEGs in SR vs. SS were shared by either SR vs. FR or SS vs. FS. GO and KEGG enrichment analysis revealed that upregulated co-DEGs in SR vs. SS were mainly enriched in photosynthesis, protein processing, hormone and cutin, suberine and wax biosynthesis. By contrast, the downregulated co-DEGs were mainly related to cell wall organization, starch and sucrose metabolism, galactose metabolism, phenylpropanoid biosynthesis, diterpenoid biosynthesis, cysteine and methionine metabolism and flavonoid biosynthesis. The protein-protein interaction (PPI) networks of the co-DEGs showed a complex interaction of genes in different pathways, and 16 hub genes were characterized to have a degree in excess of 15, among which eight genes were associated with photosynthesis. These results provide new information for the study of cassava resistance to PPD and lay a foundation for the further molecular breeding of storage-tolerant cassava varieties.

Abscisic Acid Signaling in the Regulation of Postharvest Physiological Deterioration of Sliced Cassava Tuberous Roots.

Phytohormone abscisic acid (ABA) influences the shelf life of fruit, vegetables, and tubers after harvest. However, little is known about the core signaling module involved in ABA's control of the postharvest physiological process. Exogenous ABA alleviated postharvest physiological deterioration (PPD) symptoms of sliced cassava tuberous roots, increased endogenous ABA levels, and reduced endogenous H2O2 content. The specific ABA signaling module during the PPD process was identified as MePYL6-MePP2C16-MeSnRK2.1-MebZIP5/34. MebZIP5/MebZIP34 directly binds to and activates the promoters of MeGRX6/MeMDAR1 through ABRE elements. Exogenous ABA significantly induced the expression of genes involved in this module, glutaredoxin content, and monodehydroascorbate reductase activity. We presented a hypothesis suggesting that MePYL6-MePP2C16-MeSnRK2.1-MebZIP5/34-MeGRX6/MeMDAR1 is involved in ABA-induced antioxidative capacity, thus alleviating PPD symptoms in cassava tuberous roots. The identification of the specific signaling module involved in ABA's control of PPD provides a basis and potential targets for extending the shelf life of cassava tuberous roots.

CARACTERÍSTICAS AGRONÔMICAS, COZIMENTO E CONSERVAÇÃO PÓS-COLHEITA PARA SELEÇÃO DE CLONES DE MANDIOCA DE MESA

ABSTRACT The objective of this work was to evaluate the agronomic performance, cooking time and postharvest conservation of roots of sweet cassava clones, to select those superior to the Manteiga variety control, in the Baixo Sul region of Bahia state. A randomized block design in split plot scheme, with three replications was used. Eleven genotypes were evaluated at 10 and 12 months after planting. Considering the mean of two harvests, BRS Kiriris and Saracura showed total root yield (39.85 and 33.91 t ha−1, respectively) and commercial root yield (26.54 and 26.71 t ha−1) that are higher compared to Manteiga (total root yield: 28.06 t ha−1, commercial root yield: 16.95 t ha−1). However, both had cooking time (26.76 and 28.30 min, respectively) higher than that of Manteiga (23.89 min), and BRS Kiriris was unstable regarding the cooking percentage between 10 (91.67%) and 12 months (50%). BRS Aipim Brasil, 2003 14-11, BRS Kiriris, Eucalipto, Saracura and Manteiga were more tolerant to postharvest physiological deterioration. Although some of the evaluated clones presented good performance in the evaluated traits, by analyzing the set of traits, none of them shows sufficient superiority to be indicated as a potential substitute for Manteiga, grown in the Baixo Sul region of Bahia state.

Knockdown of p-Coumaroyl Shikimate/Quinate 3'-Hydroxylase Delays the Occurrence of Post-Harvest Physiological Deterioration in Cassava Storage Roots.

Cassava storage roots are an important source of food, feed, and material for starch-based industries in many countries. After harvest, rapid post-harvest physiological deterioration (PPD) reduces their palatability and marketability. During the PPD process, vascular streaking occurs through over-accumulation of coumarins, the biosynthesis of which involves the key enzyme p-coumaroyl shikimate/quinate 3′-hydroxylase (C3′H). Repression of MeC3′H expression by RNA interference in transgenic cassava plants caused a significant delay in PPD by decreasing scopoletin and scopolin accumulation in field-harvested storage roots. This study demonstrates that MeC3′H is the key enzyme participating in coumarin biosynthesis during PPD and shows that MeC3′H is a useful target gene for editing to prolong the shelf life of cassava storage roots.

Systematic Analysis of bHLH Transcription Factors in Cassava Uncovers Their Roles in Postharvest Physiological Deterioration and Cyanogenic Glycosides Biosynthesis.

The basic helix-loop-helix (bHLH) proteins are a large superfamily of transcription factors, and play a central role in a wide range of metabolic, physiological, and developmental processes in higher organisms. However, systematic investigation of bHLH gene family in cassava (Manihot esculenta Crantz) has not been reported. In the present study, we performed a genome-wide survey and identified 148 MebHLHs genes were unevenly harbored in 18 chromosomes. Through phylogenetic analyses along with Arabidopsis counterparts, these MebHLHs genes were divided into 19 groups, and each gene contains a similar structure and conserved motifs. Moreover, many cis-acting regulatory elements related to various defense and stress responses showed in MebHLH genes. Interestingly, transcriptome data analyses unveiled 117 MebHLH genes during postharvest physiological deterioration (PPD) process of cassava tuberous roots, while 65 MebHLH genes showed significantly change. Meanwhile, the relative quantitative analysis of 15 MebHLH genes demonstrated that they were sensitive to PPD, suggesting they may involve in PPD process regulation. Cyanogenic glucosides (CGs) biosynthesis during PPD process was increased, silencing of MebHLH72 and MebHLH114 showed that linamarin content was significantly decreased in the leaves. To summarize, the genome-wide identification and expression profiling of MebHLH candidates pave a new avenue for uderstanding their function in PPD and CGs biosynthesis, which will accelerate the improvement of PPD tolerance and decrease CGs content in cassava tuberous roots.

THE RESPONSES OF ROSELLE (Hibiscus sabdariffa L.) TO THE APPLICATION OF PLANT GROWTH REGULATORS IN DEVELOPING SEEDLESS FRUIT AND MAINTAINING ITS QUALITY

Seedless fruit is a fruit developed to possess no mature seeds. Today lifestyle, consumers and/or manufacturers prefer fruit without seeds as removing it is time-consuming and troublesome. Indeed, seedless fruits have better organoleptic attributes than seeded fruits. To produce seedless roselle and maintain its postharvest quality, various spray applications of synthetic and naturally occurring plant growth regulators were investigated. Roselle is perishable and non-climacteric fruit that is exposed to rapid postharvest physiological deterioration following harvest. Thus, producing seedless fruit may reduce time and labor costs during the removing seed process. The experimental treatments were arranged in randomized complete block design with different types of plant growth regulators and spray applications. The PGRs treatments at varying frequencies were sprayed on roselle flower buds at 35, 45, 55, and 65 days after transplanting (DAT). Among all PGRs treatments, the plant treated with 800 mg/L GA3 + seaweed extract (4 sprays) had developed seedless roselle fruit by exhibiting the smallest capsule diameter, capsule volume, and a low number of seeds. In a conclusion, the application of 800 mg/L GA3 + seaweed extract (4 sprays) was the effective concentration to produce seedless roselle fruit and maintain its postharvest quality.

Exploring Farmers’ Knowledge and Approaches for Reducing Post-Harvest Physiological Deterioration of Cassava Roots in Malawi

Cassava utilisation in Malawi is negatively affected by rapid deterioration of fresh roots, primarily caused by postharvest physiological deterioration (PPD). A study was conducted to assess farmers’ knowledge and approaches used to minimize losses from PPD. Multi-stage sampling was used to identify districts, Extension Planning Areas (EPA’s) and farmers. Data were collected from 519 farmers using a structured questionnaire. Results revealed that PPD (74.0%) was the major post-harvest constraint followed by pests and diseases (62.1%). Farmers had varying knowledge levels on signs and causes of PPD. They were knowledgeable on PPD signs with 91.5% ably identifying PPD through change of pulp colour. The farmers also had moderate knowledge on causes of PPD, citing high temperature (57.6%) and over-staying of roots (56.2%) as main causes of PPD. Key methods for preventing PPD are: storage (43.0%) and piece-meal harvesting (40.4%). Only 2.6% of the farmers exploited varietal difference in dealing with PPD as some varieties (Sauti, Mpuma, Ching’amba, and Kalasa) take three to five days before showing PPD signs. Farmers’ knowledge levels and PPD preventive methods could be strengthened through: provision of training on post-harvest handling, improvement in storage and processing technologies; and application of advanced breeding techniques to exploit genetic variation in cassava germplasm.

Lysozyme inhibits postharvest physiological deterioration of cassava.

After harvest, cassava (Manihot esculenta Crantz) storage roots undergo rapid postharvest physiological deterioration, producing blue-brown discoloration in the vasculature due to the production of polyphenolics (mainly quinones and coumarins) by enzymes such as polyphenol oxidase (PPO). Here, we report the application of hen egg-white lysozyme (HEWL), a natural PPO inhibitor, in transgenic cassava to repress the symptoms of postharvest physiological deterioration. The HEWL-expressing transgenic plants had lower levels of the two main cassava coumarins tested, scopoletin and scopolin, compared with wild type. HEWL-expressing cassava also showed increased tolerance of oxidative stress. Overall, the lysozyme-PPO system proved to be functional in plants for repressing PPO-mediated commercial product browning.

Comparative study on chemical and functional properties of flours produced from selected clones of low and high postharvest physiological deterioration cassava (Manihot esculenta Crantz)

The industrial usage to which flour could be put to is essentially determined by its physical, chemical and functional characteristics. This study compared the chemical and functional properties of high quality cassava flours (HQCFs) produced from low and high postharvest physiological deterioration (PPD) cassava. Wholesome four varieties of Low PPD cassava and one variety of high PPD cassava were processed into HQCFs. The flours were analyzed for chemical and functional properties. Pertinent data generated were analyzed using SPSS 25.0, Duncan multiple range tests was applied to separate significant means. Sugar, starch, amylose, cyanogenic potential, total titratable acidity and total carotenoid ranged from 4.23±0.04-5.10±0.04%, 80.54±0.57-82.30±0.15%, 31.50±0.11-33.62±0.11%, 0.02±0.00-0.51±0.01 mg/kg, 0.04±0.00-0.06±0.01% and 0.34±0.01-3.14±0.06 μg/g. Water absorption, swelling power, solubility, starch damage, oil absorption, least gelation capacity and bulk density ranged from 416.01±2.70-547.56±2.15%, 9.03±0.04-14.02±1.23, 32.63±1.21-53.62±3.31%, 3.08±0.04-3.40±0.07%, 105.19±0.55-120.56±2.06%, 7.00±1.41-13.00±1.41% and 0.53±0.01-0.66±0.01 g/cm3. Low PPD cassava flours studied had relatively higher water absorption, swelling power, starch solubility and high gel strength than flours from high PPD, and could find application in food industry as thickeners and pharmaceutical industry for drug delivery systems.

Effects of harvest period, storage, and genotype on postharvest physiological deterioration responses in cassava

Abstract. Rahmawati RK, Khumaida N, Ardie SW, Sukma D, Sudarso. 2021. Effects of harvest period, storage, and genotype on postharvest physiological deterioration responses in cassava. Biodiversitas 23: 100-109. Postharvest physiological deterioration (PPD) is the major constraint in cassava root production. The breeding program to develop PPD tolerant cassava varieties requires a long period to complete. Although it is the first step in breeding for PPD tolerance, evaluating cassava germplasm responses for the PPD remains a major problem because it is a laborious process, and the evaluation often contains a high experimental error. This study aims to develop methods for evaluating PPD response, i.e., evaluating the effects of two harvest periods and storage on PPD responses of nine cassava genotypes. The developed scoring system based on cassava root discoloration could group the evaluated cassava genotypes into either PPD tolerant, medium tolerant, or sensitive. The tolerant varieties showed less than 10% root discoloration areas, while the medium tolerant was between 11-20%, and the sensitive was larger than 20%, respectively. ADR-24 and GJ-11 were identified as PPD tolerant, while ML-19 was sensitive using the developed scoring system. This study showed that PPD is a complex phenomenon associated with genetics and environmental factors. Root dry matter content and maximum root diameter traits may play an important role in PPD development in cassava. We have developed procedures for identifying genotype responses to PPD and showed that cassava roots harvested as early as eight months after planting and stored as late as five days under the control relative humidity were good conditions for studying PPD. Evaluating the percentages of root discoloration was a good measure for PPD response prediction. Moreover, we showed that less than 10%, 20%, and more than 20% of root discoloration might be used to group cassava into PPD tolerant, medium tolerant, and sensitive for Indonesian accessions. Therefore, the methods developed in this study may support the Indonesian cassava breeding program and provide biochemical and molecular analysis materials to elaborate the mechanisms of PPD in cassava roots.

Microbiological Quality of High Quality Cassava Flour Produced from Selected Varieties of Low Postharvest Physiological Deterioration Cassava (Manihot esculenta Crantz)

The microbial properties of food are important quality characteristics of food materials as it relates directly with the health of the consumer. This study examined the microbiological properties of high quality cassava flours produced from low postharvest physiological deterioration (PPD) cassava. Wholesome four varieties of yellow-fleshed Low PPD cassava and one variety of high PPD cassava were, peeled, washed, grated, pressed, pulverized, flash dried at 120 °C for 8 minutes, milled with cyclone hammer mill fitted with a screen of 250 µm aperture size, cooled and packed into high density polyethylene bag. The high quality cassava flours produced were analyzed for total viable fungal and bacteria count, fungi isolated were further characterized and identified using molecular methods. Data obtained were subjected to one way analysis of variance (ANOVA) using SPSS 25.0 and significant means were separated applying Duncan multiple range test. The mold count ranged from 1.50±0.71 - 2.50±0.71 cfu/ml, with flour produced from IITA-TMS-IBA-011371 and TMEB 419 having the lowest count while the highest was recorded in IITA-TMS-IBA-011368, respectively. The yeast count ranged from 1.00±0.00 - 2.0±0.00 cfu/ml, with flours produced from IITA-TMS-IBA-070593 and IITA-TMS-IBA-011371 having the lowest count while the highest was recorded in flour from IITA-TMS-IBA-011368, respectively. The total viable bacterial and fungal count (microbiological quality) of the flours prepared from IITA-TMS-IBA-011368, IITA-TMS-IBA-070593, IITA-TMS-IBA-011412, IITA-TMS-IBA-011371 and TMEB 419 cassava varieties were within the permissible limit of the microbial load of food allowed for human consumption according to the Standard Organization of Nigeria and CODEX alimentraius.

Untargeted Metabolomics Profiling of High Beta Carotene Cassava with respect to Postharvest Physiological Deterioration

Cassava roots undergo postharvest physiological deterioration (PPD), and for most varieties it sets in within 72 hours of harvest. An untargeted metabolomics approach combined with a data-driven approach for statistical analysis was used to characterize and profile high beta-carotene cassava varieties with the aim of identifying any relevant metabolite changes that occur during PPD. Sixteen cassava root samples from four cassava lines were planted in a greenhouse and harvested after four months. The samples included four of 2 conventionally bred beta carotene cassava varieties – UMUCASS 38, UMUCASS 45 and four of 2 transgenic high beta carotene cultivars - EC20-7 and EC20-8 cassava lines. Extracts of fresh cassava roots from 20-100 mg tissues were used for the analyses and data were processed using Elements for Metabolomics software. Starch and lipid metabolites were the major constituents which may help explain the observed differences in starch and dry matter content among the varieties. The results provide further insight in the understanding of PPD and suggestions on controlling this deterioration in cassava are made.

Physical and Microstructural Properties of Composite Cassava-wheat Bread Produced from Blend of Wheat and Low Postharvest Physiological Deterioration Cassava Flours

The physical and microstructural properties of bread are basic criteria in measuring and optimizing bread quality. This study investigated the physical and microstructural properties of composite cassava-wheat (CCW) bread produced with blend of wheat flour and low postharvest physiological deterioration (PPD) cassava flours. Wholesome four varieties of yellow-fleshed Low PPD cassava and one variety of high PPD cassava were processed into flour and composited with wheat flour. Composite breads produced were analyzed for physical and microstructural properties. Data obtained were subjected to one way analysis of variance using SPSS 25.0 and significant means were separated applying Duncan multiple range test. The CCW flours’ water absorption, swelling power, solubility index, oil absorption, bulk density, lightness (L*), redness (a*), and yellowness (b*) ranged from 13.53±0.05 - 13.73±0.05 %, 7.00±0.01 - 8.87±0.03 %, 8.27±0.01 - 9.55±0.06, 101.33±0.87 - 118.83±0.49 %, 0.55±0.01 - 0.62±0.01 g/cm3, 93.95±0.28 - 96.01±0.34, 0.36±0.01 - 0.77±0.10 and 9.94±0.17 - 11.74±0.24, respectively. Oven spring, loaf volume, loaf weight, specific volume, softness index, springiness, crumb moisture, crumb density, solid density, crumb porosity, bread crust lightness (L*), crust redness (a*), crust yellowness (b*), crumb lightness (L*), crumb redness (a*), crumb yellowness (b*), browning index, total number of cells and percentage area ranged from 0.20±0.00 - 1.25±0.07 cm, 570.80±6.62 - 917.60±6.23 cm-3, 245.33±0.43 - 255.83±0.45 g, 6.22±0.09 - 7.81±0.01 cm3/g, 11.09±0.36 - 12.69±0.40, 0.70±0.01 - 0.84±0.01, 36.59±0.47 - 39.24±1.67 %, 0.15±0.00 - 0.64±0.71 g/cm3, 1.14±0.86 - 1.94±0.09 g/cm3, 0.89±0.01 - 0.93±0.01, 46.49±0.07 - 59.55±1.77, 13.35±0.76 - 17.26±0.04, 25.52±0.05 - 35.66±0.47, 71.72±0.40 - 89.40±0.25, -0.25±0.05 - 6.96±0.45, 20.45±0.08 - 30.88±0.26, 88.94±5.15 - 98.77±0.06, 227.00±2.83 - 1000.00±11.5 and 50.95±11.11 - 68.67±3.07 cm2, respectively. Bread of desirable loaf qualities and microstructural properties comparable to 100% wheat flour bread were produced from low PPD cassava flour.

Genomic Analysis of the Principal Members of Antioxidant Enzymes in Simulated Stresses Response and Postharvest Physiological Deterioration in Cassava

Genomic Analysis of the Principal Members of Antioxidant Enzymes in Simulated Stresses Response and Postharvest Physiological Deterioration in Cassava

Functional, Physical and Rheological Properties of Composite Cassava-Wheat Flour Produced from Low Postharvest Physiological Deterioration Cassava (Manihot esculenta Crantz)

The functional, rheological and color (physical) properties of flours are quality attributes determining the usage, suitability and organoleptic characteristics of flours meant for industrial (baking and confectionery) application. This study investigated the functional, physical and rheological properties of composite cassava-wheat flour produced with low (PPD) cassava flours. Wholesome four varieties of yellow-fleshed Low PPD cassava and one variety of high PPD cassava were, washed, grated, pressed, pulverized, flash dried at 120 °C for 8 minutes, milled with cyclone hammer mill to which a screen having aperture size of 250 was affixed and subsequently cooled. The flours were subjected to analysis such as physical (color), functional and rheological. SPSS 25.0 was used to analyze pertinent data generated, significant means were separated applying Duncan multiple range test. The composite cassava-wheat (CCW) flours’ water absorption, swelling power, solubility index, oil absorption, bulk density, lightness (L*), redness (a*), and yellowness (b*) ranged from 13.53±0.05-13.73±0.05%, 7.00±0.01-8.87±0.03%, 8.27±0.01-9.55±0.06, 101.33±0.87-118.83±0.49%, 0.55±0.01-0.62±0.01 g/cm3, 93.95±0.28-96.01±0.34, 0.36±0.01-0.77±0.10 and 9.94±0.17-11.74±0.24, respectively. The water absorption, dough development time, dough stability, mixing tolerance index, dough consistency, farinograph quality number, breakdown time, water absorption for default moisture content and gluten content ranged from 60.70±0.00-63.70±0.14%, 1.28±0.00-1.32±0.00 min, 1.14±0.00-1.37±0.00 min, 75.00±0.00-104.00±0.00 BU, 424.00±0.00-518.00±0.00 mm, 23.00±0.00-26.00±0.00 mm, 2.10±0.00-2.38±0.00 min, 59.90±0.00-62.20±0.00% and 27.00±0.00-32.00±0.00, respectively. Comparable functional, rheological and physical properties to that of wheat flour was obtained from CCW flour prepared with blend of low PPD cassava flour and wheat which are suitable for application in the baking and confectionery industry.

Climate smart technology for storage of fresh pro-vitamin A bio-fortified cassava

Climate change is a problem affecting food security across the globe. The climate change effect of rising temperatures can be mitigated by using climate-smart crops such as cassava and climate-smart technology such as an Evaporative Cooling Structure (ECS). A 150 kg capacity Metal-in-Block evaporative cooling structure was designed and constructed to investigate its suitability for storage of fresh cassava roots. The postharvest physiological deterioration (PPD), weight loss, and deterioration rate of 12 months old biofortified cassava roots (TMS 01/1368) were evaluated, while the performance of the evaporative cooling structure was evaluated in terms of temperature drop, humidity increase, and cooling effectiveness. Results showed that the cassava was still in good condition and quality with no sign of PPD, while the total weight loss was 8.7%. The average cooling efficiency of the evaporative cooling structure was 102.7%. The result showed a drop in temperature from an average of 31.97–25.7°C and an increase in relative humidity from an average of 68.96–87.12%. The evaporative cooler was able to preserve freshly harvested cassava for at least 8 weeks. Storage of cassava in an evaporative cooling structure is thus recommended as an effective technology for medium scale cassava storage.

Comprehensive analysis and expression profiles of cassava UDP-glycosyltransferases (UGT) family reveal their involvement in development and stress responses in cassava

UDP-glycosyltransferases (UGTs) are widely involved in plant growth and stress responses. However, UGT family are not well understood in cassava. Here, we identified 121 MeUGT genes and classified them into 14 subfamilies by phylogenetic analysis. All MeUGT proteins have typical feature of the UGTs family. Tandem duplications are the crucial driving force for the expansion of MeUGT family. Cis-Acting elements analysis uncovered those 14 kinds of cis-elements associated with biotic and abiotic stress responses. Transcriptomic and qRT-PCR analyses indicated that MeUGT genes participate in postharvest physiological deterioration of storage root and the responses of biotic and abiotic stresses. Of which, MeUGT-14/41 were significantly induced after Xam treatment. Silencing of MeUGT-14 or MeUGT-41 reduced cassava resistance to Xam, verifying the accuracy of transcriptomic data for function prediction. Together, this study characterized the MeUGTs family and revealed their potential functions, which build a solid foundation for MeUGTs associated genetic improvement of cassava.

Effect of Scopoletin and Carotenoids on Postharvest Physiological Deterioration (PPD) of Transgenic High Beta Carotene Cassava

Cassava tubers suffer from postharvest physiological deterioration (PPD) which normally sets in within 72 hours of harvest. This study examines the role of scopoletin and carotenoids in the onset or delay in PPD in two transgenic varieties EC20-7 and EC20-8 compared to a wild variety TME-7. Scopoletin and carotenoids were quantified by liquid chromatography-mass spectrometry. The scopoletin content (0.10 – 0.20 nmol/g) in the fresh varieties was not significantly (P>0.05) different from the amount in stored cassava roots (12.58 – 14.90 nmol/g). The carotenoid content values in EC20-7 variety were 6.66 µg/g (α-carotene), 80.45 µg/g (β-carotene) and 5.98 µg/g (lutein). As for EC20-8, α-carotene, β-carotene and lutein values were 6.19 µg/g, 69.11 µg/g and 3.12 µg/g, respectively. There was no significant (P>0.05) difference between the varieties in α-carotene content but in their lutein content. The results indicate that carotenoids are more relevant in the delay of PPD and scopoletin content is not a major factor in PPD vascular streaking or discolouration. Hence scopoletin content of cassava varieties may not be considered as a chemical marker for determining the potential of PPD in cassava tubers.