Evaluation of Some Factors Associated with Potato Blackleg Disease

Potato blackleg (blg) caused by Pectobacterium species leads to great economic losses in agriculture worldwide. In this study, three breeding clones with varying degree of disease tolerance, i.e. tolerant (t), moderately tolerant (mt) and susceptible (s) to blg were evaluated in field trials for several disease related factors. The s-clone L 696 with its high portion of oversized tubers showed increased lenticel swellings and had a weak defense potential in its tuber tissue coinciding with low antioxidant capacities and reduced necrosis formation 48 h after incubation with Pectobacterium atrosepticum (Pba). The t-clone B 165, however, was outstanding in its tuber soft rot resistance and antioxidant levels and generated the best extent of necrosis after incubation with Pba among the genotypes. Moreover, B 165 expressed significantly higher (P < 0.05) polyphenol oxidase (PPO) and peroxidase (POD) activities in the external sprout basis (ESB) of its sprouting tubers, and histochemical analyses revealed embedding of lignin in ESB-tissue sections. Together with PPO, POD and phenols, this lignin forms a barrier that provided high protection of B 165-sprouts against Pba invasion and seems to be a key factor for blg tolerance. The mt-clone P 92388 with its medium-sized tubers had also a lower risk for infections. Hence, the oversized tubers and strong lenticel swellings can be seen as major risk factors for potato blg disease.

Laser and the Tuber: Thermal Dynamic and Volumetric Factors Influencing Seizure Outcomes in Pediatric Subjects With Tuberous Sclerosis Undergoing Stereoencephalography-Directed Laser Ablation of Tubers

INTRODUCTION Tuberous Sclerosis (TSC) is a well-known cause of Medically Refractory Epilepsy (MRE). It is well documented that early surgical management can improve patient outcomes. Stereoencephalography-directed Magnetic Resonance guided Laser Interstitial Thermal Therapy (SEEG-directed MRgLITT) is an emerging minimally invasive technique that appears aptly suited for the surgical management of this condition. Our aims are to present our experiences with patients who had undergone prior SEEG-directed MRgLITT to identify and treat cortical tubers responsible for clinical seizures and to perform an in-depth analysis of volumetric and thermal dynamic factors that may be related to seizure outcomes. METHODS We studied all pediatric patients with MRE due to TSC who underwent SEEG-directed MRgLITT, investigating seizure outcomes in relationship to thermal dynamic and volumetric factors of MRgLITT when applied to cortical tubers. RESULTS About 8 cortical tubers from 3 pediatric patients were analyzed. About 2 out of 3 patients had Engel I outcomes at last follow-up. Median follow-up was 15 mo. Average A/T (ablation volume/tuber volume) ratio for Engel I outcomes was 1.28 (variance, 0.16) and 0.84 (variance < 0.01) for all other outcomes (P = .035). When assessing thermal dynamic properties of cortical tuber tissue, there was a moderate positive correlation when comparing ablation energy to ablation volume (R2 = 0.65). When the calcified tuber is excluded from regression analysis, the correlation is stronger (R2 = 0.77). Thus, the calculated volume to ablate 1 cm3 of cortical tuber tissue is 1263.6 J (calcified tuber) or 1089.5 J (noncalcified tuber). CONCLUSION SEEG-directed MRgLITT is a safe and effective technique in the management of pediatric patients with MRE due to TSC. It appears that the A/T ratio is a useful indicator in predicting seizure outcomes.

Effects of seeding material age, storage time, and tuber tissue zone on glucomannan content of Amorphophallus muelleri Blume

Among members of the genus Amorphophallus in Indonesia, Amorphophallus muelleri produces the highest amounts of glucomannan, which is a fiber carbohydrate that plays a significant role in controlling obesity and type 2 diabetes. Glucomannan in A. muelleri is stored in the tubers. Several internal and external factors affect the glucomannan content of the tubers. In this study, we only investigated the internal factors seeding material and tuber. The objectives were: i) to investigate the effect of the seeding material on tuber glucomannan levels; and ii) to assess the influence of the storage period and the tuber part on glucomannan contents. Glucomannan was extracted via centrifugation. The result showed that tubers, which yielded from the center bulbis, have slightly higher glucomannan content than tubers from side bulbis, even though insignificant. Our results indicate significant glucomannan losses at storage times of more than 3 months. Levels decreased by 90% after storage over 3.75 months since shoot collapse. Glucomannan levels of the central and the edge parts of the tubers did not differ significantly.

Morphological and molecular characterisation of Scutellonema species from yam (Dioscorea spp.) and a key to the species of the genus

The yam nematode,Scutellonema bradys, is a major threat to yam (Dioscoreaspp.) production across yam-growing regions. In West Africa, this species cohabits with many morphologically similar congeners and, consequently, its accurate diagnosis is essential for control and for monitoring its movement. In the present study, 46Scutellonemapopulations collected from yam rhizosphere and yam tubers in different agro-ecological zones in Ghana and Nigeria were characterised by their morphological features and by sequencing of the D2-D3 region of the 28S rDNA gene and the mitochondrialCOIgenes. Molecular phylogeny, molecular species delimitation and morphology revealedS. bradys,S. cavenessi,S. clathricaudatumand three undescribed species from yam rhizosphere. OnlyS. bradyswas identified from yam tuber tissue, however. For barcoding and identifyingScutellonemaspp., the most suitable marker used was theCOIgene. Additionally, 99 newScutellonemasequences were generated using populations obtained also from banana, carrot, maize and tomato, including the first forS. paralabiatumandS. clathricaudatum, enabling the development of a dichotomous key for identification ofScutellonemaspp. The implications of these results are discussed.

Molecular and Biochemical Examination of Spraing Disease in Potato Tuber in Response to Tobacco rattle virus Infection

Field-grown tubers of potato were examined for infection by Tobacco rattle virus (TRV) and consequent production of corky ringspot or spraing symptoms. A microarray study identified genes that are differentially expressed in tuber tissue in response to TRV infection and to spraing production, suggesting that hypersensitive response (HR) pathways are activated in spraing-symptomatic tubers. This was confirmed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) of a selected group of HR-related genes and by histochemical staining of excised tuber tissue with spraing symptoms. qRT-PCR of TRV in different regions of the same tuber slice showed that nonsymptomatic areas contained higher levels of virus relative to spraing-symptomatic areas. This suggests that spraing formation is associated with an active plant defense that reduces the level of virus in the infected tuber. Expression of two of the same plant defense genes was similarly upregulated in tubers that were infected with Potato mop-top virus, a virus that also induces spraing formation.

Bioinformatic prediction of upstream microRNAs of PPO and novel microRNAs in potato

Chi, M., Liu, C., Su, Y., Tong, Y. and Liu, H. 2015. Bioinformatic prediction of upstream microRNAs of PPO and novel microRNAs in potato. Can. J. Plant Sci. 95: 871–877. MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs that play roles in many biological processes of plants. This study aimed to identify novel miRNAs and miRNAs targeting polyphenol oxidase (PPO) in potato. Small RNA-seq data (GSE32471 and GSE52599) including sequencing data of flower, leaf, stem, root, stolon and tuber tissue of potato were downloaded from Gene Expression Omnibus. After quality control and data cleaning of the raw data, the clean data were then mapped to Rfam to screen the reads corresponding to miRNA rather than other types of small RNA by Bowtie. Furthermore, the screened high-quality reads were mapped to known miRNAs in miRBase to identify and predict the novel miRNAs by miRDeep2. Finally, target gene prediction was performed for all identified miRNAs using psRNATarget and their roles in stress responses and brown spot of potato tubers through PPO genes were analyzed. A total of 18 novel potato miRNAs were identified and all of them had their specific expression patterns in different tissues. Targets prediction showed that some novel miRNAs (e.g., ST4.03ch03_9018, ST4.03ch05_15199 and ST4.03ch11_31208) could regulate the expression of potato resistance genes. Moreover, eight known miRNAs were found to target 3 PPO encoding genes, while they expressed at a low level in tuber tissue. Novel miRNAs might be associated with stress resistance of potato, and upstream miRNAs of PPO encoding genes might be important in suppression of potato brown spot.

Deposition of callose in wound tissue tuber of potato (Solanum tuberosum L.)

Fluorescent methods were used for investigation of callose deposition in cells of wound tuber tissue of potato. Potato cultivars: Tarpan, Certa and Narew were examined. Deposition of callose in cells depended on the place of the wound, type of tissue and cultivar of potato. The apical part deposited more callose than the base part and the primary bark more than the pith crown. More callose was deposited in Tarpan, less in Certa, least in Narew. The quantity of the callose corresponded to the resistance to store diseases i.e. fungal dry mixed rots. As the temperature during storage and healing of the wounded tuber was declined, the quantity of callose after injury decreased.