Genomic prediction of switchgrass winter survivorship across diverse lowland populations.

In the North-Central United States, lowland ecotype switchgrass can increase yield by up to 50% compared with locally adapted but early flowering cultivars. However, lowland ecotypes are not winter tolerant. The mechanism for winter damage is unknown but previously has been associated with late flowering time. This study investigated heading date (measured for two years) and winter survivorship (measured for three years) in a multi-generation population generated from two winter-hardy lowland individuals and diverse southern lowland populations. Sequencing data (311,776 markers) from 1,306 individuals were used to evaluate genome-wide trait prediction through cross-validation and progeny prediction (n = 52). Genetic variance for heading date and winter survivorship was additive with high narrow-sense heritability (0.64 and 0.71, respectively) and reliability (0.68 and 0.76, respectively). The initial negative correlation between winter survivorship and heading date degraded across generations (F1r = -0.43, pseudo-F2r = -0.28, pseudo-F2 progeny r = -0.15). Within-family predictive ability was moderately high for heading date and winter survivorship (0.53 and 0.52, respectively). A multi-trait model did not improve predictive ability for either trait. Progeny predictive ability was 0.71 for winter survivorship and 0.53 for heading date. These results suggest that lowland ecotype populations can obtain sufficient survival rates in the northern United States with two or three cycles of effective selection. Despite accurate genomic prediction, naturally occurring winter mortality successfully isolated winter tolerant genotypes and appears to be an efficient method to develop high-yielding, cold-tolerant switchgrass cultivars.

"Impact of Preoperative Biliary Drainage in Patients Undergoing Pancreaticoduodenectomy" - a Prospective Comparative Study from a Tertiary Care Centre in India.

Preoperative biliary drainage (PBD) was primarily introduced to reduce perioperative complications following hepato-pancreato-biliary surgeries. There is no proper consensus on the routine use of PBD before pancreaticoduodenectomy (PD). This is a prospective observational study of patients who underwent PD between July 2013 and December 2014. The study group was divided into two groups based on whether a preoperative biliary drainage was performed or not. The intraoperative and postoperative complications were compared among the two groups. A total of 59 patients, predominantly males (64.4%) with a median age of 58 years, were included in study. All except 5 (8.5%) had undergone PD for periampullary malignancy. Thirty-eight patients (64.4%) underwent an upfront PD and the remaining 21 (35.5%) had undergone PBD. Cholangitis was the indication for PBD in all patients. The mean operative time (307.89 ± 52.51 min vs. 314.29 ± 36.273; p value = 0.62) and postoperative complications like delayed gastric emptying (63.2% vs. 61.9%; p value-0.924), postoperative pancreatic fistula (21.1% vs. 33.3%; p value 0.3), post-pancreaticoduodenectomy haemorrhage (5.3% vs. 9.5%; p value-0.611) and mean in-hospital stay were comparable among two groups. Even though the incidence of positive intraoperative bile cultures is significantly higher among the stented group (95.2% vs. 26.3%; p value = 0.0), no significant difference in surgical site infections (47.6% vs. 28.9%; p value 0.152) was noted. The overall mortality was 1.7% (1/59; grade C PPH). This study showed no significant difference in the postoperative complications following PBD despite increase in bile culture positivity. However, notable differences in the spectrum of microbial growths between stented and non-stented groups were observed.

Genetic control of source-sink relationships in grain sorghum.

MAIN CONCLUSION: QTL hotspots identified for selected source-sink-related traits provide the opportunity for pyramiding favorable alleles for improving sorghum productivity under diverse environments. A sorghum bi-parental mapping population was evaluated under six different environments at Hays and Manhattan, Kansas, USA, in 2016 and 2017, to identify genomic regions controlling source-sink relationships. The population consisted of 210 recombinant inbred lines developed from US elite post-flowering drought susceptible (RTx430) and a known post-flowering drought tolerant cultivar (SC35). Selected physiological traits related to source (effective quantum yield of photosystem II and chlorophyll index), sink (grain yield per panicle) and panicle neck diameter were recorded during grain filling. The results showed strong phenotypic and genotypic association between panicle neck diameter and grain yield per panicle during mid-grain filling and at maturity. Multiple QTL model revealed 5-12 including 2-5 major QTL for each trait. Among them 3, 7 and 8 QTL for quantum yield, panicle neck diameter and chlorophyll index, respectively, have not been identified previously in sorghum. Phenotypic variation explained by QTL identified across target traits ranged between 5.5 and 25.4%. Panicle neck diameter and grain yield per panicle were positively associated, indicating the possibility of targeting common co-localized QTL to improve both traits simultaneously through marker-assisted selection. Three major QTL hotspots, controlling multiple traits were identified on chromosome 1 (52.23-61.18 Mb), 2 (2.52-11.43 Mb) and 3 (1.32-3.95 Mb). The identified genomic regions and underlying candidate genes can be utilized in pyramiding favorable alleles for improving source-sink relationships in sorghum under diverse environments.

Genetic loci associated with winter survivorship in diverse lowland switchgrass populations.

High winter mortality limits biomass yield of lowland switchgrass (Panicum virgatum L.) planted in the northern latitudes of North America. Breeding of cold tolerant switchgrass cultivars requires many years due to its perennial growth habit and the unpredictable winter selection pressure that is required to identify winter-hardy individuals. Identification of causal genetic variants for winter survivorship would accelerate the improvement of switchgrass biomass production. The objective of this study was to identify allelic variation associated with winter survivorship in lowland switchgrass populations using bulk segregant analysis (BSA). Twenty-nine lowland switchgrass populations were evaluated for winter survival at two locations in southern Wisconsin and 21 populations with differential winter survivorship were used for BSA. A maximum of 10% of the individuals (8-20) were bulked to create survivor and nonsurvivor DNA pools from each population and location. The DNA pools were evaluated using exome capture sequencing, and allele frequencies were used to conduct statistical tests. The BSA tests revealed nine quatitative trait loci (QTL) from tetraploid populations and seven QTL from octoploid populations. Many QTL were population-specific, but some were identified in multiple populations that originated across a broad geographic landscape. Four QTL (at positions 88 Mb on chromosome 2N, 115 Mb on chromosome 5K, and 1 and 100 Mb on chromosome 9N) were potentially the most useful QTL. Markers associated with winter survivorship in this study can be used to accelerate breeding cycles of lowland switchgrass populations and should lead to improvements in adaptation within USDA hardiness zones 4 and 5.

Effect of seed hydro-priming durations on germination and seedling growth of bitter gourd (Momordica charantia).

The yield and quality of an annual crop are highly dependent on uniform and rapid germination of the seeds. In case of bitter gourd (Momordica charantia), the germination and field emergence is always a problem as seeds have thick and hard seed coat. Pre-sowing hydro-priming is one of the most suitable, affordable, easily available, and cost-effective techniques in breaking down seed dormancy to enhance germination. Hence, a field experiment was conducted in Surkhet district of Nepal 2020 to assess the effect of different hydro-priming duration on germination and seedling growth of bitter gourd. The experiment was laid out in single factor Randomized Complete Block Design (RCBD) with four replications and seven treatments including different hydro-priming durations (T0: control, T1: 6 hours, T2: 12 hours, T3: 18 hours, T4: 24 hours, T5: 36 hours and T6: 48 hours) of bitter gourd seeds of Palee variety, the most popular variety among the farmers. The highest water uptake and germination were found in 48 hours of seed hydro-primed seeds whereas the lowest water uptake and germination were observed on non-primed seeds. Similarly, the tallest seedling, most vigorous seedling in terms of seedling vigour index I and II was observed in 48 hours hydro-primed seeds followed by 36 hours of seed hydro-priming and shortest seedling and the least vigorous seedling in control. Thus 48 hours of seed hydro-priming was found to be effective for increasing germination and seedling growth in bitter gourd, which needs to be further investigated under large, open-field conditions with different varieties.

Assessment of Airway Parameters for Predicting Difficult Laryngoscopy and Intubation in a Tertiary Center in Western Nepal.

BACKGROUND: The screening tests used for pre-operative evaluation of airway to predict difficult laryngoscopy and intubation have variable diagnostic accuracy. The unanticipated poor laryngeal view is gold standard for defining difficult intubation. We aimed to find out the prevalence of difficult laryngoscopy and intubation, which airway parameter better predicts difficult intubation and whether difficult laryngoscopy is associated with difficult intubation or not. METHODS: This analytic cross sectional study was conducted in 665 ASA I/II adult patients, aged 18-65, without obvious airway pathology undergoing elective surgery under general anesthesia. The pre-operative screening tests included mouth opening, modified mallampatti, ratio of height to thyromental distance, sternomentaldistance and upper lip bite test. Cormack-Lehane grade III/ IV was defined as difficult laryngoscopy and potentially difficult intubation. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy and area under curve at 95% confidence interval was calculated for all five screening tests. RESULTS: The prevalence of difficult laryngoscopy and intubation was 6.6% (44 cases). The upper lip bite test because of its highest specificity, positive predictive value, negative predictive value, accuracy and area under curve (99.7%; 93.9%; 99.7%; 95.2%; 85.1% respectively) with moderate level of sensitivity (70.5%) was better predictor of difficult intubation than other tests. The difficult laryngoscopy was associated with difficult intubation (p=0.00). CONCLUSIONS: The prevalence of difficult laryngoscopy and intubation was 6.6%.The upper lip bite test was a better predictor of difficult intubation and there was a significant association of difficult laryngoscopy with difficult intubation.

Genomic Prediction for Winter Survival of Lowland Switchgrass in the Northern USA.

The lowland ecotype of switchgrass has generated considerable interest because of its higher biomass yield and late flowering characteristics compared to the upland ecotype. However, lowland ecotypes planted in northern latitudes exhibit very low winter survival. Implementation of genomic selection could potentially enhance switchgrass breeding for winter survival by reducing generation time while eliminating the dependence on weather. The objectives of this study were to assess the potential of genomic selection for winter survival in lowland switchgrass by combining multiple populations in the training set and applying the selected model in two independent testing datasets for validation. Marker data were generated using exome capture sequencing. Validation was conducted using (1) indirect indicators of winter adaptation based on geographic and climatic variables of accessions from different source locations and (2) winter survival estimates of the phenotype. The prediction accuracies were significantly higher when the training dataset comprising all populations was used in fivefold cross validation but its application was not useful in the independent validation dataset. Nevertheless, modeling for population heterogeneity improved the prediction accuracy to some extent but the genetic relationship between the training and validation populations was found to be more influential. The predicted winter survival of lowland switchgrass indicated latitudinal and longitudinal variability, with the northeast USA the region for most cold tolerant lowland populations. Our results suggested that GS could provide valuable opportunities for improving winter survival and accelerate the lowland switchgrass breeding programs toward the development of cold tolerant cultivars suitable for northern latitudes.

Quantitative Trait Loci for Freezing Tolerance in a Lowland x Upland Switchgrass Population.

Low-temperature related abiotic stress is an important factor affecting winter survival in lowland switchgrass when grown in northern latitudes in the United States. A better understanding of the genetic architecture of freezing tolerance in switchgrass will aid the development of lowland switchgrass cultivars with improved winter survival. The objectives of this study were to conduct a freezing tolerance assessment, generate a genetic map using single nucleotide polymorphism (SNP) markers, and identify QTL (quantitative trait loci) associated with freezing tolerance in a lowland × upland switchgrass population. A pseudo-F2 mapping population was generated from an initial cross between the lowland population Ellsworth and the upland cultivar Summer. The segregating progenies were screened for freezing tolerance in a controlled-environment facility. Two clonal replicates of each genotype were tested at six different treatment temperatures ranging from -15 to -5°C at an interval of 2°C for two time periods. Tiller emergence (days) and tiller number were recorded following the recovery of each genotype with the hypothesis that upland genotype is the source for higher tiller number and early tiller emergence. Survivorship of the pseudo-F2 population ranged from 89% at -5°C to 5% at -15°C with an average LT50 of -9.7°C. Genotype had a significant effect on all traits except tiller number at -15°C. A linkage map was constructed from bi-allelic single nucleotide polymorphism markers generated using exome capture sequencing. The final map consisted of 1618 markers and 2626 cM, with an average inter-marker distance of 1.8 cM. Six significant QTL were identified, one each on chromosomes 1K, 5K, 5N, 6K, 6N, and 9K, for the following traits: tiller number, tiller emergence days and LT50. A comparative genomics study revealed important freezing tolerance genes/proteins, such as COR47, DREB2B, zinc finger-CCCH, WRKY, GIGANTEA, HSP70, and NRT2, among others that reside within the 1.5 LOD confidence interval of the identified QTL.