Predicting sojourn times across dementia disease stages, institutionalization, and mortality

INTRODUCTION

Inferring the timeline from mild cognitive impairment (MCI) to severe dementia is pivotal for patients, clinicians, and researchers. Literature is sparse and often contains few patients. We aim to determine the time spent in MCI, mild-, moderate-, severe dementia, and institutionalization until death.

METHODS

Multistate modeling with Cox regression was used to obtain the sojourn time. Covariates were age at baseline, sex, amyloid status, and Alzheimer's disease (AD) or other dementia diagnosis. The sample included a register (SveDem) and memory clinics (Amsterdam Dementia Cohort and Memento).

RESULTS

Using 80,543 patients, the sojourn time from clinically identified MCI to death across all patient groups ranged from 6.20 (95% confidence interval [CI]: 5.57-6.98) to 10.08 (8.94-12.18) years.

DISCUSSION

Generally, sojourn time was inversely associated with older age at baseline, males, and AD diagnosis. The results provide key estimates for researchers and clinicians to estimate prognosis.

Determinants of informal care time, distress, depression, and quality of life in care partners along the trajectory of Alzheimer's disease

Introduction

We evaluated determinants associated with care partner outcomes along the Alzheimer's disease (AD) stages.

Methods

We included n = 270 care partners of amyloid-positive patients in the pre-dementia and dementia stages of AD. Using linear regression analysis, we examined determinants of four care partner outcomes: informal care time, caregiver distress, depression, and quality of life (QoL).

Results

More behavioral symptoms and functional impairment in patients were associated with more informal care time and depressive symptoms in care partners. More behavioral symptoms were related with more caregiver distress. Spouse care partners spent more time on informal care and QoL was lower in female care partners. Behavioral problems and subtle functional impairment of the patient predisposed for worse care partner outcomes already in the pre-dementia stages.

Discussion

Both patient and care partner determinants contribute to the care partner outcomes, already in early disease stages. This study provides red flags for high care partner burden.

Life satisfaction across the entire trajectory of Alzheimer's disease: A mediation analysis

Introduction

We studied life satisfaction across Alzheimer's disease (AD) stages and studied mobility and meaningful activities as mediators of the associations between these AD stages and life satisfaction.

Methods

In this cross-sectional study, we included n = 269 amyloid-positive patients with subjective cognitive decline (SCD), mild cognitive impairment (MCI), and AD dementia from the Amsterdam Dementia Cohort. Life satisfaction was measured with the satisfaction with life scale. The mediating role of transportation, work, sports, and hobbies on life satisfaction was examined in single and multiple mediator models.

Results

Patients with dementia are less satisfied with life compared to SCD and MCI. These differences in life satisfaction are explained by reduced participation in meaningful activities, which in turn, was largely attributable to decreased transportation use.

Discussion

Our findings suggest that improving access to transportation, therewith allowing participation in meaningful activities help to maintain life satisfaction and may be an important target for intervention.

A more precise diagnosis by means of amyloid PET contributes to delayed institutionalization, lower mortality, and reduced care costs in a tertiary memory clinic setting

INTRODUCTION

We aim to study the effect of a more precise diagnosis, by means of amyloid positron emission tomography (PET), on institutionalization, mortality, and health-care costs.

METHODS

Between October 27, 2014 and December 31, 2016, we offered amyloid PET to all patients as part of their diagnostic work-up. Patients who accepted to undergo amyloid PET (n = 449) were propensity score matched with patients without amyloid PET (n = 571, i.e., no PET). Matched groups (both n = 444) were compared on rate of institutionalization, mortality, and health-care costs in the years after diagnosis.

RESULTS

Amyloid PET patients had a lower risk of institutionalization (10% [n = 45] vs. 21% [n = 92]; hazard ratio [HR] = 0.48 [0.33-0.70]) and mortality rate (11% [n = 49] vs. 18% [n = 81]; HR = 0.51 [0.36-0.73]) and lower health-care costs in the years after diagnosis compared to matched no-PET patients (β = -4573.49 [-6524.76 to -2523.74], P-value < 0.001).

DISCUSSION

A more precise diagnosis in tertiary memory clinic patients positively influenced the endpoints of institutionalization, death, and health-care costs.

A longitudinal study on quality of life along the spectrum of Alzheimer's disease

BACKGROUND

Quality of life (QoL) is an important outcome from the perspective of patients and their caregivers, in both dementia and pre-dementia stages. Yet, little is known about the long-term changes in QoL over time. We aimed to compare the trajectories of QoL between amyloid-positive and amyloid-negative SCD or MCI patients and to evaluate QoL trajectories along the Alzheimer's disease (AD) continuum of cognitively normal to dementia.

METHODS

We included longitudinal data of 447 subjective cognitive decline (SCD), 276 mild cognitive impairment (MCI), and 417 AD dementia patients from the Amsterdam Dementia Cohort. We compared QoL trajectories (EQ-5D and visual analog scale (VAS)) between (1) amyloid-positive and amyloid-negative SCD or MCI patients and (2) amyloid-positive SCD, MCI, and dementia patients with linear mixed-effect models. The models were adjusted for age, sex, Charlson Comorbidity Index (CCI), education, and EQ-5D scale (3 or 5 level).

RESULTS

In SCD, amyloid-positive participants had a higher VAS at baseline but showed a steeper decline over time in EQ-5D and VAS than amyloid-negative participants. Also, in MCI, amyloid-positive patients had higher QoL at baseline but subsequently showed a steeper decline in QoL over time compared to amyloid-negative patients. When we compared amyloid-positive patients along the Alzheimer continuum, we found no difference between SCD, MCI, or dementia in baseline QoL, but QoL decreased at a faster rate in the dementia stage compared with the of SCD and MCI stages.

CONCLUSIONS

QoL decreased at a faster rate over time in amyloid-positive SCD or MCI patients than amyloid-negative patients. QoL decreases over time along the entire AD continuum of SCD, MCI and dementia, with the strongest decrease in dementia patients. Knowledge of QoL trajectories is essential for the future evaluation of treatments in AD.

Development of multivariable prediction models for institutionalization and mortality in the full spectrum of Alzheimer’s disease

Background

Patients and caregivers express a desire for accurate prognostic information about time to institutionalization and mortality. Previous studies predicting institutionalization and mortality focused on the dementia stage. However, Alzheimer’s disease (AD) is characterized by a long pre-dementia stage. Therefore, we developed prediction models to predict institutionalization and mortality along the AD continuum of cognitively normal to dementia.

Methods

This study included SCD/MCI patients (subjective cognitive decline (SCD) or mild cognitive impairment (MCI)) and patients with AD dementia from the Amsterdam Dementia Cohort. We developed internally and externally validated prediction models with biomarkers and without biomarkers, stratified by dementia status. Determinants were selected using backward selection (p<0.10). All models included age and sex. Discriminative performance of the models was assessed with Harrell’s C statistics.

Results

We included n=1418 SCD/MCI patients (n=123 died, n=74 were institutionalized) and n=1179 patients with AD dementia (n=413 died, n=453 were institutionalized). For both SCD/MCI and dementia stages, the models for institutionalization and mortality included after backward selection clinical characteristics, imaging, and cerebrospinal fluid (CSF) biomarkers. In SCD/MCI, the Harrell’s C-statistics of the models were 0.81 (model without biomarkers: 0.76) for institutionalization and 0.79 (model without biomarker: 0.76) for mortality. In AD-dementia, the Harrell’s C-statistics of the models were 0.68 (model without biomarkers: 0.67) for institutionalization and 0.65 (model without biomarker: 0.65) for mortality. Models based on data from amyloid-positive patients only had similar discrimination.

Conclusions

We constructed prediction models to predict institutionalization and mortality with good accuracy for SCD/MCI patients and moderate accuracy for patients with AD dementia. The developed prediction models can be used to provide patients and their caregivers with prognostic information on time to institutionalization and mortality along the cognitive continuum of AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-022-01053-0.

Psychosocial Effects of COVID-19 Measures on (Pre-)Dementia Patients During Second Lockdown

BACKGROUND

The COVID-19 pandemic poses enormous social challenges, especially during lockdown. People with cognitive decline and their caregivers are particularly at risk of lockdown consequences.

OBJECTIVE

To investigate psychosocial effects in (pre-)dementia patients and caregivers during second lockdown and compare effects between first and second lockdown.

METHODS

We included n = 511 (pre-)dementia patients and n = 826 caregivers from the Amsterdam Dementia Cohort and via Alzheimer Nederland. All respondents completed a self-designed survey on psychosocial effects of COVID-19. We examined relations between experienced support and psychosocial and behavioral symptoms using logistic regression. In a subset of patients and caregivers we compared responses between first and second lockdown using generalized estimating equation.

RESULTS

The majority of patients (≥58%) and caregivers (≥60%) reported that family and friends, hobbies, and music helped them cope. Support from family and friends was strongly related to less negative feelings in patients (loneliness: OR = 0.3[0.1-0.6]) and caregivers (loneliness: OR = 0.2[0.1-0.3]; depression: OR = 0.4[0.2-0.5]; anxiety: OR = 0.4[0.3-0.6]; uncertainty: OR = 0.3[0.2-0.5]; fatigue: OR = 0.3[0.2-0.4]; stress: OR = 0.3[0.2-0.5]). In second lockdown, less psychosocial and behavioral symptoms were reported compared to first lockdown (patients; e.g., anxiety: 22% versus 13%, p = 0.007; apathy: 27% versus 8%, p < 0.001, caregivers; e.g., anxiety: 23% versus 16%, p = 0.033; patient's behavioral problems: 50% versus 35%, p < 0.001). Patients experienced more support (e.g., family and friends: 52% versus 93%, p < 0.001; neighbors: 28% versus 66%, p < 0.001).

CONCLUSION

During second lockdown, patients and caregivers adapted to challenges posed by lockdown, as psychosocial and behavioral effects decreased, while patients experienced more social support compared to first lockdown. Support from family and friends is a major protective factor for negative outcomes in patients and caregivers.

Psychosocial effects of Corona virus measures on (pre‐)dementia patients during 2 nd lockdown

Background

The COVID‐19 pandemic poses enormous social challenges, especially during lockdown. Recently, the second lockdown started in the Netherlands. We aimed to investigate and compare the psychosocial effects of corona measures during lockdown in memory clinic (pre‐)dementia patients and their caregivers.

Method

During second lockdown, n=137 symptomatic patients (age=67.7±6.54, 36.5%F, MMSE = 24.4±4.7; n=82 dementia, n=55 MCI), n=244 cognitively normal (age=63.6±7.56, 38.9%F, MMSE = 28.8±1.18; SCD) and n=198 caregivers of Alzheimer Center Amsterdam completed a survey on psychosocial effects of corona. Questions related to loneliness, worries for faster cognitive decline, psychological and behavioral problems. In a subset of patients (n=169) and caregivers (n=38) we were able to compare their answers to answers on a similar survey completed during first lockdown (May 2020).

Result

In total, n=17 (4.5%) patients [n=3 (2.2%) symptomatic, n=14 (5.7%) cognitively normal] and n=8 (4%) caregivers reported a positive test result for COVID‐19. Over one‐third of caregivers reported worries for faster cognitive decline [n=76 (38%)] and behavioral problems [n=70 (35%)] in patients. Feelings of loneliness were experienced by n=23 (17%) symptomatic patients, n=44 (18%) cognitively normal and n=50 (25%) caregivers. One quarter of patients [n=78 (25%)] reported more depressive feelings during lockdown [n=27 (20%) symptomatic, n=51 (21%) cognitively normal]. More feelings of fatigue were reported by n=23 (17%) symptomatic patients, n=46 (19%) cognitively normal, and n=67 (34%) caregivers. Comparing results to those obtained during the first lockdown, feelings of loneliness [Χ²=26.4, p<.001 in patients, Χ²=10.3, p<.001 in caregivers] and anxiety [Χ²=25.9, p<.001 in patients, Χ²=6.69, p=.010 in caregivers] increased. During second lockdown, less feelings of apathy [Χ²=13.0, p<.001], but more depressive feelings [Χ²=27.6, p<.001] were reported in patients compared to first lockdown. Caregivers were more worried for memory decline in patients during second lockdown [Χ²=4.09, p=.043].

Conclusion

Compared to first lockdown, feelings of loneliness, anxiety, worries for faster cognitive decline and depressive feelings increased in second lockdown. A noticeable part of (pre‐)dementia patients and caregivers report feelings of loneliness, worries for faster cognitive decline, psychological and behavioral problems in second lockdown. These psychosocial effects are more frequently reported by caregivers than patients.

Identifying relevant outcomes in the progression of Alzheimer's disease; what do patients and care partners want to know about prognosis?

BACKGROUND

Prognostic studies in the context of Alzheimer's disease (AD) mainly predicted time to dementia. However, it is questionable whether onset of dementia is the most relevant outcome along the AD disease trajectory from the perspective of patients and their care partners. Therefore, we aimed to identify the most relevant outcomes from the viewpoint of patients and care partners.

METHODS

We used a two-step, mixed-methods approach. As a first step we conducted four focus groups in the Netherlands to elicit a comprehensive list of outcomes considered important by patients (n = 12) and care partners (n = 14) in the prognosis of AD. The focus groups resulted in a list of 59 items, divided into five categories. Next, in an online European survey, we asked participants (n = 232; 99 patients, 133 care partners) to rate the importance of all 59 items (5-point Likert scale). As participants were likely to rate a large number of outcomes as "important" (4) or "very important" (5), we subsequently asked them to select the three items they considered most important.

RESULTS

The top-10 lists of items most frequently mentioned as "most important" by patients and care partners were merged into one core outcome list, comprising 13 items. Both patients and care partners selected outcomes from the category "cognition" most often, followed by items in the categories "functioning and dependency" and "physical health." No items from the category "behavior and neuropsychiatry" and "social environment" ended up in our core list of relevant outcomes.

CONCLUSION

We identified a core list of outcomes relevant to patients and care partner, and found that prognostic information related to cognitive decline, dependency, and physical health are considered most relevant by both patients and their care partners.

Tidal volumes at birth as predictor for adverse outcome in congenital diaphragmatic hernia

OBJECTIVE

To assess the predictive value of tidal volume (Vt) of spontaneous breaths at birth in infants with congenital diaphragmatic hernia (CDH).

DESIGN

Prospective study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

Thirty infants with antenatally diagnosed CDH born at Hospital Sant Joan de Déu in Barcelona from September 2013 to September 2015.

INTERVENTIONS

Spontaneous breaths and inflations given in the first 10 min after intubation at birth were recorded using respiratory function monitor. Only expired Vt of uninterrupted spontaneous breaths was included for analysis. Receiver operating characteristics (ROC) analysis was performed and the area under the curve (AUC) was estimated to assess the predictive accuracy of Vt.

MAIN OUTCOME MEASURES

Mortality before hospital discharge and chronic lung disease (CLD) at day 28 of life.

RESULTS

There were 1.233 uninterrupted spontaneous breaths measured, and the overall mean Vt was 2.8±2.1 mL/kg. A lower Vt was found in infants who died (n=14) compared with survivors (n=16) (1.7±1.6 vs 3.7±2.1 mL/kg; p=0.008). Vt was lower in infants who died during admission or had CLD (n=20) compared with survivors without CLD (n=10) (2.0±1.7 vs 4.3±2.2 mL/kg; p=0.004). ROC analysis showed that Vt ≤2.2 mL/kg predicted mortality with 79% sensitivity and 81% specificity (AUC=0.77, p=0.013). Vt ≤3.4 mL/kg was a good predictor of death or CLD (AUC=0.80, p=0.008) with 85% sensitivity and 70% specificity.

CONCLUSION

Vt of spontaneous breaths measured immediately after birth is associated with mortality and CLD. Vt seems to be a reliable predictor but is not an independent predictor after adjustment for observed/expected lung to head ratio and liver position.

Psychosocial Effects of Corona Measures on Patients With Dementia, Mild Cognitive Impairment and Subjective Cognitive Decline

Background: The recent COVID-19 pandemic is not only a major healthcare problem in itself, but also poses enormous social challenges. Though nursing homes increasingly receive attention, the majority of people with cognitive decline and dementia live at home. We aimed to explore the psychosocial effects of corona measures in memory clinic (pre-)dementia patients and their caregivers. Methods: Between April 28th and July 13th 2020, n = 389 patients of Alzheimer center Amsterdam [n = 121 symptomatic (age = 69 ± 6, 33%F, MMSE = 23 ± 5), n = 268 cognitively normal (age = 66 ± 8, 40% F, MMSE = 29 ± 1)] completed a survey on psychosocial effects of the corona measures. Questions related to social isolation, worries for faster cognitive decline, behavioral problems and discontinuation of care. In addition, n = 147 caregivers of symptomatic patients completed a similar survey with additional questions on caregiver burden. Results: Social isolation was experienced by n = 42 (35%) symptomatic and n = 67 (25%) cognitively normal patients and two third of patients [n = 129 (66%); n = 58 (75%) symptomatic, n = 71 (61%) cognitively normal] reported that care was discontinued. Worries for faster cognitive decline were existed in symptomatic patients [n = 44 (44%)] and caregivers [n = 73 (53%)], but were also reported by a subgroup of cognitively normal patients [n = 27 (14%)]. Both patients [n = 56 (46%) symptomatic, n = 102 (38%) cognitively normal] and caregivers [n = 72 (48%)] reported an increase in psychological symptoms. More than three quarter of caregivers [n = 111(76%)] reported an increase in patients' behavioral problems. A higher caregiver burden was experienced by n = 69 (56%) of caregivers and n = 43 (29%) of them reported that a need for more support. Discontinuation of care (OR = 3.3 [1.3-7.9]), psychological (OR = 4.0 [1.6-9.9]) and behavioral problems (OR = 3.0 [1.0-9.0]) strongly related to experiencing a higher caregiver burden. Lastly, social isolation (OR = 3.2 [1.2-8.1]) and psychological symptoms (OR = 8.1 [2.8-23.7]) were red flags for worries for faster cognitive decline. Conclusion: Not only symptomatic patients, but also cognitively normal patients express worries for faster cognitive decline and psychological symptoms. Moreover, we identified patients who are at risk of adverse outcomes of the corona measures, i.e., discontinued care, social isolation, psychological and behavioral problems. This underlines the need for health care professionals to provide ways to warrant the continuation of care and support (informal) networks surrounding patients and caregivers to mitigate the higher risk of negative psychosocial effects.

Current practices used for the prevention of central venous catheter-associated infection in hematopoietic stem cell transplantation recipients: a survey from the Infectious Diseases Working Party and Nurses' Group of EBMT

BACKGROUND

Central line-associated bloodstream infection (CLABSI) is one of the most common infectious complications after hematopoietic stem cell transplantation. To prevent this complication, international guidelines recommend the implementation of the CLABSI 'prevention bundle' consisting of hand hygiene, full barrier precautions, cleaning the insertion site with chlorhexidine, avoiding femoral sites for insertion, and removing unnecessary catheters. The aim of this survey was to analyze to what extent European Group for Blood and Marrow Transplantation (EBMT) centers have included the CLABSI prevention bundle in practice.

METHODS

A questionnaire used for data collection was sent to the 545 EBMT centers worldwide, 103 of which responded.

RESULTS

All 5 components of the CLABSI prevention bundle were recorded in 28% of the centers' standard operating procedures (SOP), and 21% of the centers answered that they used all of the bundle components in clinical practice. The most common recommendation absent from the SOP was specification of all the components of full barrier precautions (43% of the centers did not include at least 1 component). Skin disinfection with chlorhexidine before catheter insertion was reported by 66% centers. CLABSI rates were monitored in 21% of centers.

CONCLUSIONS

Although most of the centers lacked 1 or more of the CLABSI prevention bundle components in their SOP, improvements could easily be made by updating the centers' SOP. The first important step is introduction of CLABSI rate monitoring in this high-risk patient population.

Management of related donor care: a European survey

Donating BM or peripheral stem cells is a challenging process that requires a considerable commitment on the part of the donating individual, especially when there is a relationship between donor and recipient. In order to develop a better understanding of related donor management, the research subcommittee of the European Group for Blood and Marrow Transplantation-Nurses Group (EBMT-NG) designed a questionnaire to survey European transplant centres. This questionnaire investigated several key areas, including guidelines, patient information, donor consent and follow-up services. It was distributed to a sample of delegates (N=150) at the 2005 meeting of the EBMT-NG. Guidelines for the information given to patients were primarily from local (33, 52%), and a combination of local and national (13, 21%) sources. Transplant information was predominantly given to related donors by the recipient's transplant team (36, 57%). A total of 33 (52%) centres indicated that donors were also consented by transplant doctors, whereas 16 (25%) identified that consent was obtained by doctors who were not connected with the transplant team. At present, there is a lack of recognized standardized guidelines for the management of related donors. The development of such guidelines would assist in maintaining patient autonomy, confidentiality and access to accurate and objective information.

An interactive CD-ROM to inform patients about stem cell transplantation

OBJECTIVE

Cancer patients receiving chemotherapy or a Stem Cell Transplantation (SCT) are in need of information about their disease, treatment options and side effects. Patient education usually has to be given within limited time. Under these circumstances, patients may find it difficult to completely understand and to retain the information given.

METHODS

As a supplement to standard information methods we developed an interactive CD-ROM with information on SCT. This CD-ROM provides both medical information and more subjective patients' experiences. Part one provides information regarding the treatment course from diagnosis through to post-discharge care. The second part consists of interviews with former patients and describes their experiences. As the system is interactive, it can be utilised according to the patient's individual preferences. The CD-ROM comprises audio, video, animations, pictures, and text. Printing of certain sections is optional. The technical format of the CD-ROM makes it relatively simple to utilise the information and to make it suitable for other institutions or even other treatments. In this preliminary study the acceptability of the interactive CD-ROM by patients undergoing a SCT is described.

RESULTS

Patients' overall evaluations of the interactive CD-ROM were highly positive. For example, 90.2% (N=51) found it interesting, clear, useful and valued getting information by means of a CD-ROM. Most patients would recommend the interactive CD-ROM to other patients in the same situation.

CONCLUSION

The content of the CD-ROM on SCT as well as the computer-based interactive method are well accepted by patients.

PRACTICE IMPLICATIONS

Computer-based education may enhance patient education and thus the quality of patient care. We must now establish the program's effectiveness. Moreover, plans have been developed to disseminate the information on SCT over the Internet. Future development of comparable programs and their evaluation should be encouraged to promote the well-being of cancer patients.

Monitoring hyperhydration during high-dose chemotherapy: body weight or fluid balance?

Body weight and fluid input/output are usually monitored for checking fluid balance in case of intravenous hyperhydration during nephrotoxic chemotherapy. The reliability of measuring fluid input/output is uncertain. Moreover, this measurement is redundant, complex, labour-intensive and represents an occupational hazard for nurses and other health-care workers handling fluids or body excreta. In a prospective cohort study, we determined the concordance between body weight and fluid intake/output. We also examined the clinical consequences with respect to the safety of selecting only body weight measurement as a parameter for fluid overload. A total of 591 combined observations of fluid balances and body weights were collected. We observed a higher increase in body weight than in fluid balance. The Pearson correlation between fluid balance and body weight was relatively low (r = 0.28). With regard to the safety of measuring body weight only, we found 4 cases (0.6%) who might not have received furosemide if the fluid input/output had not been measured, without clinical consequences, however. After standardization, body weight can safely be used as the only parameter for monitoring fluid retention in case of hyperhydration during chemotherapy.

A genetic linkage map of water yam ( Dioscorea alata L.) based on AFLP markers and QTL analysis for anthracnose resistance

A genetic linkage map of the tetraploid water yam ( Dioscorea alata L.) genome was constructed based on 469 co-dominantly scored amplified fragment length polymorphism (AFLP) markers segregating in an intraspecific F(1) cross. The F(1) was obtained by crossing two improved breeding lines, TDa 95/00328 as female parent and TDa 87/01091 as male parent. Since the mapping population was an F(1) cross between presumed heterozygous parents, marker segregation data from both parents were initially split into maternal and paternal data sets, and separate genetic linkage maps were constructed. Later, data analysis showed that this was not necessary and thus the combined markers from both parents were used to construct a genetic linkage map. The 469 markers were mapped on 20 linkage groups with a total map length of 1,233 cM and a mean marker spacing of 2.62 cM. The markers segregated like a diploid cross-pollinator population suggesting that the water yam genome is allo-tetraploid (2n = 4 x = 40). QTL mapping revealed one AFLP marker E-14/M52-307 located on linkage group 2 that was associated with anthracnose resistance, explaining 10% of the total phenotypic variance. This map covers 65% of the yam genome and is the first linkage map reported for D. alata. The map provides a tool for further genetic analysis of traits of agronomic importance and for using marker-assisted selection in D. alata breeding programmes. QTL mapping opens new avenues for accumulating anthracnose resistance genes in preferred D. alata cultivars.

A genetic linkage map of Guinea yam ( Dioscorea rotundata Poir.) based on AFLP markers

A genetic linkage map of the tetraploid white yam ( Dioscorea rotundata Poir.) was constructed based on 341 co-dominantly scored amplified fragment length polymorphism (AFLP) markers segregating in an intraspecific F(1) cross. The F(1) mapping population was produced by crossing a landrace cultivar TDr 93-1 as female parent to a breeding line TDr 87/00211 as the male parent. The marker segregation data were split into maternal and paternal data sets, and separate genetic linkage maps were constructed since the mapping population was an F(1) cross between two presumed heterozygous parents. The markers segregated like a diploid cross-pollinator population suggesting that the D. rotundata genome is an allo-tetraploid (2n = 4 x = 40). The maternal map comprised 155 markers mapped on 12 linkage groups with a total map length of 891 cM. Three linkage groups consisted of maternal parent markers only. The paternal map consisted of 157 markers mapped on 13 linkage groups with a total map length of 852 cM. Three and one quantitative trait loci (QTLs) with effects on resistance to Yam Mosaic Virus (YMV) were identified on the maternal and paternal linkage maps, respectively. Prospects for detecting more QTLs and using marker-assisted selection in white yam breeding appear good, but this is subject to the identification of additional molecular markers to cover more of the genome.

A genetic linkage map of water yam ( Dioscorea alata L.) based on AFLP markers and QTL analysis for anthracnose resistance

A genetic linkage map of the tetraploid water yam ( Dioscorea alata L.) genome was constructed based on 469 co-dominantly scored amplified fragment length polymorphism (AFLP) markers segregating in an intraspecific F(1) cross. The F(1) was obtained by crossing two improved breeding lines, TDa 95/00328 as female parent and TDa 87/01091 as male parent. Since the mapping population was an F(1) cross between presumed heterozygous parents, marker segregation data from both parents were initially split into maternal and paternal data sets, and separate genetic linkage maps were constructed. Later, data analysis showed that this was not necessary and thus the combined markers from both parents were used to construct a genetic linkage map. The 469 markers were mapped on 20 linkage groups with a total map length of 1,233 cM and a mean marker spacing of 2.62 cM. The markers segregated like a diploid cross-pollinator population suggesting that the water yam genome is allo-tetraploid (2n = 4 x = 40). QTL mapping revealed one AFLP marker E-14/M52-307 located on linkage group 2 that was associated with anthracnose resistance, explaining 10% of the total phenotypic variance. This map covers 65% of the yam genome and is the first linkage map reported for D. alata. The map provides a tool for further genetic analysis of traits of agronomic importance and for using marker-assisted selection in D. alata breeding programmes. QTL mapping opens new avenues for accumulating anthracnose resistance genes in preferred D. alata cultivars.