Biology subjects

Barnard, S.

Publications and source records attributed to Barnard, S..

3 recordsLinked to original sources

bioRxiv2024

Root metaxylem area influences drought tolerance and transpiration in pearl millet in a soil texture dependent manner

O_LIPearl millet is a key cereal for food security in drylands but its yield is strongly impacted by drought. We investigated how root anatomical traits contribute to mitigating the effects of vegetative drought stress in pearl millet. C_LIO_LIWe examined associations between root anatomical traits and agronomical performance in a pearl millet diversity panel under irrigated and vegetative drought stress treatments in field trials. The impact of associated anatomical traits on transpiration was assessed using subpanels grown in different soil within a greenhouse. C_LIO_LIIn the field, total metaxylem area was positively correlated with grain weight and its maintenance under drought. In the greenhouse, genotypes with larger metaxylem area grown in sandy soil exhibited a consumerist water use strategy under irrigation, which shifted to a conservative strategy under drought. Water savings was mediated by transpiration restriction under high evaporative demand. This mechanism was dependent on soil hydraulics as it was not observed in peat soil with higher hydraulic conductivity upon soil drying. C_LIO_LIWe propose that water savings under drought, mediated by large metaxylem area and its interaction with soil hydraulics, help mitigate vegetative drought stress. Our findings highlight the role of soil hydraulic properties in shaping plant hydraulics and drought tolerance. C_LI

physiology↗

bioRxiv2022

Introducing an rbcL and trnL reference library to aid in the metabarcoding analysis of foraged plants from semi-arid eastern South African savannas

The success of a metabarcoding study is determined by the extent of taxonomic coverage and the quality of records available in the DNA barcode reference database used. This study aimed to create an rbcLa and trnL (UAA) DNA barcode sequence reference database of plant species that are potential herbivore foraging targets and commonly found in semi-arid savannas of eastern South Africa. A study-area-specific species list of 755 species was compiled. Thereafter, reference libraries for rbcLa and trnL (UAA) sequences were created mined from sequence databases according to specific quality criteria to ensure accurate taxonomic coverage and resolution. The taxonomic reliability of these reference libraries was evaluated by testing for the presence of a barcode gap, identifying a data-appropriate identification threshold, and determining the identification accuracy of reference sequences via primary distance-based criteria. The final rbcLa reference dataset consisted of 1238 sequences representing 318 genera and 562 species. The final trnL dataset consisted of 921 sequences representing 270 genera and 461 species. Barcode gaps were found for 76% of the taxa in the rbcL barcode reference dataset and 68% of the taxa in the trnL barcode reference dataset. The identification success rate, calculated with the k-nn criterion was 85.86% for the rbcL dataset and 73.72% for the trnL dataset. The datasets for rbcL and trnL combined during this study are not presented as a complete DNA reference library, but rather as two datasets that should be used in unison to identify plants present in the semi-arid eastern savannas of South Africa.

bioinformatics↗

bioRxiv2019

Development of a fixed list of descriptors for the qualitative behavioural assessment of shelter dogs

The shelter environment may have a severe impact on the quality of life of dogs, and there is thus a need to develop valid tools to assess their welfare. These tools should be sensitive not only to the animals physical health but also to their mental health, including the assessment of positive and negative emotions. Qualitative Behaviour Assessment (QBA) is an integrative whole animal measure that captures the expressive quality of an animals demeanour, using descriptors such as relaxed, anxious, and playful. In this study, for the first time, we developed and tested a fixed-list of qualitative QBA descriptors for application to dogs living in kennels. A list of 20 QBA descriptors was developed based on literature search and an expert opinion survey. Inter-observer reliability was investigated by asking 11 observers to use these descriptors to score 13 video clips of kennelled dogs. Principal Component Analysis (PCA) was used to extract four main dimensions together explaining 70.9% of the total variation between clips. PC1 characterised curious/playful/excitable, sociable demeanour, PC2 ranged from comfortable/relaxed to anxious/nervous/stressed expression, PC3 described fearful demeanour, and PC4 characterized bored/depressed demeanour. Observers agreement on the ranking of video clips on these four expressive dimensions was good (Kendalls W: 0.60-0.80). ANOVA showed a significant effect of observer on mean clip score on all PCs (p<0.05) due to a few observers scoring differently from the rest of the group. These results indicate the potential of the proposed list of QBA terms for sheltered dogs to serve as a non-invasive, easy-to-use assessment tool. However, the observers effect on mean scores points towards the need for adequate observer training. The QBA scoring tool can be integrated with existing welfare assessment protocols for shelter dogs and strengthen the power of those protocols to assess and evaluate the animals experience in shelters.

animal behavior and cognition↗