Biology subjects

Domeignoz Horta, L. A.

Publications and source records attributed to Domeignoz Horta, L. A..

3 recordsLinked to original sources

bioRxiv2024

Desmodium Volatiles in "Push-Pull' Agriculture and Protection Against the Fall Armyworm, Spodoptera frugiperda

Push-pull systems for sustainable pest management combine repellent stimuli from intercrops ("push") and attractive stimuli from border plants ("pull") to repel herbivorous insects from a main crop and attract the herbivores natural enemies. The most widespread implementation, intercropping the legume Desmodium with maize surrounded by border grass, reduces damage from the invasive fall armyworm (FAW) Spodoptera frugiperda. However, the three publications to date investigating underlying mechanisms disagree about the role of the Desmodium intercrop and whether it emits volatiles that repel FAW. Here, we synthesize knowledge on the effects of maize-Desmodium push-pull on FAW, report volatiles from two commonly used Desmodium species: Desmodium intortum and D. incanum, and test whether these affect the behavior of gravid FAW moths in bioassays. We detected 25 volatiles from field-grown Desmodium, many in the headspaces of both species, including volatiles previously reported to repel lepidopteran herbivores. In cage oviposition assays, FAW moths preferred to oviposit on maize over Desmodium, but not on maize further from, versus closer to Desmodium plants that were inaccessible to the moths, but sharing the air. In flight tunnel assays, moths approached the headspace of maize more than the shared headspace of maize and Desmodium, but pairwise differences were often insignificant. Thus, headspaces of Desmodium species include volatiles that could repel FAW moths, and gravid moths were generally more attracted to maize and its headspace than to either Desmodium species or mixed maize-Desmodium headspaces. However, our results indicate that volatiles from Desmodium are not sufficient to explain reduced FAW infestation of maize under push-pull cultivation.

ecology↗

bioRxiv2024

The potential of undersown species identity vs. diversity to manage disease in crops

O_LIIn the absence of chemical control with its negative side effects, fungal pathogens can cause large yield losses, requiring us to develop agroecosystems that are inherently disease resistant. Grassland biodiversity experiments often find plant species diversity to reduce pathogen pressure, but whether incorporating high biodiversity levels in agricultural fields have similar effects remains largely unknown. C_LIO_LIWe tested if undersown plant species diversity could reduce barley disease, and whether the effect was mediated through above- or belowground mechanisms, by combining an agricultural field trial with a soil transplant experiment. C_LIO_LIAs predicted, barley disease decreased in the presence of undersown plants. Undersown species richness had no effect, but their abundance led to early season disease reduction. Aboveground mechanisms underpinned this disease reduction. Barley yield slightly decreased with increasing undersown species richness, and undersown species varied in their impact on yield. C_LIO_LIWe identified two undersown species with similar functional traits that contributed most to disease reduction and had the potential to increase barley yield. Furthermore, our results indicate that aboveground mechanisms caused this. We show that agroecosystem functioning can be improved without trade-offs on yield by targeted selection of undersown species. C_LI

ecology↗

bioRxiv2019

Heavy and wet: evaluating the validity and implications of assumptions made when measuring growth efficiency using 18O water

1How microbes allocate carbon to growth vs. respiration plays a central role in determining the ability of soil to retain carbon. This carbon use efficiency (CUE) is increasingly measured using the 18O-H2O method, in which heavy oxygen incorporated into DNA is used to estimate growth. Here we evaluated the validity of some of the assumptions of this method using a literature search, and then tested how violating them affected estimates of the growth component of carbon use efficiency in soil. We found that the 18O method is consistently sensitive to assumptions made about oxygen sources to DNA, but that the effect of other assumptions depends on the microbial community present. We provide an example for how the tools developed here may be used with observed CUE values, and demonstrate that the original conclusions drawn from the data remain robust in the face of methodological bias. Our results lay the foundation for a better understanding of the consequences to the 18O method underlying assumptions. Future studies can use the approach developed here to identify how different incubation conditions and/or treatments might bias its CUE estimates and how trustworthy their results are. Further wet-lab work dissecting the assumptions of the 18O method in soil will help justify the scenarios under which it is reasonable to trust its results.

microbiology↗