Data from: Varietal and intrafamilial species diversity influence aphid and yellow dwarf virus pressure within mixtures of wheat and barley

Species diversity and varietal diversity within agricultural fields can
increase crop resilience to plant pathogens and insect pests. The
functional differences between two species in the same family or two
varieties of the same species are often less apparent than the differences
between species in interfamilial polycultures (e.g., cereal-legume
mixtures), but can nevertheless result in yield advantages. Intrafamilial
cereal mixtures are grown for their resilience to drought, weeds, and
disease in parts of northern Africa, Asia, and Europe, though they were
formerly widespread in those regions. Farmers plant multiple cereal
species and varieties within the same field, treating the mixture as a
single crop. In the northeastern United States, we created mixtures using
two varieties of wheat (Triticum aestivum) and two varieties of barley
(Hordeum vulgare) to test whether species and varietal diversity would
reduce the prevalence of globally important pathogens, the yellow dwarf
viruses (YDVs), and their aphid vectors. YDVs are consequential viruses in
agriculture, with localized outbreaks causing significant yield loss in
Europe, Africa, and North America during the second half of the 20th
century. This is the first experimental study of how varietal and species
diversity within an intrafamilial mixture of crop species influences YDV
infection prevalence. We found that the wheat varietal mixture had
significantly less YDV infection than the average of the wheat varieties
grown in monoculture. Aphid pressure was higher in barley monocultures and
most mixtures that contained barley, though the yields of species mixtures
resembled those of their higher-yielding component, wheat. Aphid pressure
may not have been severe enough for us to observe intrafamilial species
mixtures lowering viral prevalence, but mixing wheat and barley did not
lead to higher disease prevalence or reduced yield. Our experimental
results highlight the importance of diversity and identity within
intrafamilial mixtures.