Bees increase crop yield in an alleged pollinator-independent almond variety

Abstract

Wild pollinators are declining and the number of managed honey bee colonies is growing slower than agricultural demands for pollination. Because of these contrasting trends in pollinator demand and availability, breeding programs for many pollinator-dependent crops have focused on reducing the need for pollinators. Although numerous crop varieties are now available in the market with the label of pollinator-independent, the real dependence of these varieties on pollinators is mostly unknown. We evaluated the hypothesis of pollinator independence in the Independence almond variety, the fastest growing variety in california that is the main almond production region in the world. in this presumed pollinator-independent variety, we measured the effect of honey bees on fruit set, yield, and kernel nutritional quality at tree level. Fruit set was 60% higher in bee-pollinated than bee-isolated trees, which translated into a 20% increase in kernel yield. Despite its effect on almond production, there was no evidence that bee visitation affected almond nutritional quality. Based on these results, we recommend the use of bees, whether they are wild or managed, to maximize yield even in self-fertile almond varieties.Dependence on animal pollination is increasing in global agriculture 1 . In 2005, the total estimated value of pollination worldwide was about $172 billion and accounted for nearly 10% of the world's agricultural crop production consumed by humans 2 . However, this percentage is increasing year after year as the area cultivated with pollinator-dependent crops is continuously expanding 3 . Unfortunately, wild pollinators are declining whereas managed honey bees are growing slower than agricultural demands for pollination 4,5 . Because of these uneven trends in pollinator demand and availability, breeding programs for many pollinator-dependent crops are targeted to reducing the need of biotic transfer of pollen for ovule fertilization, and thus for seed and fruit production. Many varieties of several typically pollinator-dependent crops are now available in the market with the label of "self-fertile" and sold as pollinator-independent. However, the extent to which these varieties depend on pollinators for either yield quantity or quality under field conditions is unknown.Almond (Prunus dulcis) production in California, USA, clearly illustrates this trend. California produces more than 80% of world's almonds, and the area devoted to this crop is continuously growing 6,7 . For decades, almond varieties cultivated in California have been self-incompatible and growers have relied almost exclusively on managed honey bees (Apis mellifera) for pollen transfer and effective pollination 8,9 . Because of almond's high pollinator-dependence and high-market value, more than a million honey bee colonies are moved to California from all over the U.S. every season, representing the largest man-driven pollination event in the world 10,11 . However, the number of honey bee colonies has been dwindling in the U.S. over the last deca...

Specialized Metabolites in Floral Resources: Effects and Detection in Buff-Tailed Bumblebees

“…It occurs naturally at level of 1,889 ppm in pollen of Prunus dulcis Mill (London-Shafir et al, 2003). This Prunus species is one of the most economically valuable bee-pollinated crop species because of its high pollinator-dependence and high-market value (Sáez et al, 2020), bumblebees counting among the pollinators of almond crop fields (Dag et al, 2006;Marqués et al, 2019). Repeat consumption of such chemically defended pollen can be toxic to bees (Kevan and Ebert, 2005), especially if they are not able to detect the toxic substance.…”

“…In this study, we performed a range of bioassays and behavioral experiments with freely moving workers of the bumblebee Bombus terrestris to determine (1) whether pollen specialized metabolites affect bumblebees at the micro-colony level (resource collection, reproduction and stress response) as well as at individual level (histological damage), (2) and whether bumblebees detect these specialized metabolites and potentially display an avoidance behavior. We focused on amygdalin, scopolamine and sinigrin; three nitrogen-containing metabolites synthesized by different plant families that are actively foraged upon by bumblebees (Erickson and Feeny, 1974;King, 1993;London-Shafir et al, 2003;Ares et al, 2015;Chowański et al, 2016;Sáez et al, 2020). We assume that bumblebees must be able to detect specialized metabolites (either through pre-or post-ingestive effects, or both) that are toxic for them at either the micro-colony or individual level.…”

Additive and synergistic effects of arbuscular mycorrhizal fungi, insect pollination and nutrient availability in a perennial fruit crop

“…2). Increased pollinator visitation rate generally enhances the transfer of pollen for ovule fertilization (Sáez et al . 2020), which may improve fruit set of the plants in the open pollination treatments (Fig.…”

A Regional, Honey Bee-Centered Approach Is Needed to Incentivize Grower Adoption of Bee-Friendly Practices in the Almond Industry

“…Some of these obstacles include uncertainty of native pollinators' contribution to their crop yield, the difficulty of monitoring native pollinators' population size (to determine if there are enough to pollinate an entire crop), a lack of awareness of cost-share programs to support native pollinators, and an existing reliance on honey bees. Continued research could help explain why growers are not more invested in wild bee populations when research indicates that native bees can increase the efficacy of honey bee pollination in almond orchards (Brittain et al, 2013), increase pollination services on large agricultural fields (Carvalheiro et al, 2012), and increase yields on almond varieties that were originally considered self-pollinating, but may actually benefit from some bee pollination (Sáez et al, 2020).…”