Multiplex PCR reveals unique trends in pathogen and parasitoid infestations of alfalfa leafcutting brood cells.

The alfalfa leafcutting bee Megachile rotundata Fabricius (HYMENOPTERA: Megachilidae) is an important pollinator for multiple agricultural seed commodities in the United States. Megachile rotundata is a solitary bee that forms brood cocoons where its larvae can develop. During the developmental stages of growth, broods can be preyed upon by multiple different fungal and bacterial pathogens and insect predators and parasitoids, resulting in the loss of the developing larvae. Larval loss is a major concern for alfalfa (Medicago sativa L.) seed producers because they rely on pollinator services provided by Megachile rotundata and reduced pollination rates result in lower yields and increased production costs. In the present study, we examined the taxonomic composition of organisms found within M. rotundata brood cells using a multiplex PCR assay which was developed for the detection of the most common bacterial, fungal, and invertebrate pests and pathogens of M. rotundata larvae. Known pests of M. rotundata were detected, including members of the fungal genus Ascosphaera, the causative agent of chalkbrood. Co-infection of single brood cells by multiple Ascosphaera species was confirmed, with potential implications for chalkbrood disease management. The multiplex assay also identified DNA from more than 2,400 total species including multiple new predators and pathogenetic species not previously documented in associated with M. rotundata brood cells.

Allelopathy and Allelopathic Substances of Fossil Tree Species Metasequoia glyptostroboides

Metasequoia glyptostroboides Hu et W.C. Cheng is one of the oldest living conifer species, and it has remained unchanged for millions of years compared to its fossils from the Cretaceous period. The species are cultivated in the parks, gardens, and roadsides in many countries. We investigated the allelopathy and allelopathic substances in fallen leaves of M. glyptostroboides. An aqueous methanol extract of the fallen leaves inhibited the growth of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), Lolium multiflorum Lam., Phleum pretense L., and Vulpia myuros (L.) C.C.Gmel. The extract was then purified by several chromatographic steps, and two allelopathic substances were isolated and determined by spectral data to be (+)-rhododendrol and 9-epi-blumenol C. The compound inhibited the growth of cress and L. multiflorum. M. glyptostroboides is a deciduous perennial tree, and accumulation of its fallen leaves occur on the soil under the trees. Therefore, those allelopathic substances in the fallen leaves may be liberated into the rhizosphere soil during the decomposition process of fallen leaves and provide a competitive advantage for M. glyptostrob through the growth inhibition of competing plant species nearby. Therefore, M. glyptostroboides is allelopathic, and (+)-rhododendrol and 9-epi-blumenol C may be contribute to the allelopathy.

Comparison of six zero-till seed drill openers for establishment and persistence of sod-seeded alfalfa (Medicago sativa L.) in a cool-season perennial grass pasture

Zero-till seed drills are readily available for crop seeding in the prairie region of western Canada but have not been evaluated for sod-seeding in perennial forage. Sod-seeding a legume, such as alfalfa (Medicago sativa L.), into the existing perennial grass vegetation improves forage yield and quality for ruminant livestock grazing and production. Suppression of the existing vegetation with herbicide has been reported to increase alfalfa seedling establishment. We evaluated six commercially available zero-till seed drill openers by sod-seeding alfalfa into a crested wheatgrass [Agropyron cristatum (L.) Gaertn.] pasture with or without glyphosate suppression of the existing vegetation in Lanigan Saskatchewan. Alfalfa seedling establishment (52.2 vs. 21.9 seedlings m−1 ± 6.8), alfalfa composition (42.5% vs. 0.2% ± 8.6), and alfalfa yield (1105 kg·ha−1 vs. 12 kg·ha−1 ± 206) in 2011 were increased by the application of herbicide. Seed drill openers performed similarly for all three variables. Nine years later, in June 2020, there was greater alfalfa composition (13.3% vs. 0% ± 2.3) and forage yield (1325 vs. 957 kg·ha−1 ± 127) in the sod-seeded plots than in the unseeded controls but the alfalfa plant cover, alfalfa composition, alfalfa yield and forage yield were similar among seed drill openers. There was also no difference in these variables due to herbicide application nine years prior. Livestock producers can utilize currently available zero-till seeding equipment for sod-seeding alfalfa to rejuvenate grass pastures in the thin Black soil zone of western Canada with the expectation of persistence of alfalfa for nine years.