Biological control of bacteria with bacteriophages is a viable alternative to antibiotics. To be successful, biological control bacteriophages must be stable when exposed to the environment. Stabilization can be achieved through incorporation of bacteriophages into polymers and stabilizers that will be coated onto the seed. For this study, bacteriophages against Clavibacter michiganensis subsp. nebraskensis (Cmn), the causal agent of Goss’s wilt, were incorporated into polyvinyl polymers with alcohol, ether and pyrrolidone functional groups and coated onto maize (Zea mays L.) seeds. The objectives of this study were to evaluate polymers and stabilizers that can protect Clavibacter michiganensis subsp. nebraskensis (CN8) bacteriophages against dehydration during storage. Bacteriophages stability when coated on seed depended on the glass transition temperature (Tg), functional groups of the polymer, and the presence of stabilizers such as sugars and proteins. Polyvinyl alcohol (PVOH) provided the greatest stability for CN8 bacteriophages on seed when coatings did not contain a stabilizer. A possible reason for the greater stability of this coating is having a glass transition temperature (Tg) very close to ambient temperature. PVOH combined with whey protein isolate (WPI) maintained CN8 bacteriophage activity in storage for four months at 26 °C and seven months at 10 °C. This coating also significantly reduced bacterial loads in seedlings grown from contaminated seeds, without affecting seed germination. Bacteriophage-polymer coatings which are stable during drying and storage, and are compatible with biological systems, not only provide an alternative to traditional antibiotics in agriculture, but also provide options for food, environmental and medical applications.
The intensive corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production practices currently used in the Midwestern U.S. concern producers and stakeholders. The negative impact of these two-crop rotations on the environment affects water quality and soil erosion and increases flooding risks. Due to these concerns, cover crops and, specifically, perennial groundcover (PGC) cropping systems have gained greater interest. These perennial species have growing patterns compatible with corn and soybean, and can help rebuild the ecosystem while maintaining good cash crop yields. In addition, producers also are interested in the possible effect of seed size and planting depth on uneven emergence in corn. The successful adoption of PGC systems ultimately depends on the successful corn seedling emergence and consistent yield. The objective of the study was to understand the effects of seed characteristics and placement on emergence, grain yield, and grain quality in corn planted using a Kentucky bluegrass (Poa pratensis L.) (KBG)-PGC and a bare-soil cropping system and to determine grain quality attributes and grain moisture dry-down in a PGC field when compared to a conventional cropping system. Commercially-sized seed and seed sized in the laboratory to represent a narrower seed size distribution were planted in KBG-PGC and bare soil systems at two planting depths (3.18 and 6.35 cm). The two-year experiments were planted in a split-plot RCB design with four replications. Individual plants were flagged at emergence, and ears from each plant were harvested individually. Separating the seed lot into different size distributions did not affect seed germination under ideal (standard germination and speed of germination tests) or stressful (cold test) conditions. Seed size distribution also did not influence emergence rate and yield in a conventional tillage (bare soils) or KBG-PGC system. These results indicate that seed sizing specifications and seed size cutoffs currently used by seed companies are suitable for uniform emergence and maximum grain yield in both cropping systems. Seed placement was crucial to uniform emergence in both cropping systems, while seed size distribution did not play a role in emergence for either system. The PGC cropping system delayed seed corn emergence and reduced grain yields as much as 50%. This information is important for those producers considering adopting a PGC system because it demonstrates that uniform planting depth is more important than seed size distribution.
The lack of seedling emergence uniformity in corn (Zea mays L.) is concerning for producers in the Midwestern U.S. These producers believe that just a few hours delay in emergence can increase interplant competition and decrease single-plant yield, thus reducing overall crop yield. It is speculated that lack of uniformity in seedling emergence occurs due to a variation in seed size within a commercial bag of seed, and variation in seed depth placement at sowing throughout the field. Due to these concerns, producers evaluate size seed variation within the bag before sowing. To date, research has investigated sowing dates, growing degree days, or varying sowing depths to simulate a delay in seedling emergence. These studies are important for understanding the effects of delayed emergence on overall yield, but they fail to examine the effect of inter-plant competition on single-plant yield. The objective of this study was to understand the effect of seed size and sowing depth on emergence and subsequent single-plant yield in a bare soil and a perennial groundcover (PGC) cropping system. Commercially sized seed and seed sized further in the laboratory to obtain a narrower seed size distribution were sown in Kentucky bluegrass and bare soil systems and at two sowing depths of 3.18 and 6.35 cm. The two-year experiment was planted in a split-plot design with four replications. Individual plants were flagged at emergence, and harvested individually. Seed placement was crucial to uniform emergence in both cropping systems, while seed size did not affect emergence in either system. The PGC cropping system delayed seed corn emergence and reduced grain yield as much as 50%. Single-plant yield decreased with delayed corn emergence in both cropping systems. Yield decrease as a function of emergence date followed either a quadratic or linear trend in each growing season, likely related to post emergence environmental factors. This information is important for producers and seed companies to understand the effect of seed size and sowing depth on yield and emergence. This study demonstrates that uniform sowing depth is more important than seed size distribution.
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