Repeatable Stair-step Assay to Access the Allelopathic Potential of Weedy Rice (Oryza sativa ssp.)

Summary

Allelopathy has shown promise as a useful supplemental weed control strategy in cropping systems. To determine the allelopathic potential of a desired plant specimen, a stair-step screening method is provided.

Abstract

Weed competition contributes significantly to yield losses in cropping systems worldwide. The evolution of resistance in many weed species to continuously applied herbicides has presented the need for additional management methods. Allelopathy is a physiological process that some plant species possess that provide the plant with an advantage over its neighbors. Allelopathic crop varieties would be equipped with the ability to suppress the growth of surrounding competitors, thus reducing potential yield loss due to weed interference. This paper focuses on the construction and operation of a stair-step assay used for the screening of the allelopathic potential of a donor species (Oryza sativa) against a receiver weed species (Echinochloa crus-galli) in a greenhouse setting. The structure described in this paper serves as a stand for the plant samples and incorporates a timed watering system for the accumulation and distribution of allelochemicals. Allelochemicals produced by the plant roots are allowed to flow downward through a series of four pots separately into a collection tank and recycled back to the top plant through electric pumps. This method of screening provides an avenue for the allelochemicals from the donor plant to reach receiver plants without any resource competition, thus allowing quantitative measurement of the allelopathic potential of the selected donor plant. The allelopathic potential is measurable through the height reduction of the receiver plants. Preliminary screening data for the effectiveness of this method demonstrated height reduction in the receiver species, barnyardgrass (E. crus-galli), and thus the presence of allelopathic residues from the donor plant, weedy rice (Oryza sativa).

Introduction

Allelopathy is a natural and complex phenomenon that has been the focus of many plant scientists in the past few decades. The mechanisms relating to allelopathy for use in crops have been the subject of much research since the 1930s, when Molisch observed that a plant has a direct or indirect effect on a neighboring plant through the production and secretion of chemical compounds into the environment¹. Allelopathy is the production of secondary metabolites that have inhibitory effects on the growth and germination of some plant species. Released allopathic chemical compounds help provide the donor plants with a competitive advantage by adding p....

Protocol

1. Stand Construction

NOTE: Measurements for the wood are listed as thickness (cm) x width (cm) x length (m).

1. Cut wood into appropriate sizes and amounts as follows: five 10.16 cm x 5.08 cm x 0.91 m wooden pieces, three 10.16 cm x 5.08 cm x 0.76 m wooden pieces, three 10.16 cm x 5.08 cm x 0.61 m wooden pieces, five 10.16 cm x 5.08 cm x 0.46 m wooden pieces, three 10.16 cm x 5.08 cm x 0.3 m wooden pieces, and three 10.16 cm x 5.08 cm x 0.15 m wooden pieces.
2. For the tallest level, stand one 2.44 m board across two 0.91 m pieces on each end at the edge and drill two screws vertically into each of the 0.91 pieces. Screw on....

Results

Two preliminary screenings using this method were performed on nine weedy rice accessions (B2, S33, B83, S97, S94, B81, B8, B34, B14) and five cultivated rice lines (PI338046, Rex, Rondo, PI312777, CL163). Weedy rice accessions and rice lines were selected based on their performance in previous allelopathic screenings conducted by Shrestha (2018)¹⁸. The weedy rice seeds were collected from across the state of Arkansas. The rice lines selected are commonly grown lines in the US, some known to expre.......

Discussion

Exploiting allelopathy may potentially serve as a biological control for weeds that are difficult to manage^1,7,13. Allelopathy has shown great potential as a possible solution to the weed crisis in rice and serves as an alternative or supplement to chemicals and manual weed control practices^5,13,19. Identifying allelopathic varieties or.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1.25 in by 6 in by 8 ft standard severe weather wood board	Lowe's, Mooresville, NC	489248	N/A
2 in by 4 in by 8 ft white wood stud	Lowe's, Mooresville, NC	6005	Cut into appropriate sizes
63 mm (2.5 in) corner braces	Lowe's, Mooresville, NC	809449	N/A
Asporto 16 oz Round Black Plastic To Go Box - with Clear Lid, Microwavable – 6.25 in by 6.25 in by 1.75 in - 100 count box	Restaurantware.com, Chicago, IL	RWP0191B	black
ATP vinyl-flex PVC food grade plastic tubing, clear, 0.125 in id by 0.25 in od, 100 ft	Amazon, Seattle WA	B00E6BCV0G	N/A
Ccm-300 chlorophyll content meter	Opti-Sciences, Inc. Hudson, NH	ccm/300	N/A
Common 1 in by 2 in by 8 ft pine board	Lowe's, Mooresville, NC	1408	N/A
Contractors choice contractor 24-pack 42-gallon black outdoor plastic construction trash bag	Lowe's, Mooresville, NC	224272	Cut to cover collection tanks
EURO POTS	Greenhouse Megastore, Danville, IL	CN-EU	15 cm short black 6 in diameter 4.25 in height 1.37 qt volume
Fisher brand petri dish with clear lid	Fisher Scientific, Waltham, MA	FB0857513	N/A
Aexit Ac 220 V-240 V electrical equipment US plug 21 W 1,000 L/hr multipurpose submersible pump	Amazon, Seattle WA	B07MBMYQNT	Nozzle size should fit tubes and can be repaced
Woods 50015 WD outdoor 7 day heavy-duty digital outlet timer	Walmart, Bentonville, AR	565179767	20 settings
GE silicone 2+ 10.1 oz almond silicone caulk	Lowe's, Mooresville, NC	48394	Sealant for edges of any attached tubing
Great Value Distilled Water	Walmart, Bentonville, AR	565209428	N/A
Great Value White Basket coffee filters 200 count	Walmart, Bentonville, AR	562723371	Size may vary
Grip-rite primgaurd plus #9-3 in pollimerdex screws	Lowe's, Mooresville, NC	323974	N/A
Hoagland’s No. 2 basal salt mixture	Caisson Laboratories, INC. Smithfield, UT	HOP01/50LT	½ strength rate
JMP (14)	SAS Institute Inc. North Carolina State University, NC		N/A
Project source flat black spray paint	Lowe's, Mooresville, NC	282254	N/A
Project source utility 1.88 in by 165 ft gray duct tape	Lowe's, Mooresville, NC	488070	N/A
Rubbermaid 2 qt square food storage canister clear	Walmart, Bentonville, AR	555115144	Collection tank discard lid
Sealproof unreinforced PVC clear vinyl tubing, food-grade .5 in id by .625 in od, 100 ft	Amazon, Seattle WA	B07D9CLGV3	Connects to pump
Short Mountain Silica 50 lb Play sand	Lowe's, Mooresville, NC	10392	Sand should be purified
Steve Spangler's 1 L Soda Bottles - 6 Pack - For Science Experiment Use	Amazon, Seattle WA	UPC 192407667341	Top step tank discard lid