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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Research Project #438398

Research Project: Agronomic and Molecular Responses of Maize and Sunflower to Competition with Cover Crops and Alfalfa

Location: Sunflower and Plant Biology Research

Project Number: 3060-21220-033-010-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2020
End Date: Dec 31, 2024

Winter hardy cover crops and forages such as alfalfa provide ecosystem services including suppression of weeds, retention of soil nutrients, and habitat for pollinators in the northern Great Plains. However, competition between cover crops or forages intercropped with commodity crops such as sunflower and maize leads to yield losses. Objectives of this project are to: 1) evaluate the ecosystem benefits (weed suppression and nutrient retention) of winter camelina and alfalfa intercropped with sunflower or maize under field conditions, 2) identify molecular responses of maize and sunflower to inter-specific competition with winter camelina or alfalfa under field conditions, and 3) identify molecular responses of maize and sunflower to intra-specific competition with itself at different densities under field conditions.

Obj. 1: Ecosystem services provided by fall planted winter camelina (weed suppression and nutrient retention) will be evaluated the following spring. Maize will then be inter-cropped with over-wintering camelina at 30- and 60-inch spacing prior to bolting and the impact of inter-specific winter camelina competition on maize yield will be evaluated. Additionally, alfalfa will be inter-cropped with field plots of maize and sunflower planted at 30- and 60-inch row spacing to evaluate inter-specific competition on crop yield and establishment of inter-cropped alfalfa. In the following spring, overwintering alfalfa will be evaluated against a control plot of alfalfa grown without inter-specific competition for weed suppression and nutrient retention. Likewise, control plots of maize and sunflower grown under field conditions without inter-specific competition will also be evaluated for yield, weed suppression and nutrient content. All field plots will have soil samples collected before planting and at harvest for soil nutrient analyses. All treatments will be replicated at least two times in space or time. Obj. 2: Leaf and root samples will be collected from maize inter-cropped with winter camelina at the R4-R6 stages of development. Leaf and root samples will also be collected from alfalfa, maize and sunflower in field plots where alfalfa is inter-cropped with maize and sunflower. RNA will be extracted from all samples and Illumina libraries will be made in-house and sequenced by a commercial sequencing facility to a depth of >15 million reads per library. Sequence data obtained from the libraries will be processed using in-house resources and mapped to the reference genomes of sunflower or maize using the latest methods for transcript unit assembly and counting. Differential expression among genes will be identified by the latest bioinformatics methods and subjected to gene set enrichment and network analyses to identify overrepresented ontologies among biological pathways and molecular mechanisms. Cluster analysis will be used to identify coordinately-expressed, competition-responsive genes suitable for identifying likely regulatory factors. Testable hypotheses regarding the role of specific regulatory factors and competition induced signals will be developed for future analysis Obj. 3: Leaf and root samples at the R4-R6 stage of development will be collected from maize and sunflower planted at normal or double densities (1/2X standard spacing) to evaluate the effect of intra-specific competition on molecular mechanisms. RNA extraction, Illumina libraries and sequencing, processing, mapping, assembly and counts and bioinformatic analyses will be conducted as described in Obj. 2.