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Title: VARIATIONS AMONG U.S. ACCESSIONS OF COMMON COCKLEBUR (XANTHIUM STRUMARIUM)

Author
item WASSOM, JAMES - UNIV OF ILLINOIS
item TRANEL, PATRICK - UNIV OF ILLINOIS
item WAX, LOYD

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: The weed common cocklebur is an adaptable species found over a wide range of environments. We collected many common cocklebur accessions or biotypes from 14 states and grew 28 of them in at Urbana, IL in 1998 and 1999 to compare their growth, physiology, and morphology in a common environment to determine whether recommendations for control of specific biotypes might be practical. These plants were measured for a wide variety of characteristics, including their heights and widths at various times, flowering date, insect damage, harvest weight, photosynthesis rate, and several other characteristics. We found that years significantly affected some of the heights and widths, flowering date and insect damage. There was a significant year by accession interactions for some heights and widths, flowering date, insect damage and petiole color. The accessions were different from each other for all measured variables except maximum width in 1998 and stomatal conductance in 1999. Accessions from the northern states usually flowered earlier, however, a few of the earliest flowering accessions were from southern states. Accessions from diverse regions were sometimes grouped together by a cluster analysis procedure. We conclude that the accessions differ for traits that may affect weediness, but nearby accessions differ too frequently to recommend regional, biotype-specific management strategies. These results provide fundamental information about the biology of widely diverse common cocklebur accessions, that should be useful to public and private research and extension personnel as they plan and conduct research and develop guidelines for weed management wherever common cocklebur is a problem.

Technical Abstract: Common cocklebur is an adaptable species found in diverse environments. We grew 28 common cocklebur accession form 14 states at Urbana, IL to compare their growth, physiology, and morphology in a common environment in order to determine whether regional recommendations for control of specific biotypes might be practical. Accessions were evaluated for mid- season and maximum heights and widths, flowering date, insect damage,a nd petiole color in 1998 and 1999. Harvest weight, photosynthetic rate, stomatal conductance, chlorophyll content, and descriptors of leaf and bur morphology were also measured in 1999. Years significantly affected mid- season and maximum widths, mid-season height, flowering date, and insect damage. The year by accession interaction was significant for mid-season and maximum heights and widths, flowing date, insect damage, and petiole color. Accessions differed significantly for all measured variables except maximum width in 1998 and stomatal conductance in 1999, Accessions from northern states usually flowered earlier and flowering date was negatively correlated with latitude of origin (1998 r= -0.76, 1999 r=- 0.60). Nevertheless, some of the earliest flowering accessions were from southern states. Accessions from diverse regions were sometimes grouped together in cluster analysis. We conclude that the accessions differ for traits that may affect weediness, but proximal accessions differ too frequently to recommend regional, biotype-specific control strategies.