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  • Author or Editor: Alexandra Kravchenko x
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Hassan Salehi, Zahra Seddighi, Alexandra N. Kravchenko and Mariam B. Sticklen

Bermudagrass (Cynodon L.C. Rich.) is grown on more than 4 million ha in the southern United States. The black cutworm (Agrotis ipsilon Hufnagel) is the most commonly encountered pest of bermudagrass, especially on golf course greens. Developing insect-resistant cultivars is a very desirable substitute, both environmentally and economically, to using current synthetic pesticides. Here we report, for the first time, Agrobacterium-mediated transformation of `Arizona Common' common bermudagrass [Cynodon dactylon (L.) Pers.] with the Bacillus thuringiensis Berliner cry1Ac gene encoding an endotoxin active against black cutworm. Mature seeds were used for producing embryogenic callus, and calli were transformed with a plasmid containing a synthetic cry1Ac and the kanamycin resistance (nptII) genes. Putative transgenic calli and plantlets were selected on media containing 100 and 50 mg·L-1 G418, respectively. RNA-blot analysis of PCR-positive lines revealed the expression of the cry1Ac transgene in three out of five putative transgenic lines. The larvae fed on transgenic plant leaves experienced highly significant (over 80%) mortality.

Open access

Thomas O. Green, Alexandra Kravchenko, John N. Rogers III and Joseph M. Vargas Jr.

A major concern with many creeping bentgrass (Agrostis stolonifera) putting greens is annual bluegrass (Poa annua) invasion. The study was designed to garner data regarding the depth of soil removal needed to reduce annual bluegrass seedling emergence in a newly renovated putting green. Research was conducted in different seasons (summer and fall) to evaluate seedling emergence across five soil removal depths in four sampling sites. Cores were collected from four golf courses in southeastern Michigan, subdivided into different soil removal depths, potted in sterile soil media, and established in a growth chamber. Results suggest that excavating soil to a depth of 1.0 inch or, more prudently, to a 1.5-inch depth could minimize annual bluegrass competition in a creeping bentgrass putting green. Annual bluegrass emergence was observed to be greatest in the upper soil depths (0.5–1.5 inches) in both seasons, with minimal emergence (<1.1 plant/0.2 ft2) below the 2.0-inch soil removal depth treatment.