Submitted to: North American Strawberry Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/25/2001
Publication Date: 6/20/2002
Citation: Garces, S., Hammerschlag, F.A., Maas, J.L., Koch-Dean, M., Smith, B.J. 2002. Increased resistance to colletotrichum acutatum is exhibited by leaf explant regenerants derived from several strawberry cultivars. North American Strawberry Conference Proceedings. 5:54-57 Interpretive Summary: One of the greatest constraints to strawberry production is the loss caused by diseases, and one of the most serious diseases worldwide is anthracnose caused by the fungus Colletotrichum acutatum. Disease resistant plants offer a solution to this problem and tissue culture-induced variation provides us with one strategy for generating disease resistant crop plants. Studies were conducted to determine if strawberry plants with increased levels of anthracnose resistance could be obtained by regenerating plants from tissue cultures of several commercially important strawberry cultivars. Plants derived from tissue cultures exhibited 1.4 to 3.9-fold increases in levels of disease resistance compared to parental cultivars. These studies suggest that screening of tissue culture-induced variants may be a feasible approach to increasing levels of anthracnose resistance in strawberry cultivars. This research will be of interest to scientists who are interested in improving small fruit crops plants via other methods besides conventional breeding.
Technical Abstract: As part of a program to generate anthracnose (Colletotrichum acutatum Simmonds) resistant strawberry (Fragaria x ananassa Duch.) germplasm, tissue culture studies were conducted to determine whether increased resistance to this fungus could be detected in shoots regenerated from leaf explants derived from several strawberry cultivars differing in their response to this pathogen under field conditions. Shoots were generated (without a callus phase) from explants on MS medium containing either 1 or 10 uM thidiazuron and 0.49 uM indole-3-butyric acid (IBA), propagated on medium containing MS salts, 4.4 uM 6-benzyladenine and 5.7 uM IBA. Four weeks prior to screening, shoots were transferred to propagation medium without growth regulators. Regenerants and cultivars were screened in vitro by soaking leaves from 4-week-old cultures in a spore suspension of C. acutatum isolate Goff for 24 hr, subculturing leaves onto 0.5% water agar, and then scoring leaves for percentage infection after 7 days. Somaclonal variants exhibited 3.5-, 1.7-, 1.7-, 2.1-, 1.4- and 3.9-fold increases in levels of resistance compared to cultivars Chandler, Delmarvel, Honeoye, Latestar, Pelican and Sweet Charlie, respectively. Maximum levels of resistance to C. acutatum were exhibited by somaclonal variants CS-1 and CS-10 (from 'Chandler'), and SS-3, SS-8 and SS-9 (from 'Sweet Charlie'). CS-1, CS-10, SS-3, SS-8 and SS-9 exhibited 17.5 percent, 17.7 percent, 11.7 percent, 14.9 percent and 13.9 percent leaf infection, respectively, compared to 62.4 percent and 45.1 percent for 'Chandler' and 'Sweet Charlie', respectively.