Submitted to: North American Strawberry Growers Association Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2007
Publication Date: 12/15/2007
Citation: Chang, P., and Smith, B. J. Response of 'Treasure' and 22 Florida strawberry genotypes to the anthracnose pathogens Colletotrichum acutatum, C. fragariae, and C. gloeosporioides. Pages 69-73. In: Takeda, F., D. T. Handley, and E. B. Poling (ed.). Proc. 2007 N. American Strawberry Symposium. North American Strawberry Growers Association, Kemptville, ON Canada. p. 69-73. 2007. Interpretive Summary: Anthracnose crown rot and fruit rot caused by species of the fungal genus Colletotrichum produce significant losses in strawberry production with crown rot resulting in plant death and fruit rot resulting in unmarketable fruit. Several fungicides provide some control of this disease; however, resistant cultivars is still the most desirable management strategy. J&P Research has patented several strawberry cultivars for use in the annual hill production system used in Florida. The susceptibility of these cultivars as well as other selections from their breeding program was evaluated for resistance to the plant phase of anthracnose. All of the J&P Research clones evaluated were more resistant than the susceptible cultivar, Chandler, and all were more susceptible than the resistant cultivar, Pelican. The development of anthracnose resistant strawberry cultivars directly benefits strawberry growers in the southeastern U.S. The knowledge of the anthracnose susceptibility of breeding lines is of benefit to strawberry breeders developing resistant germplasm and to scientists studying this disease.
Technical Abstract: J&P Research has released three strawberry (Fragaria 'ananassa Duchesne ex Rozier) cultivars for the winter production: ‘Ruby’ in 2001, ‘Gem Star’ in 2002, and ‘Treasure’ in 2002. ‘Treasure’ is now one of the main cultivars grown for winter production in Florida and is a favorite of consumers due to its sweet flavor and glossy dark red color and of strawberry growers due to its high total yield, compact plant with easy to pick fruit on long stems, tolerance to heat, and resistance to anthracnose crown rot (caused by Colletotrichum fragariae and C. gloeosporioides. However, ‘Treasure’ is not resistant to anthracnose fruit rot caused by C. acutatum. With the future goal of releasing other anthracnose resistant strawberry cultivars, advanced clones from J&P Research were evaluated for anthracnose resistance in three trials. Greenhouse grown potted plants of 24 J&P Research clones and the cultivars Chandler (susceptible to anthracnose), Pelican (resistant to anthracnose), Ruby, Gem Star, and Treasure were inoculated with conidial suspensions of isolates of C. acutatum, C. fragariae, and C. gloeosporioides. Inoculated plants were incubated in a dew chamber at 100% RH and 30oC for 48 hr, and then in a greenhouse for 4 wks at a temperature of ~22'C. Disease development based on petiole lesion length and crown rot symptoms was assessed 14 and 30 days after inoculation using a disease severity scale of 0 to 6 (0 = healthy plant with no visible symptoms to 6 = dead plant). In the 2004 trial, plants inoculated with C. acutatum had significantly lower disease severity ratings than those inoculated with C. fragariae. Plants of ‘Ruby’ and the J&P Research clone JP9 had disease severity scores as low as ‘Pelican’ (1.4) In the 2005 and 2006 trials, plants inoculated with C. gloeosporioides had the highest average disease severity score (3.5), and those inoculated with C. acutatum had the lowest average score (2.7). ‘Chandler’ plants had the highest average score to all three Colletotrichum species (4.7) and ‘Pelican’ plants had the lowest score (1.4). All 21 of the J&P Research clones evaluated were more resistant than ‘Chandler’ and more susceptible than ‘Pelican’.