ISHS Acta Horticulturae 810: IX International Vaccinium Symposium
BREEDING FOR FRUIT ROT RESISTANCE IN VACCINIUM MACROCARPON |
| Authors: | J. Johnson-Cicalese, N. Vorsa, J. Polashock |
| Keywords: | cranberry, Phyllosticta vaccinii, Physalospora vaccinii, Glomerella cingulata, Colletotrichum gloeosporioides |
| Abstract:
The cranberry fruit rot complex can cause severe crop loss and requires multiple fungicide applications each year. To identify sources of fruit rot resistance, fungicides were withheld from our germplasm collection in 2003 and 2004 and the collection was rated for fruit rot. In Sept. 2003, 70% of the 562 plots had severe rot, while 6% showed some level of resistance. Visual ratings correlated with quantitative assessments. In 2004, several accessions continued to show resistance, and there was significant correlation between the 2003 and 2004 ratings (r=0.80) and counts (r=0.75). Three of the resistant accessions had previously been used in crosses and their progeny had been planted in a large progeny evaluation trial. Fungicides were withheld in 2005–2007 and the trial was rated each year for fruit rot. In 2007, disease pressure was so severe that of the 1644 progeny evaluated from 30 crosses (four of these crosses had a resistant parent), 1085 progeny exhibited nearly 100% rot, while only 13 plots had a rating of ‘2’ (<40% fruit rot). Families from resistant parents had a higher frequency of resistant progeny, indicating additive genetic effects, and the potential for improving resistance through breeding. However, a few resistant progeny originated from susceptible parents suggesting non-additive variance for field fruit rot resistance also exists. Fruit cultured from susceptible and resistant plots had the same species of fruit rot fungi present (primarily Phyllosticta vaccinii, Physalospora vaccinii and Colletotrichum gloeosporioides), suggesting broad-based resistance. DNA fingerprinting of resistant accessions identified several distinct types, offering potentially different sources of genetic resistance. These fruit rot-resistant plants have now been used in 60 crosses. Molecular markers for resistance are being developed, which will allow for more efficient progeny screening. | |
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