The 2011 ASHS Annual Conference

Approximately 1600 one-year-old ‘Redglobe’ peach trees on Guardian® rootstock were inoculated with a Prunus Latent Mosaic Viroid (PLMVd) by chip budding in September 2003.  Vegetative buds from PLMVd-infected ‘Ta Tao 5’ trees were used for the inoculation. ‘Redglobe’ trees were spaced either 3.7 (+ PLMVd), 4.3  (+PLMVd), or 4.9  (-PLMVd) m within rows that were 6.1 m apart.  Trees were trained as an open-center or vase system and located near Ridge Spring, South Carolina.  Data collection included time to summer and dormant prune trees, time to hand thin immature fruit, maturity date, yields, size distribution, and fruit quality for some or all of the years of 2006 and 2008 to 2010.   PLMVd trees bloomed 7-10 days later, and took less time to summer and dormant prune each year.  Time to hand thin viroid trees was significantly more (2 min/tree) in 2008 due to excessive buttons and doubles, but less in 2009 (6 min/tree) and 2010 (5 min/tree).  Yields of viroid-inoculated trees progressively declined on a per acre basis from 116% of the untreated controls in 2006 to only 58, 47, and 63 percent of the controls in 2008, 2009, and 2010, respectively.  Peak harvest in 2008, 2009 and 2010 for PLMVd trees were 7, 9 and 4 days later, respectively.  Fruit size was smaller for PLMVd trees in 2006 and 2010, but larger in 2009 likely due to a reduced crop load.  Fruit from viroid-inoculated trees had similar soluble solids as the controls but had significantly higher titrated acidity and were firmer.  In some years peach warts, which are symptoms of peach viroids, were common on the fruit sutures of viroid-infected fruit.