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United States Department of Agriculture

Agricultural Research Service

Ralph Scorza

Research Horticulturist

Dr. Ralph Scorza

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Research Horticulturist and Lead Scientist



Picture of Dr. Ralph Scorza



2217 Wiltshire Road

Kearneysville, WV 25430

Voice: (304) 725-3451 x322


Educational Background:


1970-72      University of Florida; major, Agronomy; B.S. 1972.

1970-72      University of Florida; Certificate in Tropical Agriculture, 1972.

1974-75      University of Florida; major, Fruit Crops Physiology; minor, Citrus
                   Culture; M.S. 1975.

1975-79      Purdue University; major, Horticulture (Genetics and Breeding); Ph.D.



1979-80      Assistant Research Scientist, Department of Fruit Crops, University
                   of Florida, Gainesville, Florida (on contract in Bolivia).

1980-92      Research Horticulturist, ARS, Appalachian Fruit Research Station,
                   Kearneysville, West Virginia.

1992-Present Lead Scientist, Breeding and Cultivar Improvement CRIS, ARS,
                       Appalachian Fruit Research Station, Kearneysville, West Virginia.


Recognitions (past 5 years):

2002          Margaret Crumley Award for Distinguished Achievement in Science,
                  Daytona Beach Community College, Daytona Beach, Florida.

2002          Co-recipient of U.S. Secretary of Agriculture Honor Awards for "Outstanding
                  biotechnology research on controlling Pierce's Disease of grapes to benefit
                  the nation's fruit and wine industries, particularly in California and Florida"
                  and for "Effectively limiting the spread of the invasive and devastating plum
                  pox virus in U.S. stone fruits by building an inclusive team of University,
                  State, Federal, and agricultural industry personnel".

2003          Senior author of the 2002 American Society for Horticultural Science
                  Outstanding Fruit Publication for 2002.

2005          Elected Fellow of the American Society for Horticultural Science

2006          U.S. Embassy Science Fellow - plant biotechnology.  Santiago, Chile.
Current Assignment:


Ralph Scorza is a Research Horticulturist and Lead Scientist for the Genetic
Improvement of Fruit Crops CRIS Work Unit at the USDA-ARS Appalachian
Fruit Research Station


The Genetic Improvement of Fruit Crops CRIS research Project

The broad objectives of the CRIS project are the development of genetic solutions to major problems affecting temperate tree fruit production and consumer acceptance of tree fruits.  This work is being accomplished through a coordinated effort of scientists within our unit and through our cooperation with other research units at our facility, other USDA labs throughout the country, and university, private and governmental laboratories in the U.S. and abroad.  We are working on improving fruit quality through traditional breeding of novel genetic material, and also through the isolation and transgenic manipulation of key genes that control fruit development, stone formation, and ripening.  We are also investigating the possibility of creating marketable stoneless stone fruit varieties.  Stoneless/seedless peaches, cherries, plums, etc. could revolutionize the way we grow, market, and consume these fruits. We are developing solutions to some of the most important disease problems affecting stone fruits and pear in order to improve the sustainability of these crops and to reduce inputs of pesticides. The improvement of resistance to fire blight and psylla in pear is being approached through hybridization of existing resistant germplasm to germplasm with high fruit quality to develop new cultivars which combine these traits.  Gene transfer is being used to produce resistance to virus diseases in stone fruits and particularly Plum pox virus which is an invasive pathogen that is threatening the viability of our stone fruit industry. Basic research on the natural plant virus defense system is underway in order to find ways to increase resistance.  In order to make the best use of the land area devoted to fruit culture and to improve the profitability of small orchard operations we are developing improved tree forms for high-density production systems in peach.  This work is being done through traditional breeding using novel peach germplasm with desirable tree growth habits such as columnar and semi-columnar.  We are developing smaller pear trees through genetic transformation.  Since our program is committed to the application of molecular technologies along with traditional approaches for fruit tree genetic improvement we are also undertaking fundamental and applied work in genetic engineering and risk mitigation.  The utilization of our findings by the industry and the availability of improved fruits to consumers is critical to our program and we evaluate the improved material from our program in collaboration with the fruit industry and through them with consumers.  

Highlights of Ralph Scorza's research program are described below.  For other aspects of the CRIS project research program please visit the sites of individual scientists in the CRIS - Drs. Richard Bell, Ann Callahan, Chris Dardick, Zongrang Liu, and Chinnathambe Srinivasan.

Ralph Scorza research program highlights:

My research program focuses on:

1)   Improvement of peach and nectarine tree form for high density production systems.

2)   Improvement of fruit quality of peaches and nectarines.

3)   Development of Plum pox virus resistant stone fruits.


Improvement of peach and nectarine tree form for high density production systems



Pillar peach trees


The AFRS peach breeding program has been actively pursuing the development of cultivars with several promising tree forms including the columnar or pillar (PI) and upright (UP) forms.  Two varieties, 'CRIMSON ROCKET' and 'SWEET-N-UP' have been released, and a number of selections are in grower tests through a Cooperative Research And Development Agreement (CRADA) with Adams County Nursery, Aspers, PA. Fruit sweetness is one of the most important characteristics related to consumer acceptance.  In order to increase the sugar content of PI and UP germplasm, advanced selections have been hybridized with standard growth habit selections with high sugar content obtained from Dr. David Ramming (ARS Parlier, CA).  This "super-sweet" germplasm is being introgressed into the PI and UP germplasm.  In order to speed this process marker, assisted selection (MAS) is being investigated.  A microsatellite marker for PI was previously isolated as part of a collaborative peach mapping project with Dr. Albert Abbott at ClemsonUniversity.  The marker mapped 12.5 cM from the PI locus and as such, was only able to identify the PI allele in a specific source of PI germplasm that is no longer used due to poor fruit quality.  Dr, Renate Horn (Universit?t Rostock, Germany) is collaborating with our program to develop SSR markers more closely linked to the PI gene such that the allele can be identified from any source.  We anticipate that one a suitable marker is established the process of developing "super-sweet" PI and UP varieties will be more efficient.


Related publications:  (IDFTA meeting Ontario 1999 Dev. Dwarf Fruit Trees; Tworkoski et al Root and Shoot characteristics of peach trees;  Glenn, Scorza, Okie Genetic and Environmental effects 2006)


Development of Plum pox virus resistant stone fruits.


'HoneySweet' plum


Deregulation of 'HoneySweet' plum.  Plum pox virus (PPV) causes Sharka disease, the most serious virus disease of stone fruits.  PPV is spread from tree to tree by aphids and through infected budwood.  Symptoms of plum pox infection include leaf and fruit yellowing, fruit deformation, premature fruit drop, and when in the presence of other Prunus viruses, PPV can cause tree decline.  Originally reported from Bulgaria in the early 1900s, PPV has spread throughout Europe where it has destroyed well over 100 million stone fruit trees.  In the past decade, it has spread from the European continent to India, Egypt, Lebanon, the Azores, Chile, Argentina, and China, and recently, the states of Pennsylvania, New York and Michigan in the U.S., and in Canada.  Plum pox virus was found in commercial peaches in Pennsylvania in the fall of 1999.  Thus far, the eradication program has cost approximately $40 million, and 1600 acres of stone fruits have been destroyed.  PPV is an invasive species and there are few sources of resistance to this virus.   In anticipation of the spread of PPV to the U.S. we began in 1990 a program of genetic engineering resistance to this devastating disease.  Our efforts were successful with the development and testing of the PPV-resistant PPV-CP transgenic plum 'HoneySweet' (formerly C5).  With the serious threat of PPV in the U.S. and its continuing spread, it is imperative to make available to breeding programs and growers 'HoneySweet' plum.  A submission for deregulation of 'HoneySweet' plum was submitted to the U.S. Animal and Plant Health Inspection Service (APHIS) in 2006 and data packages have been submitted to the U.S. Food and Drug Administration (FDA) and the Environmental protection Agency (EPA).




Related publications: Scorza et al Acta Hort 2007 Deregulation of 'HoneySweet'


Related Website: /is/br/plumpox/index.htm


Evaluation of Plum pox virus resistance derived from PPV hairpin constructs in plum. 

Our laboratory has developed a productive and efficient transformation procedure using seed-derived explants from Prunus domestica or European plum.  Using this system we are testing a number of different gene constructs for their ability to provide high levels of PPV resistance to stone fruits.  We are currently testing "hairpin" constructs and have found that these appear to provide resistance.  The level of resistance and the stability of resistance remains to be determined.  Clones that prove to be resistant in greenhouse tests will be transferred to European collaborators for field testing through Dr. Michel Ravelonandro, INRA, Bordeaux, France.  


Related publications:  Hily, Ravelonandro, Damsteegt, Bassett, Petri, Liu, Scorza.  Plum pox virus coat protein gene intron-hairpin (ihpRNA) constructs provide resistance to Plum pox virus in Nicotiana benthamiana and plum (Prunus domestica L.)  J. Amer. Soc. Hort. Sci. (In press)


Transmission of the PPV silencing signal from 'HoneySweet' rootstock to scions.  


The mechanism of silencing, responsible for PPV resistance in 'HoneySweet', has been shown to function across graft junctions in herbaceous plants.  Anecdotal reports indicate that this phenomenon may also hold true in fruit tree species.  The ability to use 'HoneySweet' as a rootstock capable of rendering any grafted variety resistant to PPV has obvious advantages.  Trees grafted to 'HoneySweet' rootstocks would produce non-transgenic pollen and fruit; preventing transgene spread and avoiding problems associated with consumer acceptance.  Moreover, the PPV resistance trait in 'HoneySweet' could be extended to numerous commercial plum cultivars.  To test this possibility, we have produced a series of grafted plants to determine if PPV susceptible cultivars become resistant when grafted to 'HoneySweet' plants. 



Additional 'HoneySweet' GE resistance to PPV publications: Damsteegt et al Prunus host range 2007; Malinowski et al field tests PD 2006; Scorza and Ravelonandro EPPO 2006 control of PPV using GM; Hily et al 2005 MPMI siRNA PPV; Hily et al 2004 Stability of Gene silencing-based resistance;

Last Modified: 8/12/2016
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