Circular 304
November 1990
Alabama Agricultural Experiment Station
Lowell T. Frobish, Director
Auburn University
Auburn, Alabama
AU-Rosa Plum Developed:
Mid-Season, High Yielding, and Disease
Resistant Cultivar Produces Excellent Fruit
|
J.D. Norton, G.E. Boyhan, D.A. Smith, and B.R. Abrahams Professor, Research Associate, former Associate Professor, and Technician of Horticulture, respectively. |
TABLE OF CONTENTS
AU-Rosa is a new plum cultivar developed by the Alabama Agriculture Experiment Station, Auburn University, for growing in areas receiving at least 700 hours of chilling temperature below 45°F. The new cultivar was selected from a cross of Santa Rosa and Starcher No.1 (Prunus angustifolia) followed by backcrossing and sibbing of elected seedlings, as shown by the pedigree below. It was developed to meet the need for disease-resistant cultivars in the Southeast where prevalance of certain diseases and susceptibility of commericial varieties had discouraged plum production.
Trees of AU-Rosa are upright with dark green leaves. In test orchards in Alabama, the trees were vigorous, disease resistant, and long lived. The plant is self-fruitful, flowers profusely, and sets a heavy crop. The cultivar has proven its ability to produce high yields of excellent quality fruit where certain fruit and tree disease problems occur. It is an early maturing cultivar that produces fruit of excellent size and quality.
AU-Rosa is highly resistant to bacterial canker (Pseudonwna syringae, Van hall), bacterial fruit spot [Xanthomonas pruni (E. F. Smith), Dows], bacterial leaf spot (X. pruni), black knot [Apisporina morbosa (Schw.) Ark.], and plum leaf scald (Xylella fastidiosa), table 1.
Fruits of AU-Rosa have dark red skin (post office red, HCC 45B)1 and yellow flesh (saffron yellow HCC 21A) 1. Fruit quality is excellent for the fresh market, which makes AU-Rosa adaptable for home, roadside, and local markets. Fruit have adequate firmness for handling, packing, and shipping to commercial markets, table 2. Maturity date is about 2 weeks after Methley,table 3. Fruits were rated acceptable in canned fruit tests, table 4.
The cultivar has been in trials as Santa Rosa A-5 at five locations in the Alabama Agricultural Experiment Station and in grower trials. It compares favorably with other cult-vars in yield. Production has been highest in central Alabama, table 5. Average yields of marketable fruit per tree were 39 pounds, 50 pounds, 89 pounds, and 81 pounds, respectively, from 3, 4, 5, and 6-year-old trees.
Fruits of AU-Rosa store as well as Crimson, AU-Producer, and Santa Rosa and better than AU-Roadside, AU-Amber, Homeside, and Methley, table 6.
Tree
vigor and tolerance to plum leaf scald are the primary improvements of
AU-Rosa. Trees of AU-Rosa are vigorous and show no evidence of plum leaf
scald, table 1, whereas trees of susceptible
varieties grow much more slowly and show obvious symptoms of plum leaf
scald. Tree vigor is a primary selection criterion in the Southeast, and
the relationship of plum leaf scald to phony peach makes resistance important.
Two other characteristics,
ripening date and skin color at maturity, may be taken collectively as
another important advantage of AU-Rosa. Its fruit ripens on the same date
and is more fully colored at any comparable stage of maturity than Santa
Rosa, tables 2 and 3.
Another improvement of AU-Rosa is increased tree longevity. In test orchards
at two locations in Alabama, trees of AU-Rosa remained in extremely vigorous
condition for 10 years.
1 Horticulture Color Chart; Royal Horticulture Society, London.