AU-Rosa

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i

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Santa Rosa

P. angustifolia (Starcher No. 1)

Santa Rosa

(P. salicina)

Pedigree for AU-Rosa

Information contained herein is available to all without regard to race, color, sex, or national origin.

FIRST PRINTING 4M, NOVEMBER 1990

Cover photos by Roy Roberson, Department of Research Information

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. Abrahams1 INTRODUCTION

AU-Rosa

is a new plum cultivar developed by the Alabama Agricultural 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 (Prunusangustifolia) followed by backcrossing and sibbing of selected seedlings, as shown by the pedigree on page 2. It was developed to meet the need for disease-resistant cultivars in the Southeast where prevalance of certain diseases and susceptibility of commercial varieties had discouraged plum production. CULTIVAR DESCRIPTION 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.
'Respectively, Professor, Research Associate, former Associate Professor, and Technician of Horticulture.

DISEASE RESISTANCE AU-Rosa is highly resistant to bacterial canker (Pseudomona 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.

TABLE 1.

DISEASE RESISTANCE OF PLUM CULTIVARS IN EXPERIMENTAL PLANTINGS AT AUBURN AND SHORTER, ALABAMA

Disease index' Cultivar Bacterial fruit spot 0 0 0 0 0 0 0 3 1 0 5 Bacterial leaf spot 0 0 0 0 0 0 0 0 5 2 1 0 5 Bacterial canker 0 0 0 0 0 0 0 1 5 2 1 0 5 Black knot 0 5 1 0 0 0 0 1 5 5 1 0 0 Brown rot 0 2 2 2 2 4 1 3 3 2 3 3 3 Plum leaf scald 0 1 0 1 1 4 3 1 4 2 4 5 5

AU-Rosa .......... AU-Rubrum..... AU-Amber ....... AU-Producer ... AU-Roadside ... Bruce ............... Crimson ........... Homeside ......... Methley ........... Morris ........... Ozark Premier Purple .............. Santa Rosa ......

'Disease index: 0 = 0,1 = 1-10, 2 = 21-40, 3 = 41-60, 4 = 61-80, and 5 = 91-100 percent of fruit, leaves, and trees infected. Ratings were taken in years when injury from diseases was severe on susceptible cultivars.

FRUIT QUALITY Fruits of AU-Rosa have dark red skin (post office red, HCC 45B) 2 and yellow flesh (saffron yellow HCC 21A) 2 . Fruit quality is excellent for the fresh market, which makes AURosa 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.

2Horticulture Color Chart; Royal Horticulture Society, London.

TABLE 2.

FRUIT CHARACTERISTICS OFPLUM CULTIVARS

Cultivar

Fset

Flesh color

Skin color

Size

Shape Flavor

Flavor

Firmnness

freoeeness
cling cling cling free semi-cling cling cling cling cling cling semi-cling semi-cling

Texture

Solidse
sld

In. AU-Rosa............ 51 AU-Rubrum ....... AU-Amber.......... 5 S AU-Producer ...... AU-Roadside. Bruce .............. 5 5 5 Crimson ............ Homeside........5 Methley
............

Pct.
51

yellow dark red yellow dark red dark red orange to red crimson red cream dark red light red cream cream red

dark red dark red dark red dark red to purple dark red orange to red
crimson red

51

1 21 4-212 13/4-2 13/4-2

5 5 5 5 5
5

5 5 5 5 3 5 5 5

5 5 5 5 3 5 5 5 5 5 .4 5

17.6 15.6 19.2 16.5 17.2 9.4 16.3 18.8 18.5 13.4 15.7 14.8 16.7

2-21/2

13/4-2
11/23/4

5

orange to light red dark red to purple

21/ -21/ 2 4

5 5
4

1-11/4
1 /4-21/4
3

Morris ............... 5 Ozark Premier ........ 5 Purple ..................... 5 Santa Rosa .......... 4

light red
red to purple dark red to purple dark red to purple

2-21/4 23/4-2
1
1

5 5
5

/4-11/2

5

5

cling

'Rating index: 5 = excellent, 4= good, 3 = fair, 2 = poor, and 1= very poor.

TABLE 3.

BLOOM AND HARVEST DATES AND YIELD OF PLUM CULTIVARS
AuburnHeadland

Variety AU-Rosa ........ AU-Rubrum.. AU-Amber ..... AU-Producer. AU-Roadside. Bruce2 . . . . . .... Crimson......... Homeside ...... 3
Methley

Bloom date Harvest date Yield' 3-24 3-22 3-17 3-20 3-22 3-20 3-22 3-20
3-22

Bloom date 3-26 3-24 3-21 3-22 3-22 3-22 3-20
3-24

Harvest date Yield 1 7-1 6-16
5-27

6-22 6-19 5-30 6-27 7-4 6-29 7-14 7-5
6-10

5 5 5 5 5 2 5 5
3

.3-18
3-22 3-23 3-28 3- 26

5 5
5

6-24 6-29 6-26 7-5 7-1
6-7

5 5 5 5 5
5

Morris ......... 3-22 Ozark Premier 3-20 Purple.......... 3-24 3- 24 Santa Rosa 4 ..
2 Trees 3 Trees 4

6-17 7-10 7-20 7- 5

5 4 5 3

6-14 7-5 7-15 7- 1

5 5 5 5

'Yield index: 0 = 10, 1 = very low, 2 = low, 3 = fair, 4 = good, and 5 = excellent.

short lived due to ring spot virus. short lived due to black knot and bacterial canker. Trees short lived due to bacterial canker.

TABLE 4.

MEAN QUALITY EVALUATIONS OF 12 CANNED PLUM CULTIVARS

1

Cultivar

Color

Texture 8 8 9 8 8 8 6 8 8 7 8 8 7

Flavor 8 8 9 8 8 8 7 8 7 6 8 8 5

Overall quality2 8.0 8.0 8.7 8.0 8.0 8.0 6.0 8.0 7.7 6.7 7.4 8.6 6.7

AU-Rosa................. 8 AU-Rubrum ............ 8 AU-Amber ............ 8 AU-Producer............ 8 AU-Roadside............ 8 Crimson .............. 8 Giant Cherry........... 5 Methley .............. 8 Morris ................ 8 Ozark Premier ......... 7 Red June .............. 6 Sapa .................. 10 Starking Delicious.....8
=

'Numerial scores as follows: 9 or 10 = highly acceptable, 7 or 8 = acceptable, 5 or 6 barely acceptable, and below 5 = unacceptable. Mean scores of an expert panel (34 panelists) were obtained on the canned plums after at least 6 weeks warmstorage. 'Overall ratings are the means of all the panelists' three quality ratings.

YIELDS
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 cultivars 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.
TABLE 5. YIELD OF FRUIT OF AU-ROSA AT AUBURN, SHORTER, HEADLAND, THORSBY, AND FAIRHOPE, ALABAMA

Fruit yield per tree Year Auburn Lb. 50 3 .......
4 ....... 70 5 ....... 80 90 6 .......

Shorter Lb. 60
----

Headland Lb. 46
63 74 82

Thorsby Lb. 201
----

Fairhope Lb. 201
171 --

Average Lb. 39
50 77 86

'Reduced crop from late frost injury.

STORAGE 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.
TABLE 6. PERCENT MARKETABLE PLUM FRUIT AFTER STORAGE AT 32°F

Cultivar 3

Marketable, by weeks of storage 6 Pct. 85 85 70 90 70 5 90 65 70 90 65 85 80 9 Pct. 65 65 20 65 20 0 65 15 20 65 15 55 45 12 Pct. 10 10 0 30 0 0 30 0 0 30 0 25 20 14 Pct. 5 5 0 15 0 0 15 0 0 15 0 8 5

Pct. AU -Rosa...................................................100 AU-Rubrum ............................................. 100 AU-Amber................................................ 95 AU-Producer.............................................100 AU-Roadside............................................ 95 B ruce ........................................................ 20 Crim son ................................................... 100 H om eside ................................................. 95 M ethley ..................................................... 95 M orris ....................................................... 100 90 Ozark Premier .......................................... Purple ....................................................... 100 ............................ 100 Santa Rosa....

OUTSTANDING CHARACTERISTICS 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.