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## Pawpaw Cultivar, Rootstock, and Training System Trials at Kentucky State University Kirk Pomper, Sheri Crabtree, and Jeremiah Lowe Kentucky State University ===== PAGE 2 ===== ## Introduction: What is Pawpaw?

Pawpaw: Asimina triloba (L.) Dunal. Native tree fruit in the southeastern U.S. Tropical-like flavor mixture of banana, mango, and pineapple. Early stages of commercial production.

===== PAGE 3 ===== ## Pawpaw Flowering and Harvest Flower on 1 year old wood Cross-pollinate Pollinated by flies and beetles Ripe fruit should yield when squeezed and give way with a gentle tug Color change not a reliable indicator of ripeness Fruit may be harvested from the same tree over several weeks

NC-1 ===== PAGE 4 ===== ## Pawpaw Pests Organic production possible? Some Past Problems Japanese beetles Zebra swallowtail butterfly-not necessarily a pest Talponia plummeriana - pawpaw peduncle borer

===== PAGE 5 ===== ## New Pawpaw Diseases and Pests? Leaf and fruit spot (Phyllosticta)

===== PAGE 6 ===== ## New Pawpaw Diseases and Pests?

Photo by Ellen Reeves Asian Ambrosia Beetle Xylosandrus crassiusculus ===== PAGE 7 ===== ## The Kentucky State University Pawpaw Research Program Program Leaders: Brett Callaway (1990-1993), Desmond Layne (1994-1997), and Kirk Pomper (1998-Present)

USDA National Clonal Germplasm Repository for Pawpaw (1994) The orchards at KSU contain more than 2000 accessions sampled from native stands from 17 different states in the papaw's native range. G4-17 ཡོད་པའི་ཆོས་ཀྱི་རྒྱལ་མཚན

===== PAGE 8 ===== ## Pawpaw Regional Variety Trial ===== PAGE 9 ===== ## Collections Neal Peterson and Dr. Harry Swartz began collecting pawpaw germplasm in 1981 They assembled a germplasm collection of about 1500 accessions Open pollinated seedlings from the historic collections of Buckman, Zimmerman, Hershey, Allard, the Blandy Experimental Farm, Ray Schlaanstine, and some modern cultivars

===== PAGE 10 ===== ## Some Desirable Pawpaw Tree characteristics Small tree size, easier harvest Precocious bearing, 4 years or less Vigorous growth with low to medium inputs Open branching with strong crotch angles High flower density High fruit set under natural pollination Consistently high fruit yields Cold hardiness and drought tolerance ===== PAGE 11 ===== ## Some Desirable Pawpaw Fruit Characteristics Some Desirable Characteristics FRUITFULNESS over 40 fruit per tree FLAVOR sweet, firm texture, delicate blend of flavors, rich but not cloying, no bitter aftertaste FLESHINESS visually: mostly flesh. By weight: less than 5% of the fruit is seed FRUIT SIZE over 10 ounces PEARLY bright clear colors, no brown mottling (ripe); even, symmetrical PECULIARITIES ## SEEDS over 45 seeds per oz., av. seeds as small as 3/4" (2 cm) long APPEARANCE bright clear colors, no brown mottling (ripe); even, symmetrical PECULIARITIES SKIN: waxy/ fuzzy/ thick and hard/ yellow/ bluish. FLESH (ripe): white/ pink/ red. SEEDS: in a single row. RIPENING TIME: early / late KEEPING ABILITY: 2+ in refriger. ===== PAGE 12 ===== ## Materials and methods 28 selections, 10 named varieties, 224 total grafted trees on PPF seedling rootstock (half-sib seed) ■ Spacing 2 m (6.5 ft) between trees, 5.5 m (18 ft) between rows Princeton, KY (1995) and Frankfort, KY (1998)

===== PAGE 13 ===== ## Commercially Available Cultivars

Clone	Genetic background
‘Middletown’	Wild seedling from Middletown, Ohio
‘Mitchell’	Wild seedling from Iuka, Ill.
‘NC-1’	‘Davis’ female × ‘Overleese’ male
‘Overleese’	Cultivated (open-pollinated) seedling from Rushville, Ind.
‘PA-Golden’	Second-generation seedling from G.A. Zimmerman collection
‘Sunflower’	Wild seedling from Chanute, Kansas.
‘Taylor’	Wild seedling from Eaton Rapids, Mich.
‘Taytwo’	Wild seedling from Eaton Rapids, Mich.
‘Wells’	Cultivated (open-pollinated) seedlings from Salem, Ind.
‘Wilson’	Wild seedling from Cumberland, Ky.

NC-1

===== PAGE 14 ===== ## Seedlings of Commercially Available Cultivars

Clone	Genetic background
1-7-1 Shenandoah	Open-pollinated seedling of ‘Overleese’
1-23	Open-pollinated seedling of ‘Taylor’
1-68	Open-pollinated seedling from ‘Overleese’
8-20	Open-pollinated seedlings of ‘Sunflower’

===== PAGE 15 ===== ## Seedlings from Collections

Clone	Open-pollinated seedling of
1-7-2 Wabash	BEF-30
2-10	BEF-30
2-54	GAZ-VA
3-11	BEF-33
3-21	BEF-43
4-2 Potomac	BEF-53
5-5	BEF-54
7-90	RS-2
8-58 Rappahannock	BEF-30
9-47	BEF-49
9-58	BEF-50
10-35	BEF-49
11-5 Susquehanna	BEF-53
11-13	BEF-53

BEF = Blandy Experimental Farm Collection, Boyce Va. GAZ = George A. Zimmerman Collection., Linglestown, Pa. RS = Ray Schlaanstine Collection, West Chester, Pa. ===== PAGE 16 ===== Fruit Production on Mature Trees 2004-2006 in Frankfort

Clone	Average fruit weight (g)	Average number of fruit per tree
Potomac	235 a	44 ghi
5-5	188 b	39 hi
Wabash	185 b	65 fg
Susquehanna	184 b	39 i
NC-1	179 bc	44 ghi
Overleese	170 bcd	54 fghi
8-20	170 bcd	59 fghi
1-68	167 bcd	90 cde
2-10	160 cde	52 fghi
Shenandoah	156 def	78 def
Sunflower	155 def	74 def
9-58	146 efg	79 def
10-35	145 efg	[F2]

===== PAGE 17 ===== Fruit Production on Mature Trees 2004-2006 in Frankfort

PA-Golden

Clone	Average fruit weight (g)	Average number of fruit per tree
3-11	137 efgh	68 ef
7-90	135 fghi	74 def
1-23	126 ghij	90 cde
11-13	124 hij	75 def
Taytwo	121 hijk	73 def
2-54	121 hijk	73 def
3-21	115 ijkl	60 fghi
Mitchell	112 jkl	58 fghi
PA-Golden	108 jklm	118 ab
Taylor	106 jklm	68 efg
Wells	104 klm	64 fgh
9-47	100 lm	74 def
Rappahannock
Wilson
Middletown

===== PAGE 18 ===== ## What cultivars should I plant? ===== PAGE 19 ===== ## NC-1 Fruit weight: 167 g Number of fruit/tree: 36 Good flavor Available from many commercial nurseries

NC-1

===== PAGE 20 ===== ## Overleese Fruit weight: 157 g Number of fruit/tree: 40 Good flavor (melon) Available from many commercial nurseries

===== PAGE 21 ===== ## Sunflower Fruit weight: 165 g Number of fruit/tree: 63 Mild flavor Available from many commercial nurseries

Sunflower

===== PAGE 22 ===== ## Potomac Fruit weight: 244 g Number of fruit/tree: 31 Good flavor Fruit cracking? Peterson Pawpaws Limited availability

Potomac

===== PAGE 23 ===== ## Shenandoah Fruit weight: 157 g Number of fruit/tree: 61 Mild flavor Peterson Pawpaws

Limited availability ## Shenandoah ===== PAGE 24 ===== ## Wabash Fruit weight: 183 g Number of fruit/tree: 51 Dark flesh Cracking issues Peterson Pawpaws Limited availability

Wabash

===== PAGE 25 ===== ## Pawpaw RVT Overview There is great variation in fruit size, yield, and quality among the pawpaw selections examined About 4 to 5 years to come into production A number of pawpaw selections in the trial show promise for production in Kentucky [Potomac, Wabash, Overleese, Shenandoah, NC-1, and Sunflower] can be recommended. ===== PAGE 26 ===== ## Rootstock and Training System Trial ===== PAGE 27 ===== ## Pawpaw Propagation and the Nursery Industry High tree prices are limiting development of an industry Seedlings $5-$10 Grafted trees $15-$30

Our goal is to identify seedling rootstocks that would enhance scion growth, improve tree establishment, and promote precocity. ===== PAGE 28 ===== ## Pawpaw Training and Pruning Tend to form narrow-angled weak branches at the trunk. Therefore, pawpaws are prone to wind damage. A central leader training system would develop a strong framework and a desirable form for harvesting. Will pruning dwarf a young tree and delay bearing in pawpaw? Will fruit suffer sunburn? ===== PAGE 29 ===== ## Objective To determine if cultivar, rootstock, and training method would influence early flower bud production in pawpaw

===== PAGE 30 ===== ## Materials and Methods The rootstock trial was planted on May 10, 2004. Rootstocks: 5 seedling rootstocks Scions: 'Sunflower' and 'Susquehanna' Two pruning systems: minimal pruning versus central leader 8 replicate blocks with each treatment combination for a total of 160 trees (2 x 5 x 2 x 8 = 160).

===== PAGE 31 ===== ## Why Did We Choose These Selections? Scions: Sunflower Noted to flower and produce fruit in 4^{th} year in Princeton, KY trial. Susquehanna' Slow to flower and to come into production. ## Seedling rootstocks: Cultivars vigorous: Sunflower and PA-Golden Cultivars lack vigor: Susquehanna and K8-2 Commercial mixed seed: RVT Studies with seedlings in containers Seed size and genetic background important ===== PAGE 32 ===== ## End of 2004

9/21/04 ===== PAGE 33 ===== ## End of 2005

3/03/06 ===== PAGE 34 ===== ## End of 2006

===== PAGE 35 ===== ## End of 2007

KENTUCKY STATE UNIVERSITY 1/28/08 ===== PAGE 36 =====

Central leader 3/23/07 Minimal pruning ===== PAGE 37 =====

Central leader 1/28/08 Minimal pruning ===== PAGE 38 =====

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===== PAGE 40 ===== ## 2008 Growing Season

Scion	Percent of Trees					Number of
Scion	Flowering	Survival	TCA	Flower Density	Clusters	Number of
Susquehanna	94%	68%	14.3	1.6	3.7
Sunflower	100%	82%	14.3	6.0	7.0
P-value	0.04*	0.06 NS	0.64 NS	0.0000***	0.011*

Rootstock	Percent of Trees					Number of
Rootstock	Flowering	Survival	TCA	Flower Density	Clusters	Number of
RVT	96%	77% a	13.8	3.8	4.1
Sunflower	96%	90% a	14.0	4.2	5.6
PA-Golden	100%	84% a	15.7	4.1	6.3
K8-2	95%	73% a	14.0	3.5	3.4
Susquehanna	100%	52% b	13.7	4.7	7.1
P-value	0.63 NS	0.005**	0.32 NS	0.13 NS	0.2041 ns

===== PAGE 41 ===== ## 2008 Growing Season

Training Method	Percent of Trees Flowering	Survival	TCA	Flower Buds Per Tree	Number of Clusters	Number of Fruit
Minimal Pruning	98%	72%	17.4	63	6.8	14.7
Central Leader	97%	79%	11.5	50	4.4	9.3
P-value	0.63 NS	0.20 NS	0.0000***	0.015*	0.0093**	0.003**

No evidence of sun scald on fruit ===== PAGE 42 ===== ## Rootstock and Training System Conclusions Genetic background of seedling rootstock did not influence scion precocity or growth. Survival of Susquehanna seedling rootstock was poor. Sunflower was more precocious than Susquehanna. Central leader training tended to reduce vigor (TCA) and the number of flowers/tree. ===== PAGE 43 ===== ## KENTUCKY STATE UNIVERSITY ### pawpaw.kysu Welcome Personnel Growing Information Recipes and Uses Calendar of Events Reports and Presentations Other KSU Information and Links FAQ and Contact Information KSU Home Page

Photograph of pawpaw flower taken on May 5, 2009. Photo by Jeremy Lowe. pawpaw.kysu provides information on how to grow and use fruit from the North American pawpaw tree.

Over 200,000 visitors since 2003! Pawpaw News Pawpaws Gain Standing as Kentucky Crop (6/28/09) Pomper and Crabtree win Shepard Award for Pawpaw Research (6/18/09) From Novel Fruits (pawpaw), a Lush Landscape in NY Times (5/20/09) Pawpaw article in Northern Nut Growers Association Nutshell Newsletter (5/13/09) Summaries of recent KSU pawpaw research projects (5/06/09) KSU Student wins award for pawpaw research project (see page 7) (5/06/09) ===== PAGE 44 =====

## Questions?