Abstract:
A new and distinct variety of nectarine tree  Prunus persica , and which is denominated varietally as ‘Burnectwenty’, and which produces an attractively colored yellow-fleshed, clingstone, nectarine which is mature for harvesting approximately September 13 to September 23 under ecological conditions prevailing in the San Joaquin Valley of central California.

Description:
Botanical designation:  Prunus persica.    
   Variety denomination: Burnectwenty. 
   BACKGROUND OF THE NEW INVENTION 
   The present invention relates to a new, novel and distinct variety of nectarine tree,  Prunus persica , and which has been denominated varietally as ‘Burnectwenty’ hereinafter. 
   The present variety of nectarine tree resulted from an on-going program of fruit and nut tree breeding. The purpose of this program is to improve the commercial quality of deciduous fruit and nut varieties, and rootstocks, by creating and releasing promising selections of  Prunus, Malus , and  Regia  species. To this end we make both controlled and hybrid cross pollinations each year in order to produce seedling populations from which improved progenies are evaluated and selected. 
   The seedling, ‘Burnectwenty’, was originated by us from a population of seedlings grown in our experimental orchards located near Fowler, Calif. The seedlings, grown on their own roots, were the result of seeds which were derived from an open pollinated seedling, B17.074 (unpatented). B17.074 was the result of a previous cross of the yellow-fleshed clingstone nectarine tree ‘September Red’ (U.S. Pat. No. 5,664), which was used as the seed parent; and the ‘Grant Diamond’ nectarine (U.S. Plant Pat. No. 4,095) which was used as the pollen parent. The open pollination of B17.074 occurred sometime during March 1998. Thereafter seeds from this open pollinated seedling were collected and then planted in September of 1998. One seedling, identified as I 9.076, which is the present variety, exhibited especially desirable characteristics, and was marked for subsequent observation. After the 2000 fruiting season, the new variety of nectarine tree was selected for advanced evaluation and repropagation. 
   ASEXUAL REPRODUCTION 
   Asexual reproduction of this new and distinct variety of nectarine tree was accomplished by budding the new nectarine tree to ‘Nemaguard’ Rootstock (unpatented). This was performed by us in our experimental orchard which is located near Fowler, Calif. Subsequent evaluations have shown those asexual reproductions run true to the original tree. All characteristics of the original tree, and its fruit, were established and appear to be transmitted through succeeding asexual propagations. 
   SUMMARY OF THE VARIETY 
   ‘Burnectwenty’ is a new and distinct variety of nectarine tree, which is considered of large size, and which has vigorous growth. This new nectarine tree is also a regular and productive bearer of relatively large, firm, yellow fleshed, acidic clingstone fruit which have a good flavor and eating qualities. This new tree has a medium chilling requirement of approximately 650 hours, and further produces relatively uniformly sized fruit throughout the tree. In addition, the fruit also appears to have good handling and shipping qualities. Still further, the ‘Burnectwenty’ nectarine tree bears fruit which are ripe for commercial harvesting and shipment on approximately September 13 to September 23 under the ecological conditions prevailing in the San Joaquin Valley Central California. In relative comparison to the seed parent, B17.074, the present nectarine tree bears fruit about 10 or more days earlier at the same geographical location. In comparison to the ‘Grand Diamond’ nectarine tree, the present variety produces a clingstone fruit, whereas ‘Grant Diamond’ produces freestone fruit. In relative comparison to other known varieties, the present variety of nectarine tree is most closely similar to the ‘September Bright’ Nectarine (U.S. Plant Pat. No. 13,475), which, when grown in its natural state, produces fruit that ripen on or about September 1st, whereas the present new variety produces fruit which has a ripening date of September 13 or later. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The accompanying drawing, is a color photograph of the present variety. The photograph depicts two whole mature fruit, and several pieces of sliced fruit dissected substantially in the sagital plane, and one piece of fruit taken from a cross sectional position. The external coloration of the fruit, as shown, as well as the exposed flesh segments, display fruit which are sufficiently matured for harvesting and shipment. Additionally, the photograph displays a sample vegetative shoot bearing typical leaves, and a stone, with the flesh removed. The colors in this photograph are as nearly true as is reasonably possible in a color representation of this type. Due to chemical development, processing and printing, the leaves and fruit depicted in these photographs may or may not be accurate when compared to the actual specimen. For this reason, future color references should be made to the color plates (Royal Horticultural Society) and other more general color descriptions provided hereinafter. 
   

   DETAILED DESCRIPTION 
   Referring more specifically to the pomological details of this new and distinct variety of nectarine tree, the following has been observed during the fourth fruiting season under the ecological conditions prevailing at orchards which are located near the town of Fowler, county of Fresno, state of California. All major color code designations are by reference to The R.H.S. Colour Chart (Fourth Edition) and which is provided by The Royal Horticultural Society of Great Britain. Common color names are also occasionally used.
     Tree:
             Size.— Generally — Considered medium-large as compared to other common commercial nectarine cultivars ripening in the early season of maturity. The tree of the present variety was pruned to a height of approximately 300.0 cm to about 310.0 cm at maturity.     Vigor.— Considered moderately vigorous. The present nectarine tree variety grew from about 130.0 cm to about 135.0 cm in height during the first growing season. The new variety was pruned to a height of approximately 125.0 cm during the first dormant season, and primary scaffolds were then selected for the desired tree structure.     Productivity.— Productive. Fruit set varies from about 1.5 to several times more than the desired crop load. Fruit set is spaced by thinning to develop the remaining fruit into the desired market sized fruit. The number of the fruit set varies with the prevailing climatic conditions, and cultural practices employed, and is therefore not distinctive of the present variety.     Bearer.— Regular. Fruit set has been heavy during the years of observation and thinning was necessary during the past 5 years.     Form.— Upright, and pruned to a vase shape.     Density.— Considered medium dense. It has been discovered that pruning the branches from the center of the tree to obtain a resulting vase shape allows for air movement and appropriate amounts of sunlight to enhance fruit color and renewal of fruiting wood throughout the tree.     Hardiness.— The present tree was grown and evaluated in USDA Hardiness Zone 9. Winter chilling requirements of the new tree are approximately 700 hours below 7.0 degrees C. The variety appears to be hardy under typical central San Joaquin Valley climatic conditions.       
       Trunk:
             Diameter.— Approximately 12.5 cm in diameter when measured at a distance of approximately 15.24 cm above the soil level. The measurement was taken at the end of the fifth growing season.     Bark texture.— Considered moderately rough, with numerous folds of papery scarfskin being present.     Lenticels.— Numerous flat, oval lenticels are present. The lenticels are relatively large, and range in size from approximately 4.0 to about 6.0 millimeters in width, and from 1.0 to about 2.0 millimeters in height.     Lenticel color.— Orange brown, (RHS Greyed-Orange Group N170 A).     Bark coloration.— Variable, but it is generally a medium grey-brown, (RHS Greyed-Orange Group 175 B).       
       Branches:
             Size.— Considered medium for the variety.     Diameter.— Average as compared to other nectarine varieties. The branches have a diameter of about 5.9 centimeters when measured during the third year after grafting.     Surface texture.— Average, and appearing furrowed on wood which is several years old.     Crotch angles.— Primary branches are considered variable, and are between about 48 to 55 degrees when measured from the horizontal axis. This particular characteristic is not considered distinctive of the variety, however.     Current season shoots.— Surface texture — Substantially glabrous.     Internode length.— Approximately 2.3 to about 2.5 cm.     Color of mature branches.— Medium brown, (RHS Greyed-Orange 177 C).     Current seasons shoots.— Color — Light green, (RHS Green Group 137 B). The color of new shoot tips is considered a bright and shiny green (RHS Green Group 143 C).       
       Leaves:
             Size.— Considered medium for the species. Leaf measurements have been taken from vigorous, upright, current-season growth, at approximately mid-shoot.     Leaf length.— Approximately 140.0 to about 165.0 millimeters.     Leaf width.— Approximately 30.0 to about 35.0 millimeters.     Leaf base shape.— Slightly oblique relative to the leaf longitudinal axis.     Leaf form.— Lancelolate.     Leaf tip form.— Acuminate.     Leaf color.— Upper Leaf Surface — Dark green, (approximately RHS Yellow-Green Group 146 A).     Leaf texture.— Glabrous.     Leaf color.— Lower Surface — Medium green, (RHS Yellow-Green Group 146 B).     Leaf venation.— Pinnately veined.     Mid - Vein.— Color — Light yellow green, (RHS Yellow-Green Group N144 C).     Leaf margins.— Slightly undulating.     Form.— Considered crenate.     Uniformity.— Considered generally uniform.     Leaf petioles.— Size — Considered medium-long. Length — About 6.0 to about 12.0 mm. Diameter — About 1.5 to about 2.0 mm. Color — Pale green, (RHS Yellow-Green Group 144 B).     Leaf glands.— Size — Considered small. Approximately 1.0 mm in length, and about 1.0 mm in height. Number — Generally one gland per margin side. Occasionally two glands per margin side may be found. Type — Reniform. Color — Pale orange (RHS Orange Group 26 A).     Leaf stipules.— Size — Medium for the variety. Number — Typically 2 per leaf bud, and up to 6 per shoot tip. Form — Lanceolate in form, and having a serrated margin. Color — Green, (RHS Green Group 143 C) when young, but graduating to a brown color, (RHS Greyed-Orange group 166 C) with advancing senescence. The stipules are considered to be early deciduous.       
       Flowers:
             Flower buds.— Generally — The floral buds, depending upon the stage of development, are approximately 7.0 millimeters wide; about 11.0 millimeters long; conic in form; and slightly appressed relative to the bearing shoot. Floral bud dimensions are highly dependent upon the timing of the measurements.     Flower buds.— Color — This characteristic is dependent upon the proximity to the bloom. The bud scales are deep purple, (approximately RHS Greyed-Purple Group N186 C). The buds are considered hardy under typical central San Joaquin Valley climatic conditions.     Hardiness.— No winter injury has been noted during the last several years of evaluation in the central San Joaquin Valley. The current variety has not been intentionally subjected to drought or heat stress, and therefore this information is not available.     Date of first bloom.— Feb. 28, 2004.     Blooming time.— Considered mid season in relative comparison to other commercial nectarine cultivars grown in the central San Joaquin Valley. The date of full bloom was observed on Mar. 6, 2004. The date of bloom varies slightly with climatic conditions and cultural practices.     Duration of bloom.— Approximately 9 days. This characteristic varies slightly with the prevailing climatic conditions.     Flower type.— The variety is considered to have a showy type flower.     Flower size.— Flower diameter at full bloom is approximately 41.0 to about 44.0 millimeters.     Bloom quantity.— Considered abundant.     Flower bud frequency.— Normally 1 or more flower buds appear per node.     Petal size.— Generally — Considered medium-large for the species. Length — Approximately 19.0 to about 21.0 millimeters. Width — Approximately 18.0 to about 20.0 millimeters.     Petal form.— Considered generally rounded.     Petal count.— Nearly always 5.     Petal texture.— Glabrous.     Petal color.— Light pink, approximately (RHS Red-Purple Group 62 D).     Fragrance.— Slight.     Petal claw.— Form — The claw is generally elongated, and has a medium size when compared to other varieties. Length — Approximately 9.0 to about 11.0 millimeters. Width — Approximately 8.0 to about 9.0 millimeters. Petal Margins — Generally considered reasonably uniform and smooth and moderately undulate.     Petal apex.— Generally — The petal apices are generally entire at the tip.     Flower pedicel.— Length — Considered medium-long, and having an average length of approximately 3.0 to about 5.0 millimeters. Diameter — Considered average, approximately 3.0 millimeters. Color — A dull green, (RHS Yellow-Green Group N144 A).     Floral nectaries.— Color — A dull orange, (RHS Greyed-Orange Group 168 A).     Calyx.— Surface Texture — Generally glabrous. Color — Brownish-red, (approximately RHS Greyed-Red Group 181 B).     Sepals.— Surface Texture — The surface has a short, fine pubescent texture. Size — Average, and ovate in form. Color — A deep brownish-red, (approximately RHS Greyed-Red Group 181 A).     Anthers.— Generally — Average in length. Color — Red to reddish-orange dorsally, (approximately RHS Greyed-Red Group 179 A). Pollen Production — Pollen is abundant, and has a yellow color, (approximately RHS Yellow-Orange Group 17 C). The present variety is considered self-fruitful and does not require a pollinator.     Filaments.— Size — Length is variable, approximately 15.0 to about 18.0 millimeters long. Color — Light pink, (RHS Red-Purple Group 65 D).     Pistil.— Number — Usually 1, rarely 2. Generally — Medium-long in size. Length — Approximately 17.0 to about 20.0 millimeters including the ovary. Color — Pale lime green, (approximately RHS Yellow-Green Group 145 C). Surface Texture — The variety has a long glabrous pistil.       
       Fruit:
             Maturity when described.— Firm ripe condition (shipping ripe). Date of first picking — Sep. 13th, 2004. Date of last picking — Sep. 23, 2004. The date of harvest varies slightly with the prevailing climatic conditions and fruit maturity harvested for preferred market requirements.     Size.— Generally — Considered large, and uniform.     Average cheek diameter.— Approximately 70.0 to about 72.0 millimeters.     Average axial diameter.— Approximately 68.0 to about 71.0 millimeters.     Typical weight.— Approximately 280.0 grams. This characteristic is highly dependent upon the prevailing cultural practices, and therefore is not particularly distinctive of the variety.     Fruit form.— Generally rounded. The fruit is generally uniform in symmetry.     Fruit suture.— Occasionally one hemisphere is extended. No apparent callousing or stitching exists along the suture line.     Suture.— Color — This has a yellow background color, (approximately RHS Yellow-Orange Group 19 C).     Ventral surface.— Form — Slightly indented.     Apex.— Rounded.     Base.— Generally retuse.     Stem cavity.— Generally uniform and rounded in shape, and moderately deep. The average depth of the stem cavity is about 9.0 mm. The average width of the stem cavity is about 16.0 mm.     Fruit skin.— Thickness — Considered medium in thickness, and tenacious to the flesh. Texture — Glabrous. Occasional speckling is usually noted toward the apex. Taste — Non-astringent. Tendency to crack — None observed.     Color.— Blush Color — This blush color is generally red (approximately RHS Orange-Red Group N35 B). The blush covers approximately 45-55% of the fruit skin surface. The percentage of the blush on the fruit skin surface can vary, and is generally dependent upon the prevailing conditions under which the fruit was grown. Ground Color — Yellow orange, (approximately RHS Yellow-Orange Group 19 C).     Fruit stem.— Medium, approximately 6.0 to about 8.0 millimeters. Diameter — Approximately 2.0 to 3.0 millimeters. Color — Pale yellow-green, (approximately RHS Yellow-Green Group 144 B).     Flesh.— Ripens — Evenly. Texture — Firm, juicy and dense. The flesh is considered non-melting. Fibers — Few, small, and tender ones are typically found. Aroma — Very slight. Eating Quality — Considered very good. Flavor — Considered sweet and slightly acidic. The flavor is considered both pleasant and balanced. Juice — Moderate. Brix — About 15.0 degrees. This characteristic varies slightly with the number of fruit per tree; prevailing cultural practices; and the surrounding climatic conditions. Flesh Color — Pale yellow-orange, (approximately RHS Yellow-Orange Group 18 B).       
       Stone:
             Type.— Clingstone.     Size.— Considered medium for the variety. The stone size varies significantly depending upon the tree vigor, crop load and the prevailing growing conditions.     Length.— Average, about 29.0 to about 32.0 millimeters.     Width.— Average, about 22.0 to about 27.0 millimeters.     Diameter.— Average, about 17.0 to about 19.0 millimeters.     Form.— Generally ovoid.     Base.— The stone is usually ovoid basally.     Apex.— Shape — Generally the stone apex has a small prominent tip.     Stone surface.— Surface Texture — Pitting, in general, is more common than furrowing, which is typically noted near, and is generally parallel with the ventral and dorsal edges. Ridges — The surface texture is generally characterized by more prominent ridges along the ventral margins. Ventral Edge — Width — Considered medium, and having a dimension of approximately 3.0 to about 4.0 millimeters when measured at mid-suture. Dorsal Edge — Shape — Oblique toward the stem end, and exhibiting a slight reduction of the margin toward the base.     Stone color.— The color of the dry stone is generally reddish brown, (approximately Greyed-Orange Group RHS 166 B).     Tendency to split.— Splitting has rarely been noted.     Kernel.— Size — The kernel is considered medium. Form — Considered generally ovoid. Pellicle — Pubescent and ridging is usually absent. Color — (RHS Greyed-Orange Group N167 C).     Use.— The subject variety ‘Burnectwenty’ is considered to be a nectarine tree of the late season of maturity, and which produces fruit that are considered firm, attractively colored, and which are useful for both local and long distance shipping.     Keeping quality.— Excellent. Fruit has stored well for up to 25 days after harvest at 1.0 degree Celsius.     Shipping quality.— Considered good. The fruit of the new nectarine tree variety showed minimal bruising of the flesh, or skin damage after being subjected to normal harvesting and packing procedures.     Resistance to insects and disease.— No particular susceptibilities were noted. The present variety has not been tested to expose or detect any susceptibilities or resistances to any known plant and/or fruit diseases.       
       

   Although the new variety of nectarine tree possesses the described characteristics when grown under the ecological conditions prevailing near Fowler, Calif., in the central part of the San Joaquin Valley of California, it should be understood that variations of the usual magnitude and characteristics incident to changes in growing conditions, fertilization, pruning, pest control and horticultural management are to be expected.