1a. Objectives (from AD-416):
Identify horticulturally useful genes and markers associated with important traits, with emphasis on increasing resistance to biotic and abiotic stresses that reduce the quality or the potential yield of blueberry, strawberry, and brambles, so that ultimately these genes and traits can be incorporated in small fruit cultivars using various biotechnological approaches. Important traits include tolerance to temperature extremes in blueberry and strawberry, disease resistance in strawberry, and repeat flowering in strawberry, blackberry, and raspberry.
1b. Approach (from AD-416):
Studies will focus on: 1) developing reliable, stable blueberry transformation system using the Biolistic method of particle bombardment, 2) developing and utilizing genomic tools, such as standard and subtracted/reverse subtracted cDNA libraries for the production of ESTs and custom microarrays, in blueberry and strawberry, for the identification and characterization of genes associated with increased production of fruit under stressful temperature conditions, 3) identifying germplasm and developing molecular markers and genetic maps useful for conferring traits of horticultural value, such as cold tolerance in blueberry, disease resistance in strawberry, and repeat flowering in strawberry, raspberry, and blackberry, and 4) evaluating somaclonal variants of strawberry for expression and stability of useful traits such as anthracnose resistance.
3. Progress Report:
ARS scientists at Beltsville, Maryland and Chatsworth, New Jersey continued to use gene sequences to examine evolutionary relationships of the various blueberry species. The markers are being analyzed in about 50-60 different individuals, including about 3 representatives of each species. ARS scientists at Beltsville, Maryland continued to add DNA markers to the genetic map of blueberry and evaluated the entire mapping population for chilling requirement for the second year. An ARS scientist at Beltsville, Maryland began studies to investigate gene flow (movement of pollen by bees) in lowbush blueberry as a possible explanation for yield differences among plants. One hypothesis is that honeybees may tend to move pollen short distances, thus they may be more likely to pollinate flowers from the same plant from which the pollen came or flowers from neighboring plants. If plants that are near each other are more likely to be closely related, then crossing these plants could result in seeds being too inbred to survive and yield fruit. Open-pollinated fruit from several plants were collected and the seed was germinated. The DNA from the seedlings, the mother plants, and the nearest 5 potential father plants were fingerprinted in an attempt to determine the most likely father for each seedling. This paternity analysis is ongoing and should establish whether bees are more likely to cross flowers in close proximity to one another or to flowers further away. ARS scientists at Beltsville, Maryland, together with scientists at the University of Maryland and Towson University in Baltimore, Maryland have obtained about 500 million short sequences representing genes that are expressed in 4 different stages of diploid strawberry carpel development, about 250 million sequences from four stages of developing receptacle cortex, and about 100 million sequences from 3 early stages of embryo development. About 100 million sequences were also obtained from seedlings and leaves. ARS scientists at Beltsville, Maryland determined that a recessive mutation in a single gene results in production of runners by a non-runnering diploid strawberry plant. ARS scientists at Beltsville, Maryland, together with scientists at the University of Maryland have profiled the carotenoids present in leaves and reproductive structures of diploid strawberry. ARS scientists at Beltsville, Maryland continued to add markers to genetic maps of strawberry. Repeat fruiting was associated with two different unrelated chromosomes in the strawberry genome. ARS scientists at Beltsville, Maryland, and Corvallis, Oregon, together with scientists at Oregon State University used molecular markers to show that existing black raspberry cultivars are closely related to each other, and that wild black raspberries contain many genes not present in current cultivars. This information indicates that progress for black raspberry cultivar development may be dependent on including the wild black raspberries in cross pollinations.
1. Raspberry genome aligned with those of strawberry, apple, and peach. Detailed knowledge of plant genes and their relationship with corresponding genes in related plants is lacking. An international team of scientists including ARS scientists from Beltsville, Maryland, developed genetic maps of red raspberry and black raspberry that were aligned with the sequenced genomes of strawberry, apple, and peach. The alignment with the strawberry genome caused the raspberry community to adopt a new corrected nomenclature for raspberry genetic linkage groups and associated chromosomes, and is expected to facilitate the identification of gene sequences associated with important horticultural traits.
2. Variation in frost tolerance of open flowers detected in different highbush blueberry varieties. Late winter and early spring frosts can cause severe damage to opening blueberry flowers and, thus, cause dramatic losses in berry yield. ARS scientists at Beltsville, Maryland; Chatsworth, New Jersey; and Kearneysville, West Virginia measured the level of frost tolerance in different flower parts of five highbush varieties. The corolla, filament, anthers, and style were most sensitive to frost. Significant differences in sensitivity were detected among varieties for three of these four tissues, the style, filament, and anthers. Identifying types of blueberry plants whose flowers are more frost tolerant should help breeders to develop more frost tolerant blueberry varieties.
Rowland, L.J., Bell, D.J., Alkharouf, N., Bassil, N.V., Drummond, F., Beers, L., Buck, E., Finn, C.E., Graham, J., Mccallum, S., Hancock, J., Olmstead, J., Main, D. 2012. Generating genomic tools for blueberry improvement. International Journal of Fruit Science. 12:276-287.