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
Blueberry evolution. Evolutionary relationships among blueberry species are poorly defined for some species. ARS scientists at Beltsville, Maryland and Chatsworth, New Jersey used gene sequences to examine evolutionary relationships of the various blueberry species. When completed, the analysis will provide a more precise understanding of species relationships and benefit breeders utilizing divergent species for blueberry improvement. Blueberry yield. Yield among lowblush blueberry plants can vary widely. ARS scientists at Beltsville, Maryland investigated reasons for yield differences. We hypothesized that yield differences may be caused by male or female sterility or that plants in close proximity to each other were closely related. Preliminary results suggest that male sterility may contribute to observed yield differences. Most pairs of plants were not closely related suggesting that inbreeding does not reduce yield. The results of this research will benefit blueberry breeders and growers. Molecular characterization of heat stress effects on strawberry. High temperature can reduce strawberry fruit yield. To better understand the effect of heat stress on fruit production, ARS scientists at Beltsville, Maryland, together with scientists at the University of Maryland and Towson University, obtained over 225 million short gene sequences representing genes expressed in 4 different stages of strawberry anther development and mature pollen. The information obtained provides a baseline for scientists characterizing at the molecular level the effect of heat stress on fruit set. Strawberry mutants. Variation in plant characteristics often helps scientists to identify and characterize the genes that influence plant attributes. ARS scientists at Beltsville, Maryland, together with scientists at the University of Maryland, produced a population of 1000 strawberry mutants. These plants include mutants in runnering, plant height, fruit shape, and leaf shape. The material will be utilized by scientists to characterize genes and physiological attributes that influence these traits. Strawberry fruit development. Plant hormones play an integral role during fruit development. ARS scientists at Beltsville, Maryland, and the Universities of Maryland and Minnesota, found a novel protein used for energy production in strawberry fruit that is bound to the plant hormone auxin. We are utilizing our data to characterize this interaction in strawberry and understand its role in fruit growth. This research will benefit scientists studying plant development and ultimately benefit efforts to improve strawberry production. Strawberry genes. Plant breeders seek to identify genes associated with economically important plant traits in order to develop efficient breeding strategies and improved cultivars. ARS scientists at Beltsville, Maryland identified multiple regions of the strawberry genome associated with bacterial angular leaf spot disease, several fruit quality traits, and repeat fruiting. The results obtained will be used to characterize genes that influence these attributes and develop molecular markers linked to these genes for use in breeding improved cultivars.
1. Gene sequences of blueberry, Vaccinium corymbosum. Few genomic resources are available for many important horticultural crops. ARS scientists at Beltsville, Maryland, completed a project to sequence expressed genes from different plant parts of blueberry. Over one million pieces of sequence were obtained from fruit at different stages of development, from flower buds at different stages of cold acclimation, and from leaves. These were deposited in a database for use by other scientists. Occurrence of the most abundant sequences was compared across plant parts to identify genes that are potentially advantageous for cold tolerance and fruit development. The sequence information was also used to develop SSR molecular markers for mapping genes important for breeding improved blueberries. The results of this research constitute an important genomic tool for the scientific community, particularly for scientists interested in genes of blueberry and related species.
2. Stages of strawberry flower development precisely defined. High temperatures affect strawberry production, in part by preventing successful pollination. An ARS scientist at Beltsville, Maryland, together with researchers at the University of Maryland, utilized manual flower dissection together with light and scanning electron microscopy to characterize stages of strawberry flower development. Precise definitions for stages in strawberry flower development were described. This new benchmark for describing strawberry flower development provides a foundation for coordination among laboratories conducting research to discover molecular mechanisms for preventing damage to reproductive organs as a result of higher than normal temperatures that may occur during strawberry production. The research provides immediate benefits to scientists working on strawberry heat stress and long term benefits for improving strawberry production.
Bell, D.J., Stommel, J.R., Rowland, L.J., Drummond, F. 2010. Yield variation among clones of lowbush blueberry as a function of kinship and self-compatibility. Journal of the American Society for Horticultural Science. 135:259-270.