1: Improve environmental stress and disease resistance in tree fruit crops. 1.A. Identify and characterize sources of fire blight resistance for use in apple scion breeding programs. 1.B. Characterize expression patterns and sequence differences of select apple drought-responsive genes in Malus sieversii lines exhibiting high and low water use efficiency. 1.C. Utilize transcriptomic and high-throughput genetic screening approaches to identify CBF-regulated and other stress-regulated genes, and characterize their functional role in stress tolerance and dormancy using transgenics and field evaluation. 2: Develop an accelerated breeding system for new tree fruit crops utilizing transgenic early-flowering lines.
Abiotic and biotic stresses play a major role in determining the economic viability of fruit crop production and postharvest quality. A single fire blight epidemic can destroy an entire young orchard and unfavorable environmental conditions, such as freezing temperatures, as well as heat and drought stress can result in significant reductions in yield, quality, and tree longevity. The overall objective of this project is to utilize genomic and molecular approaches to identify genes that convey resistance to abiotic and biotic stress in fruit crops, identify genetic markers for disease and stress resistance that can be utilized by apple breeders in marker-assisted-breeding programs, and to develop a breeding system that will facilitate the incorporation of specific traits, especially from novel genetic resources, such as Malus sieversii, into advanced selections of breeding lines. Quantitative trail loci (QTLs) and molecular markers for fire blight resistance will be developed for resistance derived from Malus sieversii and ‘Splendour’ apple. Targeted genome sequencing of the promoters of select dehydration and water use efficient responsive genes will be applied to lines of xeric-adapted Malus sieversii. Promoter analysis will identify cis-elements known to affect gene expression. Methylation differences between lines during simulated drought will be evaluated to reveal potential targets for gene regulation. The contribution of the CBF (C-repeat binding factor) family members to cold hardiness, dormancy, and growth will be evaluated. An accelerated breeding system for apple will be developed utilizing transgenic early-flowering lines to facilitate rapid integration of important genetic traits from novel apple genotypes into advanced breeding lines. The proposed research will result in the identification of genes, molecular markers, and a breeding system that can be used to efficiently develop apple germplasm with increased resistance to biotic and abiotic stress.
Host plant resistance is one of the most effective and sustainable options for managing fire blight, a devastating disease of apple and pear. 'Splendour' apple, which has excellent flavor and is resistant to fire blight, was found to transmit its resistance to 25% of its progeny and will, therefore, be a useful donor of resistance for apple breeding programs. In order to facilitate the identification of specific genetic markers for resistance, two 'Splendour' populations were genotyped with over 2,000 DNA markers. This genetic information was used to construct a genetic linkage map for the population, which will facilitate future research to identify genetic loci in 'Splendour' controlling fire blight resistance. Developing frost protection methods for flowering fruit trees during spring frost events is critical. ARS researchers in Kearneysville, West Virginia, in collaboration with an industry partner are evaluating the impact of applying novel compounds to flowering trees in order to increase freezing tolerance. Thus far, results indicate a delay in flowering after the application of the test compounds and a slight increase in freezing tolerance. The results, however, were very variable and depended on the stage of the flower bud development and the timing between when the material was applied and the occurrence of the frost event. No further studies are recommended at this time. The impact of using transgenic apple rootstocks with improved freezing tolerance, delayed budbreak, and dwarfing on these parameters in scion cultivars grafted onto the transgenic rootstock was evaluated in field conditions for three years. Results indicated that the growth of scions were impacted by the transgenic rootstock, but freezing tolerance and dormancy were unaffected. The information was published. Breeding new apple varieties takes 25-30 years due to its long juvenile phase. Rapid cycling breeding using "early flowering" transgenic apple has the potential to greatly accelerate apple breeding. Crosses of early flowering 'Pinova' T1190 with fire blight and apple scab resistant 'Crimson Crisp' and 'Splendour' resulted in the production of 850 early flowering seedlings that are being selected for disease resistance.
1. Identification of a genetic locus controlling resistance to blue mold in apple. Blue mold is the most important postharvest decay of apple worldwide and results in significant financial losses. There are no known sources of resistance to blue mold in domesticated apple; however, resistance has been described in wild Malus sieversii including Plant Introduction (PI) 613981. ARS researchers in Kearneysville, West Virginia, evaluated the fruit of 170 PI613981 progeny for their resistance to blue mold and conducted an indepth genetic analysis of the progeny utilizing next generation DNA sequencing technology to identify a genetic locus controlling resistance to blue mold in apple. A DNA marker being developed for this genetic factor will allow plant breeders to select new apple cultivars that are resistant to blue mold postharvest decay and prevent the need to treat apple fruit with fungicides to control the disease.
Tang, W., Zheng, Y., Dong, J., Yu, J., Yue, J., Liu, F., Guo, X., Huang, S., Wisniewski, M.E., Sun, J., Niu, X., Ding, J., Liu, J., Fei, Z., Liu, Y. 2016. Comprehensive transcriptome profiling reveals long noncoding RNA expression and alternative splicing regulation during fruit development and ripening in kiwifruit (Actinidia chinensis). Frontiers in Plant Science. 7(335):1-15.
Dymek, K., Dejmek, P., Gomez Galindo, F., Wisniewski, M.E. 2015. Influence of vacuum impregnation and pulsed electric field on the freezing temperature and ice propagation rates of spinach leaves. Journal of Food Science and Technology. 64:497-502.
Artlip, T.S., Wisniewski, M.E., Norelli, J.L., Arora, R. 2016. An apple rootstock overexpressing a peach CBF gene alters growth and flowering in the scion but does not impact cold hardiness or dormancy. Horticulture Research. DOI: 10.1038/hortres.2016.6.
Artlip, T.S., Wisniewski, M.E., Takatsuji, H., Bassett, C.L. 2016. Engineering carpel-specific cold stress tolerance: a case study in Arabidopsis. Physiologia Plantarum. 157:469-478.