2010 Annual Report
PDRAM #R08 Program Increase Objective: 4. Initiate a FasTrack breeding project to develop, characterize, and select early and continual fruiting lines of plum, pear, and apple, and relevant rootstocks to accelerate fruit breeding programs.
Studies on plant genes that interact with Plum pox virus (PPV) found that many of these genes are also involved in photosynthesis. When these genes were blocked or chemical inhibitors of photosynthesis were applied, plants became more susceptible to virus infection. This shows that disruption of photosynthesis by chemicals or dark leads to a response that is known to inhibit the plant defense signals. When these signals are inhibited, plants are more susceptible to virus infection.
Horticultural management experiments to improve fruit production of early flowering plums in order to speed up the breeding cycle showed that not only do these plums flower early and continually, but they also have no cold or dormancy requirement for growth and fruiting.
To develop high quality disease and insect resistant pears, seedlings were evaluated for fruit quality and resistance to fire blight bacteria, Fabraea leaf spot fungus, and pear psylla insects. Further crosses were made to introduce into the best selections improved sweetness, acidity, and increased vitamin C content.
Asian and European pear species were screened for effects on psylla insect pest larval feeding, larval development, and mortality.
To understand the inheritance of fruit quality traits in psylla-resistance pear tree populations and in peach trees with novel growth habits, fruit quality traits of seedlings were evaluated to use for linking molecular markers to fruit quality traits.
Progress was made on improving the rates of regeneration of plants from leaves of plum and pear to enable genetic engineering of improved traits.
The susceptibility of pears to the new pest, European pear sawfly, was studied, and several possible sources of genetic resistance were identified in Asian pears and hybrids.
To better engineer plant sterility in transgenic plants, genetic enhancers for gene silencing have been developed and tested. Enhancer DNA is a powerful gene silencer. Silencing the genes that lead to pollen and seed development holds promise as a method for preventing the spread of genes from transgenic plants (transgenes) into the environment where they may not be wanted.
The 'HoneySweet' plum genome was sequenced using NextGen, an advanced, rapid and cost efficient sequencing method.
Continued evaluation of pollen movement (year 10) from a block of transgenic plums shows very limited movement of trangenes with the highest rate of gene transfer at 2% within 33-77 meters from the block rapidly decreasing to zero at most sites over 300 m from the block.
Dardick, C.D., Callahan, A.M., Chiozzotto, R., Schaffer, R., Piagnani, M., Scorza, R. 2010. Stone formation in peach fruit exhibits spatial coordination of the lignin and flavonoid pathways and similarity to Arabidopsis dehiscence. BioMed Central Biology. 8:13. Singer, S.D., Hily, J., Liu, Z. 2009. A 1-kb bacteriophage lambda fragment functions as an insulator to effectively block enhancer-promoter interactions in Arabidopsis thaliana. Plant Molecular Biology Reporter. 28:69-76.
Yang, Y., Singer, S., Liu, Z. 2010. Two similar but distinct second intron fragments from tobacco AGAMOUS homologs confer identical floral organ-specific expression sufficient for generating complete sterility in plants. Planta. 231:1159-1169.
Petri, C., Scorza, R. 2010. Factors affecting adventitious regeneration from in vitro leaf explants of 'Improved French' plum, the most important dried plum cultivar in the USA. Annals of Applied Biology. 156:79-89.
Petri, C., Scorza, R., Dardick, C.D. 2009. Genetic engineering of plum (Prunus domestica L.) for plant improvement and genomics research in Rosaceae. In: Folta, K.M. Gardiner, S.E., editors. Genetics and Genomics of Rosaceae. New York, NY: Springer. p. 277-290.
Yang, Y., Singer, S., Liu, Z. 2010. Petunia AGAMOUS enhancer-derived chimeric promoters specify a carpel-, stamen- and petal-specific expression pattern sufficient for engineering male and female sterility in tobacco. Plant Molecular Biology Reporter. DOI 10.1007/s11105-010-0215-z
Sun, Q., Sun, H., Li, L., Bell, R.L. 2009. In vitro colchicine-induced polyploid plantlet production and regeneration from leaf explants of the diploid pear (Pyrus communis L.) cultivar, 'Fertility'. Journal of Horticultural Science and Biotechnology. 84(5):548-552.
Hu, D., Scorza, R. 2009. Analysis of the 'A72' peach tree growth habit and its inheritance in progeny obtained from crosses of 'A72' with columnar peach trees. Journal of the American Society for Horticultural Science. 134(2):236-243.