SMALL FRUIT AND ORNAMENTAL GENETIC RESEARCH FOR THE MID-SOUTH
Location: Southern Horticultural Research
Title: Inter- and Intra- Specific Hybrid Breeding in Crape Mrytle (Lagerstroemia)
Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: February 12, 2010
Publication Date: August 2, 2010
Citation: Wang, X., Pounders Jr, C.T., Cabrera, R.I., Rinehart, T.A., Mccormick, J. 2010. Inter- and Intra- Specific Hybrid Breeding in Crape Mrytle (Lagerstroemia). Southern Nursery Association Research Conference. 55:58-62.
Interpretive Summary: The woody ornamental genus Lagerstroemia L. is native to tropical regions of Southeastern Asia and Indo-Malaysia, and to date, these shrubs and trees are cultivated, and in some cases naturalized, in temperate and tropical regions worldwide. There are over 50 species in this genus, which includes the popular cultivated “common” crape myrtle L. indica L. The disease-resistant ability of these L. indica cultivars have been significantly improved since another species, L. fauriei Kohene, was introduced from Japan by the U.S. National Arboretum (1). L. fauriei is resistant to powdery mildew and successfully improved and added to the ornamental traits of L. indica cultivars in interspecific breeding programs. To date, however, there are no Lagerstroemia cultivars possessing resistance to other diseases and insects, nor tolerance to abiotic stresses, or other novel horticultural traits, like newer flower colors, or interesting growth habits, etc. Our inter- and intra-specific breeding programs are aimed at providing new breeding germplasm and cultivar(s) with broad adaptation, possessing the most desired horticultural traits, and become a source of new germplasm for the nursery industry across the U. S.
The long term goal of these breeding programs is to develop new crape myrtle cultivar(s) with broad adaptation to heat, drought, cold tolerance, disease and insect resistance, and unique/novel flower colors. The objectives of this long-term study are 1) to develop new germplasm with unique horticultural traits and 2) to create a mapping population to address the genetics of disease and insect resistance.
From the existing collections at Texas AgriLife Research and Extension Center at Dallas and the USDA-ARS breeding program in Poplarville, MS (USDA-ARS SCA Agreement # 58-6404-9-395N), several different cultivars and breeding lines, which have either desirable flower color, powdery mildew and insect resistance, or environmental stress tolerance, we selected cultivars to make 17 cross combinations. Of these crosses, two complementary cultivars, ‘Carolina Beauty’ and ‘Natchez’ were used to create a genetic mapping population. ‘Carolina Beauty’, is a L. indica shrub or small tree with red flowers and aphid resistance, but susceptible to powdery mildew, whereas ‘Natchez’, an interspecific hybrid of L. indica L. and L. fauriei Kohene, has white flowers, powdery mildew and flea beetle resistance, but is susceptible to aphids (under greenhouse conditions). All parent trees were grown in 5-gallon containers under greenhouse conditions. Controlled pollinations were made during summer 2009 following previously published procedures. Pollen was collected from the male parent tree in the early morning before anthesis. A minimum of 60 flowers were emasculated before the flowers opened or anthers dehisced on each maternal tree. Previously collected pollen was applied to stigmas using a fine-tipped brush. After pollination, each maternal tree was covered with mesh until pod development (about 2 weeks). As a control, one panicle (50 or more flowers) was covered with mesh throughout pollination to exclude foreign pollen. Pods were harvested when they were dark brown or black and stored in a covered plastic box. These pods were dried under sunlight until all seeds were expelled. Seeds were counted and seeds per pod calculated.