Search Results

You are looking at 1 - 4 of 4 items for

  • Author or Editor: Chunsheng Lu x
Clear All Modify Search
Free access

Chunsheng Lu and Mark Bridgen

Self-pollinations of a diploid (2n = 2x = 16) interspecific hybrid from the cross of Alstroemeria aurea × A. caryophyllaea resulted in no seed set. Pollen viability studies with the hybrid demonstrated that only 5% of the pollen grains were viable. Cytological observations with the hybrid pollen mother cell (PMC) revealed abnormal chromosome behaviors, such as no pairing in Prophase I and Metaphase I, and bridges in the Anaphase I and II. Although the development of microspores appeared normal in shape until the stage of tetrad release, some chromosomes did not remain in the nucleus after completing meiosis, formed isolated groups of 1 to 4, and remained in the cytoplasm. This genetic imbalance of the microspores could be one of the causes for the abortion of the pollen grains in the late stage of development. Additional meiotic cytological studies with colchicine-induced tetraploids (2n = 4x = 32) derived from the hybrid plants showed that chromosome pairings were normal in most cases. However, self-pollination with the tetraploid plants failed to set seeds. These studies with the tetraploids further demonstrate that the sterility of the hybrid is due not only to chromosomal differences, but also to complex genic interactions.

Free access

Chunsheng Lu and Mark Bridgen

During the winter of 1991-92. four cultivars of Alstroemeria: `F-180'. `l-5'. `Parigo Pink' and `Parigo Red' were treated with eight different overwintering covers: straw, straw with plastic covering, sawdust, sawdust with plastic covering, hoops with plastic covering, hoops with microfoam covering, microfoam and a control with no cover. All covers had significant effects on the survival of `Parigo Pink' and `Parigo Red'; mulching with straw only gave the best winter protection. There were also significant genotypic differences among the four cultivars: 73% of `Parigo Pink' and `Parigo Red' plants survived after winter, but none of `F-180' or `l-5' survived. In addition, pre-winter evaluation indicated that there were significant genotypic differences among the four cultivars with cold resistance. The cold resistance was highly correlated with winter hardiness. It was concluded that: (1) pre-winter evaluation could be an efficient indicator for winter hardiness selection on Alstroemeria and (2) application of straw provided sufficient winter protection for zone 6 Alstroemeria. Other approaches of mulching need to be further identified in order to protect all Alstroemeria for overwintering in the northeastern United States.

Free access

Chunsheng Lu and Mark Bridgen

An interspecific hybrid of Alstroemeria aurea × Alstroemeria caryophyllaea was rescued by immature ovule culture and was completely sterile. To restore the fertility of the hybrid, young, vigorous shoots and buds were treated aseptically with three colchicine levels (0.2, 0.4, and 0.6% in DMSO solution) at four treatment durations (6, 12, 18, and 24 hours), before being cultured onto a shoot regeneration medium for regrowth and development. The growth and development of all treated shoots were retarded by the colchicine. New shoots were regenerated from 61% of the surviving cultures after one month. The degree of recovery was not significantly different among treatments, although the highest concentration (0.6%) and the longest time treatment (24 hours) resulted in some morphological abnormalities. Cultures with newly regenerated shoots/buds were able to initiate roots and, eventually, sixty plantlets were transplanted into the greenhouse after acclimatization. Cytological examination of the root tip cells of the plantlets indicated that tetraploids (2n=4x=32) as well as aneuploids plants were generated from the colchicine treatment, whereas all plants from the control were diploids (2n=2x=16). Details explaining cytological changes and the fertility of the colchiploids will be presented.

Free access

Chunsheng Lu, Yiqin Ruan and Mark Bridgen

Micropropagation has been used to rescue Leontochir ovallei, an endangered Chilean species in the Alstroemericeae. Cultures were initiated by aseptically germinating seeds of Leontochir on a medium containing 1/10 MS salts and vitamins and 0.3% sucrose. Three types of cytokinins (BAP, 2-iP and kinetin) at four concentrations (0, 2, 4, and 8 uM) were studied for shoot proliferation. In the 4 uM BAP treatment, new shoots were produced at an average of six per culture after four weeks of culture. Overall, there was an average of four shoots/culture/4 weeks for all BAP treatments. This was significantly higher than the 2-iP and kinetin treatments. Moreover, the increase of culture fresh weight over time was significantly greater in BAP treatments than those in other treatments. A rooting study compared the effect of NAA and IBA on root initiation. Over 85% of the cultures in 10 and 20 uM NAA treatments produced healthy and large roots. This was significantly higher than the 10 and 20 uM IBA treatments. In summary, a concentration of 4 uM BAP combined with 1 uM IBA in MS salts and vitamins supplemented with 146 mg glutamine/l is the best for shoot proliferation of leontochir; an MS basal medium containing 10 uM NAA is the best for root initiation. Micropropagated plantlets have been successfully transplanted into the greenhouse for further genetic and breeding studies.