论文信息 - MEIOSIS AND POLYPLOIDY IN ONTARIO SPECIES OF CRATAEGUS IN RELATION TO THEIR SYSTEMATICS

MEIOSIS AND POLYPLOIDY IN ONTARIO SPECIES OF CRATAEGUS IN RELATION TO THEIR SYSTEMATICS

Chromosome number determinations of 68 accessions of about 20 species in 11 series of Crataegus (hawthorn), Rosaceae, occurring in southern Ontario are presented. This is the first extensive documentation of chromosome numbers in North American Crataegus since Longley's (1924) account which was based on sectioned material. Our results, taken in the context of our cytological work proving the presence of apomixis in the genus, and taxonomic studies, clearly establish that in Ontario Crataegus is part of an extensive agamic complex consisting of diploids (2n = 34), polyploids (3x and 4x) and some aneuploids. Cytological observations of the triploids (2n = 51) and tetraploids (2n = 68) that have indicated the occurrence of meiotic irregularities and various degrees of pollen sterility in some of the polyploid taxa studied, underline the significance of apomixis in Crataegus evolution. One of the common Ontario species, C. punctata, is shown to be a probable sexual diploid and further cytological work should ...

J. B. Phipps | M. Muniyamma

[1] A. T. Natarajan,et al. The role of the diffuse stage in the cytological problems of meiosis in Rosa. , 2009, Hereditas.

[2] Á. Löve. IOPB CHROMOSOME NUMBER REPORTS XXII , 1969 .

[3] G. A. Mulligan,et al. Flora of the Queen Charlotte Islands , 1968 .

[4] C. D. Darlington. Chromosome Botany and the Origins of Cultivated Plants , 1973 .

[5] J. Shoemaker. Pollen Development in the Apple, with Special Reference to Chromosome Behavior , 1926, Botanical Gazette.

[6] A. E. Longley. CYTOLOGICAL STUDIES IN THE GENUS CRATAEGUS , 1924 .

[7] K. B. Blackburn,et al. The Status of the British Rose Forms as determined by their Cytological Behaviour , 1921 .

[8] L. Standish. WHAT IS HAPPENING TO THE HAWTHORNS?Half a Century Ago Only Ten Species Were Recognized in North America, Now There Are More Than 700-Several Lines of Evidence Indicate That Many of the New Forms Are Not New Species but Natural Hybrids , 1916 .