Genome sizes and ploidy levels in Mexican cactus pear species Opuntia (Tourn.) Mill. series Streptacanthae Britton et Rose, Leucotrichae DC., Heliabravoanae Scheinvar and Robustae Britton et Rose uri icon

abstract

  • The ploidy levels and amounts of DNA of 23 Opuntia species from Mexico were determined by flow cytometry. Four different ploidy levels (2n = 2x, 2n = 4x, 2n = 6x, 2n = 8x) with 2C-DNA amount ranging from 4.17 pg (Opuntia incarnadilla Griffiths) to 6.53 pg (Opuntia heliabravoana Scheinvar) were determined among the samples analyzed. Polyploidy is widespread (93%) among these Opuntia species. Opuntia helia-bravoana Scheinvar was the sole diploid species. Opuntia leucotricha DC. (2C = 5.71 pg), Opuntia spinulifera Salm-Dyck (2C = 5.51 pg), Opuntia robusta Wendl. ex Pfeiff. var. larreyi (F. A. C. Weber) Bravo (2C = 4.98 pg), and Opuntia elizondoana E. Sanchez et Villasenor (2C = 5.29 pg) were tetraploids. Opuntia oligacantha C. F. Forst. (2C = 5.33 pg), Opuntia incarnadilla Griffiths and Opuntia matudae Scheinvar (2C = 5.25 pg) were hexaploids. Opuntia zamundioi Scheinvar (2C = 4.35 pg), Opuntia lasiacantha Pfeiff. (2C = 4.88 pg), Opuntia hyptiacantha F. A. C. Weber (2C = 4.84 pg), Opuntia streptacantha Lem. ssp. streptacantha (2C = 4.64 pg) and Opuntia streptacantha Lem. subsp. aguirrana Scheinvar et A. Rodriguez (2C = 4.43 pg), Opuntia megacantha Salm-Dyck (2C = 5.01 pg), Opuntia joconostle F.A.C. Weber. ex Diguet (2C = 4.70 pg), Opuntia ficus-indica (L.) Miller (2C = 4.90 pg), Opuntia albicarpa Scheinvar (2C = 4.80 pg), Opuntia amarilla Griffiths (2C = 4.84 pg), Opuntia chavena Griffiths (2C = 4.70 pg), Opuntia cochinera Griffiths (2C = 5.10 pg), Opuntia fuliginosa Griffiths (2C = 4.64 pg), Opuntia pachona Griffiths (2C = 4.70 pg), Opuntia cretochaeta Griffiths (2C = 4.35 pg), Opuntia rzedowskii Scheinvar (2C = 4.77 pg), Opuntia robusta Wendl. ex Pfeiff. ssp. robusta ( 2C = 4.98 pg) and Opuntia robusta Wendl. ex Pfeiff. var. guerrana (Griffiths) Sanchez-Mejorada (2C = 5.05 pg) were all octoploids. The series Streptacanthae Britton et Rose showed a high level of ploidy with octoploid species except for Opuntia heliabravoanae Scheinvar (2n = 2x), Opuntia elizondoana E. Sanchez and Villasenor (2n = 4x) and O. matudae Scheinvar (2n = 6x). Opuntia spinulifera Salm-Dyck was determined to be as a tetraploid species. Series Leucotrichae DC. grouped tetraploid and hexaploid species. The monospecific series Heliabravoanae Scheinvar has one species: Opuntia heliabravoana Scheinvar diploid (2n = 2x). The monospecific series Robustae Britton et Rose seems to be a contradictory group; containing three varieties: Opuntia robusta Wendl. ex Pfeiff. ssp. robusta and Opuntia robusta Wendl. ex Pfeiff. var. guerrana (Griffiths) Sanchez-Mejorada as octoploid taxa and: Opuntia robusta Wendl. ex Pfeiff. var. larreyi (F. A. C. Weber) Bravo which is tetraploid. In earlier report Rafael del Castillo and Mario Gonzalez-Espinosa (1988) indicate that the arborescent varieties of this species are diploid and the postrate variety tetraploid. Implications for botanical systematics, genetic resources and breeding are discussed.

publication date

  • 2007
  • 2007