Genetic-evolutionary studies on cultivated cannas

Abstract

Hybridization has played a dominant and decisive role in the origin of ornamental cannas. This has been made possible by the ecospecific differentiation of the parental species, which implies lack of barriers and a good deal of recombination associated with reasonably high fertility.Colour differences between species are controlled by a number of genes and their intensifiers, inhibitors, lethals, etc. From recombination in interspecific hybrids of such a wide range of genes, segregating simultaneously and involving complex segregation, arises a wide array of heterozygous genotypes with new colours and colour combinations, releasing much genetic diversity.Hybridization has also been responsible for transgressive segregation, particularly in length and breadth of staminodia and luxuriance, affecting not only plant height but also flower size. Perhaps the most important single factor responsible for the evolution of ornamental cannas has been the repeated cycles of hybridization which have led to the breakage of size and other barriers; this seems to have been exploited continuously until very large flower size was built up and combined with other useful vegetative and floral characters such as colour and number of flowers per inflorescence, extended blooming period, cold resistance, etc. The efficient vegetative propagation made fixing of the useful genotypes no problem, although they may contain a high degree of heterozygosity and sexual sterility.Along these lines, Année (hybrids between C. indica and C. glauca) and Ehemann (hybrids between C. iridiflora and C. warscwiczii) cannas came into being in 1848 and 1863 respectively. Although both were a distinct improvement over the original species, they were still relatively small-flowered and major improvements came roundabout 1868, when Crozy, Gladiolus or French Dwarf cannas (C. X generalis Bailey) were released. This group arose from hybrids and back crosses of the first two groups and contains diploids, interchange heterozygotes and autotriploids. When further intercrossing, inbreeding and selection yielded no significant improvement, "new blood" in the form of C. flaccida was introduced. The result was the release of Italian, Iris, Orchid or Giant flowered cannas (C. X orchiodes Bailey) in 1872. These are asynaptic seedless diploids and allo- or segmental allotriploids. By and large, Crozy cannas are the result of exploiting new genetic diversity and transgression, while Italian cannas owe their excellence to the luxuriance accompanying the introduction of C. flaccida.Next to hybridization, triploidy (14%) has been an important mechanism in the origin of cultivars with thicker, more durable and larger flower parts. The two types of triploids, autotriploids and segmental allotriploids, are distinguishable by their morphological and cytogenetical properties.It is evident that during the 44 years 1848-1892 the speed of evolution was rapid and its direction governed by the following principles of selection: increase in hardiness, reduction in height, spikes well ab...

Estudios citogenéticos en cuatro taxones de Canna (Cannaceae) de la provincia de Buenos Aires, Argentina

“…1C), el bajo número de células en metafase y el reducido tamaño cromosómico no permitieron determinar sus fórmulas cariotípicas. Los numerosos taxones que incluye el grupo C. x generalis proceden de cruzamientos entre C. indica y C. glauca, y entre C. iridiflora y C. warscewiczii, y han sido considerados diploides desinápticos estériles o alotriploides (Khoshoo & Mukherjee 1970). El número cromosómico del material de C. x generalis analizado aquí no entra en contradicción con la hipótesis de su origen, ya que C. indica, uno de los padres presuntos, muestra el mismo número cromosómico, que es igual al reportado para las demás especies progenitoras (Tanaka et al 2009).…”

“…El material de C. x generalis aquí estudiado es un híbrido estéril, que no forma semillas a la madurez; si bien se forman óvulos en el ovario estos no aumentan de tamaño y no se desarrollan y es posible que la viabilidad baja registrada por Ciciarelli & Passarelli (2015) para híbridos del grupo C. x orchioides también se presente aquí. En consecuencia, el resultado aquí obtenido en el material de C. x generalis procedente de humedales bonaerenses, no contradice la idea de Khoshoo & Mukherjee (1970), aunque resta corroborar esta propuesta mediante futuros estudios de comportamiento meiótico. coccinea.…”

“…Bailey (1949) los incluyó sub C. x generalis Bailey (presencia de pétalos erguidos) o sub C. x orchioides Bailey (presencia de pétalos reflejos). Estudios gené-ticos previos consideraron a algunos de estos taxones como diploides desinápticos estériles o alotriploides (Khoshoo & Mukherjee 1970). Ciciarelli & Passarelli (2015) señalaron que la viabilidad del polen era elevada (82,5%) en la especie silvestre parental C. warscewiczii, mientras que muy baja (4,5%) en un híbrido del grupo C. x orchioides.…”

IAPT chromosome data 28

“…Coefficients of variation (CVs) of samples and internal standard were 1.27%-3.09% (mean 2.35%) and 1.05%-3.18% (mean 1.75%), respectively. Previously, this species was known to have chromosome number of n = 10 ( Kamble, 1997), 2n = 20 (Sastry, 1981) Previously, this species was known to have chromosome number of n = 9 (Khoshoo & Mukherjee, 1970) from India and 2n = 18 from outside India (Hanson & al., 2001). Previously, this species was reported to have 2n = 44 by Renugadevi & Sampathkumar (1983 Previously, the species was reported with n = 15 (Alam & Sharma, 1984;Patwary & al., 1987;Umoh & al., 1991), 2n = 18 (Zheng & al., 1989), 2n = 28 (Palomino & al., 1990), 2n = 30 (Cristobal de Hinojo & al., 1998), n = 45 (Grabiele, 2005) and 2n = 72 (Faden & Suda, 1980).…”

Cytogenetics of aquatic ornamentals. II. Cytology of Nymphaeas.

“…After 48 hours of fixation, the anthers were squashed in 1% iron-acetocarmine. Somatic preparations were made only in few cases from root-tips following the technique of Khoshoo and Mukherjee (1970). Voucher specimens have been deposited in the Herbarium of National Botanic Gardens, Lucknow.…”