Polyploidy effects on frost tolerance and winter survival of garden pansy genotypes

Abstract

Pansies (Viola × wittrockiana Gams) are a commercially important ornamental plant, grown and marketed during autumn and spring (ADAMS et al. 1997).Two hexadecaploid (16x) genotypes were obtained by induced polyploidy in octoploid garden pansy cultivars (AJALIN et al. 2002). The hexadecaploids were selfed in advanced generations (LAGIBO, KOB-ZA 2004a,b) and used also for further breeding in order to exploit the induced desirable traits such as improved compactness and general vigour effect in plant height and in flower size. As a result, the genotypes with 2n = 10x, 2n = 12x, and 2n = 14x ploidy levels were produced from crosses and backcrosses which are included in this study.According to LEVIN (1983), polyploidy, induced or natural, may greatly alter the cytological, genetic and physiological characteristics, and it often alters resistance to cold. Moreover, the effect of polyploidy on frost tolerance may vary from species to species and in some plants it has been demonstrated to show an increase or decrease with higher ploidy level. For instance, in Brassica campestris, autotetraploids were more resistant to frost than their diploid counterparts (CHOUDHURY et al. 1968). On the other hand, GORAL et al. (1964) found lower resistance of tetraploids to frost in Trifolium repens and higher resistance of tetraploids in Trifolium pratense.In this study, in addition to induced polyploidy, since pansies are commonly planted in autumn for spring flowering, frost tolerance is one of the most important factors to be assessed in new genotypes. Therefore, this study was conducted to identify ABSTRACT: This study was conducted to interpret the differences in frost tolerance and winter survival between 8x, 10x, 12x, 14x, and 16x ploidy levels of garden pansy (Viola × wittrockiana Gams) genotypes grown in the field conditions. Plants of each genotype were analyzed for their ploidy levels using flow cytometry. The chlorophyll fluorescence parameters were measured with portable chlorophyll fluorometer in the greenhouse and in the field at different time intervals. Increased frost stress generally reduced the fluorescence values in all genotypes. However, the genotypes differed significantly in their responses to frost as they were exposed to minimum temperatures of 1°C to -7.7°C in the field. Based on the percentage reduction in F V /F M values against -7.7°C temperature the hexadecaploids were ranked as sensitive to intermediate followed by 12x (sensitive), and genotypes with 10x and 14x ploidy levels were tolerant as the controls. The winter survival rate of hexadecaploids was by 7 to 9% lower than in the controls followed by the genotype with 12x and both genotypes with 10x and 14x ploidy levels were about equal to the controls. On the other hand, the content of photosynthetic pigments (chlorophyll a, b and total carotenoids) was the highest in hexadecaploids and tended to increase with increasing ploidy level. Further, the results gave insight that chlorophyll fluorescence could be applied directly in the field conditions ...

Impact of Ploidy Change on Secondary Metabolites and Photochemical Efficiency in Solanum Bulbocastanum

“…In Vicia villosa Tulay, Unal [30] observed more chlorophyll in tetraploids. Similar results were reported for black wattle [31], watermelon [32] and garden pansy [33]. By contrast, in Atriplex confertifolia chlorophyll content did not change at various levels of ploidy [34].…”

Karyologic and Heterosis Studies of the Artificial Inter- and Intraspecific Hybrids of Viola ×wittrockiana and Viola cornuta

“…Viola •wittrockiana Gams ex Kappert., known as garden pansy, is one of the most common bedding plants worldwide, exhibiting rich flower colors, cold tolerance, and other charming characteristics, such as odor and taste (Fernandes et al, 2017;Lagibo et al, 2005;Li et al, 2014, and literature cited therein). This species is also studied as a promising source of natural antioxidants (Vukics et al, 2008).…”

“…New pansy varieties with different colors, such as shades of pink, rose, or orange, and unusual bicolor designs have been introduced and are available to gardeners. Studies using a simple selection method to reduce the ploidy level by crossing with diploids to improve uniformity, as well as an increase of polyploidy by mutagenesis to maximize plant morphologic and physiologic characters, have already been performed (Dalbato et al, 2013;Kroon, 1972;Lagibo et al, 2005). Lagibo et al (2005) demonstrated the positive influence of increased polyploid level on frost tolerance and winter survival of garden pansy.…”

Efeito da alotetraploidização em espécies silvestres de Arachis e mapeamento de QTLs de resistência à ferrugem (Puccinia arachidis Speg.) em população F6 de genoma B

“…Quando é feita a correlação entre SCMR e LA, há uma diferença nos resultados, aproximando-os do que é visto para os materiais cultivados, pois folhas mais espessas geralmente têm densidade mais elevada de clorofila por unidade de área foliar e, portanto, têm uma maior capacidade fotossintética quando comparadas com folhas mais delgadas (Warner et al, 1987). Resultado similar também foi observado por Warner et al (1987) (Lagibo et al, 2005). De acordo com os resultados podemos inferir que, de maneira geral, SCMR e clorofila total aumentam juntas em direção ao maior nível de ploidia, apresentando uma mesma tendência diante da tetraploidização, além de combinar genótipos mais tolerantes com melhores características estéticas (Lagibo et al, 2005).…”

“…Resultado similar também foi observado por Warner et al (1987) (Lagibo et al, 2005). De acordo com os resultados podemos inferir que, de maneira geral, SCMR e clorofila total aumentam juntas em direção ao maior nível de ploidia, apresentando uma mesma tendência diante da tetraploidização, além de combinar genótipos mais tolerantes com melhores características estéticas (Lagibo et al, 2005).…”