Mitotic and Meiotic Polyploidization in Lily Hybrids for Transferring Botrytis Resistance

Abstract

In an effort to transfer Botrytis resistance from Oriental lilies to Asiatic hybrids (Lilium, 2n=2x=24) we made a large number of F 1 hybrids between these two distantly related species. Because these species belong to two different taxonomic sections, the F 1 hybrids were totally sterile and could not be directly used in breeding. Therefore, two approaches were used for utilizing the F 1 hybrids. First, the somatic chromosome number of the F 1 s was doubled by treating with oryzalin that resulted in allotetraploids (mitotic doubling). These allotetraploids were used for crossing with the parents. Second, 2n gametes were used directly for crossing with the parents for producing sexual polyploids (meiotic doubling). The two types of BC 1 progenies were monitored for resistance against Botrytis elliptica through a "leaf tip test". Disease severity was evaluated on a nominal scale, ranging from 1 resistant (no lesions) to 6 (a high degree of necrosis with mycelium or even spores). In both populations the resistance varied from very susceptible to highly resistant. However, the occurrence of transgression of resistance, meaning that the degree of resistance in some seedlings exceeded that of the parent, was higher in meiotically doubled polyploids as compared to those derived from mitotic doubling. This was explained from the fact that the typical allotetraploids produce uniformly a single genotype of 2x gametes containing both parental genomes because of autosyndetic pairing so that there is no scope for genetic variation. On the contrary, in the case of meiotic polyploids intergenomic recombination occurs between the alien chromosomes that could lead to considerable amount of genetic variation. This phenomenon might be an explanation for the observed transgression of Botrytis resistance in the meiotic polyploid progenies.

Production and Identification of a Tetraploid Germplasm of Edible Lilium davidii var. unicolor Salisb via Chromosome Doubling

“…Genome amplification is a critical step for improving the genetic characteristics of plants (Beers et al, 2005;Dean et al, 2002;Pinard et al, 2006). The key step for successful induction depended on the concentration of the inducer and the processing time in the induction stage.…”

“…These phenomena are widespread in many species, including Zantedeschia (Cohen and Yao, 1996), Triticum aestivum L. (Hansen and Andersen, 1998), and Miscanthus sinensis (Petersen et al, 2002). Genetic adaptability and tolerance to environmental changes can also be increased by polyploidy (Beers et al, 2005;Dhooghe et al, 2011;Xiong et al, 2006). Moreover, duplicated genetic material can restore fertility, but not for all species (Dunn and Lindstrom, 2007); the reason for such differences between species remains unclear.…”

Stimulatory Effect of Silver Nanoparticles on the Growth and Flowering of Potted Oriental Lilies

“…The most attractive cultivars include oriental hybrids with large, scented flowers. These are also the most difficult to grow, mostly due to their high sensitivity to fungal pathogens [24,25]. The decorative value of ornamental plants may be enhanced by using growth stimulators [26,27].…”

Fire Blight Susceptibility in Lilium spp. Correlates to Sensitivity to Botrytis elliptica Secreted Cell Death Inducing Compounds

“…A study by Gao et al (2018) , however, classified Oriental × Trumpet and Oriental hybrid cultivars as resistant, while Asiatic and Trumpet hybrids were classified as susceptible. Crosses between resistant and susceptible cultivars provided evidence for very complex inheritance of susceptibility to B. elliptica in hybrid progenies, with hybrid offspring displaying a large spectrum of susceptibility ( Beers et al, 2005 ; Hu et al, 2017 ).…”

“…These previous studies, however, show several limitations that hamper obtaining a clear overview of the variation in susceptibility in lily and the variation in virulence in the B. elliptica population. Several studies included a single fungal isolate ( Beers et al, 2005 ; Hu et al, 2017 ; Gao et al, 2018 ; Jang et al, 2018 ) and distinct inoculation methods. Sometimes agar plugs were used as inoculum ( Hu et al, 2017 ; Gao et al, 2018 ), while in another case, leaf tips were inoculated with fungal conidia ( Beers et al, 2005 ).…”