Factors affecting seed set in the crosses between Dendranthema grandiflorum (Ramat.) Kitamura and its wild species

Abstract

Reproductive barriers often exist in the crosses between Dendranthema grandiflorum (Ramat.) Kitamura and its wild species and seriously result in low seed set, consequently reducing breeding efficiency. For the purpose of revealing the factors leading to low seed set, we investigated pollen viability, germination behavior of pollen grains on stigmas and embryo development in the crosses between D. grandiflorum and three wild species, D. nankingense (Nakai) Tzvel., D. indicum (L.) Des Moul. and D. zawadskii (Herb.) Tzvel. using technique of paraffin section, and light, fluorescence and scanning electron microscopy. The results indicated pollen viability of three wild species ranged from 20 to 25%. In the cross between D. grandiflorum and D. nankingense, very few pollen grains germinated on stigmas after pollination and most of them germinated abnormally. In addition, normal embryos were observed in 12% ovaries at 8 days after pollination and thereafter all the embryos aborted. In other two crosses, many pollen grains germinated on stigmas and pollen tubes penetrated stigmas normally after pollination.Moreover, normal embryos were observed in over 50% ovaries from 8 to 15 days after pollination in the cross between D. grandiflorum and D. indicum, and seed set was 59%. In the cross between D. grandiflorum and D. zawadskii, normal embryos were observed in 52% ovaries at 8 days after pollination. After that, however, most embryos degenerated and seed set was only 9%. These data suggest that pollen viability has no significant effects on seed set of the three crosses. Very few germinated pollen grains on stigmas and abnormal growth of most pollen tubes before fertilization, and embryo abortion are the main factors causing failure of the cross between D. grandiflorum and D. nankingense, whereas only embryo abortion is a main factor resulting in low seed set in the cross between D. grandiflorum and D. zawadskii and no barriers occur in the cross between D. grandiflorum and D. indicum.

Interspecific hybrids between Chrysanthemum grandiflorum (Ramat.) Kitamura and C. indicum (L.) Des Moul. and their drought tolerance evaluation

“…However, according to our knowledge, there have been no studies reporting the improvement of chrysanthemum drought tolerance through interspecific hybridization. Moreover, we indeed did not know whether interspecific cross could be successfully used in improving chrysanthemum drought tolerance before carrying out the earlier (Sun et al 2010) and present studies. Therefore, with a goal of introducing droughttolerance trait of some wild species in Chrysanthemum into chrysanthemum cultivars, we carried out several interspecific crosses between an important commercial cultivar (C. grandiflorum 'Yuhuaxingchen') with high ornamental quality but low drought tolerance and three wild species (C. nankingense, C. indicum and C. Zawadskii) with exceptional drought tolerance in our earlier study (Sun et al 2010).…”

Comparative analysis of genetic diversity among species of Chrysanthemum and its related genera using inter-simple sequence repeat and sequence-related amplified polymorphism markers

“…The transfer of these excellent genes to cultivated chrysanthemums would be useful to improve cultivated chrysanthemums. Fortunately, several studies have shown the cross compatibility between cultivated chrysanthemums and species of Chrysanthemum and related genera (Fukai et al, 2000;Sun et al, 2010b), Thus far, potentially useful F 1 hybrids between cultivated chrysanthemums and species of Chrysanthemum and related genera have been produced through inter-specific or inter-generic hybridization with embryo rescue (Watanabe, 1977;Furuta et al, 2004). Recently, Deng et al (2010Deng et al ( , 2012) transferred resistance to aphid and Alternaria leaf spot from Artemisia vulgaris to cultivated chrysanthemums, and the same authors obtained some F 1 hybrids with enhanced cold tolerance through the hybridization of cultivated chrysanthemum and Ajania przewalskii .…”

Reproductive barriers in the intergeneric hybridization between Chrysanthemum grandiflorum (Ramat.) Kitam. and Ajania przewalskii Poljak. (Asteraceae)

“…Chrysanthemum (synonym of Dendranthema) and Ajania are taxonomically placed in the subtribe Chrysantheminae or Chrysanthemum sensu lato (Anthemideae, Asteraceae) (Bremer and Humphries 1993;Shih and Fu 1983). Chrysanthemum (Chrysanthemum grandiflorum (Ramat.)…”

“…is distributed in the northwestern alpine and/ or arid parts of China at a.s.l. 2,804-4,500 m (Shih and Fu 1983) and has high tolerance to cold and dry stresses (Zhao et al 2009). Moreover, its silver color leaves, compact and high branching ability promised it an excellent germplasm in breeding groundcover chrysanthemum with high resistance to abiotic (cold and dry) and/or biotic (pests) stress by intergeneric hybridization Yang et al 1992;Zhao et al 2009).…”