Cross Compatibility Between Interspecific Hybrids Derived From Lilium Lancifolium Thunb. And Asiatic Lily Cultivars And Embryo Culture

In lily breeding,the hybridization between wild species and cultivars could integrate good traits,and the hybrid offspring could possess higher ornamental value.The triploid species Lilium lancifolium Thunb.was used as the female parent to hybridize with the tetraploid Asiatic lily cultivars ’Brurano’ in 2012,and the interspecific hybrids were obtained by embryo culture(Lei and Wu,2012).In this study,the crosses between the interspecific hybrids and Asiatic lily cultivars were carried out.Several interspecific hybrids,LB38(2n =45),LB44(2n = 44),LB61(2n = 38),and LB81(2n = 4x = 48),and Asiatic lily cultivars,’Tresor’(2n = 4x = 48),’Dazzling’(2n = 3x = 36),and ’Pollyanna’(2n = 2x = 24),were used as parents.The botanical characteristics and the pollen viability of the hybrid parents were measured.The growth of pollen tubes was observed by fluorescence microscopy,and the hybrid seedlings were obtained by embryo culture.The aims were to explore the compatibility,which will provide a help to lily interspecific hybridization.The botanical characteristics of the interspecific hybrids and Asiatic lily cultivars were different.In stem characteristics,Asiatic lily cultivars used in this study did not have stem hairs.LB38 and LB61 had stem hairs,and LB38 and LB81 did not have stem hairs.In leaf characteristics,the leaves of Asiatic lily cultivar ’Dazzling’ were the widest and thickest,with the smallest number of leaves per plant.In flower characteristics,all the flowers had spots except for ’Dazzling’.In capsule and seed characteristics,the capsules of Asiatic lily cultivars were enlarged well,while there were no enlarged capsules obtained in the interspecific hybrids.In bulbil characteristics,all interspecific hybrids had bulbils,and Asiatic lily cultivars did not have bulbils.The pollen viability of the interspecific hybrids and Asiatic lily cultivars were different.The pollen viability of Asiatic lily cultivars was higher than that of the interspecific hybrids.The germination rate was followed by Pollyanna>Tresor>Dazzling>LB44>LB61>LB81>LB38.The germination rate of ’Pollyanna’ was 66.49%,followed by ’Tresor’ was 65.91%,and LB38 was only 5.56%which was the lowest.The fruit setting of different crosses were investigated and the compatibility of different crosses were different,the compatibility index was used to evaluate accurately the hybridization compatibility.A total of 12 crosses were carried out,and the fruit setting of different crossed were investigated after pollination 40 d.It was found that enlarged capsules were obtained from all cross combinations except for LB38 × Dazzling and LB61 × Dazzling.The rate of swollen capsules and the rate of seeds with embryos were inconsistent,such as Dazzling × LB61,the rate of swollen capsules was 95.56%,but the rate of seeds with embryos was only 0.78%.The higher of compatibility index,the more compatible of cross combination.The compatibility index of LB61 × Tresor was 19.93,and the compatibility index of Pollyanna × LB61 was only 0.28.It was concluded that the LB61 × Tresor was more affinity,and the hybridization compatibility of Pollyanna × LB61 was weak.The pollen germination and pollen tube growth were observed by aniline blue staining.There were many anomalies in the process of growth of pollen tubes.Pollen tube had been observed to extend into the ovary and ovule in LB81 × Pollyanna,Dazzling × LB38 and Pollyanna x LB81,except for LB38 × Dazzling.A few pollen grains stuck on the stigma and the pollen grains began to germinate until pollination 12 h in LB38 × Dazzling.While the stigma covered by a large quantity pollen grains and most pollen grains started to germinate at pollination 4 h in LB81 × Pollyanna,Dazzling x LB38 and Pollyanna x LB81.Pollen tubes bending back folded,twisted into a group and the terminal enlarged.Meanwhile,abundant calloses appeared in the pollen tube,papilla and canal cell.The embryos obtained from different cross combinations were cultured in vitro.The embryos at 40～50 d after pollination were the most suitable for embryo culture,and the embryos without seed coat and endosperm were the most appropriate for germination in vitro.The germination rate of the same cross combination was almost same on different media,but the growth of seedlings was different.The optimum medium for embryo growth was MS+NAA 0.5 mg/L+BA 0.5 mg/L.For the plantlets from LB44 × Tresor,the appropriate multiplication medium was MS+NAA 1.0 mg/L+BA 1.0 mg/L with the multiplication coefficient of 1.93.The suitable medium for rooting was 1/2 MS + NAA 1.0 mg/L with the rooting rate of 78.3%.