Studies On Genetic Characteristic Of Petal Ornamentation Of Gazania Rigens L.

Gazania rigens L. originating in South African and The Republic of Mozambique,is a perennial plant and belongs to the Medal genus, Asteraceae. Gazania has many good characteristics such as: evergreen, flowering in three seasons, good resistance, once planted the landscape can be kept for many years and so on, which makes it a perfect candidate as groundcover plant used for dressing up urban landscape, enriching groundcover plant diversity and building low carbon gardens.This study investigated the genetic characteristics of gazania by observing the morphological, ecological habits, growth process of gazania, and the morphology of the pollen and stigma. Natural hybridization and artificial hybridization was used to cultivate hybrids to analyze the petals texture and root production was used to observe chromosomes. This research aimed to offer methods to improve gazania breeding efficiency, providing a theoretical reference for studying genetic aspects of other plants of Compositae. The main results are as follows:(1) The capitulum including external ray flowers and internal tubular flowers, ray flowers are asexual while tubular flowers are bisexual. Anthers and style were coated in the tubular petals. Ray florets were born in the edge of inflorescence and tubular flowers constituted by pistil and stamen were born above the torus, which is beneficial for the insects’ attachment and pollination because of the flat and large faceplate. The growing and mature way from inside to outside could improve the efficiency of cross-pollination as well as dichogamy. Floral organs opening and closing movement is not caused by a single factor light, rain and cold can also stimulate the petals to close.(2) Hybrids showed strong variability and a certain separation ratio in the gazania hybridization experiments. Compared with yellow, white had better genetic ability and heritability was about 58% in different combinations. The proportion of gazania eyes was close to 3:4 in hybrids F1, which we could speculate that eye trait was dominant inheritance controlled by a pair of alleles Aa. As for spots trait, the hybrids with spots:without spots was 95: 109(close to 1:1) in 204 hybrids F1 although hybrids’ parents didn’t contain spots. According to it, we could speculate that spot trait was dominant inheritance controlled by 2 pairs of alleles(Bb, Cc).(3) Hybrids F1 showed streak-free trait in the reciprocal crosses combination during artificial hybridization experiments. Hybrids F1 showed streak trait in the natural hybridization experiments while hybrids’ parents had streak trait, which indicated streak trait was dominant inheritance or maternal inheritance.(4) The number of chromosomes of gazania varieties ‘Moonglow’, ‘Sunglow’ and hybrids F1 were 2n = 10, ‘K10’ was 2n = 20. It is speculated that the cardinal number of chromosomes in gazania plants was x = 5,while the ‘K10’ was tetraploid. The results of chromosome analysis denoted that the original flowers maybe the cultivar whose chromosomes’ number was 10.