Characterization, Genetic Analysis Of Polyembryony And Apomixes In Coffee And Their Utilization For Breeding

Coffee (Coffea) is known globally as one of the most important beverage crops and extensively cultivated and distributed in many tropical countries. Production of inter-specific hybrids between Robusta and Arabica with both parents' elite genes is a major goal of coffee breeding presently. In traditional hybridization breeding program, it would taken more than 20 years to develop a new cultivar because of long vegetable growth period, difficulty in selection and lower propagation rate of elite individuals. But utilization of apomixis in breeding procedure could significantly shorten time of selection and fix heterosis. Although high genetic diversity including variation of ploidy level, polyembryony and twin-embryonic phenomenon existed in the genus Coffea (Rubiaceae), there was less study on how about the apomixes in coffee. No bred apomictic materials have been reported still now. In this study, it is confirmed that being of apomixes in coffee and discovered that higher frequent polyembryony and apomixes types took place in coffee populations by ways of observation of plants with polyembryonic and apomictic phenomenon, morphology and cytogenetic identification, and analysis to fingerprint of peroxidase (POD) isozyme and simple sequence repeat (SSR) marker. The principal results shown as following:(1) Polyembryonic phenomenon is commonly occurred in coffee cultivars with embryo number of 1-4 and a majority of them being twin-embryos. The polyembryonic frequencies are 2.80‰~40.30‰. The frequency of polyembryony and twin-embryony in tetraploid species are generally higher than those of diploid. Four types of twin-embryonic bud (big-big type, big-small type, big-abnormal type, abnormal-abnormal type)_can be classified in according with the size and developmental intactness of twin embryos. And two types of bud (near close location and separate location of the twin-embryos at the base of the seed) can be divided in the light of the rooting position of twin embryos. There are five morphological types of in vitro seedlings geminated in twin-embryonic seeds: big-big type, big-small type, big-abnormal type, abnormal-abnormal and Siamese twin type.(2) It was confirmed that facultative apomixes is existed in coffee species based on emasculating treatment, cyto-genetic observe and SSR marker detection. It was found that...