Genetic diversity in rice (Oryza sativa) and estimation of outcrossing rate using morphological markers

English: Rice is an important food crop with two domesticated species namely Oryza glaberrima Steud. also known as African rice and O. sativa L. also known as Asian rice. Rice is a self-pollinating plant that shows some level of outcrossing under field conditions. Understanding the levels of gene flow is important for managing the conservation and maintenance of germplasm for gene banks and plant breeding programmes. It is equally important for the production of quality rice seed. There is also the concern of gene flow between genetically modified rice and other rice species; wild relatives and weedy (red) rice. This study used agro-morphological and microsatellite markers to evaluate the diversity in a collection of 36 accessions consisting of intraspecific (O. sativa and O. glaberrima) and interspecific (O. sativa x O. glaberrima) hybrid genotypes. The Shannon-Weaver diversity index was low measured by agro-morphological markers. The highest level of diversity was detected in the Indica accessions and the lowest diversity in the O. glaberrima accessions. Japonica accessions had brown or green apiculus and were awnless. O. glaberrima and landrace accessions had purple apiculus and some were awned. The Japonica group comprised mostly of improved varieties with a white pericarp whilst O. glaberrima accessions and landraces had a red pericarp. Selected interspecific hybrids combined traits of O. sativa and O. glaberrima to varying degrees. Microsatellite markers showed a total of 321 alleles with an average of 11.9 alleles per locus and an average major allele frequency of 0.29 per locus. The average gene diversity value was 0.81 and polymorphism information content was 0.80 per locus. Diversity indices for interspecific hybrids were intermediate between O. sativa and O. glaberrima, but closer to the O. sativa Japonica group. Two populations were revealed which corresponded to the O. sativa Indica group and O. sativa Japonica group. Interspecific hybrid accessions wer
Afrikaans: Rys is ‘n belangrike voedselgewas met twee aangeplante spesies naamlik Oryza glaberrima Steud., ook bekend as Afrika rys en O. sativa L., ook bekend as Asiese rys. Rys is ‘n selfbestuiwende gewas met ‘n persentasie kruisbestuiwing onder veldtoestande. ‘n Begrip van die hoeveelheid geenvloei is belangrik vir die bestuur en onderhoud van kiemplasma vir geenbanke en planteteelt programme. Dit is net so belangrik vir die produksie van kwaliteit ryssaad. Daar is ook kommer oor geenvloei tussen GM rys en ander rys spesies; wilde verwantes en onkruidagtige (rooi) rys. Hierdie studie het agro-morfologiese en mikrosatelliet merkers gebruik om diversiteit in ‘n versameling van 36 inskrywings bestaande uit intraspesifieke (O. sativa L. en O. glaberrima Steud.) en interspesifieke (O. sativa x O. glaberrima) rys genotipes te bepaal. Resultate van kwalitatiewe en kwantitatiewe eienskappe het verskille in diversiteit tussen die inskrywings getoon. Die waargenome diversiteit in O. glaberrima was laer as in O. sativa. Interspesifieke rys het intermediêre vlakke van diversiteit getoon. Die Shannon-Weaver diversiteitsindeks was laag gemeet aan agro-morfologiese merkers. Die hoogste diversiteitsvlak is gesien in die Indica inskrywings en die laagste diversiteit in die O. glaberrima inskrywings. Japonica inskrywings het bruin of groen aarpunte gehad en was baardloos. O. glaberrima en landrasinskrywings het pers aarpunte gehad, en sommige het baarde gehad. Die Japonica groep het meestal bestaan uit verbeterde variëteite met ‘n wit perikarp terwyl O. glaberrima inskrywings en landrasse ‘n rooi perikarp gehad het. Die interspesifieke basters het eienskappe van O. sativa en O. glaberrima gekombineer in verskillende grade. Mikrosatelliet merkers het ‘n total van 321 allele getoon met ‘n gemiddeld van 11.9 allele per lokus en ‘n gemiddelde major alleel frekwensie van 0.29 per lokus. Die gemiddelde geendiversiteitswaarde was 0.81 en die polimorfisme informasie inhoud was 0.80 per lo
Africa Rice Center (AfricaRice)