Distribution of wild rice species and hybridization between cultivated rice and Oryza longistaminata in Tanzania.

Abstract

Wild rice species of genus Oryza are distributed across Asia, Central and South America, Australia and Africa. Wild rice species, such as O. longistaminata, with an AA genome can hybridize with cultivated rice under field conditions and produce F₁ hybrids. Such hybridization may cause ecological and evolutionary consequences. An understanding of the distribution of wild relatives of rice and hybridization between cultivated rice and its wild relatives is an important aspect for biosafety in assessing risks caused by gene escape from crop to wild relatives. Despite the presence of five wild rice species in Tanzania, little is known about the distribution of wild rice species that are weeds of rice, or hybridization between cultivated rice and O. longistaminata under field conditions. The aim of this study was to generate baseline data on the distribution of wild rice species and hybridization between cultivated rice and O. longistaminata under field conditions. A field survey was conducted in 28 rice fields from seven regions and hybridization was determined by morphological and molecular analysis. Oryza punctata, Oryza barthii and O. longistaminata were common wild rice species that are weeds of cultivated rice and hybridization between cultivated rice and O. longistaminata were detected under field conditions. Frequencies of hybridization were estimated as 2.2% for crop-to-wild and 0.1% for wild-to-crop. Wild rice species found growing proximity to cultivated rice and hybridization occurs in Tanzania under field conditions with a noticeable frequency from crop-to-wild and wild-to-crop.