The occurence of a hybrid swarm involving O. longistaminata A. Chev. et Roehr., Oryza glaberrima Steud. and Oryza sativa Linn. in Jebba, Nigeria

Abstract

A hybrid swarm involving Oryza longistaminata, O. glaberrima and O. sativa was discovered at Jebba in Nigeria. A preliminary study in 2000 paved the way for this study which used extensive morphological and anatomical markers to identify and characterise putative hybrids and their advanced generation segregants. The factors favouring the occurrence of the hybrid swarm were identified as the existence of large population of O. longistaminata as natural vegetation in this location, peasant farming based on O. sativa in cleared plots inside O. longistaminata leading to interphases between cultivated rice (O. sativa and O. glaberrima) and the wild. The key favourable husbandry practices identified are minimum tillage, harvesting by straw-clipping, saving of hybrid forms on the plot at harvest and ratoons from harvested crop both allowing for introgression, and the timing of the planting of the rice crop which synchronizes with the flowering of O. longistaminata about September. Inspite of the upsurge of rice farming in this location, O. longistaminata still grows around natural impoundments which the peasant farmers still sustain. The population dynamics of the three rice species arising from the factors identified are discussed.The stability and the future of their hybrid swarmare speculated.

Keywords: Oryza longistaminata, O. glaberrima, O. sativa , Hybrid Swarms, Peasants, Population Dynamics.