Botanical indices of ploidy levels in some African accessions of Oryza punctata Kotschy ex Steud

Twenty-nine accessions of Oryza punctata Kotschy ex Steud, from local and other African habitats were studied to establish the attributes that can delineate the two ploidy levels based on agro-botanical, foliar epidermal and nodal anatomical characteristics. The diploid plants of O. punctata are early-maturing annuals with a small biomass, while the tetraploids are large, vigorous perennials. From the anatomical and morphological traits: the diploids have narrower leaves (0.95 - 1.36 cm wide) than the tetraploids (1.9 - 2.3 cm); the culms of diploids are generally thin (0.28 - 0.35 cm in diameter) compared to the tetraploids (0.37 - 0.57 cm); the diploids have longer spikelets (6.20 - 7.04 mm) with length/breadth > 3; longer awns (52 - 86 mm) than the tetraploids (20 - 31 mm). The basal cells of microhairs in the diploids are about twice the length of apical cells, but only slightly longer than the apical cells in the tetraploids; prickle hairs are sparse in the intercostal zone of diploids, but abundant in tetraploids; short cells are paired and abundant in the intercostal zone of diploids, but sparse and solitary in the tetraploids. These indices delineated the ploidy levels and are reliable for use as identification aids.Keywords: Agro-botanical characteristics, diploid punctata, tetraploid punctata, delineation, identification aids

Issues concerning reproductive isolation in a rice hybrid swarm involving Oryza sativa Linn., O. longistaminata A. Chev. et Roehr. and Oryza glaberrima Steud. located in Jebba Nigeria

A hybrid swarm involving O. sativa, O. glaberrima and O. longistaminata occuring in Jebba, Nigeria was studied to investigate the processes  involved in the population dynamics. Reproductive parameters such as pollen stainability, pollen size, anther structure, seed set were  investigated. The chromosomes of the hybrid population were also studied. The study reveals post-zygotic mechanism involving segregational as well as developmental hybrid sterility to be the major isolating mechanism involved the reproductive isolation existing among the parent populations in the swarm. Hybridization and introgression have played significant roles in creating this hybrid swarm which holds a lot of promise for speciation in the genus.© 2013 International Formulae Group. All rights reserved. 2040Keywords: Rice swarm, population dynamics, hybrid sterility, isolating mechanism, introgression