Infraspecific Variations and Similarities among Onion (Allium cepa L.) Varieties Using Floral and Palynological Markers

Abstract

Infraspecific Variations and Similarities among Onion (Allium cepa L.) Varieties Using Floral and Palynological Markers Efficient utilization of plant genetic resources for nutrition and crop improvement requires systematic understanding of the important traits. Despite the potentials of onions to enhance food security and economic livelihoods, systematic information about it by farmers in sub-Saharan Africa is scanty. Eight onion varieties namely Ex-Dutsi, Ex-Huguma, Ex-Kudan, Ex-Kura, Ex-Kwadon, Ex-Romi, Waɓe and Wuyan Bijimi were cultivated under field experiment using a randomized complete block design with five replications and their pollen grains collected, acetolysed and fixed during flowering to compare their palynological features. Results obtained showed low infraspecific variations in the eight varieties. Two types of pollen aperture (mococolpoate and inaperturate), spherical shape with microreticulate sculpture were observed in all the varieties using light microscope. Variety ‘Wuyan-bijimi and Ex-Romi recorded the highest percentage occurrence of monocolpoate pollen (92%) but with the lowest percentage occurrence of inaperturate pollen (8%). DMRT of monocolpate density indicated that Waɓe was significantly different (p≤0.05), it had 56.60±2.52 (mm2) while the lowest density was recorded by Ex-Dutsi (15.40±2.18 mm2). Varieties Ex-Dutsi and Ex-Kura not significantly different but otherwise with other varities by the peduncle diameter. Numbers of anther and peduncle length are not good diagnostic characters among the varieties. There was no significant difference recorded in the pollen polar length, equatorial diameter, and exine thickness among the varieties. Multivariate analysis showed three principal components contributing 21.53% of observed variability, while cluster analysis yielded two groups (Ex-Kwadon, Ex-Kura, Ex-Romi and Wuyan-bijimi in cluster 1 while Ex-Dutsi, Ex-Huguma, Ex-Kudan and Waɓe formed cluster 2) at 89.7% similarity coefficient.  Varieties in the different clusters obtained can be exploited for desired nutritional traits.