Morphology and fitness components of wild × crop F1 hybrids of Sorghum bicolor (L.) in Ethiopia: implications for survival and introgression of crop genes in the wild pool

Abstract

Natural hybridization between wild/weedy and crop species often results in rare hybrids, which can be more weedy and difficult to control. Moreover, the advent of transgenic crop plants raises questions of biosafety risk assessment on the consequences of rare hybrids with possible fitness enhancing genes on the environment. This study aimed at measuring the fitness components of wild–crop sorghum hybrids for various juvenile survival and adult morphological and fertility characters as part of the risk assessment of transgenic sorghum in Africa where the crop was believed to have first domesticated and serves as the major staple. Out of a pool of hybrids made in 2010 from 23 wild sorghum accessions and two released cultivated sorghum varieties using hand emasculation techniques, seven were selected for the field study of their fitness components in 2011. The study confirmed that crop–wild hybrids of sorghum are fertile. Two approaches were followed (relative fitness and mid-parent heterosis) which showed that most of the hybrids were as fit as their wild parents, and in some cases they showed mid-parent heterosis for the measured traits. The results of this study highlighted a potential risk that hybrids carrying crop genes (including herbicide resistance transgenes) could pose because they could be more weedy than their wild/weedy parents if transgenic sorghum is deployed in regions where the wild and cultivated sorghum populations coexist, such as in Ethiopia and in other parts of Africa.