Ecotypic variation for seed dormancy, longevity and germination requirements in wild/weedy Sorghum bicolor in Ethiopia: implications for seed mediated transgene dispersal and persistence

Abstract

Seed dispersal is one of the vehicles of gene flow in plants. If a seed carrying transgene(s) is dispersed into the environment, the fate can be determined by its persistence in the soil bank, which can also vary in different ecotypes of a species and the physical environment of the soil including temperature and moisture. This study aimed at investigating ecotypic differences in wild sorghum for dormancy and longevity and their response to varying levels of temperature and moisture for seed germination to aid efforts to predict the potential risk of transgene flow via seeds and persistence in the soil. Wild sorghum seed was collected from different geographical regions in Ethiopia and buried for a maximum of 24 months in the soil. In a separate study, three levels of constant temperature and five levels of osmotic potential (Ψs) were used to investigate variation in wild sorghum ecotypes for seed germination. Viability of buried seeds declined over time, but the rate of decline differed among ecotypes. Better seed longevity was observed at 20 cm soil depth than 10 cm in two wild sorghum ecotypes. Crop seeds depleted within the first six months regardless of the burial depth whereas on the average 1.24% viability was observed in wild sorghum seed after 24 months of burial in the soil. Ecotypic differences were also evident in response to varying temperature and Ψs. Therefore, dispersed seeds carrying crop genes (including transgenes) could persist in the soil for considerable period of time, which may have implications for transgene flow and persistence.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-248) contains supplementary material, which is available to authorized users.

How an improved sorghum variety evolves in a traditional seed system in Mali: Effects of farmers’ practices on the maintenance of phenotype and genetic composition

“…Seeds for these plants is often disseminated in the fields via animal manure and it can survive for several years as seed banks in the soil (Jacques et al, 1974;Adugna, 2013). Farmers indicated during interviews that they generally eliminate weedy types before harvest; however, our observations suggested the presence of offtypes resembling wild-weedy sorghums at the maturity stage, especially in M 7 and W 1 Soumba fields.…”

Indirect estimates reveal the potential of transgene flow in the crop–wild–weedSorghum bicolorcomplex in its centre of origin, Ethiopia

“…Furthermore, the crop–wild hybrids were found to be fitter than their wild parents for the measured fitness traits. The seeds of these hybrids were also found to persist longer in the soil than the crop (Adugna, 2013).…”

“…The Africa Biofortified Sorghum (ABS) Project developed the first transgenic sorghum (‘Golden sorghum’), which has high levels of pro-vitamin A and aminoacids (lysine and threonine) and low phytate (, accessed 14 January 2016). As part of a project on risk assessment of transgenic sorghum in Africa, separate reports have been published (Adugna, 2013; Adugna and Bekele, 2013a, b; Adugna et al , 2013a, b; Adugna and Bekele, 2015). This paper intends to compile and present in a summarized form the major findings and recommendations on risk of crop–wild gene flow in the crop–wild–weed Sorghum bicolor complex in Ethiopia based on indirect estimates.…”

Evaluation of Seed Persistence in Cow Cockle

“…High seed persistence in weedy or wild populations acts as a buffer against reproductive failure and local extinction (Teo‐Sherrell et al, 1996). For example, in sorghum ( Sorghum bicolor L.), Adugna (2013) reported differences in seed longevity between crop and wild populations. The crop seeds were depleted within the first 6 mo.…”

“…5). Seed dormancy partially determines persistence in soil seed banks (Gu et al, 2003; Adugna, 2013). Furthermore, a positive relationship between seed longevity (laboratory) and seed dormancy has been suggested (Jurado and Flores, 2005) but has not been established.…”