Abstract
Sorghum (Sorghum bicolor) is an important grain and forage crop grown across the US. In some areas, sorghum can become feral along roadsides and other ruderal areas, as a result of seed spill during harvest or transport. In some of these situations, feral sorghum grows in or near established johnsongrass (S. halepense) populations. Johnsongrass, a wild relative of sorghum and an incredibly noxious weed, is capable of hybridizing with cultivated sorghum. Because commercial hybrid sorghum cultivars are produced with cytoplasmic male sterility, progeny of the hybrid crop which compose the founder feral populations also segregate for male sterility. Consequently, male sterility in feral sorghum may increase the risk of outcrossing with johnsongrass. Using field surveys and spatial modelling, the present study aimed at documenting the occurrence of feral sorghum and understanding the anthropogenic and environmental factors that influence its distribution. Further, this research documented the sympatry of feral sorghum and johnsongrass in the roadside habitat. A total of 2077 sites were visited during a systematic field survey conducted in fall 2014 in South Texas. Feral sorghum and johnsongrass were found in 360 and 939 sites, while the species co-existed at 48 sites (2.3% of all surveyed sites). The binary logistic analysis showed a significant association between the presence of feral sorghum and road type, road body-type, micro-topography of the sampling site, nearby land use, and the presence of johnsongrass, but no association with the distance to the nearest grain sorting facility. The probability of finding feral sorghum away from johnsongrass patches was generally higher than finding them co-occur in the same location. A probability map for spatial distribution of feral sorghum was developed using the nearby land use type and the regional habitat suitability for johnsongrass as two key predictors. Overall, results show that feral sorghum and johnsongrass co-occur at low frequencies in the roadside habitats of South Texas, but these low levels still present a significant opportunity for hybridization between the two species outside of cultivated fields.
Highlights
Escape and establishment of crop species outside of agricultural systems, known as crop ferality, can be a concern if the escaped crop contains novel traits and establishes self-perpetuating populations within agricultural landscapes [1,2,3]
Using a binary logistic model, we modelled the probability of the presence of feral sorghum as a function of the road type, road body-type, micro-topography of the surveyed site, the nearby land use, presence/ absence of johnsongrass and distance to grain sorting facilities
Roadsides are known to be the main corridors for the escape of crops away from the agricultural fields
Summary
Escape and establishment of crop species outside of agricultural systems, known as crop ferality, can be a concern if the escaped crop contains novel traits and establishes self-perpetuating populations within agricultural landscapes [1,2,3]. A feral population can be found by the dispersal of seeds from the agricultural fields to adjacent habitats such as the roadsides. Humanmediated dispersal, such as seed spill from farm machinery (during planting and harvest) and seed transport trucks or hitchhiking on a vehicle, is the main vector for crop seed dispersal out of agricultural fields [4,5]. While propagule dispersal is a critical first step for the establishment of feral crop populations in natural areas, certain habitat characteristics such as vegetation density and drainage potential can influence the establishment of feral populations in these areas [9]. Seed dormancy and the ability to establish a seedbank would allow the feral populations to persist in natural habitats and enable recovery from stochastic fluctuations of the environment [10,11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
