Genetic variation in populations of Western Australian wild radish

Abstract

Raphanus raphanistrum L. (wild radish) is a major problematic weed worldwide. Random amplified polymorphic DNA (RAPD) was used to estimate the degree of genetic diversity between and within 2 populations of wild radish (WARR 5 and WARR 6), found to exhibit multiple herbicide resistance compared with a susceptible population (WARR 7). It is believed that weed species with high degrees of genetic variation show potential for developing resistance to herbicides. Of the 13 RAPD primers screened, 9 primers generated 97 polymorphic bands concomitant with a high level of polymorphism (82%) between the wild radish populations, characteristics of an outbreeding species. Analysis of molecular variance (AMOVA) showed a markedly higher proportion of diversity within populations (87%) as opposed to between populations (13%). Principal component analysis (PCA) further highlighted the large amount of variation between individuals within populations. Only one marker, OPC19–8, was found to be unique to the WARR 7 population but absent in WARR 5 and in most individuals of the WARR 6 populations. This marker may potentially be correlated with herbicide susceptibility. The 2 resistant wild radish populations were found to be closely related (0.7% dissimilar) to each other, whereas the susceptible population was genetically dissimilar to them by 2.3%. This higher level of dissimilarity between the susceptible and resistant populations may be explained by limited gene flow between them since the susceptible population is geographically located further away from the resistant populations. Hence, it may be concluded that the underlying genetic structure of the 3 wild radish populations seems to be similar despite WARR 6 and WARR 5 having been exposed to mixed herbicide usage for over 17 years.

Genetic Diversity of Radish (Raphanus sativus L.) Germplasm Resources Revealed by AFLP and RAPD Markers

“…In this study, 66.1% bands generated by RAPD assay were polymorphic, which was lower than the polymorphic proportion of 78.2% detected by RAPD among Pakistan radish germplasms (Rabbani et al 1998), 88.5% among Australian radish cultivars (Pradhan et al 2004), 85.4% among late-bolting radish cultivars (Liu et al 2008), and 82% in wild radish population (Raphanus raphanistrum L.) (Madhou et al 2005). As for AFLP marker, the polymorphic rates of 58.4% and 76.5% were detected among wild radishes (Huh and Huh 2001) and cultivated radish varieties (Muminovic et al 2005), respectively.…”

“…Many molecular markers, such as random amplified polymorphic DNA (RAPD) (Yamagishi et al 1998;Matveeva et al 2002;Huh and Ohnishi 2003;Madhou et al 2005) and amplified fragment length polymorphism (AFLP) (Huh and Huh 2001;Huh and Ohnishi 2002), have been applied respectively to estimate the genetic diversity of radish. Multiple types of makers were also employed simultaneously to examine genetic diversity of radish germplasm.…”

Molecular characterisation of radish cultivars

“…These results indicate a great genetic diversity among Brazilian cultivars which can be explained by the high polymorphism found in both the species and the crop. In a study with RAPD in radish populations, 82% polymorphism was detected (MADHOU et al, 2005), 78.2% in the germplasm bank of Pakistan (RABBANI et al, 1998) and 85.4% between the radish cultivars (LIU et al, 2008).…”

Identification of the first glyphosate‐resistant wild radish (Raphanus raphanistrum L.) populations

“…Seeds are innately dormant, and this characteristic contributes to a persistent soil seed bank . Continuous herbicide use on large genetically diverse populations has resulted in the evolution of resistance to multiple herbicides, including inhibitors of acetolactate synthase (ALS), phytoene desaturase (PDS), photosynthetic electron transport (PSII) and synthetic auxin herbicides …”