Growth rate and genetic structure of Sinapis arvensis susceptible and herbicide resistant populations originating from Greece

Abstract

Weed resistance to herbicides is a serious agricultural issue that threatens the sustainability of world food production, as its widespread appearance has reduced the diversity of weed control practices and posed economic and environmental risks. Wild mustard (Sinapis arvensis), a very competitive weed in winter cereals, has evolved resistance to ALS-inhibiting herbicides used in Greece. As growth rate and genetic structure of weeds affect their competitive ability against crops, the purpose of this work was to study the effect of geographical origin and resistance profile on growth rate and genetic structure of five S. arvensis populations. In particular, the cross-resistant to tribenuron and imazamox P2, P3 and P4 populations originating from the counties of Larissa, Phthiotida, and Pieria, respectively, the resistant to tribenuron P1 originating from Chalkidiki and the susceptible PS originating from Thessaloniki were evaluated. The growth rate was studied by determining fresh weight, number of leaves, height, and seed weight of plants, whereas the genetic structure by using six inter simple sequence repeat (ISSR) molecular markers. Regarding growth rate, the b slope values of the linear equation fitted on fresh weight regression against sampling time were 10.87, 9.94 and 11.41 for P2, P3 and P4 populations, respectively, which were higher than those of P1 (8.03) and PS (6.79) populations, while the b slopes of leaf number were 3.8 and 4.63 for P3 and P1 populations, which were higher than those of PS (2.1), P2 (2.79) and P4 (2.84). The use of ISSR markers showed also differences between populations in their genetic structure parameters [genetic diversity (h), Shannon index (I), number of alleles (Na), percentage of polymorphic loci for each population (P%), variance among and within populations, and FST value, that is a measure of differentiation among populations due to genetic structure], which attributed to origin and herbicide resistance profile. The ISSR bands indicated that 80% of the molecular variation was within populations and 20% among populations. In addition, the dendrogram produced by the combination of GenALEx and MEGA7 statistical software, along with the corresponding PCoA graphical output indicated similar groups of the individuals belonging in these populations.