Evaluation of winter hardiness in some crucifer crops by microsatellite (SSR) markers

Abstract

In Serbia and other countries of the European Southeast, the autumn-sown grain and forage crucifer crops are traditionally dominant over those that are sown in spring (Marjanović Jeromela et al. 2017). Following the same trend on a global scale, rapeseed (Brassica napus L.) is the most important, with about 13,500 ha in 2016 (FAOSTAT 2017) and generally increasing over the years (Marinković et al. 2004). At the same time, fodder kale (Brassica oleracea L. var. viridis L.) is highly appreciated as the first fresh forage in the spring, with a beneficial effects in the nutrition of milk cows (Mikić et al. 2014). Due to its typical continental climate, with moderately cold winters and often unexpected dry springs, the breeding programme on grain and forage crucifers in the Institute of Field and Vegetable Crops (IFVCNS) in Novi Sad prefers developing the autumn-sown cultivars to the spring-sown ones, especially since the yields of both oil-rich grain and protein-abundant forage is significantly higher in the former (Marjanović Jeromela et al. 2012). Apart from yield and its quality, one of the most significant goals in breeding autumn-sown crucifers is enhancing winter hardiness, that is, the overall tolerance to the duration and the intensity of low temperatures, which is shared with the research on autumn-sown annual legumes (Mikić et al. 2011). The screening methods allowing accurate and precise assessment of winter survival are critical for winter crop research programs. The most commonly used method is carried out by determining the ratio between the plant number before and after the winter, that is, the so-called winter survival percentage. The inherent difficulties in field trials constantly stimulate defining the improved tests complementing the screening in field conditions in contrasting environments (Rife 1996, Kole et al. 2002, Sun et al. 2007, Waalen et al. 2013). The genetic variability of current rapeseed breeding material is narrow due to its limited geographic range and intensive breeding for specific oil and seed quality traits (Hasan et al. 2006). Many studies have demonstrated the suitability of molecular marker techniques for evaluation of genetic variation in rapeseed. Some of the breaking-through approaches to investigate the genetic distance in this crop were investigated by random amplification of polymorphic DNA (RAPD, Mailer et al. 1994), restriction fragment length polymorphism (RFLP, Diers et al. 1994) and sequence-related amplified polymorphisms (SRAP) (Riaz et al. 2001). Cluster analysis using microsatellite or simple sequence repeat (SSR) markers covering the whole rapeseed genome proves as quite suitable and precise to clearly differentiate winter and spring rapeseed from each other (Plieske & Struss 2001). The goal of our study was to identify the heterotic groups in three crucifer crops for winter survival using SSR molecular markers considered close to quantitative trait loci (QTLs) relatd to this important agronomic characteristic.