Impact of Cre and peroxidase genes of selected new wheat lines on cereal cyst nematode (Heterodera avenae woll) resistance.(Report)

Introduction

The Cereal Cyst Nematodes (CCN: Heterodera avenae Woll) have a global distribution and cause significant economic yield losses in many countries of the world (Nicol et al., 2003). Developing high yielding cultivars with tolerance to abiotic and biotic stresses is one of the main challenges, and in light of the new information on CCN in Saudi Arabia, it is also necessary in some regions to identify, confirm and incorporate nematode resistance into new high yielding cultivars. Resistance is considered one of most appropriate control methods as it is cost-effective, environmentally friendly and achievable with collaboration of research groups around the world. The use of the former conventional method of screening for resistance involved in a biological assay, which was time-consuming, prone to inconsistencies and relatively expensive (Ogbonnaya et al., 2001) is greatly reduced. Eight genes for resistance to CCN have been identified in hexaploid wheat and its relatives: Cre1 (Cereal root eelworm--locus 1) (Triticum aestivum 2B) (Williams et al. 1994), Cre2 (transferred to wheat from Aegilops ventricosa) (Delibes et al. 1993), Cre3 (2D, transferred from A. tauschii) (Eastwood et al. 1994), Cre4 (A. tauschii) (Eastwood et al. 1991), Cre5 (2A, VPM1 segment from A. ventricosa) (Jahier et al. 2001), Cre6 (A. ventricosa 5NV) (Ogbonnaya et al., 2001), Cre7 (A. truincialis) (Romero et al., 1998) and Cre8 (T. aestivum 6B) (Williams et al. 2003). CCN resistance genes have also been mapped in rye (6R, Taylor et al., 1998) and barley (2H, Kretschmer et al., 1997). A linkage disequilibrium study (Paull et al. 1998) found an RFLP locus, Xcdo347, that was associated with the Festiguay-derived CCN resistance of the wheat cultivars Molineux, Frame and Barunga. Williams et al. (2003) used this RFLP as a starting point to genetically locate, with RFLP markers, the gene Cre8 which provides CCN resistance (tolerance) in the cultivar Molineux. Cre1 confers resistance to several European H. avenae pathotypes as well as the Australian pathotype, albeit with varying levels of nematode reproduction in different genetic backgrounds of the host. Comparison of Cre1 with the nematode resistance gene Cre3, derived from the diploid D genome progenitor of wheat, Aegilops tauschii, showed that both provide resistance to the Australian pathotype, but differ in their specificity to European and Middle Eastern pathotypes (Ogbonnaya et al., 2001). Cre1 and Cre3 are located on the long arms of chromosomes 2B and 2D, respectively (Eastwood et al. 1994; Williams et al. 1994).

Resistant plants react to nematode infection by activating a number of inducible responses that are thought to be disease resistance related. Incompatible interaction between H-93-8 or TR-3531 lines and the CCN induces hypersensitive response (HR) with previous formation of syncitial cells and active oxygen species (AOS). Plants possess both enzymatic and nonenzymatic antioxidant defense systems to counteract AOS generated under stress conditions (Delibes et al., 2008). The antioxidant enzymes include peroxidase (PER, EC 1.11.1.7), esterase (EST, EC 3.1.1.2) and superoxide dismutase (SOD, EC 1.15.1.1). Isoelectrofocusing (IEF) isoenzyme analysis, four and seven days after infection, revealed that PER, EST and SOD activities increased with time in roots of lines H-93-8 and TR-3531, carrying Cre2, Cre5 and Cre7 genes, respectively, in comparison with the susceptible control (Andres et al., 2001; Montes et al., 2004). Recently, twenty wheat peroxidase genes were shown to fall into seven groups (TaPrx108 to TaPrx114) (Simonetti et al., 2009). The objectives of the present investigation were to: (1) study the genetic variation in yield, yield components, and resistance to CCN in a field infected with CCN, (2) screen wheat lines for resistance genes using SSR and RAPD markers developed for known resistance genes (Cre genes), and (3) investigate the presence of the peroxidase genes in wheat lines by PCR analysis.

Materials and methods

Field experiment

Field experiment was conducted in a CCN infected wheat field at NADC Hail project, Saudi Arabia, during the growing seasons 2007/2008 and 2008/2009. Eight selected bread wheat lines and adapted susceptible cultivar were sown on 20th December 2007 and 24th December 2008 with a seeding rate of 140 kg/ha. These included cultivar Yecora Rojo as well as 8 advanced lines (F10) selected from the wheat breeding program at the Plant Production Department, College of Food and Agriculture Sciences, King Saud University (Table 1). The plot size was 4 rows, 3 m long with row to row spacing of 20 cm. The recommended fertilizer …