Progress in breeding wheat for tolerance and resistance to root-lesion nematode (Pratylenchus thornei)

Root-lesion nematode (Pratylenchus thomei) is a serious pathogen of wheat and other crops and is estimated to cost the Australian wheat industry $36M per year in lost production. Use of tolerant and resistant wheat cultivars is the most important component of integrated control of this nematode. A targeted approach has been adopted to develop such cultivars for the northern grain belt of Australia. Methods are described that have been used successfully to screen for tolerance in the field and resistance in the glasshouse. Backcross programs used to incorporate superior tolerance into locally adapted cultivars have doubled tolerance levels, which translates into double the grain yield on severely infested sites. Resistance from the bread wheat line GS50a backcrossed into locally adapted cultivars has reduced the nematode multiplication rate more than tenfold in advanced lines. New sources of resistance have been located in Aegilops tauschii, in durum wheat and in synthetic hexaploid wheats derived from them. Other new sources have been identified in landrace wheats and wheat cultivars from the Middle East and North Africa. A concerted effort is required to exploit these new found resistances and knowledge to accelerate the production of suitable cultivars for farmers' use.