Leaf rust on high yielding winter wheats in Chile
The physical environment and farming system in Chile are conducive to high yields from winter/alternate wheat cultivars. The national average yields for 2012-2014 were 6.5 t/ha for pasta wheat and 5.3 t/ha for bread wheat grown on 19,000 and 239,000 ha, respectively. The most efficient farmers obtain averages of 8-9 t/ha, and experimental plots at southern INIA sites are as high as 14 t/ha. The most important diseases are Septoria leaf blotch, stripe rust, powdery mildew, and BYDV. Recent increases of leaf rust on winter cultivars from near non-existence to the level of a major threat are a concern. Wheat cultivars such as Bicentenario INIA showed yield increases of 31.7% to reach 12.4 t/ha yield when sprayed twice with a mixture of strobilurin and triazol compared to 9.4 t/ha for the unsprayed control. Susceptible winter cultivars being introduced by private companies require complete chemical protection. In order to understand the virulences present in the pathogen population the Thatcher NILs were grown in 2014/15 under non-inoculated conditions in central [Chillan] and southern [Osorno] Chile. The Morocco check showed 100S, Thatcher 60S, TcLr1 40S, TcLr2b 30S, TcLr2c 40S, TcLr3a 30S, TcLr3ka 20S, TcLr3bg 30S, TcLr9 20S, TcLr10 60S, TcLr11 80S, TcLr12 60S, TcLr13 70S, TcLr14a 70S, TcLr15 50S, TcLr16 60S, TcLr17a 30S, TcLr18 20MR, TcLr19 0, TcLr20 30S, TcLr21 0, TcLr22a 0, TcLr23 70S, TcLr24 60S, TcLr25 0, TcLr26 60S, Lr27+31 80S, TcLr28 10MR, TcLr29 40MS, TcLr30 60S, TcLr32 70S, TcLr33 60S, TcLr34 70S, TcLr35 10MR–MS, Lr36 0, and TcLr37 0. The most significant differences (>40%) in response between the two locations were for TcLr2b, TcLr2c, TcLr11 and TcLr33. The Cereal Disease Laboratory (U.S.A.) tested 68 isolates from 55 samples from 2012/13 and identified 14 races, including one Triticum turgidum race (BBBQJ 26%). Significant breeding efforts are currently underway to address the leaf rust problem in Chile.