Seedling and adult plant resistance to leaf rust in 46 Chinese bread wheat landraces and 39 wheat lines with known Lr genes

Wheat leaf rust,caused by Puccinia triticina(Pt),is an important foliar disease that has an important influence on wheat yield.The most economic,safe and effective way to control the disease is growing resistant cultivars.In the present study,a total of 46 wheat landraces and 34 wheat lines with known Lr(leaf rust resistance)genes were inoculated with 16Pt pathotypes for postulating seedling resistance gene(s)in the greenhouse.These cultivars and five wheat differential lines with adult plant resistance(APR)genes(Lr12,Lr22b,Lr34,Lr35 and Lr37)were also evaluated for identification of slow rusting resistance in the field trials in Baoding,Hebei Province of China in the 2014–2015 and 2015–2016 cropping seasons.Furthermore,10 functional molecular markers closely linked to 10 known Lr genes were used to detect all the wheat genotypes.Results showed that most of the landraces were susceptible to most of the Pt pathotypes at seedling stage.Nonetheless,Lr1 was detected only in Hongtangliangmai.The field experimental test of the two environments showed that 38 landraces showed slow rusting resistance.Seven cultivars possessed Lr34 but none of the landraces contained Lr37 and Lr46.Lr genes namely,Lr9,Lr19,Lr24,Lr28,Lr29,Lr47,Lr51 and Lr53 were effective at the whole plant stage.Lr18,Lr36 and Lr45 had lost resistance to part of pathotypes at the seedling stage but showed high resistance at the adult plant stage.Lr34 as a slowing rusting gene showed good resistance in the field.Four race-specific APR genes Lr12,Lr13,Lr35 and Lr37 conferred good resistance in the field experiments.Seven race-specific genes,Lr2b,Lr2c,Lr11,Lr16,Lr26,Lr33 and LrB had lost resistance.The 38 landraces showed slow rusting resistance to wheat leaf rust can be used as resistance resources for wheat resistance breeding in China.

QTL mapping of adult plant resistance to stripe rust and leaf rust in a Fuyu 3/Zhengzhou 5389 wheat population

Stripe or yellow rust(YR)and leaf rust(LR)cause large losses in wheat production worldwide.Resistant cultivars curtail the levels of losses.The present study aimed to identify quantitative trait loci(QTL)for YR and LR resistance in 147 F2:6 recombinant inbred lines(RIL)derived from the cross Fuyu 3/Zhengzhou 5389.The RIL population and parents were genotyped with the Wheat55 K single nucleotide polymorphism(SNP)array and simple sequence repeat(SSR)markers.All materials were also phenotyped for YR severity at Mianyang in Sichuan province and Baoding in Hebei province in the 2015/2016,2016/2017,and 2017/2018 cropping seasons,and LR severity at Zhoukou in Henan province and at Baoding in 2017/2018.Eleven QTL for YR resistance and five for LR resistance were detected using inclusive composite interval mapping(Ici Mapping).Four of these QTL on chromosomes 1 BL,2 BS,3 AL,and 5 AL conferred resistance to both YR and LR.The QTL on 1 BL was Lr46/Yr29,and that on 7 BL might be Lr68.The QTL on chromosome 2 BS was detected at a similar position to previously detected loci.QYr.hebau-3 AL/QLr.hebau-3 AL,QYr.hebau-5 AL/QLr.hebau-5 AL,QYr.hebau-7 DL,QYr.hebau-4 BS,QYr.hebau-6 DL,and QYr.hebau-2 AS are likely to be new.An SSR marker for QYr.hebau-7 DL was developed and validated in a diverse wheat panel from China,suggesting effectiveness in different genetic backgrounds.These QTL with closely linked SNP and SSR markers could be useful for marker-assisted selection in wheat breeding programs targeting durable resistance to both diseases.

Identification of leaf rust resistance genes in common wheat varieties from China and foreign countries

Wheat leaf rust,triggered by Puccinia triticina Eriks(Pt),is among the most important diseases of wheat worldwide.Deploying resistant varieties against leaf rust is the most effective,environmentally-friendly and economic way to control the disease.In the present study,66 wheat varieties form China and foreign countries were tested with 17 Pt races for gene postulation during the seedling stage in the greenhouse.All the varieties were also planted to identify slow rusting responses to leaf rust at the adult plant stage in Baoding and Zhoukou field trials during the 2016/2017 to 2017/2018 cropping seasons.Moreover,12 closely linked molecular markers to known leaf rust resistance(Lr)genes were used for assessing all the varieties.The results of both gene postulation and molecular marker identification showed that a total of eight Lr genes,Lr1,Lr10,Lr17,Lr20,Lr26,Lr34,Lr37 and Lr46,either singly or in combination were detected in 32 varieties.Known Lr genes were not identified in the remaining 34 varieties.Seventeen varieties were found to have slow rusting resistance.The resistance sources identified in this study can be used as resources for resistance against leaf rust in wheat breeding programs in China and the respective foreign countries.

High-temperature wheat leaf rust resistance gene Lr13 exhibits pleiotropic effects on hybrid necrosis

Dear Editor,Wheat is one of the most important staple food crops.Leaf rust caused by Puccinia triticina Eriks.(Pt)is a destructive foliar disease that threatens world wheat production.Complementary wheat genes Necrosis 1(Ne1)and Necrosis 2(Ne2)on chromosome arms 5BL and 2BS,respectively,cause hybrid necrosis(Caldwell and Compton,1943;Chu et al.,2006).Ne2 shows extremely tight genetic linkage with leaf rust resistance gene Lr13(Zhang et al.,2016).We previously identified a temperature-sensitive leaf rust resistance gene LrZH22 in Chinese wheat cultivar Zhoumai 22(ZM,Figure 1A)that was effective against most Chinese Pt pathotypes(Wang et al.,2016)and shared an overlapping genetic interval with Lr13.In a separate study,a recessive early leaf senescence 1(els1)gene(Figure 1B)shared an overlapping interval with LrZH22/Lr13/Ne2(Chu et al.,2006;Wang et al.,2016;Zhang et al.,2016;Li et al.,2018).However,the function and relationship of LrZH22/Lr13/Ne2/els1 remained unknown for decades.Here,we report the map-based cloning of LrZH22 and els1 and characterize their relationship with Lr13 and Ne2 in conjunction with a companion paper(Hewitt et al.t 2021)studying the same gene.