The wheat Lr34 multipathogen resistance gene confers resistance to anthracnose and rust in sorghum.

Wendelin Schnippenkoetter,Wai Lung Chan,Beat Keller,Ricky Milne,Evans Lagudah,Katherine Dibley,Eunjung Kwong,Simon G Krattinger,Alexander Zwart,Jodie White,Clive Lo,Guoquan Liu,Ian Godwin

doi:10.1111/pbi.12723

Abstract

SummaryThe ability of the wheat Lr34 multipathogen resistance gene (Lr34res) to function across a wide taxonomic boundary was investigated in transgenic Sorghum bicolor. Increased resistance to sorghum rust and anthracnose disease symptoms following infection with the biotrophic pathogen Puccinia purpurea and the hemibiotroph Colletotrichum sublineolum, respectively, occurred in transgenic plants expressing the Lr34res ABC transporter. Transgenic sorghum lines that highly expressed the wheat Lr34res gene exhibited immunity to sorghum rust compared to the low‐expressing single copy Lr34res genotype that conferred partial resistance. Pathogen‐induced pigmentation mediated by flavonoid phytoalexins was evident on transgenic sorghum leaves following P. purpurea infection within 24–72 h, which paralleled Lr34res gene expression. Elevated expression of flavone synthase II, flavanone 4‐reductase and dihydroflavonol reductase genes which control the biosynthesis of flavonoid phytoalexins characterized the highly expressing Lr34res transgenic lines 24‐h post‐inoculation with P. purpurea. Metabolite analysis of mesocotyls infected with C. sublineolum showed increased levels of 3‐deoxyanthocyanidin metabolites were associated with Lr34res expression, concomitant with reduced symptoms of anthracnose.

Highlights

Sorghum (Sorghum bicolor) is ranked as the fifth most commonly cultivated cereal in the world (FAOSTAT, 2016)
Genomic blot analysis showed that line Lr34-2 carried a single copy of the Lr34 multipathogen resistance gene (Lr34res) gene, whereas multiple copies were detected in lines Lr34-5 and Lr34-6
We investigated by site directed mutagenesis whether changes to Sb01g016775 involving the two critical amino acids to a modified Sb01g016775 with a deleted phenylalanine (ΔF525) and tyrosine to histidine (Y613H) was capable of conferring resistance to sorghum rust as observed with Lr34res

Summary

Introduction

Sorghum (Sorghum bicolor) is ranked as the fifth most commonly cultivated cereal in the world (FAOSTAT, 2016). Some of its useful attributes are tolerance to dry environments, high sugar content, high yields of forage biomass per unit of cultivated area and as a rich source of distinct phytochemicals such as dhurrin, sorgoleone and 3-deoxyanthocyanidins. Protecting yield losses from diseases such as anthracnose (Colletotrichum sublineolum) and rust (Puccinia purpurea), which can be variable in different agro-ecological regions continues to be a goal of sorghum improvement. Grain size and yield losses over 50% have been reported with anthracnose epidemics (Thakur and Mathur, 2000). Rust is problematic in late-sown crops (White et al, 2012) with yield losses up to 65% (Bandyopadhyay, 2000)

Results

Discussion

Conclusion