The plant leaf cuticle is a chemically complex but largely waxy outer shell that limits water loss and also prevents some pathogens from gaining access to internal mesophyll. Rust fungi are obligate parasites, and most bypass the cuticle by thigmotropically locating stomata, growing through the stomatal openings, and then parasitizing mesophyll cells with haustoria. It is thought that even non-hosts of a given rust fungus do not resist until their mesophyll cells are contacted in this way. In other words, it is thought that the cuticle plays no role in non-host resistance. Here, we tested the hypothesis that poplar leaf cuticles might contribute to non-host resistance to rust fungi by chemically impeding the germination and growth of urediniosporelings of Melampsora larici-populina. Following an initial survey in China of the resistance of 36 genotypes of various species and interspecific hybrids of Populus to M. larici-populina, we selected three genotypes for the initial test of hypothesis: (1) A Populus purdomii genotype that is fully susceptible; (2) a Populus deltoides cv. ‘I-69’ that is incompletely resistant (i.e., a resistant host); and (3) a Populus tomentosa genotype that is a non-host to M. larici-populina. Urediniospores were assayed for germination in extracts of the cuticles of the three genotypes. Germination was most reduced by the P. tomentosa non-host cuticular extracts that also reduced the growth of germ tubes to 36 times less than that in controls or in the extract of the susceptible P. purdomii. Four cuticular components were identified as putative defense compounds given greater concentrations in P. tomentosa than in P. purdomii: Aucubin, hexakis(trimethylsilyl) ether, catechol, 7,9-Di-tert-buty l-1-oxaspiro (4,5) deca-6, 9-diene-2,8-dione and trifluoroacetamide. These four compounds were then tested, and they reduced urediniospore germination and uredinial density in inoculations of normally susceptible P. purdomii with Melampsora larici-populina. Thus, the cuticle of P. tomentosa can contribute to pre-haustorial, non-host resistance to M. larici-populina.

VRS1-5 genes determine spike row types during the early stages of spike development in barley ( Hordeum vulgare ), yet their functions for the determination of grain yield during the late stages of spike development are largely unknown. To assess the role of VRS1-5 genes in determining grain yield components, we sequenced VRS1-5 genes from 894 worldwide barley accessions and measured 19 spike morphology traits in four environments. Single nucleotide polymorphism SNP markers and gene marker-based haplotypes for VRS1-5 displayed close associations with spike morphology traits. We further developed a spatiote-temporal transcriptome atlas (255 samples) at 17 stages and five positions along the spike, that linked spike morphology to spikelet development and expression patterns of VRS1-5 genes. Phenotypic measurements demonstrated that mutations in VRS1-5 suppress the initiation of spikelet primordia and, trigger spikelet abortion by increasing cytokinin content and improving sensitivity of spikelet primordia to cytokinin. Our integrated results illustrate how breeding can globally alter spike morphology through diversity at the VRS1-5 genes, which show great potential in increasing barley grain yield.