Tetep is a rice cultivar known for broad-spectrum resistance to blast, a devastating fungal disease. The molecular basis for its broad-spectrum resistance is still poorly understood. Is it because Tetep has many moreNLRgenes than other cultivars? Or does Tetep possess multiple majorNLRgenes that can individually confer broad-spectrum resistance to blast? Moreover, are there many interactingNLRpairs in the Tetep genome? We sequenced its genome, obtained a high-quality assembly, and annotated 455 nucleotide-binding site leucine-rich repeat (NLR) genes. We cloned and tested 219NLRgenes as transgenes in 2 susceptible cultivars using 5 to 12 diversified pathogen strains; in many cases, fewer than 12 strains were successfully cultured for testing. Ninety clonedNLRs showed resistance to 1 or more pathogen strains and each strain was recognized by multipleNLRs. However, fewNLRs showed resistance to >6 strains, so multipleNLRs are apparently required for Tetep’s broad-spectrum resistance to blast. This was further supported by the pedigree analyses, which suggested a correlation between resistance and the number of Tetep-derivedNLRs. In developing a method to identifyNLRpairs each of which functions as a unit, we found that >20% of theNLRs in the Tetep and 3 other rice genomes are paired. Finally, we designed an extensive set of molecular markers for rapidly introducing clustered and pairedNLRs in the Tetep genome for breeding new resistant cultivars. This study increased our understanding of the genetic basis of broad-spectrum blast resistance in rice.

Development of soft wheat (Triticum aestivum L.) cultivars with excellent cookie quality is an important breeding objective in southern China. Seventeen Chinese soft wheat genotypes grown at three locations in the 2000–2001 and 2001–2002 seasons in the southern winter wheat region, were uniformly evaluated for their solvent retention capacities (SRC), pentosan content, dough rheology, and suitability for making sugar snap cookies, to identify the main parameters that could be used in wheat breeding programs for improving cookie quality. Significantly negative correlations were found between water SRC, sucrose SRC, and sugar snap cookie diameter, and between sodium carbonate SRC, alkaline water retention capacity (AWRC), and water soluble pentosan, while significantly positive correlations were obtained between water, sodium carbonate, lactic acid, and sucrose SRC and AWRC. Alveograph parameters were more closely associated with sugar snap cookie quality compared with parameters from farinograph and extensograph except for water absorption. Water SRC was highly and significantly associated with farinograph water absorption, extensograph extensibility, alveograph P (tenacity), and P/L (the ratio of tenacity and extensibility). Regression analyses showed that sucrose SRC and flour particle size could be used to predict the sugar snap cookie diameter. Cluster analysis based on sugar snap cookie diameter indicated that ‘Jianmai 1’, ‘Wanmai 19’, and ‘Wanmai 48’ were characterized by good cookie quality, with low water soluble and total pentosans, water and particularly sucrose SRC, water absorption, and P and P/L values. It also indicated that substantial progress for soft wheat sugar snap cookie quality improvement could be achieved through appropriate use of current elite germplasm.

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Development of a high-density SNP map and evaluation of QTL shed light on domestication events in tetraploid wheat and the potential utility of cultivated emmer wheat for durum wheat improvement. Cultivated emmer wheat (Triticum turgidum ssp. dicoccum) is tetraploid and considered as one of the eight founder crops that spawned the Agricultural Revolution about 10,000 years ago. Cultivated emmer has non-free-threshing seed and a somewhat fragile rachis, but mutations in genes governing these and other agronomic traits occurred that led to the formation of today's fully domesticated durum wheat (T. turgidum ssp. durum). Here, we evaluated a population of recombinant inbred lines (RILs) derived from a cross between a cultivated emmer accession and a durum wheat variety. A high-density single nucleotide polymorphism (SNP)-based genetic linkage map consisting of 2,593 markers was developed for the identification of quantitative trait loci. The major domestication gene Q had profound effects on spike length and compactness, rachis fragility, and threshability as expected. The cultivated emmer parent contributed increased spikelets per spike, and the durum parent contributed higher kernel weight, which led to the identification of some RILs that had significantly higher grain weight per spike than either parent. Threshability was governed not only by the Q locus, but other loci as well including Tg-B1 on chromosome 2B and a putative Tg-A1 locus on chromosome 2A indicating that mutations in the Tg loci occurred during the transition of cultivated emmer to the fully domesticated tetraploid. These results not only shed light on the events that shaped wheat domestication, but also demonstrate that cultivated emmer is a useful source of genetic variation for the enhancement of durum varieties.

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