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Novel genetic diversity from synthetic wheats in breeding cultivars for changing production conditions

Synthetic hexaploid wheat and its utilization for wheat genetic improvement in China

Leaf rust and powdery mildew, caused by Puccinia triticina and Blumeria graminis f. sp. tritici, respectively, are widespread fungal diseases of wheat (Triticum aestivum L.). Development of cultivars with durable resistance is crucially important for global wheat production. This paper reviews the progress of genetic study and application of adult plant resistance (APR) to wheat leaf rust and powdery mildew. Eighty leaf rust and 119 powdery mildew APR quantitative trait loci (QTL) have been reported on 16 and 21 chromosomes, respectively, in over 50 publications during the last 15 yr. More important, we found 11 loci located on chromosomes 1BS, 1BL, 2AL, 2BS (2), 2DL, 4DL, 5BL, 6AL, 7BL, and 7DS showing pleiotropic effects on resistance to leaf rust, stripe rust, and powdery mildew. Among these, QTL on chromosomes 1BL, 4DL, and 7DS also correlate with leaf tip necrosis. Fine mapping and cloning of these QTL will be achieved with the advent of cheaper high-throughput genotyping technologies. Germplasm carrying these potential resistance genes will be useful for developing cultivars with durable multidisease resistance. In addition to its non-NBS–LRR (nucleotide binding site–leucine rich repeat) structure, the senescence-like processes induced by Lr34 could be the reason for durability of resistance; however, more information is needed for a full understanding of the molecular mechanism related to durability. Adult plant resistance genes have been used by CIMMYT for more than 30 yr and have also been transferred to many Chinese wheat varieties through shuttle breeding.

Overview and Application of QTL for Adult Plant Resistance to Leaf Rust and Powdery Mildew in Wheat

Stripe rust is best controlled by utilizing genetic resistance. Resistance to stripe rust has been studied for more than a century, but most progresses have been made during the last three decades. Two major types of resistance, all-stage resistance (ASR) and adult-plant resistance (APR) or high-temperature adult-plant (HTAP) resistance, have been characterized and used in breeding for resistant cultivars in both wheat and barley. So far, 78 permanently named, 67 temporarily designated and 327 quantitative trait loci (QTL) have been reported in various wheat varieties. The majority of these genes and QTL have been located to wheat chromosomes. Although some of the genes or QTL are the same, these numbers indicate that there are abundant resistance genes in wheat germplasm, which can be used for improving stripe rust resistance in commercially grown cultivars. Although the number is smaller, more than 50 resistance loci have been reported in barley for resistance to stripe rust, and about 30 loci have been mapped to barley chromosomes. Based on the characteristics of different types of resistance and the rich sources of resistance genes and molecular markers, we discuss different strategies for developing resistant cultivars and propose to use the combination of genes for durable APR or HTAP resistance and effective ASR to achieve more effective and sustainable control of stripe rust.

Stripe Rust Resistance

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Erikss., is a severe foliar disease of common wheat (Triticum aestivum L.) worldwide. Use of adult-plant resistance (APR) is an efficient approach to provide long-term protection of crops from the disease. The German spring wheat cultivar Naxos showed a high level of APR to stripe rust in the field. To identify the APR genes in this cultivar, a mapping population of 166 recombinant inbred lines (RILs) was developed from a cross between Naxos and Shanghai 3/Catbird (SHA3/CBRD), a moderately susceptible line developed by CIMMYT. The RILs were evaluated for maximum disease severity (MDS) in Sichuan and Gansu in the 2009–2010 and 2010–2011 cropping seasons. Composite interval mapping (CIM) identified four QTL, QYr.caas-1BL.1RS, QYr.caas-1DS, QYr.caas-5BL.3 and QYr.caas-7BL.1, conferring stable resistance to stripe rust across all environments, each explaining 1.9–27.6, 2.1–5.8, 2.5–7.8 and 3.7–9.1 % of the phenotypic variance, respectively. QYr.caas-1DS flanked by molecular markers XUgwm353–Xgdm33b was likely a new QTL for APR to stripe rust. Because the interval between flanking markers for each QTL was less than 6.5 cM, these QTL and their closely linked markers are potentially useful for improving resistance to stripe rust in wheat breeding.

QTL mapping of adult-plant resistance to stripe rust in a population derived from common wheat cultivars Naxos and Shanghai 3/Catbird

Stripe rust,caused by Puccinia striiformis f.sp.tritici,and powdery mildew,caused by Blumeria graminis f.sp.tritici,are the devastating diseases in common wheat(Triticum aestivum L.) worldwide.Use of adult-plant resistance(APR) genes is an important method for the development of durable resistant cultivars.A total of 72 quantitative trait loci(QTLs) for APR to stripe rust and 82 QTLs for APR to powdery mildew were integrated into a linkage map based on the information of DNA markers linked to individual QTL.Eight gene clusters(≥5 QTLs) conferred resistance to both stripe rust and powdery powdery,among them,Yr18/Lr34/Pm38,Yr29/Lr46/Pm39,and Yr46/Lr67 showed resistance to stripe rust,leaf rust and powdery mildew.Yr18/Lr34/Pm38 and Yr36 have been cloned.Xiannong 4 and Xiaoyan 6 were very important resistant germplasm for APR to stripe rust and powdery midew.The application of APR to wheat breeding in China was summarized.The use of APR genes will be a major method for improving stripe rust and powdery mildew resistance in wheat breeding.The strategies for APR on wheat breeding were also discussed.

Progress and perspective in research of adult-plant resistance to stripe rust and powdery mildew in wheat

In 1966,the first CIMMYT released wheat variety Penjamo 62 was introduced into Sichuan;in 1989,the agreement of China-CIMMYT wheat shuttle breeding collaborative project was signed in Beijing and Sichuan was designated one of the three spring wheat shuttle sites in China.Since then,wheat breeders in Sichuan started to use CIMMYT germplasm and breeding technologies regularly for improving wheat breeding in Sichuan.In this long period of cooperation with CIMMYT,we realized that the very important and helpful things we got from CIMMYT in our wheat improvement in Sichuan were basically three areas:the exchange of useful breeding germplasm;the offering of new breeding strategies and technologies;and the exchange of scientists,especially the training course for young breeders from Sichuan.What we should do and how we could do to use these CIMMYT germplasm and advanced technologies in improving wheat breeding work in Sichuan? Our basic experience are as followings:(i)screen introduced CIMMYT germplasm under Sichuan ecologic environments intesively;(ii)based on the breeding programs in our academy and breeding materials and breeding systems they have,several CIMMYT basic,new and advanced breeding technologies and strategies were chose,such as winter/spring,shuttle breeding,modified-bulked selection,and multi-minor genes durable resistance of yellow rust,to improve and form a more effective breeding system in Sichuan with the DH population method and RILs we learned from a China-ACIAR Sichuan wheat improvement project;(iii)because the big difference of ecologic environments and the genetic background of germplasm between CIMMYT and Sichuan,we emphasize that introducing is just for improving and creating our own new breeding system,for example,we introduced winter/spring method from CIMMYT but now we modified it into winter/spring//spring,or CIMMYT/Sichuan//Sichuan and these were indicated very helpful breeding pattern in using CIMMYT germplasm in Sichuan;(IV)formed a scientific research team based on the wheat breeders who know both CIMMYT wheat breeding and Sichuan wheat breeding very well,especially the young trainees backed from CIMMYT training curse,this is a very important work base for continuing,insistant and successful cooperation with CIMMYT;and(V)strengthen the exchange of scientists and training the young wheat breeders in CIMMYT to enhance the understanding of scientists between CIMMYT and Sichuan in their breeding philosorph,breeding strategies,ecologic environments,their breeding materials and the growth of breeding materials in field,and in this way the scientists of both side can help each other and therefore making the cooperation more effective and smoothly.By year 2006,19 CIMMYT germplasm derived wheat varieties were released in Sichuan,among them 4 were also released by national level and one was the first commercial common wheat variety in the world derived from a CIMMYT synthetic hexaploid wheat.These new released CIMMYT germplasm derived wheat varieties were performed very well in Sichuan in their resistance to stripe rust by incoporated some new resistant genes,the broken through of breeding for high quality by releasing of the first strong gluten varieties in Sichuan,and the broken through of breeding for high yield potential indicated by a new record of yield of 6.13 t/hm2 in provincial yield trial by new variety chuanmai 42.It is expected that in near future there will be more CIMMYT derived new wheat varieties to be released in Sichuan.All of these give us a confident information that CIMMYTgermplasm and breeding strategies and breeding technologies are now one of the very important factors to create new technologies and develop new type of wheat varieties in Sichuan.For future,the collaboration of Sichuan-CIMMYT on wheat breeding should be continued and strenthened.Recent years,some quite new and more interesting research areas in improving wheat breeding in both side are iditified by CIMMYT and Sichuan scientists,for example,(i)the development of new breeding materials of high yielding potential with good adaptable type and their genetic studies(may be based on Chuanmai 42);(ii)studies and new varieties development on durable stripe rust resistance in Sichuan,and in particularly the exploitation of new resource of durable resistant new genes(based on present research and some core-germplasm in Sichuan);(iii)screening and developing new breeding materials and varieties of stable performance on high quality characters(particularly for high quality noodles) under Sichuan ecological environments;and(IV)exploiting the new cultivation systems for high yield with high quality under more saving,easy operating and more environment protection.To ensure this cooperation could be continuing insistently and maintain more active,more efficient and more fruitful,it is especially important that the training of young scientists from Sichuan in CIMMYT and the exchanging of scientists through some sepcial studies and programs should be continuing and strethening.

Utinization of CIMMYT germplasm and breeding technologies in wheat improvement in Sichuan, China.

A new wheat variety, Chuanmai 42 derived from synthetics (Triticum durum×Aegilops tauschii) was bred by Sichuan Academy of Agricultural Sciences. In Sichuan provincial and national yield trials, the yield of Chuanmai 42 increased by 46.50?% and 16.3?% in comparison with that of the control,respectively.The average yield of Chuanmai 42 exceeded 6t/ ha in two years,and was the first officially released variety from synthetics (Triticum durum×Aegilops tauschii) in the world. Chuanmai 42 was resistant or immune to Chinese new stripe rust races,and was a heavy and large spike variety with high quality.Chuanmai 42 was a useful genetic resource for wheat production and breeding in Sichuan.

Analysis of agronomic characters of new wheat variety Chuanmai 42 derived from synthetics (Triticum durum×Aegilops tauschii)

This book analyzes the relationship between trust and social capital in contemporary Chinese society. It attempts to clarify the differences in degree among various types of trust in China today and the logic of social actions, hoping to provide a new perspective from which China's local social relationship networks can be understood.The book contributes to the field of contemporary Chinese sociology in the numerous ways. First, it improves the methods for comparing the ways in which different types of trust are measured. Second, it analyzes the regional differences in trust (especially universal trust) across China. Third, it discusses the impact of social capital (social relations and their embedded resources) on trust and tests the relationship for linearity and curvilinearity. Fourth, it explores whether the relationship between social capital and universal trust is regulated by institutional structural resources. The analysis of the regulatory role of structural resources paves the way for a more comprehensive theory of the relationship between social capital and trust. The book will be of interest to students and scholars of sociology, contemporary China, and East Asian studies. It will also be a valuable source of reference for policymakers on the improvement of social institutions. 

Zou YuChun

Papers

Progress and perspective in research of adult-plant resistance to stripe rust and powdery mildew in wheat

Utinization of CIMMYT germplasm and breeding technologies in wheat improvement in Sichuan, China.

Analysis of agronomic characters of new wheat variety Chuanmai 42 derived from synthetics (Triticum durum×Aegilops tauschii)

The Relationship Between Trust and Social Capital of China’s Urban Residents