Review and New Progress in Wheat Wide Hybridization for Improving the Resistance to Biotic and Abiotic Stresses
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Abstract Since 1956, our group has been working on the wide hybridization between wheat and tall wheatgrass (Thinopyrum ponticum Liu & Wang, 2n = 70). During the past 56 years, we developed a set of partial amphiploids (octoploids), addition lines, substitution lines, translocation lines. A series of wheat cultivars named as Xiaoyan, such as Xiaoyan 4, 5, 6, 54, 60 and 81 were released. They generally have multiple disease resistance and good adaptability to various environments. These traits might derive from tall wheatgrass, especially with respect of resistance to biotic and abiotic stresses. In this paper, we briefly review the history of this study focusing on research background, alien parental selection, establishment of breeding procedure, new germplasms and their application, as well as the newest varieties and their performance to biotic and abiotic stresses.
Keywords Wheat breeding • Tall wheatgrass • Translocation
In 1951–1955, our group worked in Beijing engaging in forage research. Because the national development need, we moved to the Northwest, Yangling, Shaanxi in 1956, where is one of the major wheat production area of Huanghuai winter wheat zone in China.
At that time, the local wheat production was just suffering a serious damage caused by stripe rust (Puccinia striiformis f. sp. tritici). Nearly all of the local varieties at that time lost their resistance because of appearance of race, CY1. In general, the disease caused about 20–30 % yield decline. The total loss in northern China was about 6 Mts each year (Zhuang 2003).
To search a novel way for wheat breeding with persistent resistance to disease, we began the research of wide hybridization between wheat and wild Triticeae species. Twelve grass species were crossed with common wheat. Three of them were successfully hybridized with wheat. They were Agropyron elongatum (Thinopyrum ponticum Liu & Wang, 2n = 70), Agropyron intermedium (Th. intermedium Dewey) and Agropyron trichophorum (Th. trichophorum Lōve). The best one was Th. ponticum based on the performance of their vigorous.
The Establishment of Breeding Procedure
Common wheat was used as female parent, tall wheatgrass as male parent in cross. The F1 hybrids were very like the tall wheatgrass, but almost all of them were male sterile. Therefore, they were back-crossed with common wheat. BC1F1 were becoming wheat-like gradually, but it was not enough, hence they were continually backcrossed with common wheat. The BC2F1 individuals were self-crossed. Then, through selection and identification, four types of hybrids were obtained, including partial amphiploids, addition lines, substitution lines, translocation lines (Fig. 43.1; Li et al. 1960, 1962, 1977, 1990; Zhang et al. 1992, 1996).
It is well known that the partial amphiploids usually have middle characteristics between wheat and tall wheatgrass. It could not be used directly in wheat production. Alien addition lines are unstable. Alien substitution lines usually convey no favored characters besides the wanted ones. Therefore, the translocation lines were the final objects in wide hybridization breeding. The translocated small segments can be easily integrated into wheat genome. Hence, on second stage of research work, we focused on the application of translocation lines in wheat breeding. We developed three batches new wheat varieties. Their major characteristics, particularly resistance to biotic and abiotic stresses, planted regions, and the actual effects are introduced below.
Fig. 43.1 Four types of hybrids derived from cross between wheat and tall wheatgrass
The First Released Variety, Xiaoyan 6
During early 1980s, we developed the first batch of new wheat varieties, named Xiaoyan 4, 5 and 6, respectively. Xiaoyan 4 and 5 passed the local variety registration and released in Shaanxi province while Xiaoyan 6 passed the national registration and released in 10 provinces (Li 1986).
Xiaoyan 6 has durable rust resistance and wide adaptability to various environments. So, it was released in all Huanghuai winter wheat area. Specially, as one of major wheat varieties, Xiaoyan 6 was cultivated for 16 years (1980–1995) in Shaanxi province, accumulatively cultivated about 10 Mha. Xiaoyan 6 was also used as a founder genotype in wheat breeding; more than 50 new varieties were created from its hybrids with other varieties in China. Its derivatives were cultivated more than 20 Mha accumulatively.
Favorable Characters Support the Sustainable Use of Xiaoyan 6 in Production and Breeding
Broad-Spectrum Resistance to Yellow Rust In 1950s, the yellow rust was frequently epidemic in winter wheat regions of northern China. New rust races created constantly. Up to the 1980s, eight physiological races of yellow rust had been identified. Because of their epidemic, nearly all of wheat varieties at that time lost their
Fig. 43.2 Reaction of Xiaoyan6 to yellow rust races
resistance. In general, the disease caused about 20–30 % loss of yield. In the most serious year, the total loss in northern China was about 6 Mt (Wang et al. 1995).
Artificial infection of 8 yellow rust races (CY22, CY23, CY25, CY26, CY27, CY28, CY29-1 and CY29-2) on Xiaoyan 6 and Mingxian 169 (CK) showed that Xiaoyan 6 resisted to all of the tested epidemic races of yellow rust pathogens during 1980–1990s in North China. Xiaoyan 6 showed characters of a typical slowrusting resistance variety, such as longer latent period, lower disease severity, and less loss of kernel weight (Fig. 43.2; Wang et al. 1996).
Higher and Stable Yield In 1979 trials test, grain yield of Xiaoyan 6 was 5.96 t/ha in average, boosting 15–31.9 % than the control Zhengyin 1, Fengchan 3, and Abodenza in Shaanxi province. In 1980 yield trail, it had 8.5–28 % more yield than the same controls. So, it easily passed the local and national registration of new cultivars.
Good End Use Quality Xiaoyan 6 has not only higher and stable yield, but also good flour quality. It is suitable for making both bread and Chinese favorable traditional foods, such as Chinese noodles, dumplings, steamed bread, and other traditional cakes (deeply fried dough cake) (Wei et al. 2000; Zhang et al. 2002).