Molecular Cytogenetic Identification of a New Wheat-Rye 6R Chromosome Disomic Addition Line with Powdery Mildew Resistance

Rye (Secale cereale L.) possesses many valuable genes that can be used for improving disease resistance, yield and environment adaptation of wheat (Triticum aestivum L.). However, the documented resistance stocks derived from rye is faced severe challenge due to the variation of virulent isolates in the pathogen populations. Therefore, it is necessary to develop desirable germplasm and search for novel resistance gene sources against constantly accumulated variation of the virulent isolates. In the present study, a new wheat-rye line designated as WR49-1 was produced through distant hybridization and chromosome engineering protocols between common wheat cultivar Xiaoyan 6 and rye cultivar German White. Using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization), mc-GISH (multicolor GISH) and EST (expressed sequence tag)-based marker analysis, WR49-1 was proved to be a new wheat-rye 6R disomic addition line. As expected, WR49-1 showed high levels of resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt) pathogens prevalent in China at the adult growth stage and 19 of 23 Bgt isolates tested at the seedling stage. According to its reaction pattern to different Bgt isolates, WR49-1 may possess new resistance gene(s) for powdery mildew, which differed from the documented powdery mildew gene, including Pm20 on chromosome arm 6RL of rye. Additionally, WR49-1 was cytologically stable, had improved agronomic characteristics and therefore could serve as an important bridge for wheat breeding and chromosome engineering.     

Mapping QTLs for yield and nitrogen-related traits in wheat: influence of nitrogen and phosphorus fertilization on QTL expression

Key message

The present study identified some new important genomic regions and demonstrated the availability of conditional analysis in dissecting QTLs induced by environmental factors.

Abstract

The high input and low use efficiency of nutrient fertilizers require knowledge of the genetic control of crop reaction to nutrient supplements. In this study, 14 morphological and 8 physiological traits of a set of 182 wheat (Triticum aestivum L.) recombinant inbred lines (Xiaoyan 54 × Jing 411) were investigated in six environments to map quantitative trait loci (QTLs). The influence of nitrogen (N) and phosphorus (P) fertilization on QTL expression was studied by unconditional and conditional analysis. A total of 117 and 30 QTLs were detected by unconditional and conditional analysis, respectively, among which 21 were common for both methods. Thirty-four QTL clusters were identified. Eighteen conserved QTLs (15.4 % of the 117 QTLs) between years, but within nutritional treatment were found. The three major QTLs on chromosomes 2D, 4B and 6A were coincident with Rht8, Rht-B1b and TaGW2, respectively. The other two important intervals on chromosomes 4B and 7A for yield component traits were newly detected QTLs that warrant further study. By conditional analysis, spikelet number per spike was found to be induced by P fertilization mostly, whereas N fertilization had more effects on the expression of the QTLs for nitrogen concentration and utilization efficiency traits. QTLs that respond to N and P interactions were also detected. The results are helpful for understanding the genetic basis of N utilization efficiency in wheat under different N and P supplement environments and provide evidence for the availability of conditional analysis in dissecting QTLs induced by environmental factors.     

TaDA1, a conserved negative regulator of kernel size,has an additive effect with TaGW2 in common wheat (Triticum aestivum L.)

Kernel size is an important trait determining cereal yields. In this study, we cloned and characterized TaDA1, a conserved negative regulator of kernel size in wheat (Triticum aestivum). The overexpression of TaDA1 decreased the size and weight of wheat kernels, while its down‐regulation using RNA interference (RNAi) had the opposite effect. Three TaDA1‐A haplotypes were identified in Chinese wheat core collections, and a haplotype association analysis showed that TaDA1‐A‐HapI was significantly correlated with the production of larger kernels and higher kernel weights in modern Chinese cultivars. The haplotype effect resulted from a difference in TaDA1‐A expression levels between genotypes, with TaDA1‐A‐HapI resulting in lower TaDA1‐A expression levels. This favourable haplotype was found having been positively selected during wheat breeding over the last century. Furthermore, we demonstrated that TaDA1‐A physically interacts with TaGW2‐B. The additive effects of TaDA1‐A and TaGW2‐B on kernel weight were confirmed not only by the phenotypic enhancement arising from the simultaneous down‐regulation of TaDA1 and TaGW2 expression, but also by the combinational haplotype effects estimated from multi‐environment field data from 348 wheat cultivars. A comparative proteome analysis of developing transgenic and wild‐type grains indicated that TaDA1 and TaGW2 are involved in partially overlapping but relatively independent protein regulatory networks. Thus, we have identified an important gene controlling kernel size in wheat and determined its interaction with other genes regulating kernel weight, which could have beneficial applications in wheat breeding.     

Molecular detection of a gene effective against powdery mildew in the wheat cultivar Liangxing 66

Since it was commercialized in 2008, Liangxing 66 is one of the most widely grown cultivars of wheat (Triticum aestivum L.) in winter and facultative wheat-producing regions in northern China. This cultivar displays broad-spectrum resistance to isolates of powdery mildew. To identify the powdery mildew resistance gene in Liangxing 66, genetic analysis and molecular mapping were conducted using the F₂ populations and F_2:3 families derived from the reciprocal crosses of Liangxing 66 and the susceptible cultivar Jingshuang 16. A single dominant gene, tentatively designated PmLX66, conferred resistance in Liangxing 66 to the powdery mildew isolate E09. The results of molecular mapping indicated that this gene was located on the short arm of chromosome 5D and flanked by SCAR203 and Xcfd81 at genetic distances of 0.4 and 2.8?cM, respectively, which is similar to the position of locus Pm2. However, PmLX66 and Pm2 showed different reactions to five of the 42 isolates of powdery mildew tested. Together, these results indicated that PmLX66 was most likely an allele of Pm2. Based on its superior yield and agronomic performance, in combination with powdery mildew resistance, Liangxing 66 is useful as a promising parent for control of powdery mildew and for the development of new disease-resistant cultivars.     

Mapping QTLs for nitrogen uptake in relation to the early growth of wheat (Triticum aestivum L.)

The objective of this study was to map QTLs for N uptake (NUP) in wheat, and to investigate factors influencing NUP. Two independent field trials with low N (LN) and high N (HN) treatments were conducted in the growing seasons of 2002–2003 (trial 1) and 2003–2004 (trial 2) to measure NUP per plant (N accumulated in the aerial part at maturity stage) of a doubled haploid (DH) population consisting of 120 DH lines derived from winter wheat varieties Hanxuan 10 and Lumai 14. A hydroponic culture with all nutrients supplied sufficiently was conducted to investigate shoot dry weight (SDW), root dry weight (RDW), tiller number (TN) and NUP (total plant N uptake) per plant of this mapping population at seedling stage. SDW, RDW, TN and NUP investigated in the hydroponic culture were significantly and positively correlated with each other, and with NUP under both LN and HN conditions in the field trials. Nine and eight QTLs for NUP were detected under LN and HN conditions in the field trials, respectively. Four to five QTLs for SDW, RDW, TN and NUP were detected in the hydroponic culture. One SDW QTL, three RDW QTLs, two TN QTLs detected in the hydroponic culture were linked with QTLs for NUP under LN or HN condition in the field trials. The positive correlation and genetic linkage for the traits between the field trials and the hydroponic culture demonstrated that greater seedling vigor of root and shoot is an important factor influencing N uptake in wheat. Diaoguo An and Junying Su: These authors contributed equally to this work. Section Editor: H.J. Kronzucker     

Genome-wide association and validation of key loci for yield-related traits in wheat founder parent Xiaoyan 6

Xiaoyan 6, one of the most important founder parents in wheat, possesses many superior agronomic traits and has played a crucial role in Chinese wheat breeding programs. In this study, a panel of 66 elite wheat accessions derived from Xiaoyan 6 was planted in four growing seasons; genome-wide association study (GWAS) was performed for six yield-related traits using the wheat 90K genotyping assay. A total of 803 significant marker-trait associations (MTAs) that explained up to 35.0% of the phenotypic variation were detected. Of these, the locus QTkw-5B which contains 19 MTAs for thousand kernel weight (TKW) was consistently detected in three growing seasons and confirmed in a recombinant inbred line (RIL) population by developing simple sequence repeats (SSR) and kompetitive allele-specific PCR (KASP) markers. The locus QPh-3A containing eight repetitive MTAs for plant height (PH) was consistently identified in all the four growing seasons and validated in a RIL population by developing SSR markers. The transmission of Xiaoyan 6 allele indicated that the favorite allele of QPh-3A was strongly selected in breeding programs. Comparing with previous studies, QTkw-5B and QPh-3A should be novel QTL. The locus QFss-2D for fertile spikelet number per spike (FSS) was identified and then validated in three bi-parental populations. This locus controlled various spike-related traits and may be a key spike polymorphic locus. This study could provide insight into dissecting yield-related traits in the breeding population and reliable molecular markers that might be valuable for marker-assisted selection in wheat high-yield breeding programs.     

烯效唑在小麦幼胚培养中的应用

试验结果表明低浓度烯效唑有促进远缘杂交幼胚再生植株生长的作用,高浓度儿唑有抑制作用。附加２．５ｍｇ／Ｌ烯效唑和２％蔗糖的１／２ＭＳ培养基壮苗效果显著,当烯效唑浓度提高到５．０ｍｇ／Ｌ时,植株变矮,但根系发达,结合低温保存,可使幼胚再生植株顺利越夏,移栽时成活率达９６．９％。不同基因型的幼胚再生植株对烯效唑反应无明显差异。     

The gene PmWFJ is a new member of the complex Pm2 locus conferring unique powdery mildew resistance in wheat breeding line Wanfengjian 34

Molecular Breeding - Molecular identification of wheat powdery mildew resistance (Pm) genes in breeding lines or cultivars is important for resistance breeding. Wanfengjian 34, a Chinese wheat...