Introgression of hexaploid sources of crown rot resistance into durum wheat

Triticum turgidum ssp. durum (tetraploid durum) germplasm is very susceptible to crown rot, caused by the fungus Fusarium pseudograminearum. Screening activities to date have failed to identify even moderately susceptible lines. In contrast partial resistance to this disease has been identified in a number of Triticum aestivum (hexaploid wheat) lines, including 2-49 and Sunco. This study describes the successful introgression of partial crown rot resistance from each of these two hexaploid wheat lines into a durum wheat background. Durum backcross populations were produced from two 2-49/durum F₆ lines which did not contain any D-genome chromosomes and which had crown rot scores similar to 2-49. F₂ progeny of these backcross populations included lines with field based resistance to crown rot superior to that of the parent hexaploid wheat.     

Inheritance and allelism of resistances to the Russian wheat aphid in seven wheat lines

Summary Studies were conducted to determine the inheritance and allelic relationships of genes controlling resistance to the Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), in seven wheat germplasm lines previously identified as resistant to RWA. The seven resistant lines were crossed to a susceptible wheat cultivar Carson, and three resistant wheats, CORWA1, PI294994 and PI243781, lines carrying the resistance genes Dn4, Dn5 and Dn6, respectively. Seedlings of the parents, F₁ and F₂ were screened for RWA resistance in the greenhouse by artificial infestation. Seedling reactions were evaluated 21 to 28 days after the infestation using a 1 to 9 scale. All the F₁ hybrids had equal or near equal levels of resistance to the resistant parent indicating dominant gene control. Only two distinctive classes were present and no intermediate types were observed in the F₂ segregation suggesting major gene actions. The resistance in PI225262 was controlled by two dominant genes. Resistance in all other lines was controlled by a single dominant gene. KS92WGRC24 appeared to have the same resistance gene as PI243781 and STARS-9302W-sib had a common allele with PI294994. The other lines had genes different from the three known genes.     

Genetic analysis of flowering and maturity time in high latitude spring wheat

Due to the short growing season in the high northern latitudes, the development of early maturing spring wheat (Triticum aestivum L.) cultivars is important to avoid frost damage which can lower production and quality. We investigated earliness of flowering and maturity, and some associated agronomic traits, using a set of randomly selected high northern latitude adapted spring wheat cultivars (differing in maturity) and their F₁ and F₂ crosses made in a one-way diallel mating design. The parents, and their F₁ and F₂ crosses were evaluated under field conditions over 2 years. Anthesis and maturity times were controlled by both vernalization response and earliness per se genes, mainly acting additively. Non-additive genetic effects were more important in controlling grain fill duration, grain yield and plant height. Additive × additive epistatic effects were detected for all traits studied except time to anthesis. Segregation analyses of the F₂ populations for time to anthesis indicated the presence of different vernalization response genes. Molecular genetic analyses revealed the presence of Vrn-A1 and Vrn-B1 genes in the parental cultivars. Narrow-sense heritability was medium to high (60–86%) for anthesis and maturity times but low to medium (13–55%) for grain fill duration, plant height and grain yield. Selection for early flowering/maturity in early segregating generations would be expected to result in genetic improvement towards earliness in high latitude spring wheats. Incorporation of the vernalization responsive gene Vrn-B1 in combination with vernalization non-responsive gene Vrn-A1 into spring wheats would aid in the development of early maturing cultivars with high grain yield potential for the high latitude wheat growing regions of the northern hemisphere.     

Allelic variation and composition of HMW-GS in advanced lines derived from d-genome synthetic hexaploid / bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The objective of this study was to identify allelic variations at Glu-1 loci of wheat (Triticum aestivum L.) advanced lines derived from hybridization of bread wheat and synthetic hexaploid wheats (2n = 6x = 42; AABBDD). Locally adapted wheat genotypes were crossed with synthetic hexaploid wheats. From the 134 different cross combinations made, 202 F₈ advanced lines were selected and their HMW-GS composition was studied using SDS-PAGE. In total, 24 allelic variants and 68 HMW-GS combinations were observed at Glu-A1, Glu-B1, and Glu-D1 loci. In bread wheat, the Glu-D1 locus is usually characterized by subunits 1Dx2+1Dy12 and 1Dx5+1Dy10 with the latter having a stronger effect on bread-making quality. The subunit 1Dx5+1Dy10 was predominantly observed in these advanced lines. The inferior subunit 1Dx2+1Dy12, predominant in adapted wheat germplasm showed a comparative low frequency in the derived advanced breeding lines. Its successful replacement is due to the other better allelic variants at the Glu-D1 locus inherited in these synthetic hexaploid wheats from Aegilops tauschii (2n = 2x = 14; DD).     

Conferring resistance to pre-harvest sprouting in durum wheat by a QTL identified in <Emphasis Type="Italic">Triticum spelta</Emphasis>

Pre-harvest sprouting (PHS) causes significant yield loss and degrade the end-use quality of wheat, especially in regions with prolonged wet weather during the harvesting season. Unfortunately, the gene pool of Triticum durum (tetraploid durum wheat) has narrow genetic base for PHS resistance. Therefore, finding out new genetic resources from other wheat species to develop PHS resistance in durum wheat is of importance. A major PHS resistance QTL, Qphs.sicau-3B.1, was mapped on chromosome 3BL in a recombinant inbred line population derived from ‘CSCR6’ (Triticum spelta), a PHS resistant hexaploid wheat and ‘Lang’, a PHS susceptible Australian hexaploid wheat cultivar. This QTL, Qphs.sicau-3B.1, is positioned between DArT marker wPt-3107 and wPt-6785. Two SCAR markers (Ph3B.1 and Ph3B.2) were developed to track this major QTL and were used to assay a BC₂F₈ tetraploid population derived from a cross between the durum wheat ‘Bellaroi’ (PHS susceptible) and ‘CSCR6’ (PHS resistant). Phenotypic assay and marker-assisted selection revealed five stable tetraploid lines were highly PHS resistant. This study has successfully established that PHS-resistance QTL from hexaploid wheat could be efficiently introgressed into tetraploid durum wheat. This tetraploid wheat germplasm could be useful in developing PHS resistant durum cultivars with higher yield and good end-use quality.     

Inheritance of Russian wheat aphid resistance in PI 140207 spring wheat

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has become a serious, perennial pest of wheat (Triticum aestivum L.) in many areas of the world. This study was initiated to determine the inheritance of RWA resistance in PI 140207 (a RWA-resistant spring wheat) and to determine its allelic relationship with a previously reported RWA resistance gene. Crosses were made between PI 140207 and ‘Pavon’ (a RWA-susceptible spring wheat). Genetic analysis was performed on the parents, F₁, F₂, backcross (BC) population and F₂-derived F₃ families. Analyses of segregation patterns of plants in the F₁, F₂, and BC populations, and F₂-derived F₃ families indicated single dominant gene control of RWA resistance in PI 140207. Results of the allelism test indicated that the resistance gene in PI 140207, while conferring distinctly different seedling reactions to RWA feeding, is the same as Dn 1, the resistance gene in PI 137739.     

野生二粒小麦导入普通小麦的抗白粉病基因MlWE29分子标记定位

小麦白粉病是严重影响小麦生产的重要病害之一,培育和应用抗病品种是有效控制和减少病害的最经济有效的方法。野生二粒小麦是硬粒小麦和普通小麦的四倍体野生祖先种,是小麦抗病性遗传改良的重要基因资源。本研究利用来自以色列的野生二粒小麦WE29与普通小麦杂交,再用普通小麦连续回交和自交,育成高抗白粉病(Blumeria graminis f. sp. tritici)小麦新品系3D258(系谱为燕大1817/WE29//5*87-1, BC₄F₆)。将3D258和高感小麦白粉病的普通小麦品种薛早配制杂交组合,对其F₁、F₂代分离群体和F₃代家系进行白粉病抗性鉴定和遗传分析。结果表明3D258携带抗白粉病显性单基因,暂命名为MlWE29。利用集群分离分析法(BSA)和分子标记分析,发现6个SSR标记(Xgwm335、Xgwm213、Xgwm639、Xwmc415、Xwmc289和Xwmc75)和5个EST-STS标记(BE494426、BE442763、CD452476、BE445282和BE407068)与抗白粉病基因MlWE29连锁。利用中国春缺体-四体系、双端体系和缺失系将抗白粉病基因MlWE29标记物理定位于5BL染色体的0.59–0.79区域。这一普通小麦抗白粉病种质资源的创制及其连锁分子标记的建立为小麦抗病基因分子标记辅助选择、基因积聚和分子育种提供了新的物质基础。     

Inheritance of resistance to wheat midge, Sitodiplosis mosellana, in spring wheat

Inheritance of resistance to a wheat midge, Sitodiplosis mosellana (Géhin), was investigated in spring wheats derived from nine resistant winter wheat cultivars. F₁ hybrids were obtained from crosses between resistant winter wheats and susceptible spring wheats, and used to generate doubled haploid populations. These populations segregated in a ratio of 1:1 resistant to susceptible, indicating that a single gene confers the resistance. The F₂ progeny from an intercross among spring wheats derived from the nine resistance sources did not segregate for resistance. Therefore, the same gene confers resistance in all nine sources of resistance, although other genes probably affect expression because the level of resistance varied among lines. Heterozygous plants from five crosses between diverse susceptible and resistant spring wheat parents all showed intermediate levels of response, indicating that resistance is partly dominant. Susceptible plants were reliably discriminated from heterozygous or homozygous resistant ones in laboratory tests, based on the survival and development of wheat midge larvae on one or two spikes. This powerful resistance gene, designated Sm1, is simply inherited and can be incorporated readily into breeding programmes for spring or winter wheat. However, the use of this gene by itself may lead to the evolution of a virulent population, once a resistant cultivar is widely grown.     

野生二粒小麦导入普通小麦的抗白粉病基因MlWE29分子标记定位

小麦白粉病是严重影响小麦生产的重要病害之一,培育和应用抗病品种是有效控制和减少病害的最经济有效的方法。野生二粒小麦是硬粒小麦和普通小麦的四倍体野生祖先种,是小麦抗病性遗传改良的重要基因资源。本研究利用来自以色列的野生二粒小麦WE29与普通小麦杂交,再用普通小麦连续回交和自交,育成高抗白粉病(Blumeria graminis f. sp. tritici)小麦新品系3D258(系谱为燕大1817/WE29//5*87-1, BC₄F₆)。将3D258和高感小麦白粉病的普通小麦品种薛早配制杂交组合,对其F₁、F₂代分离群体和F₃代家系进行白粉病抗性鉴定和遗传分析。结果表明3D258携带抗白粉病显性单基因,暂命名为MlWE29。利用集群分离分析法(BSA)和分子标记分析,发现6个SSR标记(Xgwm335、Xgwm213、Xgwm639、Xwmc415、Xwmc289和Xwmc75)和5个EST-STS标记(BE494426、BE442763、CD452476、BE445282和BE407068)与抗白粉病基因MlWE29连锁。利用中国春缺体-四体系、双端体系和缺失系将抗白粉病基因MlWE29标记物理定位于5BL染色体的0.59–0.79区域。这一普通小麦抗白粉病种质资源的创制及其连锁分子标记的建立为小麦抗病基因分子标记辅助选择、基因积聚和分子育种提供了新的物质基础。     

Identification of quantitative trait loci for flowering-related traits in the D genome of synthetic hexaploid wheat lines

The gene pool of Aegilops tauschii, the D-genome donor of common wheat (Triticum aestivum L.), can be easily accessed in wheat breeding, but remains largely unexplored. In our previous studies, many synthetic hexaploid wheat lines were produced through interspecific crosses between the tetraploid wheat cultivar Langdon and various A. tauschii accessions. The synthetic hexaploid wheat lines showed wide variation in many characteristics. To elucidate the genetic basis of variation in flowering-related traits, we analyzed quantitative trait loci (QTL) affecting time to heading, flowering and maturity, and the grain-filling period using four different F₂ populations of synthetic hexaploid wheat lines. In total, 10 QTLs located on six D-genome chromosomes (all except 4D) were detected for the analyzed traits. The QTL on 1DL controlling heading time appeared to correspond to a flowering time QTL, previously considered to be an ortholog of Eps-A ^m 1 which is related to the narrow-sense earliness in einkorn wheat. The 5D QTL for heading time might be a novel locus associated with wheat flowering, while the 2DS QTL appears to be an allelic variant of the photoperiod response locus Ppd-D1. Some of the identified QTLs seemed to be novel loci regulating wheat flowering and maturation, including a QTL controlling the grain filling period on chromosome 3D. The exercise demonstrates that synthetic wheat lines can be useful for the identification of new, agriculturally important loci that can be transferred to, and used for the modification of flowering and grain maturation in hexaploid wheat.     

SSR and STS markers for wheat stripe rust resistance gene <Emphasis Type="Italic">Yr26</Emphasis>

Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating wheat diseases worldwide. Triticum aestivum-Haynaldia villosa 6VS/6AL translocation lines carrying the Yr26 gene on chromosome 1B, are resistant to most races of Pst used in virulence tests. In order to better utilize Yr26 for wheat improvement, we attempted to screen SSR and EST-based STS markers closely linked with Yr26. A total of 500 F₂ plants and the F_2:3 progenies derived from a cross between 92R137 and susceptible cultivar Yangmai 5 were inoculated with race CYR32. The analysis confirmed that stripe rust resistance was controlled by a single dominant gene, Yr26. Among 35 pairs of genomic SSR markers and 81 pairs of STS markers derived from EST sequences located on chromosome 1B, Yr26 was flanked by 5 SSR and 7 STS markers. The markers were mapped in deletion bins using CS aneuploid and deletion lines. The closest flanking marker loci, Xwe173 and Xbarc181, mapped in 1BL and the genetic distances from Yr26 were 1.4 cM and 6.7 cM, respectively. Some of these markers were previously reported on 1BS. Eight common wheat cultivars and lines developed from the T. aestivum-H. villosa 6VS/6AL translocation lines by different research groups were tested for presence of the markers. Five lines with Yr26 carried the flanking markers whereas three lines without Yr26 did not. The results indicated that the flanking markers should be useful in marker-assisted selection for incorporating Yr26 into wheat cultivars.     

Inheritance and genetic mapping of a gene for seedling resistance to powdery mildew in wheat line X3986-2

Identification and mapping new powdery mildew resistance (Pm) genes is important for resistance breeding in wheat. Common wheat (Triticum aestivum L.) line X3986-2 was tested against 27 isolates of Blumeria graminis f. sp. tritici. To identify the Pm gene(s) in X3986-2, an F₂ population and its derived F_2:3 lines were developed from a cross between X3986-2 and susceptible line Mingxian169. Segregation ratios indicated the presence of a single dominant Pm locus, tentatively designated PmX3986-2. Bulked segregant analysis was applied to screen for molecular markers linked to PmX3986-2. Two sequence characterized amplified region (SCAR) markers SCAR112 and SCAR203, and five simple sequence repeat markers CFD40, CFD78, CFD81, GWM293 and WMC443 on chromosome 5D were linked to PmX3986-2, with CFD81 and SCAR112 flanking PmX3986-2 at 0.6 and 1.5 cM, respectively. This suggests that PmX3986-2 may be a novel allele of loci Pm2, Pm46 and PmLX66 on chromosome arm 5DS. PmX3986-2 with its tightly linked DNA markers should be useful for broadening the genetic basis of Pm and rapidly transferring the resistance gene to susceptible cultivars or for us in gene pyramiding for resistance breeding.     

Molecular mapping of a stripe rust resistance gene in wheat cultivar Wuhan 2

Stripe rust (or yellow rust), caused by Puccinia striiformis f. sp. tritici, is one of the most destructive diseases of wheat worldwide. Growing resistant cultivars is the best approach to control the disease. To identify and map genes for stripe rust resistance in wheat cultivar ‘Wuhan 2', an F₂ population was developed from a cross between the cultivar and susceptible cultivar Mingxian 169. The parents, 179 F₂ plants and their derived F_2:3 lines were evaluated for responses to Chinese races CYR30 and CYR31 of the pathogen in a greenhouse. A recessive gene for resistance was identified. DNA bulked segregant analysis was applied and resistance gene analog polymorphism (RGAP) and simple sequence repeat (SSR) techniques were used to identify molecular markers linked to the resistance gene. A genetic map consisting of five RGAP and six SSR markers was constructed. The recessive gene, designated Yrwh2, was located on the short arm of chromosome 3B and flanked by SSR markers Xwmc540 and Xgwm566 at 5.9 and 10.0 cM, respectively. The chromosomal location of the resistance gene and its close marker suggest that the locus is different from previously reported stripe rust resistance genes Yr30, QYr.ucw-3BS, Yrns-B1, YrRub and QYrex.wgp-3BL previously mapped to chromosome 3B. Yrwh2 and its closely linked markers are potentially useful for developing stripe rust resistance wheat cultivars if used in combination with other genes.     

Seedling emergence,coleoptile length,and plant height relationships in crosses of dwarf and standard-height wheats

Summary Seedling emergence was closely correlated with coleoptile length and plant height among parents, F₂ and F₃, populations of crosses involving dwarf wheats Olesen Dwarf (CI 14497), Norin 10 derivative D6301, Tom Thumb derivative D6899, and the standard-height varieties Ramona 50 and Nainari 60. Genetic mechanisms that governed plant height also influenced coleoptile length, but the relative effects of genes showing dominant or epistatic effects appeared to be different. With respect to the two parents involved in each of 15 crosses, mean F₂ coleoptile lengths were consistently closer to the low parent value than were corresponding mean F₂ plant heights. A slight curvilinear relationship was also found between coleoptile length and plant height of F₃ lines. The results suggest that selection of semidwarf wheats with long coleoptiles and improved emergence properties from crosses involving the dwarf wheats of this study would be unlikely.     

Development of SCAR markers for identification of stem rust resistance gene Sr31 in the homozygous or heterozygous condition in bread wheat

The stem rust resistance gene Sr31, transferred from rye (Secale cereale) into wheat (Triticum aestivum L.) imparts resistance to all the virulent pathotypes of stem rust (Puccinia graminis f. sp. tritici) found in India. Wheat genotypes including carriers and non‐carriers of the Sr31 gene were analysed using arbitrary primed polymerase chain reaction (AP‐PCR). AP‐PCR markers viz. SS30.2_580(H) associated with the Sr31 gene and SS26.1₁₁₀₀ associated with the allele for susceptibility were identified. Linkage between the markers and phenotypes was confirmed by analysing an F₂ population obtained from a cross between a resistant and a susceptible genotype. The markers were tightly linked to the respective alleles. Both the AP‐PCR markers were converted into sequence characterized amplified region (SCAR) markers, viz. SCSS30.2₅₇₆ and SCSS26.1₁₁₀₀ respectively. The markers were validated in two more segregating populations and 49 wheat genotypes. Using both markers it was possible to distinguish the homozygous from the heterozygous carriers of the Sr31 gene in the F₂ generation. The markers developed in this study can be used for pyramiding of the Sr31 gene with other rust resistance genes and in marker‐assisted selection.     

Inheritance and allelism of Russian wheat aphid resistance in several wheat lines

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) has caused serious reduction in wheat production in 17 Western states of the United States since 1986. Inheritance of resistance to RWA in seven wheat lines and the allelism of the resistance genes in these lines with three known resistance genes Dn4, Dn5, and Dn6 were studied. The seven resistant lines were crossed to a susceptible wheat cultivar ‘Carson’ and three resistant wheats: CORWA1 (Dn4), PI 294994 (Dn5), and PI 243781 (Dn6). Seedlings of the parents, F₁, and F₂ were screened for RWA resistance in the greenhouse by artificial infestation. Seedling reactions were evaluated 21–28 days after the infestation using a 1–9 scale. The resistance level of all the F₁ hybrids was similar to that of the resistant parent, indicating dominant gene control. Only two distinctive classes were present and no intermediate types were observed in the F₂ population, suggesting qualitative, nonadditive gene action, in which the presence of any one of the dominant alleles confers complete resistance to RWA. Resistance in CI 2401 is controlled by two dominant genes. Resistance in CI 6501 and PI 94365 is governed by one dominant gene. Resistance in PI 94355 and PI 151918 may be conditioned by either one dominant gene or one dominant and one recessive gene. No conclusion can be made on how many resistance genes are in AUSVA1-F₃, since the parent population was not a pure line. Allelic analyses showed that one of resistance genes in CI 2401 and PI 151918 was the same allele as Dn4, the resistance gene in CI 6501 was the same allele as Dn6, and AUS-VA1-F₃ had one resistance gene which was the same allele as one of the resistance genes in PI 294994. One non-allelic resistance gene different from the Dn4, Dn5, and Dn6 genes in CI 2401, PI 94355, PI 94365, and PI 222668 was identified and should be very useful in diversifying gene sources in wheat breeding.     

Resistance to Septoria nodorum blotch in several Triticum species

Summary Resistance to septoria nodorum blotch in Triticum monococcum, T. tauschii, T. timopheevii, T. dicoccum and T. durum was evaluated on plants at the three-leaf stage in greenhouse tests. A high frequency of resistant genotypes was found in T. monococcum, T. tauschii and T. timopheevii, but not in T. dicoccum and T. durum. The resistance of F₁ plants of crosses of resistant T. monococcum (PI 289599) and T. timopheevii (PI 290518) accessions with susceptible common wheat cv. Park and durum wheat cv. Wakooma, respectively, was evaluated on the basis of percentage leaf necrosis, lesion number, lesion size and incubation period. No dominance was found for long incubation period, but various dominance relationships occurred for low percentage leaf necrosis, low lesion number and small lesion size, depending on the cross. Multiple regression analysis showed that lesion number contributed more to percentage leaf necrosis than lesion size or incubation period. Resistance to septoria nodorum blotch was transferred successfully from T. timopheevii to cultivated durum wheat. Resistant BC₁F₇ lines, recovered from the T. timopheevii (PI 290518) × Wakooma cross, showed normal chromosome behaviour at meiosis (14 bivalents) and were self-fertile. However, an effective level of resistance was not recovered in lines derived from the other interspecific crosses.     

Reproductive Behavior of Hexaploid/Diploid Wheat Hybrids 1

The bottleneck restricting introgression of useful genes directly from diploid into hexaploid wheats is the low number of BC₁F₁ seeds obtained. In crosses between hexaploid wheat (Triticum aestivum L.; AABBDD) and Aegilops squarrosa L. (DD) or T. urartu Thum. (AA), this bottleneck may be overcome simply by pollinating a sufficient number of F₁ spikes. However, hybrids between hexaploid wheat cultivars (T. aestivum) and T. monococcum L. (AA) generally are highly female-sterile, often having no pistils. One T. monococcum accession, PI 355520, when crossed with T. aestivum, produced hybrids with female fertility in the same range as that of T. aestivum/A. squarrosa or T. aestivum/T. urartu hybrids, ca. 0.5 to 1.0 backcross seed per spike. We found that female fertility was controlled by two duplicate genes in PI 355520, and that this accession can be used as a bridging parent to introgress genes from other T. monococcum accessions into hexaploid wheat. Pairing of homologous chromosomes was less frequent and weaker in such crosses than in T. aestivum/A. squarrosa crosses, but homoeologous bivalents occurred at a rate of almost 0.5 II per cell. Restitution division was detected in crosses involving all three diploid species and was confirmed cytologically in crosses with PI 355520. Chromosome numbers of BC₁F₁ plants ranged from 35 to 67; plants with 49 or more chromosomes occurred at frequencies of 0.09 to 0.21 among progeny of A. squarrosa and T. urartu and 0.29 in progeny of T. aestivum/T. monococcum crosses involving PI 355520. These results are consistent with those of previous studies, demonstrating the potential of direct Hexaploid/diploid crosses for rapidly introgressing useful genes into Hexaploid wheat with minimum disturbance of the background genotype.     

Honeycomb selection for yield in early generations of spring wheat

Summary The effectiveness of the honeycomb selection method for yield in spring wheat (Triticum aestivum L.) was evaluated using progenies from two wheat crosses, Glenlea x NB131 and Glenlea x Era. Honeycomb selection was carried out in the F₂ and F₃ generations, grown at the University of Manitoba in the summers of 1980 and 1981, respectively. In both generations, divergent selection was made for both high and low yield. Plants selected in the F₃ generation were entered in an F₄ yield test in the summer of 1982. Results of the experiment showed that honeycomb selection for yield in the F₂ and F₃ generations was effective in identifying parents of high- and low-yielding lines. F₃ plants from highyielding F₂ selections gave higher yields than those from low-yielding F₂ selections by 11.5% and 13.0% for Glenlea x NB131 and Glenlea x Era crosses, respectively. The F₄ yield test showed that high yielding selections from both crosses significantly outyielded by 8.9% low yielding selections and by 14.4% the unselected composite lines. It is concluded that the honeycomb selection method can be used for early generation selection in spring wheat.     

Prevalence of a novel puroindoline b allele in Yunnan endemic wheats (Triticum aestivum ssp. yunnanense King)

Grain hardness is a major factor influencing the classification and end-use quality of bread wheat. In this study, 40 Yunnan endemic wheats, 21 historical cultivars and 66 current cultivars and advanced lines were investigated for kernel hardness and puroindoline alleles using molecular and biochemical markers. The frequencies of soft, mixed and hard genotypes were 10.0%, 5.0% and 85.0%, respectively, in Yunnan endemic wheats, whereas the corresponding frequencies were 47.6%, 23.8% and 28.6% in historical cultivars, and 36.3%, 6.1% and 57.6% in current cultivars and advanced lines. Four known puroindoline alleles, Pina-D1b, Pinb-D1b, Pinb-D1d and Pinb-D1e, were found in the hard wheat cultivars. Compared with endemic wheats and historical cultivars, current cultivars from Yunnan province have relatively high frequencies of Pina-D1b and Pinb-D1b alleles at 43.5% and 16.1%, respectively. All 32 hard Yunnan endemic wheats (Triticum aestivum ssp. yunnanense King) contained a new puroindoline b allele, designated Pinb-D1u, that was characterized as a single nucleotide (G) deletion at position 127 in the coding sequence of the Pinb gene, leading to a shift of the open reading frame (ORF) from position 14 in the deduced amino acid sequence and a stop codon corresponding to position Leu-18. The average SKCS hardness of genotypes with Pina-D1b (68.2) is significantly higher than those of Pinb-D1b (60.3) and Pinb-D1u (60.5). The study of puroindoline alleles in Yunnan germplasm could provide useful information for improving processing quality and further understanding the molecular basis of kernel hardness in bread wheat.