Identification of New Genes for Mildew Resistance of Barley at the Mia Locus in Lines Derived from Hordeum spontaneum

Genetical studies have been conducted with lines derived from H. spontaneum showing that these lines carry dominant mildew resistance genes located at or near the Mla, locus. The resistance spectra of the lines ‘RS170—10 × Piccolo A’, ‘Diamant × 1B-20’, ‘RS1—8 × Piccolo E’ and ‘Diamant × 1B-151’ obtained from 10 European and Israeli isolates differ from previously-identified Mia alleles. Therefore, it is suggested that these genes should be designated as Mla 25, Mla 26, Mla.27 and Mla 28, respectively. In addition, the RFLP-patterns of these lines and their crossing parents were studied by hybridization with probes MWG 1H036, MWG 1H060 and MWG 1H068, which are very closely linked to the Mia locus. Two double crossover events have been identified. The use of RFLP markers for the identification of mildew resistance genes is discussed.     

Localization of the Laevigatum Resistance Gene MlLa against Powdery Mildew in the Barley Genome by the Use of RFLP Markers

RFLP markers which were previously assigned to chromosome 2 (2H) were found to detect polymorphism between the cv. ‘Pallas’ and a near isogenic line carrying the Laevigatum resistance gene MlLa. Linkage analysis carried out with two sets of DH lines derived from the crosses ‘RisøS’בSultan’ and ‘Alf’בVogelsanger Gold 2’ confirmed three DNA probes closely linked with the MlLa locus.     

Powdery Mildew Resistance Genes in 127 Northwest European Spring Barley Varieties

One hundred and twenty-seven spring barley varieties grown in Denmark since 1979 were characterized for resistance genes using 30 powdery mildew isolates. The resistance genes are traced in the pedigrees to verify the results. Eleven named genes, 12 tentatively named genes/resistances and six unknown resistances were found. Resistance in many varieties was based on combinations of either known genes or of known and new factors. The following five new or relatively new resistance genes more or less effective against the present powdery mildew populations were detected: the ‘Mlo’ resistance conferred by the recessive mlo gene with the characteristic infection type 0/(4), ‘Ricardo’ and ‘Turkish’ sources having gene Mla3 in common and ‘Turkish’ with Ml(Tu2) in addition. In three varieties the new resistance Ml(IM9) was found in combination with different Mia alleles. Variety ‘Jarek’ has two new unidentified resistances.     

Mapping seedling resistance to net form of net blotch (Pyrenophora teres f. teres) in barley using detached leaf assay

To develop molecular markers against Pyrenophora teres f. teres in barley, a detached leaf assay was conducted on two DH populations with a set of 11 single conidial lines (SCLs). Out of these, three showed different reactions in the DH population ‘Uschi × HHOR3073’ and two in ‘(P x V) × HHOR9484’. For SCL ‘QLB’, a 1r : 1s (χ² = 2.78) segregation was observed in the population ‘Uschi × HHOR3073’. In contrast to this, a continuous variation was observed for the SCL ‘WvB’ and ‘d8_4’ in the DH population ‘Uschi × HHOR3073’ and for ‘AR’ and ‘net1840’ in ‘(P × V) × HHOR9484’. With respect to resistance to the SCL ‘QLB’, a single major gene was located on chromosome 7H, and for resistance against SCL ‘WvB’, two QTLs were detected on chromosome 3H and 7H, and against SCL ‘d8_4’, two loci were mapped on chromosome 3HS in ‘Uschi × HHOR3073’. In the DH population ‘(P x V) × HHOR9484’, one locus conferring resistance to the SCL ‘AR’ was located on chromosome 3H. For resistance to SCL ‘net1840’, two QTLs were mapped on chromosome 4H and 5H.     

Race-Specific Resistance Genes Against Erysiphe graminis f. sp. hordei in Old and Recent French Barley Accessions

Leaf segments from seedlings of 68 old barley varieties and 38 more recent cultivars of past or current importance in France were infected with 6—9 powdery mildew isolates in order to identify race-specific resistance genes. No resistance gene was apparent in the 21 old winter varieties, 43 of 47 old spring varieties, 10 recent winter and 3 recent spring cultivars. Two old spring varieties (‘Colmar S 142’ and ‘Johanna’) were postulated to have Mlg and Ml(CP), and two others (‘Pontrieux’ and ‘Finistère 62-5’) had an unidentified, weakly effective gene. Mlg, Ml(CP), Mlb, Mla6 and Mlal3 were the only genes detected in recent winter cultivars. Recent spring cultivars presented the greatest diversity; the presence of one or several genes among Mlal, Mla6, Mla9, Mla12, Mlg, Ml(CP), Ml(La), Mlk and mlo was postulated in several lines.     

Regional distribution of resistances to powdery mildew in winter and spring barley cultivars grown in the northern part of France

The spatio-temporal distribution of race-specific resistances to powdery mildew was analysed in northern France (the east, the north and the west of Paris). Resistances were identified in 26 winter and six spring barley cultivars. Seedling leaf segments were inoculated with 20 powdery mildew isolates, chosen to identify 14 resistance alleles. As opposed to other European countries, the resistance alleles differed between winter and spring cultivars grown in the three regions. Most of the winter cultivars had no resistance allele, or only the widespread resistance alleles Mlra and/or Mlh, plus Mlg in the west. Mla9 and Mla13 were also present in the north, but at a low frequency. Spring cultivars carried the alleles Mla7, Mla9, Mla12, Mlk, Mlg or MlLa in the east, where a diversification of resistances has occurred since 1987, particularly because of the use of ‘Volga’ (Mla7, Mlk, Mlg and MlLa). In the north and the west, Mla12 dominated after a decrease in the frequency of Mla7, Mla13 has recently been introduced in the north and the west with the cultivar ‘Vodka’.     

Powdery mildew resistance in Czech and Slovak barley cultivars

Fifteen powdery mildew resistance genes and the gene MlaN81 derived from ‘Nepal 81’were found in 76 Czech and Slovak spring and winter barley cultivars when tested for reaction to a set of powdery mildew isolates. Nine cultivars (‘Donum’, ‘Expres’, ‘Jubilant’, ‘Orbit’, ‘Primus’, ‘Progres’, ‘Stabil’, ‘Vladan’ and ‘Zlatan’) are composed of lines with different resistance genes. The Mlat gene is present in nine cultivars and was transferred from the Anatolian landrace ‘A‐516′. The resistances derived from ‘KM‐1192’and ‘CI 7672’were identical and designated Ml(Kr). Five winter barley cultivars possess the Ml(Bw) resistance. The winter barley line ‘KM‐2099’carries the mlo gene. The parental cultivar ‘Palestine 10’was also tested in which the genes Mlk1, MlLa were identified. The German cultivar ‘Salome’, a parent of seven cultivars tested, probably carries the gene MlLa in addition to mlo and Mla7. The gene mlo6 may be present in the cultivar ‘Heris’. Most of the results were confirmed by the pedigrees of the cultivars.     

Expression of a Triticum turgidum var. dicoccoides source of Fusarium head blight resistance transferred to synthetic hexaploid wheat

Yield and quality reductions caused by Fusarium head blight (FHB) have spurred spring wheat (Triticum aestivum L.) breeders to identify and develop new sources of host plant resistance. Four wheat synthetic hexaploids (×Aegilotriticum sp.) were developed, each having a quantitative trait locus (QTL), Qfhs.ndsu‐3AS, providing FHB resistance from Triticum turgidum L. var. dicoccoides chromosome 3A. Synthetics were produced by hybridizing a ‘Langdon’‐T. dicoccoides‐ recombinant chromosome 3A substitution line (2n = 4x = 28, AABB with two accessions of T. tauschii (2n= 2x = 14, DD). Synthetics were inoculated and evaluated for FHB resistance in two separate greenhouse seasons. One synthetic, 01NDSWG‐5, exhibited FHB severity ratings of 36% and 32% in the separate seasons, compared with ratings of 9% and 30% for ‘Alsen’, a FHB‐resistant spring cultivar, and ratings of 70% and 96% for ‘McNeal’, a susceptible spring cultivar, respectively. Synthetic × Alsen backcross‐derived lines were produced to initiate combining different sources of FHB resistance.     

Identification and mapping of a QTL for rachis internode length associated with cleistogamy in barley

General knowledge of the closed flowering trait, or cleistogamy, of barley is still limited. The relationship between cleistogamy and spike morphology characters was studied and linkage of cleistogamy genes with a highly significant quantitative trait locus (QTL) for rachis internode length on the long arm of chromosome 2H was detected. The mapping populations consisted of 129 doubled haploid lines of ‘Mikamo Golden’ × ‘Harrington’ and 150 F₂ plants of ‘Misato Golden’ × ‘Satsuki Nijo’. The phenotypic variance explained by this QTL accounted for 77.5% and 82.6% of the variance in rachis internode lengt, respectively, in these two populations. The peaks of the QTL coincided with the positions of the cleistogamy gene loci.     

Cytoplasmic Systems in Different Male-Sterile Lines of Rice

In order to characterize the cytoplasmic system in seven cytoplasmic-genic male-sterile lines (CMS; A lines) of rice, viz., V 20A, ‘Zhenshan 97A’, IR 46831A, ‘Madhu A’ (cms-WA), ‘Yar-Ai-Zhao A’ (cms-Gam), ‘Pankhari 203A’ (cms-TN) and Wu 10A (cms-bo) and their isonuclear maintainers (B lines), all possible crosses were made between CMS lines and maintainers (A × B) as well as between the maintainers themselves (B × B). Based on F₁ pollen and spikelet fertility the CMS lines V 20A, ‘Zhenshan 97A’, IR 46831 A, ‘Madhu’ A possessing cms-WA cytoplasm were found to be genetically different from ‘Pankhari 203A’ (cms-TN), Wu 10A (cms- bo) and ‘Yar-Ai-Zhao A’ (cms-Gam) cytoplasms. Cms-bo and cms-TN cytoplasms appeared to be identical. Since the cytoplasms of the A lines are different from those of the B lines, the nuclear genes operating to cause the sterility might also be different in (A × B) and (B × B) crosses.     

Identification and Inheritance of Fertility Restorer Genes for 'tour' CMS in Rapeseed (Brassica napus L.)

Eighteen genotypes of Brassica napus were crossed to a cytoplasmic male sterile (CMS) line of B. napus BO 15 carrying B. tournefortii cytoplasm (‘tour’ cytoplasm). Fourteen genotypes were found to be stable maintainers of the ‘tour’ CMS. Of the remaining four genotypes, GSL-1 and ‘Asahi-natane’ were found to be heterozygous and ‘Mangun’ and ‘Yudal’ were homozygous for the restorer gene. Analysis of the F₁ and F₂ progenies of (CMS) BO 15 בMangun’ and (CMS) BO 15 בYudal’ showed that fertility restoration is controlled by a single dominant gene. The availability of a number of stable maintainer lines and the simple inheritance pattern of fertility restorer gene makes ‘tour’ CMS a useful system for hybrid seed production in rapeseed.     

Inheritance of resistance to Fusarium wilt (race 2) in chickpea

The inheritance of resistance to Fusarium wilt (race 2) of chickpea was studied in a set of three crosses, i.e. ‘WR315’בC104’ (resistant × susceptible), ‘WR315’בK850’ (resistant × tolerant) and ‘K850’בGW5/7’ (tolerant × tolerant) in order to investigate the number of genes involved, their complementation and to find out whether resistant segregants are possible in a cross between two tolerant cultivars. Tests of F₁, F₂ and F₃ generations of these crosses under controlled conditions at ICRISAT, Patancheru, India, indicated involvement of three loci (two recessive and one dominant alleles). The homozygous recessive form at the first two loci conferred resistance whereas susceptibility occurred when the first two loci were in the dominant form. A dominant allele at the third locus can complement the dominant alleles at the other two loci to confer tolerance. Occurrence of resistant segregants in a cross between two tolerant cultivars was observed.     

Molecular cytogenetic analysis of a durum wheat ×Thinopyrum distichum hybrid used as a new source of resistance to Fusarium head blight in the greenhouse

Fusarium head blight (FHB, scab), caused by Fusarium graminearum Schwabe, is a serious and damaging disease of wheat. Although some hexaploid wheat lines express a good level of resistance to FHB, the resistance available in hexaploid wheat has not yet been transferred to durum wheat. A germplasm collection of Triticum durum× alien hybrid lines was tested as a potential source of resistance to FHB under controlled conditions. Their FHB reaction was evaluated in three tests against conidial suspensions of three strains of F. graminearum at the flowering stage. Two T. durum×Thinopyrum distichum hybrid lines, ‘AFR4’ and ‘AFR5′, expressed a significantly higher level of resistance to the spread of FHB than other durum‐alien hybrid lines and a resistant common wheat line ‘Nyu‐Bay’. Genomic in situ hybridization using total genomic DNA from alien grass species demonstrated that ‘AFR5’ had 13 or 14 alien genome chromosomes plus 27 or 28 wheat chromosomes, while ‘AFR4’ had 22 alien genome and 28 wheat chromosomes. All of the alien chromosomes present in these two lines belonged to the J genome. ‘AFR5’ is likely to be more useful as a source of FHB resistance than ‘AFR4’ because of its relatively normal meiotic behaviour, high fertility and fewer number of alien chromosomes. ‘AFR5’ shows good potential as a source for transferring FHB resistance gene into wheat. The development of T. durum addition lines carrying resistance genes from ‘AFR5’ is underway.     

Incompatibility and resistance to woolly apple aphid in apple

The study investigated the reported linkage of the locus for resistance to woolly apple aphid with the locus for incompatibility. Apple seedlings from the cross ‘Northern Spy’(heterozygous for resistance) בTotem’(susceptible) were scored for resistance, and for incompatibility genotype, by analysis of stylar ribonucleases, and for Got‐1, the isoenzyme marker for incompatibility. Cosegregation analysis provided no evidence that the loci for resistance and incompatibility are linked. Two rootstock cultivars,‘M9’and ‘Merton 789′, which in early work had been reported to give poor set in crosses with ‘Northern Spy’, were found to have the same incompatibility genotype as ‘Northern Spy’, namely S₁S₃.‘M4’and ‘Irish Peach’, two other cultivars that had given poor set when crossed on to ‘Northern Spy’, appeared to be homozygous at the incompatibility locus and to have the genotypes S₃S₃ and S₁S₁, respectively.     

Genetic control of crossability of triticale with rye

Limited genetic knowledge is available regarding crossability between hexaploid triticale (2n= 6x= 42, 21″, AABBRR, amphiploid Triticum turgidum L.‐Secale cereale L.) and rye (2n= 14, 7″, RR). Our objectives were to determine (1) the crossability between triticales and rye and (2) the inheritance of crossability between F₂ progeny from intertriticale crosses and rye. First, ‘8F/Corgo’, a hexaploid triticale, was crossed as a female with two landrace ryes, ‘Gimonde’ and, ‘Vila Pouca’ and two derived north European cultivars, ‘Pluto’ and ‘Breno’. These crosses produced 21.7, 20.9, 5.9, and 5.6%, seed‐set or crossability, respectively, showing that the landrace ryes produced higher seed‐set than the cultivars. Second, ‘Gimonde’ rye was crossed as a male with four triticales for 3 years. The control cross, ‘Chinese Spring’ wheat × rye, produced 80‐90% seed‐set. Of the four triticales, ‘Beagle’ produced 35.7‐56.8% seed‐set. The other three triticales produced less than 20% seed‐set, showing that the triticales differ in crossability with ‘Gimonde’ rye. Third, six FiS from intertriticale crosses (‘8F/Corgo’בBeagle’, ‘Beagle’בCachirulo’, ‘Lasko’בBeagle’, ‘8F/Corgo’בCachirulo’, ‘Lasko’בCachirulo’, ‘Lasko’ב8F/Corgo’) were crossed to ‘Gimonde’ rye. Results indicated that lower crossability trait was partially dominant in the two F₁S from crosses involving ‘Beagle’(high crossability) with‘8F/Corgo’ and ‘Cachirulo’(low crossability) and completely dominant in the ‘Beagle’בLasko’ cross, as it happens in wheat. Fourth, segregants in four F₂ populations (‘Lasko’בBeagle’, ‘8F/Corgo’בBeagle’, ‘Lasko’ב8F/Corgo’, and‘8F/Corgo’בCachirulo’) were crossed with rye. Segregation for crossability was observed, although distinct segregation classes were blurred by environmental and perhaps other factors, such as self‐incompatibility alleles in rye. Segregation patterns showed that ‘Beagle’, with high crossability to rye, carries either Kr1 or Kr2. The three triticales with low crossability with rye were most likely homozygous for Kr1 and Kr2. Therefore, it is likely that the Kr loci from A and B genomes acting in wheat also play a role in triticale × rye crosses.     

Recessive genes controlling resistance to Helminthosporium leaf blight in synthetic hexaploid wheat

A study was conducted under controlled environment conditions in a phytotron to determine the nature of the inheritance of resistance Helminthosporium leaf blight (HLB) in a synthetic hexaploid wheat line, ‘Chirya‐3’, against the isolate KL‐8 of Bipolaris sorokiniana from the major wheat growing region of India. Crosses were made between two susceptible lines ‘WH 147’ and ‘Chinese Spring’. Analyses of F₁ and F₂ populations of these two crosses (‘WH 147’בChirya‐3’ and ‘Chinese Spring’בChirya‐3’) showed that resistance against the isolate in ‘Chirya‐3’ was governed by two recessive genes functioning in a complementary interaction giving an F₂ segregation pattern of 1 : 15 (resistant : susceptible). The segregation pattern of the resistant F₂ progenies in F₃ families from both crosses confirmed that two homozygous recessive genes were responsible for resistance to the isolate of Bipolaris sorokiniana in the synthetic line ‘Chirya‐3’. It is proposed that the genes be designated as hlbr1 and hlbr2.     

Evaluation of a barley (Hordeum vulgare) chromosome 2 drought tolerance quantitative trait locus in genomic backgrounds of two cultivars

A barley drought tolerance Quantitatif Trait Locus (QTL) on chromosome 2 was transferred from tolerant cultivar ‘Tadmor’ to susceptible ‘Baronesse’ and ‘Aydanhanım’. Effects of this QTL on drought tolerance and other traits were studied using near-isogenic lines under controlled environments and field trials for two years. This QTL resulted in 5.0% and 9.1% improvement in leaf relative water content of ‘Baronesse’ and ‘Aydanhanım’ cultivars, respectively, under controlled environments. The QTL accelerated heading and maturity by 2.5 days in ‘Baronesse’ and by 5–6 days in ‘Aydanhanım’. It was associated with shorter stature and more ears. This QTL region increased grain yields by 1.1 and 0.6 t/ha in ‘Baronesse’ and ‘Aydanhanım’, respectively, mainly by increasing the number of tillers. There were previous reports related to yield promoting effects of this region harbouring flowering locus eps2 (barley HvCEN gene). However, sequencing of 1025 bp fragment encompassing HvCEN coding region revealed that our parents and near-isogenic lines had no Single Nucleotide Polymorphism (SNP) variation, ruling out direct involvement of eps2. These findings pointed to the possible effect of another flowering locus in the QTL region.     

Genetic Variation in the Ability of Detached and Partially Dehydrated Leaves of Rice to Accumulate Abscisic Acid, Measured by Radioimmunoassay

Variation in the ability o) 60 rice (Oryza saliva L.) varieties and three wild species to accumulate abscisic acid (ABA) in response to drought stress, drought-induced ABA accumulation (DIAA), was assessed using a standard detached-leaf lest. The range in DIAA amongst these genotypes was compared with the range amongst F₂ plants and F₆, lines derived from the O. saliva cross ‘IR20’ב63–83’ which were selected through several generations solely on the basis of differences in DIAA. ABA was measured by radioimmunoassay (RIA) or by gas chromatography (GC). DIAA in the 60 varieties was normally distributed with a six-fold range, from 245 to 1580 ng g^?1 FW. Wild species varied two-fold in DIAA, from 375 to 889 ng g^?1 FW. DIAA in F₂ plants from the ‘1R20’ב63–83’ cross was also normally distributed. The extremes of DIAA for the low-ABA and higb-ABA F₆ lines (330 and 1435ng g^?1 FW) were similar to those for the varieties. Measurements by RIA and GC gave similar results. These findings are discussed in the context of producing further sets of closely-related genotypes with similar leaf areas to study the association between DIAA and water-use efficiency.     

Identification and validation of an over‐dominant QTL controlling soybean seed weight using populations derived from Glycine max × Glycine soja

Heterosis, or hybrid vigour, has been used to improve seed yield in several important crops for decades and it has potential applications in soybean. The discovery of over‐dominant quantitative trait loci (QTL) underlying yield‐related traits, such as seed weight, will facilitate hybrid soybean breeding via marker‐assisted selection. In this study, F₂ and F_2 : 3 populations derived from the crosses of ‘Jidou 12’ (Glycine max) × ‘ZYD2738’ (Glycine soja) and ‘Jidou 9’ (G. max) × ‘ZYD2738’ were used to identify over‐dominant QTL associated with seed weight. A total of seven QTL were identified. Among them, qSWT_13_1, mapped on chromosome 13 and linked with Satt114, showed an over‐dominant effect in two populations for two successive generations. This over‐dominant effect was further examined by six subpopulations derived from ‘Jidou12’ × ‘ZYD2738’. The seed weight for heterozygous individuals was 1.1‐ to 1.6‐fold higher than that of homozygous individuals among the six validation populations examined in different locations and years. Therefore, qSWT_13_1 may be a useful locus to improve the yield of hybrid soybean and to understand the molecular mechanism of heterosis in soybean.     

Associations between 23 Quantitative Traits and 10 Genetic Markers in a Barley Cross

Associations of 23 quantitative traits and 10 genetic marker characters were examined in 63 chromosome-doubled lines (DH-lines) derived from the F₁- generation of a cross between an old and a modern spring barley variety. One fourth of the marker × trait combinations showed significant associations. More than two thirds of these associations were to earliness (heading date). Earliness was found to be controlled by two loci: the previously known eak locus and a new locus designated Ea. It is concluded that the associations of quantitative traits with the earliness loci were caused by pleiotropy. Associations were found between two absolutely linked C-bands on chromosome 3 and QTLs (quantitative trait loci) for lodging, straw diameter, and length of top internode of the straw. The three loci on chromosome 5, eak and the two linked powdery mildew loci, Mla9 and Mlk, were associated with a possible QTL for magnesium concentration in grain. Association to the C-band on chromosome 6 suggests QTLs for TGW (thousand grain weight), straw diameter and magnesium concentration in grain. Locus Estl on chromosome 3 was not associated with any of the quantitative traits.