Influence of winter and spring wheat genetic backgrounds on haploid induction parameters and trait correlations in the wheat × maize system

The interactive influence of winter and/or spring wheat genetic background on haploid induction parameters and trait correlation was studied by hybridizing five elite and diverse genotypes each of winter and spring wheat and their F₁s (winter × winter, spring × spring, and winter × spring, generated in a diallel design excluding reciprocals) with a single genotype of maize. Data were recorded with respect to per cent seed formation, embryo formation, and regeneration. High genetic variability was present among the wheat genotypes (parents + F₁s) for the three haploid induction parameters. Significant differences were obtained within and between different groups viz., spring wheats, winter wheats, spring × spring wheats, winter × winter wheats, and winter × spring wheats with respect to the three haploid induction parameters based on ANOVA. The winter genotypes (winter parents and winter × winter wheat hybrids) responded better than the spring groups (spring wheat parents, spring × spring and winter × spring wheat hybrids) with respect to embryo formation and winter × spring wheat hybrids yielded significantly the highest numbers of regenerants. Correlation studies amongst the haploid induction parameters indicated that the genes controlling seed formation and haploid plantlet regeneration are negatively correlated when the genetic backgrounds of both ecotypes are combined in winter × spring hybrids. Haploid embryo formation had no association with seed formation and regeneration in all genetic backgrounds, suggesting independent inheritance.     

Distribution and Origin of Hybrid Necrosis Genes in German Winter Wheat (Triticum aestivum L.) Cultivars

Hybrid necrosis in Triticum is known to be caused by the interaction of two complementary dominant genes. In the present paper, the genotypes for hybrid necrosis of 64 winter wheat cultivars are presented. 41 cultivars were found to possess the Ne₂ necrosis gene, whereas 23 cultivars were non-carriers. The Ne₁ gene was not found in any of the cultivars analyzed.     

Genetic variation for resistance to Fusarium head blight in bread wheat

Summary During a four year period, a total of 258 winter and spring wheat genotypes were evaluated for resistance to head blight after inoculation with Fusarium culmorum strain IPO 39-01. It was concluded that genetic variation for resistance is very large. Spring wheat genotypes which had been reported to be resistant to head blight caused by Fusarium graminearum were also resistant to F. culmorum. The resistant germplasm was divided into three gene pools: winter wheats from Eastern Europe, spring wheats from China/Japan and spring wheats from Brazil. In 32 winter wheat genotypes in 1987, and 54 winter wheat genotypes in 1989, the percentage yield reduction depended on the square root of percentage head blight with an average regression coefficient of 6.6. Heritability estimates indicated that for selection for Fusarium head blight resistance, visually assessed head blight was a better selection criterion than yield reduction.     

Distribution of the photoperiod insensitive <Emphasis Type="Italic">Ppd-D1a</Emphasis> allele in Chinese wheat cultivars

Photoperiod response is of great importance for optimal adaptation of bread wheat cultivars to specific environments, and variation is commonly associated with allelic differences at the Ppd-D1 locus on chromosome 2D. A total of 926 Chinese wheat landraces and improved cultivars collected from nine wheat growing zones were tested for their genotypes at the Ppd-D1 locus using allele-specific markers. The average frequency of the photoperiod-insensitive Ppd-D1a allele was 66.0%, with the frequencies of 38.6 and 90.6% in landraces and improved cultivars, respectively. However, the Ppd-D1a allele was present in all improved cultivars released after 1970 except for spring wheats in high latitude northwestern China, and winter wheats in Gansu and Xinjiang. The presence of the Ppd-D1a allele in landraces and improved cultivars increased gradually from north to south, illustrating the relationship between photoperiod response and environment. Ppd-D1a in Chinese wheats is derived from three sources, Japanese landrace Akagomughi and Chinese landraces Mazhamai and Youzimai. The current information is important for understanding the broad adaptation of improved Chinese wheat cultivars. F. P. Yang and X. K. Zhang contributed equally to this work.     

Eighth supplementary list of wheat varieties classified according to their genotype for hybrid necrosis

Summary The eight supplement contains 901 varieties etc. viz. 163 (18.1%) Ne ₁-, 153 (17.0%) Ne ₂- and 585 (64.9%) non-carriers. The total number of varieties etc. tested is 1461 (26.4%) Ne ₁-, 1184 (21.4%) Ne ₂- and 2885 (52.2%) non-carriers, together 5530.Various aspects of hybrid necrosis like the geographical distribution of the Ne-genes and their alleles, linkage, Green Revolution, durum wheat and the cause have been discussed. Some information is given on some of the listed varieties etc.This is my last supplement.     

Inheritance of resistance to two Septoria tritici isolates in spring and winter bread wheat cultivars

Summary All possible crosses (including reciprocals) were made among four winter bread (Aurora, Bezostaya 1, Kavkaz, and Trakia) and two Israeli spring wheat cultivars (spring x winter diallel), and among two South American spring wheats (Colotana and Klein Titan) with the same Israeli cultivars (spring x spring diallel) to study the inheritance of resistance to septoria tritici blotch. Parents, F₁, F₂ and backcrosses were grown in two separated blocks in the field over two years. One block was inoculated with isolate ISR398A1 and another with ISR8036. Each plant was assessed for plant height (cm), days to heading (from emergence or transplanting), and percent pycnidia coverage on the four uppermost leaves. Plant height and maturity had insignificant effects on pycnidia coverage. No cytoplasmic effects could be detected. In the spring x winter diallel general combining ability (GCA) was the major component of variation. Significant specific combining ability (SCA) was present in all cases. Partial dominance was operative in populations inoculated with ISR398A1. Resistance in the winter wheats was controlled by a small number of genes (usually two). The four winter wheats derive their resistance to ISR398A1 from their common parent Bezostaya 1 which lacks the 1B/1R wheat-rye translocation. Their resistance is readily overcome by ISR8036. Inheritance of the South American wheats can be explained by additive effects, with a small number of genes of recessive mode affecting resistance to both isolates. Breeding strategies that favor additive, and additive x dominance gene action should be pursued.     

A gene for hybrid necrosis in an inbred line of rye (Secale cereale L.)

Summary An inbred line of rye (Secale cereale L.) has been found to carry a gene for hybrid necrosis. This gene was detected in crosses with a highly crossable wheat (Triticum aestivum L.) genotype which carries the gene Ne₂. This appears to be the first report of a gene for hybrid necrosis being present in the rye genome.     

Growth habit in common wheat (Triticum aestivum L. em. Thell.)

Summary A study of the Vrn genotypes of 642 spring wheats supports the theory that only Vrn1, Vrn2 and Vrn3 exist in Tricticum aestivum. In none of the varieties investigated Vrn4 was present. Seven varieties, which according to literature carry Vrn4, showed to carry Vrn1, Vrn2 and/or Vrn3. Some varieties were mixtures of Vrn-genotypes, which could mislead geneticists in pooled data analysis. Other causes for misinterpretation of the data could be hybrid necrosis, hybrid dwarfness or a wrong determination of plants with a winter habitus. Only Hope was dominant on another Vrn locus. Its haploid Vrn-genotype is Vrn1 vrn2vrn3 Vrn5.     

The influence of flowering time genes on environmental adaptability in European wheats

Summary In order to obtain high levels of environmental adaptability in wheat varieties it is essential they flower at times appropriate to particular environmental conditions. The influence of three distinct genetic systems that together determine time of flowering is reviewed here.Vernalization genes are seen to be particularly important to winter wheats for their direct or indirect effects on winter hardiness. Vernalization genes play a minor role in determining flowering time in autumn sown winter wheats but insensitivity is essential if spring sown wheats are to flower.Day length sensitive photoperiod genes play a major role in determining flowering time and adaptability of autumn sown wheats. Insensitivity can promote yield advantages of over 35% in Southern European environments. 15% in Central Europe and offers benefits even in the UK. At present only a single allele of Ppd1 appears to have been introduced into commercial European wheat varieties. The merits of alternative Ppd1 alleles or different loci are discussed.The influence of earliness per se genes that determine flowering time independently of environmental stimuli is less well documented than the effect of photoperiod and vernalization genes. It is likely that genes on chromosomes belonging to groups 2, 3, 4, 6 and 7 may act to modify flowering time independently of environmental stimuli probably by determining numbers of vegetative and floral primordia being initiated or the rate of initiation of the primordia. Earliness per se genes appear to be widespread in European wheats and play a significant role in determining the exact time plants flower.     

Winter × spring wheat hybridization - a promising avenue for yield enhancement

Introgression of the winter gene pool into spring wheat is being considered as one of the strategies to break through the yield plateau. However, little information is available on the combining ability of these two important but distinct groups of wheats in Indian conditions. Therefore, the present study was undertaken to determine the combining ability and gene action of yield and yield attributes in winter × spring wheat crosses. Seventy F₁ progenies developed by 14 winter and five spring wheat lines using a line × tester design were evaluated, along with their parents, for yield and yield attributes in a randomized complete block design under field conditions. The mean squares for all the characters studied showed highly significant differences. The mean squares due to female × male interactions were significant for all the characters studied except for grains per ear and grain weight per ear. Additive genetic effects were found to play a key role in controlling the expression of days to heading, plant height and spikelets per ear.‘MV 19’ and ‘Stepniak’/‘Karvuna’ among winter and ‘PBW 65’ among spring wheats were good general combiners for most of the yield attributes studied. The estimates for specific combining ability effects suggested that, although general combining ability (GCA) effects of most winter wheats are either average or poor, their combination can give desirable genotypes with spring wheat parents possessing a high GCA.     

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.     

Sources and distribution of the complementary genes for hybrid necrosis in wheat

Hybrid necrosis in wheat is based on 2 complementary genes Ne ₁ and Ne ₂. Unitl now among the 509 varieties and selections tested 89 Ne ₁-and 207 Ne ₂-carriers were found. By tracing the descendence of these carriers several sources of the necrosis genes (mostly land varieties) could be detected. At the same time it was demonstrated that notably the frequent use of certain carrier-varieties as parents in crosses has promoted the distribution of the necrosis genes.     

High Frequencies of Fertilization and Haploid Seedling Production in Crosses Between Commercial Hexaploid Wheat Varieties and Maize

Nineteen commercial hexaploid wheat varieties were crossed with the maize F₁ hybrid ‘Seneca 60’. Fertilization frequencies ranged from 32.1 % to 47.5 % of pollinated florets (mean 39.5 %) in the 14 winter wheat varieties and from 40.7 % to 51.4 % (mean 47.8 %) in the five spring wheat varieties. In some cases only an endosperm was formed and the frequencies of embryo formation were therefore slightly lower, being 28.2 % to 45.9 % (mean 36.4 %) for winter wheats and 39.8 % to 48.6 % (mean 45.1 %) for spring wheats. Mean values were significantly higher in the spring wheats but no significant variation was found between varieties within the spring or winter categories. In the five spring wheats the mean yield of embryos, and hence the potential yield of haploid plants, was 3.4-fold higher than with the tetraploid Hordeum bulbosum clone PB179. For the 14 winter wheats the figure was 10.9-fold higher. These differences were highly significant (p < 0.001) in all varieties. A single 2,4-D treatment given to spikes one day after pollination with maize enabled embryos to be recovered from all 19 varieties. A total of 311 embryos were recovered from 950 florets (an average of 7.3 embryos per spike) of which 191 germinated, giving an average yield of one haploid plant for every 5.0 florets pollinated (4.4 haploid plants per spike).     

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.     

Hybrid necrosis as a problem for the wheat breeder

Hybrid necrosis is the premature gradual death of leaves and leaf sheaths in certain wheat hybrids. It is based on two complementary genes Ne ₁ and Ne ₂. Hitherto 89 Ne ₁-carriers and 207 Ne ₂-carriers from many countries are known (table 1 and 2). This corresponds with more than 18,000 different necrotic cross combinations.The degree of necrosis in the F₁'s varies greatly, due to multiple allelism of Ne ₁ and Ne ₂. Nine necrosis grades are described in table 3. Grades 6–8 are called severe necrosis (no seed is produced), 3–6 moderate necrosis (premature seed), 0–3 weak necrosis (normal seed). Most severely necrotic F₁'s could be brought to seed production by raising them under extra favourable conditions in a small growth-chamber. Growing moderately necrotic F₁'s in pots outside, at a high fertility level of the soil, resulted in a striking increase of the seed production.On the basis of the above mentioned data and results some practical advice is given to the breeders about the handling of necrotic crosses. In addition some ways to preclude hybrid necrosis are indicated, though the wheat breeder is advised against a systematic avoiding of necrosis because many combinations of excellent varieties then remain untried.     

Variations in pathogenicity patterns ofMycosphaerella graminicola withinTriticum spp. in Israel

Summary Pathogenicity patterns of 42Mycosphaerella graminicola (Septoria tritici) isolates secured from the major wheat growing regions in Israel, were assessed on seedlings of 16 bread and durum wheats. The spring bread wheat cultivar Titan (CI12615), the winter bread wheats Bezostaya 1, Kavkaz, NE7060 and the durum wheats Nursit 163 and Zenati Bouteille, all exhibited a high level of resistance. Significant cultivar × isolate interactions were recorded for isolates from the different regions in relation to the response of the 16 cultivars organized in 6 reponse classes to the test isolate ISR8036. Number of genes for resistance in the 16 cultivars was estimated, based on the assumption of a gene-for-gene relationship. Twelve complementary genes were hypothesized in the 42M. graminicola isolates × 16 wheat cultivars matrix. There was considerable variation in virulence frequencies between regions and between locations within the same region. The overall frequency of Bezostaya-Kavkaz virulence was low throughout the country (5–7%). The frequency of designated hypothesized virulence genes VST OLAF, VST COLOTANA, VST IAS 20 in Israel, was high in most locations. The reported analytical approach enables the identification of virulence hot-spots and assists in designing breeding for resistance strategies.     

Third supplementary list of wheat varieties classified according to their genotype for hybrid necrosis

Summary New data about the geographical distribution of necrosis genes support the previous conclusion, viz. the Old World can be divided by a rough line running through the Mediterranean and Black Sea countries to Lake Baikal and from these to northern Japan. The Ne ₁-area lies south and east and the Ne ₂ area north and west of this line. There are indications that Ne ₁-carrying wheat varieties exist in the Leningrad district.The third supplement contains 441 varieties and selections of which the genotype for hybrid necrosis is given. The total number of tested varieties etc. is now 1150.     

Measurement of response to vernalization in Australian wheats with winter habit

Summary Development in wheat is strongly controlled by sensitivity to vernalization and photoperiod, and to a lesser degree by non-vernalizing temperature and intrinsic earliness. A method to measure effect of vernalization in wheats with winter habit is described. Twenty seven wheats with winter habit and eight with spring/facultative habit were studied, comprising breeding lines and cultivars with maturities suited to south-central New South Wales. Effect of vernalization on the development of these wheats was quantified by integrating responses to vernalizing treatments of differing duration. Intrinsic earliness was measured as time for vernalized seedlings to grow to ear emergece in an 18h photoperiod with day/night temperature of 21/16°C, and response to photoperiod as the difference in time to ear emergence between 9 and 18h daylengths. Integrated response to vernalization is sensitive to both cumulative and thresh-hold responses and is applicable to wheats of all habit type. Integrated response to vernalization and intrinsic earliness were positively associated within wheats with winter habit. Wheats were largely of restricted origin, so that there were few allelic differences at Vrn loci to disrupt this association, which suggests intrinsic earliness may modify response to vernalization. Though integrated response to vernalization was measured with artificial treatments, it was strongly associated with ear emergence for wheats with winter habit when grown at a site in New South Wales.     

Genetics of androgenesis in winter and spring wheat genotypes

Androgenetic response and its inheritance was studied in nine winter type and two spring type wheat genotypes by crossing them in line × tester fashion. The 18 F₁ and 11 parental genotypes were raised in completely randomized block design with three replications and subjected to anther culture. Data were recorded with respect to per cent calli induction, percent regeneration and per cent green plant development. Analysis of variance revealed considerable genetic variation for all the three component traits of androgenesis. Both additive and non-additive genetic variances were involved in the androgenetic response with the preponderance of non-additive gene action in case of calli induction and additive gene action for regeneration and green plant development. Low estimates of heritability (narrow sense) for calli induction and moderate for regeneration and green plantlet development were obtained. The genotypes, Henies VII, Pnfjoumee, Saptdhara, Sentry, Purthi of winter wheat and HPW147 of spring wheat were identified as good general combiners for almost all the androgenetic parameters and have potential use in future haploidy breeding programmes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Alien introgression of spring habit dominant genes into bread wheat

Summary Alien dominant genes of spring habit were introgressed into bread wheat. The introgression was undertaken by simple crossing of winter bread wheat to related spring species or genera, followed by backcrossing to winter bread wheat, and did not involve the use of the ph mutants or embryo culture. The introgressed genes were located mostly on chromosomes of homoeologous group 5, and were allelic to the known Vrn genes in bread wheat. Nevertheless three groups of lines were discovered with the genes possibly located on other chromosomes. These genes were non-allelic to each other and to known Vrn genes and were designated Vrn6 ^Sc , Vrn7 ^Sc (introgressed from Secale cereale) and Vrn8 ^Ts (from Triticum sphaerococcum).