Genetic resistance to cereal cyst nematode Heterodera avenae Woll. in wild oat Avena sterilis I. 376

Summary Three dominant genes A, B and C are involved in the resistance of Avena sterilis I. 376 to Heterodera avenae. When associated, genes A and B are responsible for the high level of resistance in I. 376. In the absence of the first two genes, gene C confers intermediate resistance characterized by the presence of a limited number of cysts on the roots. Only the completely recessive genotype allows the nematode to develop normally.     

Investigations on resistance of oats to Heterodera avenae: Location of resistance genes

Summary By using 15 available mono/nullisomic lines of Sun II back ground, the Heterodera avenae resistance gene in Nelson (from Avena sativa CI 3444) and Panema (from A. sterilis I. 376) were located on monosome XV. Genes with smaller effects were located on monosomes VIII and X. The absence of these genes derived from Sun II would increase cyst production on plants lacking major resistance genes.     

Breeding for resistance to cereal cyst nematode in wheat

Summary The progress of a backcross breeding programme to introduce resistance against the cereal cyst nematode into wheat is described. Methods of resistance screening and criteria for selection are detailed and the results discussed with reference to alternative procedures for the introduction of new resistance genes into major breeding programmes.     

Expression of nuclear-cytoplasmic interactions and heterosis in quantitative traits of oats (Avena spp.)

Summary Nuclear and cytoplasmic genes from 10 diverse Avena sterilis L. accessions were introgressed into four Corn Belt oat (A. sativa L.) cultivars. Grain and straw yield, harvest index, heading date, height, unit straw weight, and vegetative growth index were evaluated in the BC₂ generation of 76 cytoplasmic isopopulations. Means of all seven traits in the BC₂ of Tippecanoe matings were greater than Tippecanoe due to introgression of A. sterilis germplasm, whereas means of all seven traits in BC₂ populations of Ogle were inferior to those of Ogle. BC₂ populations of matings involving CI 9170 and CI 9268 were variable, with some trait means being greater than those of the recurrent parents and some being lower.The phenomena of nuclear-cytoplasmic interaction effects and nuclear-cytoplasmic heterosis also were investigated. In matings where significant differences were present between cytoplasmic isopopulations, those with A. sterilis cytoplasm usually were superior, but no trait exhibited a consistent cytoplasmic effect across all matings. These results suggest that all seven traits were influenced by nuclear-cytoplasmic interactions. Nuclear-cytoplasmic heterosis for grain yield was present in two of 38 isopopulations with A. sterilis cytoplasm; both were from matings involving Tippecanoe. Nuclear-cytoplasmic heterosis for each of the remaining traits was observed in four to eight of the 38 isopopulations with A. sterilis cytoplasm.     

Influence of vernalization and photoperiod to the vegetation period of wild species of oats (Avena spp.)

This paper presents the results of a six year field study of wild Avenaspecies and their response to vernalization and photoperiod. The accessions of twenty one wild and weedy species were tested under 12-hr and 18-hr daylength and cold temperatures (for 40 days at +2 ^°C) treatments and without it (as a control). The results demonstrate that for the majority of species evaluated, cold temperature requirements had a greater influence on heading date and the duration of the vegetative period than daylength. Genotypes with neutral, weak and strong reactions to all treatments were found and spring and winter types were selected. The results further demonstrated that daylength-insensitive forms occurred in the south Mediterranean region and adjacent southern territories.     

Utilization of deletions to localize a gene for resistance to the cereal cyst nematode, Heterodera avenue, on an Aegilops ventricosa chromosome

A previous RFLP analysis showed that the Aegilops ventricosa chromosome 6M^V which compensates for the absence of 6D in 6M^V (6D) wheat substitution lines was a 2/6 translocated chromosome, either 2S–6S.6L or 2S–6L.6S. The distal part of its long arm consists of a translocated segment belonging to homoeologous group 2. Chromosome 6M^V carries a gene(s) for resistance to cereal cyst nematode. In order to define the part of 6M^V (2S or 6S or 6L) involved in this resistance, addition lines with a 6M^V deleted either for its short arm or for the distal part of its long arm were evaluated. It was shown that the gene(s) is carried by the group 2 translocated segment. The hypothesis that the gene(s) could be allelic to Cre2, another gene conferring resistance to the nematode introduced into the wheat complement from Ae. ventricosa is discussed.     

Partial resistance of sugarbeet to beet cyst eelworm (Heterodera schachtii Schm.)

Summary Within Beta vulgaris and B. maritima origins some partial resistance to beet cyst eelworm was found which could be raised to a very limited extent by selection. However after the second backcross to commercial sugar beet varieties and successive selection of the inbreds this resistance was lost. It was demonstrated that in the rootsystem of resistant plants as much nematodes penetrate and develop as in susceptible ones but the ratio between males and females is different. It was therefore quite probable that this resistance is polyfactorial and merely recessive.     

RFLP mapping of a new cereal cyst nematode resistance locus in barley

Cereal cyst nematode (CCN) ( Heterodera avenae Woll.) is an economically damaging pest of barley in many of the worlds cereal growing areas. The development of CCN-resistant cultivars may be accelerated with the application of molecular markers. Three resistance genes against the pest have been mapped previously to chromosome 2 ( Ha 1, Ha 2 and Ha 3). In this study, a third gene present in the Australian barley variety 'Galleon' derived from the landrace 'CI3576' was located. Segregation analysis of CCN resistance data derived from doubled haploid populations of the cross 'Haruna Nijo'×'Galleon' identified a single major locus controlling CCN resistance in the variety 'Galleon'. This locus mapped to the long arm of chromosome 5H estimated to be 6.2 cM from the known function restriction fragment length polymorphism marker XYL (xylanase). While five genes for CCN resistance, including Ha2, have been mapped to group 2 chromosomes in the Triticeae, no gene other than Ha4 has been identified on group 5 chromosomes.     

Breeding wheat for resistance to Heterodera avenae in Southeastern Australia

Breeding wheat for resistance to Heterodera avenae in southern Australia has been in progress for nearly 30 years and recently a number of resistant varieties have been released. Early breeding work was hampered by three factors: • a lack of appreciation of the role and extent of the problem, • inaccurate, slow screening methods, ultimately being replaced by the 'tube' test and soon by linked molecular markers, • inappropriate breeding strategies, so that varietal releases have taken place only when the breeding has been fully integrated into the main programs. The experiences in southern Australia will be relevant to many other areas in the world where H. avenae is the major pest. This revised version was published online in August 2006 with corrections to the Cover Date.     

The genetics of naked oats (Avena nuda L.)

Summary The inheritance of the character complex of naked grain and multiflorous spikelets was studied in a diallel set of crosses comprising five varieties of naked oats (Avena nuda)-As 78, Manu, Caesar, Nuprime and AJ86/2/1-and one variety of husked oats (A. sativa), Maris Oberon. In the F₁ generation the distribution of multiflorous spikelets was in all cases similar to that of the mid-parent. Crosses between the varieties of A. nuda produced only naked grain on plants in the F₁ and F₂ generations, indicating that nakedness in the varieties studied was determined by the same loci.The three-gene model proposed by Moule (1972) for the determination of A. nuda characters was inadequate to account for the observed F₂ segregation in naked x husked crosses. An extension of this model is proposed to include a third modifying gene, N₃, which in the homozygous dominant condition produces the husked phenotype when the principal gene, N, is heterozygous. The model assumes complex epistatic relationships between the three modifying genes N₁, N₂ and N₃. Published information and further experimental data suggest that the genotype NN--N₃N₃ is uncommon. The expression of the genes determining nakedness was greatly influenced by the environment.     

Genetic analysis of resistance to soybean cyst nematode in PI 438489B

Soybean (Glycine max L. Merr.) plant introduction PI 438489B is a unique source that has resistance to all known populations of soybean cyst nematode (Heterodera glycines Ichinohe, SCN). This PI line also has many desirable agronomic characteristics, which makes it an attractive source of SCN resistance for use in a soybean breeding program. However, characterization of SCN resistance genes in this PI line have not been fully researched. In this study, we investigated the inheritance of resistance to populations of SCN races 1, 2, 3, 5, and 14 in PI 438489B. PI 438489B was crossed to the susceptible cultivar ‘Hamilton’ to generate F₁ hybrids. The random F₂ plants and F₃ lines were evaluated in the greenhouse for reaction to these five populations of SCN races. Resistance to SCN races 1, 3, and 5 were mostly conditioned by three genes (Rhg Rhg rhg). Resistance to race 2 was controlled by four genes (Rhg rhg rgh rgh). Three recessive genes were most likely involved in giving resistance to race 14. We further concluded that resistance to different populations of SCN races may share some common genes or pleiotropic effects may be involved. This revised version was published online in July 2006 with corrections to the Cover Date.     

Breeding for resistance to cereal cyst nematode in wheat II. Use of test tube cultures in selection

Summary The use of soil. naturally infested with Heterodera avenae, to select resistant heterozygotes in backcross progenies of wheat, was tested for reliability. Selfed progenies from plants selected as resistant were cultured monoxenically in test tubes with nematodes hatched from single cysts, while backcross progenies from the same parent plants were grown in pots of naturally infested soil. Cyst counts were made after two months' growth. The results showed that over 50% of the backcross lines, screened in previous generations with naturally infested soil, had been erroneously selected as resistant. The test tube cultures clearly differentiated lines carrying resistance from those which were susceptible and corroborated results from pot tests.     

Inheritance of groat-oil content and high-oil selection in oats (Avena sativa L.)

Summary The potential for breeding for high groat-oil content in oats was investigated by (a) conducting generation means analyses on data from three matings among adapted Avena sativa L. cultivars, (b) practicing one cycle of phenotypic recurrent selection in a segregating population derived from eight species backcrosses (Avena sativa x (A. sativa x A. sterilis)) among 24 parents, and (c) identifying transgressive segregates from interspecific (A. sativa x A. sterilis) matings.Additive gene action was the most important component in explaining the variation among generation means for groat-oil content. Dominance and epistatic interactions involving dominance were not significant in any mating. Significant residual genetic variation occurred in one mating, even after additive, dominance, and three digenic interactions were fitted. The importance of additive genes action implies that desired allelic combinations for high groat-oil content can be obtained in pure-line cultivars.One cycle of phenotypic recurrent selection using single plants as the selection units resulted in a genetic gain of 1.7 to 2.1% in groat-oil content. Individual plants selected for initiating the second cycle had from 9.5 to 12.6% groat oil.Over all 12 interspecific matings, the F₂ progeny means were similar to the midparent values. Only two were significantly deviant. Transgressive segregates for high and low groat-oil content from these matings provided evidence that A. sterilis possesses alleles for high and low groat-oil content that are different from those in the gene pool of cultivated oats.Journal Paper No. J-11340 of the Iowa Agric. and Home ECon. Exp. Stn., Ames, Iowa 50011. Project 2447. This study was supported in parts by grants from the Iowa Committee for Agricultural Development and the International Harvester Company.     

Genetic analysis of resistance to root-lesion nematode (Pratylenchus thornei) in wheat

The inheritance of resistance to root‐lesion nematode was investigated in five synthetic hexaploid wheat lines and two bread wheat lines using a half‐diallel design of F₁ and F₂ crosses. The combining ability of resistance genes in the synthetic hexaploid wheat lines was compared with the performance of the bread wheat line ‘GS50a’, the source of resistance to Pratylenchus thornei used in Australian wheat breeding programmes. Replicated glasshouse trials identified P. thornei resistance as polygenic and additive in gene action. General combining ability (GCA) of the parents was more important than specific combining ability (SCA) effects in the inheritance of P. thornei resistance in both F₁ and F₂ populations. The synthetic hexaploid wheat line ‘CPI133872’ was identified as the best general combiner, however, all five synthetic hexaploid wheat lines possessed better GCA than ‘GS50a’ The synthetic hexaploid wheat lines contain novel sources of P. thornei resistance that will provide alternative and more effective sources of resistance to be utilized in wheat breeding programmes.     

Genetic resistance to root-knot nematode (Meloidogyne javanica) in eggplant (Solanum melongena)

A germplasm collection of 39 eggplant Solanum melongena genotypes and one accession of S. torvum was evaluated for resistance to the root-knot nematode (Meloidogyne javanica) by using controlled greenhouse tests. Different degrees of resistance to the disease caused by this nematode species were observed among the genotypes tested. Complete resistance (no nematode egg mass formation up to 7 weeks after inoculation) was detected in one accession belonging to domesticated S. melongena species. Good levels of incomplete resistance were also observed in some commercial eggplant genotypes. This is apparently the first report of a source of complete resistance to M. javanica within the S. melongena gene pool and our finding could greatly facilitate the incorporation of this trait into commercial eggplant cultivars. S. torvum, previously described as resistant to several root-knot nematode species (including M. javanica, M. arenaria, and M. incognita) was also confirmed as a source of resistance to this Brazilian population of M. javanica. Therefore, S. torvum can be considered as one of the most promising sources of broad-spectrum resistance genes against root-knot nematodes. Broad-spectrum resistance is of paramount importance for breeding programmes focused on the development of cultivars for tropical and subtropical areas of the world where multiple infestation of soils with distinct Meloidogyne species is a very common feature.     

Relationship between genealogical distance and breeding behaviour in oats (Avena sativa L.)

Summary Eight oat cultivars and experimental lines from four germplasm sources were crossed in a diallel mating design without reciprocals. F₁ heterosis for grain yield was evaluated in two experiments, and 48 F₂-derived lines from each of the 28 matings were evaluated for bundle weight, grain yield, straw yield, harvest index, height, and heading date in two experiments. Number of transgressive segregates per trait and generalized genetic variance were calculated for each mating. Genealogical distance for each mating was obtained by using coefficient of kinship based on the pedigree of the parents. The relationship between genealogical distance and the three types of breeding behaviour was examined via correlation and regression. Significant correlations occurred only for genealogical distance with numbers of transgressive segregates for height and with generalized genetic variances. Both were positive. Significant heterosis was observed for matings of more distantly related parents. Regressions on genealogical distance, when significant, were linear. Genealogical distance between parents was positive associated with diversity on the basis of breeding behavior.Journal Paper No. J-11874 of the Iowa Agriculture and Home Economics Station, Iowa State Univ., Ames, IA 50011. Project 2447.     

Inheritance of resistance to Puccinia coronata var. avenae in six selections of Avena sterilis

Summary Six selections of Avena sterilis, introduced from Israel as sources of resistance to oat crown rust, were crossed with susceptible A. byzantina Frazier. The number of genes conditioning resistance to culture H-14 of race 326 of Puccinia coronata var. avenae in each of the six selections was determined from studies of F₁, F₂ and F₃ populations from the crosses. P.I. 287211, P.I. 295919 and P.I. 296244 each appeared to have a single dominant gene for resistance, and P.I. 296265 and P.I. 296266 each two dominant ones. C.I. 8295 had a single partially dominant gene for resistance. Crosses among the A. sterilis parents indicated that at least four different genes conditioned resistance to culture H-14.Association between F₂ reaction to crown rust and morphological characters of the spikelet was determined with the % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiabeE8aJnaaCa% aaleqabaGaaGOmaaaaaaa!39FC!\[\chi ^2 \] test for independence. In four crosses, all spikelet characters appeared to be independent of rust reaction. In Frazier x P.I. 296244, basal pubescence of the lemma on the secondary floret appeared to be associated with reaction to crown rust. Strong association between reaction to crown rust and lemma pubescence on the primary floret was evident in Frazier x P.I. 296265.     

Sugar beets homozygous for resistance to beet cyst nematode (Heterodera schachtii Schm.), developed from monosomic additions of Beta procumbens to B. vulgaris

Summary Monosomic additions of Beta vulgaris x B. procumbens with resistance to beet cyst nematode (Heterodera schachtii Schm.) were used for the production of resistant diploids through incorporation of the B. procumbens chromosome fragment bearing the resistance gene(s) into one of the sugar beet chromosomes. The heterozygotes obtained accordingly were selfed for producing homozygotes. These homozygotes differed morphologically from commercial sugar beet varieties, but produced reasonable amounts of pollen. Female transmission of resistance was 100%, whereas male transmission, apart from some exceptions, was more than 90%. The number of hypersensitivity reactions to penetrated larvae was related to the degree of susceptibility. Larval development was severely retarded in the resistant plants, preventing most of them to produce cysts. If cysts were formed, their content was considerably less as compared to those in the susceptible plants.     

小麦品种太空6号对Heterodera avenae郑州群体的抗性遗传分析

通过多年接虫和田间病圃抗性鉴定,发现普通小麦品种太空6号对燕麦孢囊线虫(Heterodera avenae)郑州群体具有较好的抗性。以抗病品种太空6号为父本、感病品种豫麦47为母本配置杂交组合构建遗传分离群体,通过田间病圃鉴定和室内接虫鉴定对太空6号进行了抗性遗传分析,发现豫麦47×太空6号杂种F₂代单株孢囊量为连续分布,具有数量性状特征;F₂代群体单株孢囊量分布图呈偏态分布,说明存在明显的主效基因。应用植物数量性状主基因+多基因混合遗传模型单个分离世代分析方法,分析豫麦47×太空6号杂种F₂代群体在室内接种二龄幼虫和田间病圃中对H. avenae郑州群体的抗性遗传效应均符合B-2模型,推测太空6号对H. avenae的抗性由2对主基因+多基因控制,主基因表现为加性-显性效应,在室内人工接种和田间病圃鉴定条件下主基因的遗传率分别为73.54%和86.90%,说明太空6号对燕麦孢囊线虫郑州群体的抗性是主效基因起主要作用。