Recurrent selection in autogamous species under forced random mating

Summary Artificial selection in autogamous species is investigated applying standard algebraic techniques to conventional self-pollinating breeding systems as well as to recurrent cross-pollinating ones for both one and two-locus models. More than two loci are considered by means of computer simulations. Allelic and non-allelic genotypic interactions as well as genes with a large effect are considered whenever possible. The overall picture shows a clear superiority of recurrent selection systems over self-pollinating breeding systems when negative linkage disequilibrium is either present or generated as is expected in actual breeding populations. When epistatic interaction enhances the selective advantage of new recombinants the superiority of recurrent selection is even greater.     

Relation in the inheritance of resistance to Pseudoperonospora cubensis rost and Sphaerotheca fuliginea poll. in cucumber (Cucumis sativusl. L.)

Summary Among the genes for resistance against Sphaerotheca fuliginea, the gene s for resistance of the hypocotyl is linked to or identical with gene p for resistance to Pseudoperonospora cubensis. This gene s is present in the cultivars Ashley, Poinsett, Natsufushinari, Pixie, Taipei and in accessions PI 179676. PI 212233 and PI 234517.Although gene s initially brings about some resistance of the true leaf, it appears that when s is present. other genes are necessary for complete resistance to S. fuliginea.     

Inheritance of zucchini yellow mosaic virus resistance in Cucumis melo L.

Summary Resistance to zucchini yellow mosaic virus has been found in the muskmelon line PI 414723 from India. This resistance is effective against the ZYMV strains E15 and 1318 belonging respectively to the NF and F pathotypes. Resistance to E15 (no vein clearing and yellowing symptoms) is governed by one dominant gene (symbol Zym) according to segregations observed in F₁, F₂ and BC₁ progenies. This gene is epistatic dominant over Fn, which induces wilting and necrosis after inoculation with F pathotype. Linkage studies suggest that Zym inherits independently from Fom-1, Fom-2, Vat, Wmv and Fn but is linked with a (13.1 ±2.4 units).     

Identification of RAPD markers linked to the rust (<Emphasis Type="Italic">Uromyces fabae</Emphasis>) resistance gene in pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>)

Summary Two RAPD markers linked to gene for resistance (assayed as pustule number cm⁻² leaf area) to rust [Uromyces fabae (Pers.) de Bary] in pea (Pisum sativum L.) were identified using a mapping population of 31 BC₁F₁ [HUVP 1 (HUVP 1 × FC 1] plants, FC 1 being the resistant parent. The analysis of genetics of rust resistance was based on the parents, F₁, F₂, BC₁F₁ and BC₁F₂ generations. Rust resistance in pea is of non-hypersensitive type; it appeared to be governed by a single partially dominant gene for which symbol Ruf is proposed. Further, this trait seems to be affected by some polygenes in addition to the proposed oligogene Ruf. A total of 614 decamer primers were used to survey the parental polymorphism with regard to DNA amplification by polymerase chain reaction. The primers that amplified polymorphic bands present in the resistant parent (FC 1) were used for bulked segregant analysis. Those markers that amplified consistently and differentially in the resistant and susceptible bulks were separately tested with the 31 BC₁F₁ individuals. Two RAPD makers, viz., SC10-82₃₆₀ (primer, GCCGTGAAGT), and SCRI-71₁₀₀₀ (primer, GTGGCGTAGT), flanking the rust resistance gene (Ruf) with a distance of 10.8 cM (0.097 rF and LOD of 5.05) and 24.5 cM (0.194 rF and a LOD of 2.72), respectively, were identified. These RAPD markers were not close enough to Ruf to allow a dependable maker-assisted selection for rust resistance. However, if the two makers flanking Ruf were used together, the effectiveness of MAS would be improved considerably.     

QTL mapping of volatile compounds in ripe apples detected by proton transfer reaction-mass spectrometry

The availability of genetic linkage maps enables the detection and analysis of QTLs contributing to quality traits of the genotype. Proton Transfer Reaction Mass Spectrometry (PTR-MS), a relatively novel spectrometric technique, has been applied to measure the headspace composition of the Volatile Organic Compounds (VOCs) emitted by apple fruit genotypes of the progeny ‘Fiesta’ × ‘Discovery’. Fruit samples were characterised by their PTR-MS spectra normalised to total area. QTL analysis for all PTR-MS peaks was carried out and 10 genomic regions associated with the peaks at m/z = 28, 43, 57, 61, 103, 115 and 145 were identified (LOD > 2.5). We show that it is possible to find quantitative trait loci (QTLs) related to PTR-MS characterisation of the headspace composition of single whole apple fruits indicating the presence of a link between molecular characterisation and PTR-MS data. We provide tentative information on the metabolites related to the detected QTLs based on available chemical information. A relation between apple skin colour and peaks related to carbonyl compounds was established. The two authors contributed equally to this work.     

RFLP/AFLP mapping of a brown planthopper (Nilaparvata lugens Stål) resistance gene Bph1 in rice

We have constructed a linkage map of the rice brown planthopper (BPH)resistance gene, Bph1. RFLP and AFLP markers were selected by thebulked segregant analysis and used in the mapping study of 262 F₂sthat were derived from a cross of `Tsukushibare', a susceptible japonica cultivar, and `Norin-PL3', an authentic japonicaBph1-introgression line. Twenty markers were mapped within a 28.9-cMregion containing the Bph1 locus on the long arm of rice chromosome12. Combining the result of segregation analysis of BPH resistance by themass seedling test and that of the markers, the Bph1 locus wasmapped within a 5.8-cM region between two flanking markers. The closestAFLP markers, em5814N and em2802N, was at 2.7 cM proximal to theBph1 locus. Together with the previously constructed high-resolutionmap of bph2 locating the locus at ca. 10 cM proximal to the Bph1 locus, this improved version of the linkage map would facilitatepyramiding these two important BPH resistance genes.     

Broad-few-leaflets and outwardly curved wings: two new mutants of chickpea

This study was aimed at the induction of morphological mutations for increasing genetic variability and making available additional genetic markers for linkage studies in chickpea (Cicer arietinum L.). A wilt‐resistant, well‐adapted chickpea cultivar of central India,‘JG 315’(Jawahar gram 315), was used for the induction of mutations. Seeds presoaked in distilled water for 2 h were treated with ethyl methane sulphonate (EMS) using six different concentrations (0.1, 0.2, 0.3, 0.4, 0.5 and 0.6%) and two different durations (6 and 8 h). Several morphological mutants were identified in M₂. One of the mutants, isolated from a treatment of 0.3% EMS for 8 h, had five to nine large leaflets per leaf in comparison with 11‐17 normal‐sized leaflets per leaf observed in the parental cultivar ‘JG 315′. The mutant was designated broad‐few‐leaflets. Many leaves of this mutant showed a cluster of three to five overlapping leaflets at the terminal end. The other mutant, designated outwardly curved wings, was isolated from the 0.5% EMS treatment for 6 h. In this mutant, the wings were curved outwards, exposing the keel petal, while the wings in typical chickpea flowers are incurved and enclose the keel. The lines developed from the broad‐few‐leaflets and outwardly curved wings mutants were named JGM 4 (Jawahar gram mutant 4) and JGM 5, respectively. Inheritance studies indicated that each of these mutant traits is governed by a single recessive gene. The gene for broad‐few‐leaflets was designated bfl and the gene for outwardly curved wings was designated ocw. The locus bfl was found to be linked with the locus lg (light green foliage) with a map distance of 18.7 ± 6.3 cM.     

Orientation and integration of the classical and molecular genetic maps of chromosome 11 in rice

Summary The classical genetic map and molecular map of rice chromosome 11 were oriented to facilitate the use of these maps for genetic studies and rice improvement. Three morphological markers (d-27, z-2, and la) were crossed to a rice breeding line, IRBB21, which has the Xa-21 gene for bacterial blight resistance. Three F₂ populations were analyzed with RFLP markers known to be located on chromosome 11. Segregation analysis of molecular markers and morphological markers was used to construct an RFLP map for each population. The recombination frequency between markers varied from population to population although the marker order on the maps was the same for all three populations. Based on a common set of markers mapped in the three populations, an integrated map was generated consisting of both RFLP and morphological markers. The genetic distance between markers on this map was determined by taking a weighted average of the data from the three populations. The oriented map serves as a bridge to understand the relationship between the classical and molecular linkage maps. Based on this information, the location of several genes on the classical map can be approximated with respect to RFLP markers without having to map them directly.     

Cytoplasmic male sterility,resistance to gall mite and mildew,and season of leafing out in black currants

Summary Cytoplasmic male sterility (cms) is described in the F₁ hybrids Ribes × carrierei (R. glutinosum albidum × R. nigrum) and R. sanguineum × R. nigrum. In backcrosses to R. nigrum, progenies with R. glutinosum cytoplasm were either all male sterile, or segregated for full male fertility (F) and complete (S) and partial (I) male sterility. Ratios of F:I+S suggested that two linked genes controlled cms, F plants being dominant for one (Rf ₁) and recessive for the other (Rf ₂).Segregation for cms in relation to three linded genes, Ce (resistance to the gall mite, Cecidophyopsis ribes), Sph ₃(resistance to American gooseberry mildew, Sphaerotheca mors-uvae) and Lf ₁(one of two dominant additive genes controlling early season leafing out) indicated that Rf ₁and Rf ₂were in this linkage group. The gene order and approximate crossover values appeared to be: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% aabaqaciGacaGaamqadaabaeaafaaakeaacaWGdbGaamyzamaamaaa% baGaaiiiaiaacccacaGGWaGaaiOlaiaacgdacaGG0aGaaiiiaiaacc% caaaGaaiiiaiaacccacaGGGaGaamOuaiaadAgaliaaigdakmaamaaa% baGaaiiiaiaacccacaGGGaGaaiiiaiaaccdacaGGUaGaaiOmaiaacs% dacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaaaacaWGsbGaamOzaSGa% aGOmaOWaaWaaaeaacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaiaacc% cacaGGGaGaaiiiaiaacccaaaGaamitaiaadAgaliaaigdakmaamaaa% baGaaiiiaiaacccacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaiaacc% cacaGGGaGaaiiiaiaacccacaGGGaaaaiaadofacaWGWbGaamiAaSGa% aG4maaaa!6E4D!\[Ce\underline { 0.14 } Rf1\underline { 0.24 } Rf2\underline { } Lf1\underline { } Sph3\]. Crossover values of 0.36 for Ce-Lf ₁, and 0.15 for Lf ₁-Sph ₃were estimated from the relative mean differences in season of leafing out between seedlings dominant and recessive for Ce and Sph ₃.It is suggested that competitive disadvantage of lf ₁-carrying gametes and/or zygotes at low temperatures may be implicated in the almost invariable deficit of plants dominant for the closely linked mildew resistance allele Sph ₃. Poor performance of lf ₁- (and possibly lf ₂-) carrying gametes and young zygotes during periods of low temperature at flowering might also account for the liability of some late season cultivars and selections to premature fruit drop (running off).     

Inheritance studies of characters associated with floating habit and their linkage relationship in rice

Summary Deep water rice varieties in general have certain peculiar characters which are associated with floating habit. These characters are (i) early nodal differentiation, (ii) nodal rooting, (iii) spreading habit, (iv) awned grains, (v) brown hull colour, (vi) red pericarp (red rice), and (vii) seed dormancy. Inheritance of these characters and linkage relationship of genes governing these characters were studied in a cross between Pankaj (non floating) and Nageribao (floating) rice varieties. Nageribao, a cultivar from Assam possesses these characters.Early nodal differentiation was observed to be controlled by a single dominant gene, designated as Nd. Nodal rooting was controlled by two dominant complementary genes, designated as Nr ₁ and Nr ₂. We found an inhibitory factor for spreading habit and one for brown hull colour in Pankaj; the operation of two dominant duplicate genes An ₁ and An ₂ for controlling awning characters, a single dominant gene Rd for red pericarp colour and a single dominant gene Gd for grain dormancy. Joint segregations between these characters resulted in the assignment of genes in the X linkage group of indica rices with estimated map distances based on the cross-over values. The genes An (awning), Es (spreading habit), Nr (nodal rooting) and Nd (nodal differentiation) were observed to be associated with each other. The gene for red pericarp (Rd) was observed to be linked with the grain dormaney gene Gd.