Studies on linkage relations of genes controlling disease and insect resistance and nature of endosperm in rice

Summary Five hundred F₃ lines derived from the cross TN1/IR2061-464-6 were examined for the nature of endosperm and resistance to bacterial blight, brown planthopper, and grassy stunt. TN1 has non-glutinous endosperm and is susceptible to bacterial blight, grassy stunt, and brown planthopper. IR2061-464-6 has a glutinous endosperm and is homozygous resistant to bacterial blight, grassy stunt, and brown planthopper. The F₃ data fit the 1:2:1 ratio expected for monogenic control of each trait. A two-way classification for all the traits indicated that these four traits are inherited independently. Thus, it should be possible to recombine these four traits in various combinations in rice varieties.     

Selection response under random mating and under selfing in the progeny of a cross of homozygous parents

Summary Response to individual selection under random mating and under selfing in the progeny of a cross of homozygous parents is studied by means of computer simulation. The effects of environmental variation, the number of loci involved and the degree of linkage are described. The results predict that the short term effect of intermating is negligable in general. In the long run, random mating is superior to selfing, expecially when many loci are involved.     

Linkage studies in rice (Oryza sativa L.): Flowering,awning and awn colour,panicle density and exsertion,liguleless, bent node and pigmentation

Summary The cross of two indica types of rice T9 and M35, provided scope for the inheritance study of 16 characters such as flowering, awning and awn colour, panicle density and panicle exsertion, presence of ligule, bent node, and pigmentation in ten other characters. Besides the purple colour, yellow and chalky white were studied for their inheritance. Two to five pairs of factors were found to govern the 16 characters under study. Complementary, duplicate, complementary duplicate, inhibitory complementary and inhibitory duplicate action of genes was observed. Independent dominant action of individual genes which is equivalent to the action of two or three genes is recorded in respect of panicle density and awning and awn colour. Inheritance of the 16 characters shows the involvement of 59 genes unreported in the past. Out of them 19 are inhibitors. Combined segregation data have revaled the existence of many pleiotropic genes acting on two or more characters and exhibiting differential expression in some of them, which is an interesting part of the present study. Linkage analysis has resulted in the assignment of the record number of 17 genes to a single group, nine of them being inhibitors. The linkage map constructed in the order of genes as suggested by the cross over values shows a good agreement. This linkage group is concluded not to form part of any group propounded by Misro et al. (1966) in indica rice.     

Inheritance of isoenzymes and their linkage relationships in two interspecific cherry progenies

Two interspecific cherry progenies, Prunus avium 'Napoleon' × P. incisa E621 and × P. nipponica F1292, were analysed by polyacrylamide gel electrophoresis for 14 enzyme systems: aconitase (ACO), acid phosphatase (ACP), alcohol dehydrogenase (ADH), amylase (AMY), glutamate oxaloacetate transaminase (GOT), glucose–6-phosphate isomerase (GPI), isocitrate dehydrogenase (IDH), leucine aminopeptidase (LAP), malate dehydrogenase (MDH), malic enzyme (ME), phosphogluconate dehydrogenase (PGD), phosphoglucomutase (PGM), shikimate dehydrogenase (SKD) and superoxide dismutase (SOD). Thirty-one loci were deduced from segregating banding patterns, Aco–2, Acp–1 to –5, Acp–8, –9, Adh–1 to –6, Amy–2, –3, Got–1 to –3, Gpi–2, Idh–1 to –4, Lap–1, Me–1, –2, Mdh–2, Pgd–1, –2 and Sod–2. Only ten of these had previously been established. Seven putative loci were polymorphic but did not segregate in the progenies. Analysis of cosegregations and calculation of recombination fractions revealed that 15 loci could be grouped into four linkage groups: Acp–1/–2/–3–-Acp–5; Gpi–2–- Got–2–-Got–1–-Lap–1; Adh–4/–6– -Amy–2; and Adh–1–-Adh–5–-Adh–2–- Me–2. These consolidate two previously reported linkage groups and establish three new groups. The previously reported linkage of Lap–1 with Me–1 was not confirmed. Fourteen cultivars of P. avium were analysed for the same 14 enzyme systems and showed polymorphism for just 17 of the established loci and for none of the putative loci, indicating far less scope for linkage analysis in intraspecific progenies from crosses among these cultivars.     

Expression of Introduced Genes after Tuber Propagation of Transgenic Potato Plants

The linkage relationship between eighteen isozyme loci and the morphological markers hypocotyl colour (R-r), monogerm character (M-m), pollen fertility (X) and stem fasciation (Verb.) are tested. Three linkage groups could be set up, involving all morphological marker loci and eight of the isozyme loci. Est-2, R-r, Fdp-2, Got2 and Icd-1 belong to linkage group I, linkage group II includes the loci Fas-fas M-m, Est-3 and Aco-1, linkage group III contains the loci X, Mdh-1 and Est-5. When analysing the inheritance of isozymes and RFLPs, deviations are usually found in some lines from the expected frequencies of a 3 : 1 or 1 : 2 : 1 segregation at single marker loci. In many cases these data can still be used for the estimation of recombination values with linked loci under the control of selection. Procedures to estimate linkage in such cases are given and applied to experimental data in Beta vulgaris.     

Molecular Mapping of Three Loci Conferring Resistance to Maize mays L.） Rough Dwarf Disease

Maize rough dwarf disease (MRDD) is a viral disease that is widely distributed in the world and causes great losses in grain yield.     

Association of Eyespot Resistance in Wheat cv. 'Cappelle-Desprez' with Endopeptidase Profile

To test for the association of the eyespot of wheat cv. ‘Cappelle-Desprez’ with the structural gene encoding the isozyme Ep-A1, F₃, families from the cross ‘Cappelle-Desprez’ (resistant) X ‘Chinese Spring’ (susceptible) were selected on the basis of endopeptidase phenotype. Analysis of eyespot reaction showed that Ep-Alb homozygotes were associated with a higher level of resistance than Ep-Al a homozygotes. Thus selection of the Ep-Alb allelc should assure concurrent selection of at least a part of the eyespot resistance of ‘Cappelle-Desprez’.     

A genetic linkage map of Spinacia oleracea and localization of a sex determination locus

A genetic map of Spinach (Spinacia oleracea) was constructed in a classical back cross population using 101 AFLP and 9 microsatellite markers. The map was divided into seven linkage groups with a total length of 585 cM and an average distance between the markers of 5.18 cM. The linkage map was constructed with LOD 3.5, but was quite stable with seven linkage groups remaining until LOD 7.0. Gender segregated 1 male to 1 female in the mapping population and was mapped to a small area of one linkage group with a distance of 1.9 cM to a microsatellite marker termed SO4. This small chromosomal region co-segregating with sex determination in the species is in contrast to previous reports on a heterologous XY chromosome system in spinach. Microsatellite markers used as anchors in the map construction were isolated from sequences of known nuclear encoded genes in spinach. This enabled simultaneous positioning on the map of these genes: Rubisco activase (Rca), Photosytem 1 subunit V (PsaG), Protein Kinase (Pk), Nitrate reductase (Nir), ferrodoxin:thioredoxin reductase (Ftr), Ribosomal protein L1 (Rps22), Choline monooxygenase (Cmo), Pseudogene for BZIP protein (Bzip), Glycerol-3-phosphate acyltransferase (Act1) and stromal ascorbate peroxidase, thylakoid-bound ascorbate peroxidase (Apx2). Spinach has a small genome, which makes it suitable for basic genomic studies and many physiologically important genes have been cloned from the species. The present map anchored with user friendly microsatellite markers will be useful for future studies of physiology and genetics of the species as well as studies of the nature of gender determination.     

Inheritance of Seed Coat Thickness in Chickpea (Cicer arietinum L.) and its Evolutionary Implications

The desi and kabuli chickpeas are characterized, among other things, by their seed coats being thicker in the desi than in the kabuli type. The inheritance of seed coat thickness, and its relation to flower colour and seed size, was studied. Seed coat thickness exhibits monogenic inheritance, the thin kabuli seed coat being the recessive character. Linkage was found between seed coat thickness and flower colour, the recombinant fraction being 0.19. No relationship was found between seed coat thickness and seed size. The role of these characters in the evolution of the chickpea is discussed.     

Linkage map construction and mapping QTL for cotton fibre quality using SRAP, SSR and RAPD

Tetraploid cotton is one of the most extensively cultivated species. Two tetraploid species, Gossypium hirsutum L. and G. barbadense L., dominate the world's cotton production. To better understand the genetic basis of cotton fibre traits for the improvement of fibre quality, a genetic linkage map of tetraploid cotton was constructed using sequence‐related amplified polymorphisms (SRAPs), simple sequence repeats (SSRs) and random amplified polymorphic DNAs (RAPDs). A total of 238 SRAP primer combinations, 368 SSR primer pairs and 600 RAPD primers were used to screen polymorphisms between G. hirsutum cv. Handan208 and G. barbadense cv. Pima90 which revealed 749 polymorphic loci in total (205 SSRs, 107 RAPDs and 437 SRAPs). Sixty‐nine F₂ progeny from the interspecific cross of ‘Handan208’בPima90’ were genotyped with the 749 polymorphic markers. A total of 566 loci were assembled into 41 linkage groups with at least three loci in each group. Twenty‐eight linkage groups were assigned to corresponding chromosomes by SSR markers with known chromosome locations. The map covered 5141.8 cM with a mean interlocus space of 9.08 cM. A × test for significance of deviations from the expected ratio (1: 2: 1 or 3: 1) identified 135 loci (18.0%) with skewed segregation, most of which had an excess of maternal parental alleles. In total, 13 QTL associated with fibre traits were detected, among which two QTL were for fibre strength, four for fibre length and seven for micronaire value. These QTL were on nine linkage groups explaining 16.18‐28.92% of the trait variation. Six QTL were located in the A subgenome, six QTL in the D subgenome and one QTL in an unassigned linkage group. There were three QTL for micronaire value clustered on LG1, which would be very useful for improving this trait by molecular marker‐assisted selection.