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1.
The two-spotted spider mite ( Tetranychus urticae Koch) is an important pest of tomato ( Lycopersicon esculentum Mill.) crops in temperate regions as this spider mite has a very large capacity for population increase and causes severe
tomato yield losses. There is no described tomato cultivar fully resistant to this pest, although resistant accessions have
been reported within the green-fruited tomato wild species L. pennellii (Corr.) D’Arcy and L. hirsutum Humb. & Bonpl. We observed a L. pimpinellifolium (Jusl.) Mill. accession, ‘TO-937’, which seemed to be completely resistant to mite attacks and we crossed it with the susceptible
L. esculentum cultivar. ‘Moneymaker’ to obtain a family of generations consisting of the two parents, the F 1, the F 2, the BC 1 to L. esculentum, and the BC 1 to L. pimpinellifolium. This family was evaluated for mite resistance in a polyethylene greenhouse using an experimental design in 60 small complete
blocks distributed along 12 double rows. Each block consisted of five F 2 plants in one row and one plant of each of the two parents, the F 1, the BC 1 to L. esculentum, and the BC 1 to L. pimpinellifolium in the adjacent row. Plants at the 10–15 leaf stage were artificially infested by putting on them two pieces of French bean
leaf heavily infested with T. urticae. After two months, evaluations of infestation were made by visual observation of mite nets and leaf damage. Plants that were
free of signs of mite reproduction on the top half were considered as resistant, plants with silky nets only on their basal
leaves, intermediate, and plants with mite reproduction on both basal and top canopies were scored as susceptible. Dominance
for resistance appeared because all the ‘To-937’, BC 1 to L. pimpinellifolium, and F 1 plants were resistant. Not all ‘Moneymaker’ plants behaved as susceptible because 35% of plants were intermediate. In the
BC 1 to L. pimpinellifolium and the F 2, most plants were scored as resistant, only 7 % BC 1 and 3 % F 2 plants were intermediate, and a single F 2 plant (0.3 %) was susceptible. With these figures, resistance seemed to be controlled by either four or two genes according
to whether segregation in the BC 1 or in the F 2, respectively, were considered. These results could in part be explained because of appearance of negative interplot interference
due to the high frequency of resistant genotypes within most of the generations. Therefore, the family was evaluated again
but using a different experimental design. In the new experiment, 16 ‘TO-937’, 17 ‘Moneymaker’, 17 F 1, 37 BC 1 to L. pimpinellifolium, 38 BC 1 to L. esculentum, and 125 F 2 plants were included. Each of these test plants was grown besides a susceptible ‘Moneymaker’ auxilliary plant that served
to keep mite population high and homogeneous in the greenhouse. Negative interplot interference was avoided with this design
and all the ‘TO-937’, F 1, and BC 1 to L. pimpinellifolium plants were resistant, all ‘Moneymaker’ test plants were susceptible, and 52 % BC 1 to L. esculentum and 25 % F 2 plants were susceptible, which fitted very well with the expected for resistance governed by a single dominant gene. The
simple inheritance mode found will favour sucessful introgression of mite resistance into commercial tomatoes from the very
close relative L. pimpinellifolium. 相似文献
2.
The complex Mla locus of barley determines resistance to the powdery mildew pathogen Erysiphe graminis f. sp. hordei. With a view towards gene isolation, a population consisting of 950 F 2 individuals derived from a cross between the near-isogenic lines ‘P01’ ( Mla1) and ‘P10’ ( Mla12) was used to construct a high-resolution map of the Mla region. A fluorescence-based AFLP technique and bulked segregant analysis were applied to screen for polymorphic, tightly
linked AFLP markers. Three AFLP markers were selected as suitable for a chromosome-landing strategy. One of these AFLP markers
and a closely linked RFLP marker were converted into sequence-specific PCR markers. PCR-based screening of approximately 70 000
yeast artificial chromosome (YAC) clones revealed three identical YACs harbouring the Mla locus. Terminal insert sequences were obtained using inverse PCR. The derived STS marker from the right YAC end-clone was
mapped distal to the Mla locus.
Received: 17 July 1998 / Accepted: 9 August 1998 相似文献
3.
The Guatemalan black bean ( Phaseolus vulgaris L.) plant introduction (PI) 181996 is resistant to all known US races of the bean rust fungus Uromyces appendiculatus (Pers. ex Pers.) Unger var. appendiculatus [syn. U. phaseoli (Reben) Wint.]. We report on two random amplified polymorphic DNA (RAPD) markers OAC20 490 tightly linked (no recombinants) in coupling phase and OAE19 890 linked in repulsion phase (at 6.2±2.8 cM) to PI 181996 rust resistance. These RAPDs, generated by single decamer primers in the polymerase chain reaction, were identified in near-isogenic bulks of non-segregating resistant and susceptible BC 4F 2 (NX-040*4/PI 181996) lines. Linkage of the RAPD markers was confirmed by screening 19 BC 4F 2 and 57 BC 4F 3 individuals segregating for PI 181996 resistance. Utility of the RAPDs OAC20 490 and OAE19 890 was investigated in a diverse group of common bean cultivars and lines. All cultivars into which the PI 181996 resistance was introgressed had the RAPD OAC20 490. A RAPD similar in size to OAC20 490, observed in some susceptible common bean lines, was confirmed by Southern blotting to be homologous to the RAPD OAC20 490. Use of the RAPDs OAC20 490 and OAE19 890 in marker-assisted selection (MAS) is proposed. The coupling-phase RAPD is most useful for MAS of resistant BC nF 1individuals during traditional backcross breeding. The repulsion-phase RAPD has greatest utility in MAS of homozygous-resistant individuals in F 2 or later-segregating generations.Mention of a trademark or a proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable. 相似文献
4.
Barley ( Hordeum vulgare L.) Mla (Mildew resistance locus a) and its nucleotide-binding, leucine-rich-repeat receptor (NLR) orthologs protect many cereal crops from diseases caused by fungal pathogens. However, large segments of the Mla pathway and its mechanisms remain unknown. To further characterize the molecular interactions required for NLR-based immunity, we used fast-neutron mutagenesis to screen for plants compromised in MLA-mediated response to the powdery mildew fungus, Blumeria graminis f. sp. hordei. One variant, m11526, contained a novel mutation, designated rar3 ( required for Mla6 resistance3), that abolishes race-specific resistance conditioned by the Mla6, Mla7, and Mla12 alleles, but does not compromise immunity mediated by Mla1, Mla9, Mla10, and Mla13. This is analogous to, but unique from, the differential requirement of Mla alleles for the co-chaperone Rar1 (required for Mla12 resistance1). We used bulked-segregant-exome capture and fine mapping to delineate the causal mutation to an in-frame Lys-Leu deletion within the SGS domain of SGT1 (Suppressor of G-two allele of Skp1, Sgt1ΔKL308–309), the structural region that interacts with MLA proteins. In nature, mutations to Sgt1 usually cause lethal phenotypes, but here we pinpoint a unique modification that delineates its requirement for some disease resistances, while unaffecting others as well as normal cell processes. Moreover, the data indicate that the requirement of SGT1 for resistance signaling by NLRs can be delimited to single sites on the protein. Further study could distinguish the regions by which pathogen effectors and host proteins interact with SGT1, facilitating precise editing of effector incompatible variants. 相似文献
5.
Summary
Oryza minuta J. S. Presl ex C. B. Presl is a tetraploid wild rice with resistance to several insects and diseases, including blast (caused by Pyricularia grisea) and bacterial blight (caused by Xanthomonas oryzae pv. oryzae). To transfer resistance from the wild species into the genome of cultivated rice ( Oryza sativa L.), backcross progeny (BC 1, BC 2, and BC 3) were produced from interspecific hybrids of O. sativa cv IR31917-45-3-2 (2n=24, AA genome) and O. minuta Acc. 101141 (2n=48, BBCC genomes) by backcrossing to the O. sativa parent followed by embryo rescue. The chromosome numbers ranged from 44 to 47 in the BC 1 progeny and from 24 to 37 in the BC 2 progeny. All F 1 hybrids were resistant to both blast and bacterial blight. One BC 1 plant was moderately susceptible to blast while the rest were resistant. Thirteen of the 16 BC 2 progeny tested were resistant to blast; 1 blast-resistant BC 2, plant 75-1, had 24 chromosomes. A 3 resistant: 1 susceptible segregation ratio, consistent with the action of a major, dominant gene, was observed in the BC 2F 2 and BC 2F 3 generations. Five of the BC 1 plants tested were resistant to bacterial blight. Ten of the 21 BC 2 progeny tested were resistant to Philippine races 2, 3, and 6 of the bacterial blight pathogen. One resistant BC 2, plant 78-1, had 24 chromosomes. The segregation of reactions of the BC 2F 2, BC 2F 3, and BC 2F 4 progenies of plant 78-1 suggested that the same or closely linked gene(s) conferred resistance to races 2, 3, 5, and 6 of the bacterial blight pathogen from the Philippines. 相似文献
6.
The level of transgene expression in crop × weed hybrids and the degree to which crop-specific genes are integrated into hybrid populations are important factors in assessing the potential ecological and agricultural risks of gene flow associated with genetic engineering. The average transgene zygosity and genetic structure of transgenic hybrid populations change with the progression of generations, and the green fluorescent protein (GFP) transgene is an ideal marker to quantify transgene expression in advancing populations. The homozygous T 1 single-locus insert GFP/ Bacillus thuringiensis (Bt) transgenic canola ( Brassica napus, cv Westar) with two copies of the transgene fluoresced twice as much as hemizygous individuals with only one copy of the transgene. These data indicate that the expression of the GFP gene was additive, and fluorescence could be used to determine zygosity status. Several hybrid generations (BC 1F 1, BC 2F 1) were produced by backcrossing various GFP/Bt transgenic canola ( B. napus, cv Westar) and birdseed rape ( Brassica rapa) hybrid generations onto B. rapa. Intercrossed generations (BC 2F 2 Bulk) were generated by crossing BC 2F 1 individuals in the presence of a pollinating insect ( Musca domestica L.). The ploidy of plants in the BC 2F 2 Bulk hybrid generation was identical to the weedy parental species, B. rapa. AFLP analysis was used to quantify the degree of B. napus introgression into multiple backcross hybrid generations with B. rapa. The F 1 hybrid generations contained 95–97% of the B. napus-specific AFLP markers, and each successive backcross generation demonstrated a reduction of markers resulting in the 15–29% presence in the BC 2F 2 Bulk population. Average fluorescence of each successive hybrid generation was analyzed, and homozygous canola lines and hybrid populations that contained individuals homozygous for GFP (BC 2F 2 Bulk) demonstrated significantly higher fluorescence than hemizygous hybrid generations (F 1, BC 1F 1 and BC 2F 1). These data demonstrate that the formation of homozygous individuals within hybrid populations increases the average level of transgene expression as generations progress. This phenomenon must be considered in the development of risk-management strategies.Communicated by J. Dvorak 相似文献
7.
Bacterial blight (BB) is a serious disease of rice in India. We have used molecular marker-assisted selection in a backcross breeding program to introgress three genes ( Xa21, xa13, and xa5) for BB resistance into Triguna, a mid-early duration, high yielding rice variety that is susceptible to BB. At each generation in the backcross program, molecular markers were used to select plants possessing these resistance genes and to select plants that have maximum contribution from the Triguna genome. A selected BC3F1 plant was selfed to generate homozygous BC 3F 2 plants with different combinations of BB resistance genes. Plants containing the two-gene combination, Xa21 and xa13, were found to exhibit excellent resistance against BB. Single plant selections for superior agronomic characteristics were performed on the progeny of these plants, from BC 3F 3 generation onwards. The selected plants were subjected to yield trials at the BC 3F 8 generation and were found to have a significant yield advantage over Triguna. The newly developed lines are being entered into national multi-location field trials. This work represents a successful example of the application of molecular marker-assisted selection for BB resistance breeding in rice. 相似文献
8.
Summary The genetic variance among random-mated lines derived from backcrossing (BC gS 1 lines) depends upon the backcross generation (g) and the number (n) of BC gF 1 plants crossed in generations 1 through g. There is little effect of n on genetic variance for n > 6. The genetic variance among BC gF 2-derived lines is greater than that among BC gS 1 lines for all g. If either BC gF 2-derived or BC gS 1 lines are used as a base population for recurrent selection, 8, 16, 32, and 64 BC 1F 1, BC 2F 1, BC 3F 1, and BC 4F 1 plants, respectively, should be used to avoid loss of donor alleles to drift.Joint contribution of USDA-ARS and Journal Paper No. J-11224 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2471Formerly Research Geneticist, USDA-ARS, Ames, Iowa, USA 相似文献
9.
Fusarium graminearum Schwabe, the conidial form of Gibberella zeae, is the causal fungal pathogen responsible for Gibberella stalk rot of maize. Using a BC 1F 1 backcross mapping population derived from a cross between ‘1145’ (donor parent, completely resistant) and ‘Y331’ (recurrent
parent, highly susceptible), two quantitative trait loci (QTLs), qRfg1 and qRfg2, conferring resistance to Gibberella stalk rot have been detected. The major QTL qRfg1 was further confirmed in the double haploid, F 2, BC 2F 1, and BC 3F 1 populations. Within a qRfg1 confidence interval, single/low-copy bacterial artificial chromosome sequences, anchored expressed sequence tags, and insertion/deletion
polymorphisms, were exploited to develop 59 markers to saturate the qRfg1 region. A step by step narrowing-down strategy was adopted to pursue fine mapping of the qRfg1 locus. Recombinants within the qRfg1 region, screened from each backcross generation, were backcrossed to ‘Y331’ to produce the next backcross progenies. These
progenies were individually genotyped and evaluated for resistance to Gibberella stalk rot. Significant (or no significant) difference in resistance reactions between homozygous and heterozygous genotypes
in backcross progeny suggested presence (or absence) of qRfg1 in ‘1145’ donor fragments. The phenotypes were compared to sizes of donor fragments among recombinants to delimit the qRfg1 region. Sequential fine mapping of BC 4F 1 to BC 6F 1 generations enabled us to progressively refine the qRfg1 locus to a ~500-kb interval flanked by the markers SSR334 and SSR58. Meanwhile, resistance of qRfg1 to Gibberella stalk rot was also investigated in BC 3F 1 to BC 6F 1 generations. Once introgressed into the ‘Y331’ genome, the qRfg1 locus could steadily enhance the frequency of resistant plants by 32–43%. Hence, the qRfg1 locus was capable of improving maize resistance to Gibberella stalk rot. 相似文献
10.
Summary The C-banding pattern of the satellited chromosomes in Thinopyrum distichum and Triticum durum was established. Both T. durum and Th. distichum contained two pairs of satellited chromosomes, which could be distinguished from one another. In the amphiploids [ T. durum× Th. distichum (2x=56)] and in the backcross T. durum/( T. durum× Th. distichum) 2, BC 1F 3, and BC 1F 5 (2n = 42) the satellite was visible on only 1B and 6B of T. durum. The vector pTa 71 containing the rRNA gene from wheat hybridized to two pairs of chromosomes (four hybridization sites) in T. durum and Th. distichum, to eight sites in the amphiploid hybrid (2n=56), and to six sites in the backcross populations BC 1F 1. BC 1F 3, and BC 1F 5 (2n=42). The two satellite pairs in Th. distichum could be distinguished by the chromosomal location of the rRNA site (median or subterminal) and by the centromere position. One copy of each pair was present in the BC 1F 1, but in the BC 1F 3 and BC 1F 5 populations the pair with the subterminal location of rRNA genes was absent. Silver nitrate staining indicated that the rRNA genes of T. durum did not completely suppress those of Th. distichum. The octoploid amphiploid (2n = 56) contained a maximum of four large and four small nucleoli and the hexaploid BC 1s (2n=42), four large and two small nucleoli. 相似文献
11.
Gametophytic selection can drastically reduce the number of selection cycles during crop improvement programs. The objective
of the present investigation was to test whether the nature of inheritance of two unlinked disease-resistant loci, h
1 and h
2, against Fusarium wilt in chickpea ( Cicer arietinum L.) under gametophytic (pollen) selection was similar to that already observed at sporophytic level. A homozygous dominant
( H
1
H
1
H
2
H
2) susceptible genotype JG-62 was crossed to a recessive ( h
1
h
1
h
2
h
2) resistant genotype WR-315 to produce 20 F 1 hybrid seeds. In the following generation, flower buds of 10 F 1 hybrid plants were subjected to toxin stress before anthesis and the remaining ten control F 1 plants’ flowers were sprayed with water. Thirty-four selected BC 1 plants were generated by test crossing resistant WR-315 individuals with pollen from toxin-stressed F 1 individuals. Both control and treated F 1 plants were selfed to produce respective F 2 generations. Two DNA markers, CS-27 700bp and A07C 430bp, linked to susceptible alleles H
1 and H
2, respectively, were used to study the inheritance patterns of h
1 and h
2 loci in the F 2 and BC 1 generations. One hundred and forty-four selected F 2, 129 control F 2, and 34 selected backcross individuals were tested for the presence or absence of DNA markers. Except for the control F 2, observed ratios of selected F 2 and BC 1 populations exhibited significant chi-square deviations from expected monogenic and digenic ratios. Our results suggest that
gametophytic selection is as effective as that realized at the sporophytic level, and that the gametophytic selection can
be an effective breeding tool for plant breeding programs. 相似文献
12.
Crosses were made between four varieties (Mahsuri, Setanjung, MR84 and MR103) of Oryza sativa L. (2n=24, AA) and one accession of O. minuta (2n= 8, BBCC). The seed set obtained ranged between 9.5% and 25.1% depending on the rice variety used. By rescuing 14-day-old embryos and culturing them on 25%-strength MS medium we obtained a total of 414 F 1 hybrids. The F 1s were vigorous, tillered profusely, were perennial and male-sterile. The hybrids were triploid (ABC) with 36 chromosomes and showed irregular meiosis. The average frequency and range of chromosome associations at metaphase I or early anaphase I pollen mother cells of F 1 plants were 29.31(16–36) Is +3.32(0–10) IIs+0.016(0–1) IIIs+0.002(0–1) IVs. Upon backcrossing the original triploid hybrids and colchicine-treated hybrids to their respective recurrent parents, and further embryo rescue, 17 backcross-1 (BC 1) plants were obtained. Of all the crosses using MR84, no BC 1 plant was obtained even after pollinating 13 894 spikelets of the triploid hybrid. The BC 1s were similar in appearence to the F 1s and were male-sterile, their chromosome number ranged from 44 to 48. By backcrossing these BC 1s and nurturing them through embryo rescue, we obtained 32 BC 2 plants. Of these, however, only 18 plants grew vigorously. One of these plants has 24 chromosomes and the other 17 have chromosome numbers ranging between 30 and 37. The 24-chromosome plant was morphologically similar to the O. sativa parent and was partially fertile with a pollen and spikelet fertility of 58.8% and 12.5% respectively. All of the F 1 and BC 1 plants were found to be resistant to five Malaysian isolates (XO66, XO99, XO100, XO257 and XO319) of Xanthomonas campestris pv oryzae. Amongst the BC 2s, the reaction varied from resistant to moderately susceptible. The 24-chromosome BC 2 plant was resistant to the four isolates and moderately resistant to isolate XO100 to which the O. sativa parent was susceptible.Part of PhD thesis submitted by first author to Universiti Kebangsaan Malaysia, Bangi 相似文献
13.
Bacterial Blight (BB) caused by Xanthomonas oryzae pv. oryzae is a major disease of rice in tropical Asia. Since all the Basmati varieties are highly susceptible and the disease is prevalent in the entire Basmati growing region of India, BB is a severe constraint in Basmati rice production. The present study was undertaken with the objective of combining the important Basmati quality traits with resistance to BB by a combination of phenotypic and molecular marker-assisted selection (MAS). Screening of 13 near-isogenic lines of rice against four isolates of the pathogen from Basmati growing regions identified the Xa4, xa8, xa13 and Xa21 effective against all the isolates tested. Two or more of these genes in combination imparted enhanced resistance as expressed by reduced average lesion length in comparison to individual genes. The two-gene pyramid line IRBB55 carrying xa13 and Xa21 was found equally effective as three/four gene pyramid lines. The two BB resistance genes present in IRBB55 were combined with the Basmati quality traits of Pusa Basmati-1 (PB-1), the most popular high yielding Basmati rice variety used as recurrent parent. Phenotypic selection for disease resistance, agronomic and Basmati quality characteristics and marker-assisted selection for the two resistance genes were carried out in BC 1F 1, BC 1F 2 and BC 1F 3 generations. Background analysis using 252 polymorphic amplified fragment length polymorphism (AFLP) markers detected 80.4 to 86.7% recurrent parent alleles in BC 1F 3 selections. Recombinants having enhanced resistance to BB, Basmati quality and desirable agronomic traits were identified, which can either be directly developed into commercial varieties or used as immediate donors of BB resistance in Basmati breeding programs. 相似文献
14.
Head smut is one of the most devastating diseases in maize, causing severe yield loss worldwide. Here we report identification
and fine-mapping of a major quantitative trait locus (QTL) conferring resistance to head smut. Two inbred lines ‘Ji1037’ (donor
parent, highly resistant) and ‘Huangzao4’ (recurrent parent, highly susceptible) were crossed and then backcrossed to ‘Huangzao4’
to generate BC populations. Four putative resistance QTLs were detected in the BC 1 population, in which the major one, designated as qHSR1, was mapped on bin 2.09. The anchored ESTs, IDPs, RGAs, BAC and BAC-end
sequences in bin 2.09 were exploited to develop markers to saturate the qHSR1 region. The recombinants in the qHSR1 region
were obtained by screening the BC 2 population and then backcrossed again to ‘Huangzao4’ to produce 59 BC 2:3 families or selfed to generate nine BC 2F 2 families. Individuals from each BC 2:3 or BC 2F 2 family were evaluated for their resistances to head smut and genotypes at qHSR1. Analysis of genotypes between the resistant
and susceptible groups within the same family allows deduction of phenotype of its parental BC 2 recombinant. Based on the 68 BC 2 recombinants, the major resistance QTL, qHSR1, was delimited into an interval of ~2 Mb, flanked by the newly developed markers
SSR148152 and STS661. A large-scale survey of BC 2:3 and BC 2F 2 progeny indicated that qHSR1 could exert its genetic effect by reducing the disease incidence by ~25%.
Yongsheng Chen, Qing Chao and Guoqing Tan contributed equally to this work. 相似文献
15.
Our previous studies have hypothesised that a complementary epistasis between a QTL located on chromosome 12 and a QTL located
on chromosome 7 was one of the major genetic factors controlling partial resistance to Rice yellow mottle virus (RYMV). We report research undertaken to verify this hypothesis and to introgress the resistant allele of these two QTLs
from an upland resistant japonica variety, Azucena, into a lowland susceptible indica variety IR64. Three cycles of molecular marker-assisted back cross breeding were performed using RFLP and microsatellite
markers. Resistance to RYMV was evaluated in F 2 and F 3 offspring of the BC 1 and BC 2 generations. Marker-assisted introgression (MAI) was very efficient: in the selected BC 3 progeny the proportion of the recipient genome was close to 95% for the ten non-carrier chromosomes, and the length of the
donor chromosome segment surrounding the two QTLs was less than 20 cM. The relevancy of the complementary epistasis genetic
model proposed previously was confirmed experimentally: in BC 1 and BC 2 generations only F3 lines having the allele of the resistant parent on QTL 12 and QTL 7 show partial resistance to RYMV. Comparison of our experimental process of MAI with the recommendations of analytic and simulation
studies pointed out the methodological flexibility of MAI. Our results also confirmed the widely admitted, but rarely verified,
assumption that QTL-alleles detected in segregating populations could be treated as units of Mendelian inheritance and that
the incorporation of these alleles into elite lines would result in an enhanced performance. The next step will be the design
of tools for the routine use of molecular markers in breeding for partial resistance to RYMV and the development of material
for the analysis of resistance mechanisms and the structure of a virus resistance gene in rice.
Received: 11 August 2000 / Accepted: 20 March 2001 相似文献
16.
A rice mutant, G069, characteristic of few tiller numbers, was found in anther culture progeny from the F
1 hybrid between an indica-japonica cross, Gui630×02428. The mutant has another two major features: delayed tillering development and yellowing apex and margin
on the mature leaves. As a donor parent, G069 was further backcrossed with the recurrent parent, 02428, for two turns to develop a BC
2F 2 population. Genetic analysis in the BC
2F 2 population showed that the traits of few-tillering and yellowing apex and margin on the mature leaves were controlled by
one recessive gene. A pool of equally mixed genomic DNA, from few-tillering individual plants in BC
2F 2, was constructed to screen polymorphism with simple sequence repeat (SSR) markers in comparison with the 02428 genome. One SSR marker and three restriction fragment length polymorphism (RFLP) markers were found possibly linked with
the recessive gene. By using these markers, the gene of few-tillering was mapped on chromosome 2 between RFLP marker C424
and S13984 with a genetic distance of 2.4 cM and 0.6 cM, respectively. The gene is designated ft1. 相似文献
17.
To combat the dreaded diseases in rice like bacterial blight (BB) and blast, host plant resistance has been advocated as the most suitable and sustainable method. Through the present study, we have successfully incorporated three major BB resistance genes, namely Xa21, xa13 and xa5 into NLR3449, a high yielding, blast resistant, fine-grain type, popular rice variety through marker-assisted backcross breeding. Foreground selection was carried out using polymerase chain reaction based, gene-specific markers, namely pTA248 (Xa21), xa13prom (xa13) and xa5FM (xa5) at each generation of backcrossing, while 127 polymorphic SSR markers spanning on 12 chromosomes were used for background selection and backcrossing was limited to two rounds. At BC2F1 generation, a single plant (NLR-87-10) with 89.9% recovery, possessing all the three BB resistance genes was forwarded to BC2F2 generation. A solitary BC2F2 plant, namely NLR-87-10-106 possessing all the three resistance genes and 96% genome recovery was identified and advanced through selfing until BC2F4 generation by adopting pedigree-method of selection. Three best BC2F4 lines, possessing high level of resistance against BB and blast, and equivalent or superior to NLR 34449 in terms of yield, grain quality and agro-morphological traits were identified and advanced for multi-location trials. 相似文献
18.
Ketan Nangka, the donor of wide compatibility genes, showed sterility when crossed to Tuanguzao, a landrace rice from Yunnan
province, China. Genetic and cytological analyses revealed that the semi-sterility was primarily caused by partial abortion
of the embryo sac. Genome-wide analysis of the linkage map constructed from the backcross population of Tuanguzao/Ketan Nangka//Ketan
Nangka identified two independent loci responsible for the hybrid sterility located on chromosomes 2 and 5, which explained
18.6 and 20.1% of phenotypic variance, respectively. The gene on chromosome 5 mapped to the previously reported sterility
gene S31(t), while the gene on chromosome 2, a new hybrid sterility gene, was tentatively designated as S32(t). The BC 1F 2 was developed for further confirmation and fine mapping of S32(t). The gene S32(t) was precisely mapped to the same region as that detected in the BC 1F 1 but its position was narrowed down to an interval of about 1.9 cM between markers RM236 and RM12475. By assaying the recombinant
events in the BC 1F 2, S32(t) was further narrowed down to a 64 kb region on the same PAC clone. Sequence analysis of this fragment revealed seven predicted
open reading frames, four of which encoded known proteins and three encoded putative proteins. Further analyses showed that
wide-compatibility variety Dular had neutral alleles at loci S31(t) and S32(t) that can overcome the sterilities caused by these two genes. These results are useful for map-based cloning of S32(t) and for marker-assisted transferring of the neutral allele in hybrid rice breeding. 相似文献
19.
The corn earworm, Helicoverpa zea (Boddie), is a perennial economic pest of field crops in the United States. Maize, Zea mays L., is the major host crop promoting the build-up of devastating corn earworm populations that limit full production of cotton,
soybean, peanut, and grain sorghum. Resistance to the corn earworm in maize and in particular sweet maize, would provide an
environmentally safe, economical method of control for this pest insect. Antibiotic effects of corn silks on this insect are:
small larvae, extended developmental period, and reduced fecundity. Silks from individual maize plants of resistant and susceptible
lines and progeny in six generations consisting of parents (P 1, P 2), F 1, F 2, and backcrosses BC 1.1 (F 1 × P 1) and BC 1.2 (F 1 × P 2) from each of four crosses were used to determine the genetic basis of the antibiotic resistance of silks to the corn earworm.
In the cross of Zapalote Chico × PI340856, genes controlling resistance in the silks to the corn earworm larvae are dominant
in PI340856 to those in Zapalote Chico. The cross of Zapalote Chico × GT114 involves parents differing in degree of resistance,
and possibly differing for the genetic mechanism by which the resistance is inherited. The inheritance of resistance may involve
non-additive (dominance and epistasis) genetic variance. A digenic 6-parameter model indicated (1) the resistance in this
cross is controlled by more than one pair of genes and (2) some or all of the genes interact to cause non-allelic interaction.
Thus, the resistance in this cross may be controlled by both dominant and recessive genes. The resistance of Zapalote Chico
× CI64, an intermediate inbred, is influenced by additive gene effects. The digenic model adequately predicts all generation
means of the cross of GT3 × PI340856 except for the F1. Thus, it appears that the additive-dominance model is not satisfactory
for this cross involving susceptible and resistant parents. Generation mean analysis indicates that resistance to silk-feeding
by corn earworm larvae is under genetic control, but gene action differs from one type of cross to another. 相似文献
20.
The maize inbred lines 1145 (resistant) and Y331 (susceptible), and the F 1, F 2 and BC 1F 1 populations derived from them were inoculated with the pathogen Pythium inflatum Matthews, which causes stalk rot in Zea mays. Field data revealed that the ratio of resistant to susceptible plants was 3:1 in the F 2 population, and 1:1 in the BC 1F 1population, indicating that the resistance to P. inflatum Matthews was controlled by a single dominant gene in the 1145×Y331 cross. The gene that confers resistance to P. inflatum Matthews was designated Rpi1 for resistance to P. inflatum) according to the standard nomenclature for plant disease resistance genes. Fifty SSR markers from 10 chromosomes were first
screened in the F 2 population to find markers linked to the Rpi1 gene. The results indicated that umc1702 and mmc0371 were both linked to Rpi1, placing the resistance gene on chromosome 4. RAPD (randomly amplified polymorphic DNA) markers were then tested in the F 2population using bulked segregant analysis (BSA). Four RAPD products were found to show linkage to the Rpi1 gene. Then 27 SSR markers and 8 RFLP markers in the region encompassing Rpi1 were used for fine-scale mapping of the resistance gene. Two SSR markers and four RFLP markers were linked to the Rpi1 gene. Finally, the Rpi1 gene was mapped between the SSR markers bnlg1937 and agrr286 on chromosome 4, 1.6 cM away from the former and 4.1 cM distant
from the latter. This is the first time that a dominant gene for resistance to maize stalk rot caused by P. inflatum Matthews has been mapped with molecular marker techniques. 相似文献
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