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1

Electronic Resource

Molecular mapping of rice chromosomes (1988)

McCouch, S. R. ; Kochert, G. ; Yu, Z. H. ; [et al.]

Springer

Theoretical and applied genetics 76 (1988), S. 815-829

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ISSN: 1432-2242

Keywords: Oryza sativa ; Molecular markers ; RFLP ; Genetic map ; Trisomies ; DNA methylalion

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary We report the construction of an RFLP genetic map of rice (Oryza sativa) chromosomes. The map is comprised of 135 loci corresponding to clones selected from a PstI genomic library. This molecular map covers 1,389 cM of the rice genome and exceeds the current classical maps by more than 20%. The map was generated from F2 segregation data (50 individuals) from a cross between an indica and javanica rice cultivar. Primary trisomics were used to assign linkage groups to each of the 12 rice chromosomes. Seventy-eight percent of the clones assayed revealed RFLPs between the two parental cultivars, indicating that rice contains a significant amount of RFLP variation. Strong correlations between size of hybridizing restriction fragments and level of polymorphism indicate that a significant proportion of the RFLPs in rice are generated by insertions/delections. This conclusion is supported by the occurrence of null alleles for some clones (presumably created by insertion or deletion events). One clone, RG229, hybridized to sequences in both the indica and javanica genomes, which have apparently transposed since the divergence of the two cultivars from their last common ancestor, providing evidence for sequence movement in rice. As a by product of this mapping project, we have discovered that rice DNA is less C-methylated than tomato or maize DNA. Our results also suggest the notion that a large fraction of the rice genome (approximately 50%) is single copy.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00273666

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2

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Inheritance of partial resistance to powdery mildew in spring wheat (1987)

Hautea, R. A. ; Coffman, W. R. ; Sorrells, M. E. ; [et al.]

Springer

Theoretical and applied genetics 73 (1987), S. 609-615

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ISSN: 1432-2242

Keywords: Erysiphe graminis f. sp. tritici ; Triticum aestivum L. ; Disease resistance ; Additive gene action ; Genetics of resistance

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Four spring wheat (Triticum aestivum L.) cultivars exhibiting partial resistance to powdery mildew induced by Erysiphe graminis f.sp. tritici were crossed to a common susceptible cultivar to study the inheritance of resistance. The genetic parameters contributing to resistance were estimated by generation means analyses. Additive gene action was the most important genetic component of variation among generation means in all four crosses. Additive by additive effects were significant in one cross and both additive by additive and additive by dominance effects were significant in another. Dominance effects were not significant. The F2/F3 correlations in three crosses ranged from 0.27 to 0.43. Three additional crosses among resistant cultivars were employed to study the effectiveness of selection in improving resistance. By selecting the most resistant plants from the F2 and evaluating the progenies in the F4, increases in resistance ranging from 21% to 31% were obtained. In all crosses, there was transgressive segregation in both directions indicating that the genes conferring resistance to these cultivars differ and exhibit additive effects.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00289202

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Genetic Evaluation and Utilization (GEU) program (1977)

Khush, G. S. ; Coffman, W. R.

Springer

Theoretical and applied genetics 51 (1977), S. 97-110

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ISSN: 1432-2242

Keywords: Rice Breeding ; Germ Plasm Collection ; Interdisciplinary Research ; Disease and Insect Resistance ; International Cooperation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The Genetic Evaluation and Utilization (GEU) program of the International Rice Research Institute (IRRI) is an interdisciplinary program for the improvement of rice crops. Scientists trained in diverse disciplines such as plant breeding, plant pathology, entomology, agronomy, cereal chemistry, plant physiology, and soil chemistry work together and contribute their specialized skills to this joint endeavor. The program has five interrelated components: (1) germ plasm collection and conservation, (2) research in disciplinary areas, (3) development of improved germ plasm, (4) distribution, evaluation and exchange of germ plasm internationally, (5) training of young scientists. Over forty thousand rice varieties from different countries are being maintained in the IRRI germ plasm bank. These varieties have been screened for grain quality, resistance to various diseases and insects, and tolerance to various environmental stresses such as drought, high and low temperatures and problem soils. Donor parents for resistances to each of the problem areas have been identified. These parents were utilized for developing improved germ plasm. Varieties with resistance to as many as five diseases and five insect species have been developed. These multiple resistant varieties are grown on millions of hectares of rice land. Seeds of improved breeding materials are exchanged internationally and 194 scientists from different countries have been trained in rice improvement work.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00273821

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4

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Heritability and gain from selection for quantitative resistance to Xanthomonas campestris pv. vesicatoria in Capsicum annuum L. (1991)

Poulos, J. M. ; Reifschneider, F. J. B. ; Coffman, W. R.

Springer

Euphytica 56 (1991), S. 161-167

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ISSN: 1573-5060

Keywords: Capsicum annuum ; pepper ; Xanthomonas campestris pv. vesicatoria ; bacterial spot ; non-hypersensitive response ; horizontal resistance ; disease screening

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary Breeding for disease resistance in peppers (Capsicum spp.) to the bacterial spot pathogen (Xanthomonas campestris pv. vesicatoria (Doidge) Dye) has been based on either qualitative or quantitative evaluation methods. Quantitative evaluation of components of resistance, lesion number and lesion diameter, has been useful for determining quantitative resistance, but few breeders have applied these methods in routine selection programs. This study was aimed at determining the heritability and gain from selection for resistance to the bacterial spot pathogen based on three components of resistance. Random selections from a diverse intermated population of Capsicum annuum L. were self-pollinated for two generations to create S1 and S2 families. Thirty S1 families, corresponding S2 families and four homozygous check lines were evaluated. At forty-two days after seeding, two different leaves of each plant were inoculated by leaf infiltration with low concentrations (5×103 colony forming units) of Group 2 (XCV PT, race 1) and 4 (XCV P, race 1) of the bacterium, respectively. After 15 days, lesion number cm-2 and lesion diameter were measured. Total lesion area was calculated. Narrow-sense heritabilities for lesion number, lesion diameter, and total lesion area were 0, 43, and 31%, respectively, with Group 2, and 26, 43, and 33%, respectively, with Group 4. Actual S2 gain from 20% selection pressure in the S1 was approximately 50%, when selection towards resistance was based on total lesion area.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00042060

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