Bu-1 andTh-1, two loci determining surface antigens of B or T lymphocytes in the chicken

Alloantisera were prepared by reciprocal immunizations with bursal or thymic lymphoid cells between chickens of two inbred lines identical at theB major histocompatibility locus. In cytotoxic assays, antibursa sera were specific for donor-line bursa cells without absorption; antithymus sera were similarly specific for donor-line thymus cells. Both types of sera cytolyzed some peripheral lymphoid cells from spleen, bone marrow, and blood. Absorption of either type of serum with peripheral blood leukocytes removed all cytotoxic reactivity for central lymphoid cells. The inheritance of the alloantigens detected by these specific antisera was studied in F₁, F₂, and backcross progeny from the two lines. Phenotypes were determined by a method in which antisera preabsorbed with progeny leukocytes were reacted against⁵¹Cr-labeled bursal or thymic cells from chickens of both lines. The results established two independent autosomal loci-Bu-1 andTh-1-determining antigens expressed, respectively, on bursal cells and peripheral B lymphocytes or on thymic cells and peripheral T lymphocytes. Cytotoxic testing of bursal or thymic cells from chickens of other inbred lines and F₁ populations led to the tentative conclusion that the number of alleles atBu-1 is restricted, whileTh-1 exhibits considerable multiple allelism.     

Lymphoma induced by herpesvirus: Resistance associated with a major histocompatibility gene

Studies with crosses of inbred chicken lines demonstrate that resistance to Marek's disease, a herpesvirus-induced lymphoma of chickens, is associated with an allele (B ²¹) of the major histocompatibility locus (theB locus). TheB ²¹ allele is thus the first genetic marker for resistance to herpesvirus-induced neoplastic disease, and our studies suggest the means whereby similar associations might be found in man.     

Major histocompatibility (B) complex effects on acquired immunity to cecal coccidiosis

The influence of the major histocompatibility (B) complex on acquired immunity to the avian coccidium Eimeria tenella was studied in 217 F₄ segregants (B ² B ², B ² B ⁵, B ⁵ B ⁵) of a cross between inbred lines 6₁ (B ² B ²) and 15₁ (B ⁵ B ⁵) and segregating haplotype combinations of UNH105 (B ²³ B ²³ B ²³ B ²⁴, B ²⁴ B ²⁴), a noninbred line of New Hampshire chickens. Chickens were immunized at 6 weeks of age with 500 oocysts daily for 5 days, then challenged 14 days later with 10000 oocysts. Responses to infection were evaluated by cecal lesion scores, body weight gain, delayed wattle reaction (DWR), and spleen weight. The F₄ segregants of genotypes B ² B ⁵ and B ⁵ B ⁵ exhibited greater immunity to challenge than B ² B ² chickens. B ⁵ B ⁵ chickens showed a significantly greater DWR following immunization and larger spleens 6 days after the challenge than either of the other genotypes. However, both BIBS and B ⁵ B ⁵ chickens demonstrated significantly lower lesion scores than B ² B ² chickens. There were no significant differences in weight gain among these genotypes. Among 139 line UNH105 segregants, B ²³ B ²³ hosts had significantly lower lesion scores than B ²⁴ B ²⁴ chickens. No other differences in immune response among line UNH105 genotypes were detected.     

Biochemical polymorphic systems in inbred lines of chickens: A survey

Biochemical polymorphic gene frequency profiles from blood samples of two outbred and seven inbred lines of chickens were studied for hemoglobin, albumin, transferrin, alkaline phosphatase, esterase II, and leucine aminopeptidase, and from egg samples of these lines for ovoalbumen, ovoglobulin (G₂ and G₃), and conalbumen. Complete gene fixation was found for hemoglobin, albumin, transferrin, ovalbumin, ovoglobulin, and conalbumin. The same alleles were fixed in each system in each line. For four systems, a particular allele within a system predominated in seven populations; gene frequencies ranged from 0.60 to 0.98. For esterases I and II, the genes Es-I ^B and Es-II ^S ranged in frequency between 0.82 and 0.97, and between 0.64 and 0.93, respectively. For ovoglobulin, G ₂ B ranged between 0.75 and 1.00 with four lines fixed for this allele. The rather remarkable similarity of gene frequency profiles among lines, several of which are only remotely related, suggests that certain characteristic polymorphic frequencies for these biochemical polymorphisms possess higher adaptive values in an evolutionary sense.     

Influence of non-MHC T lymphocyte alloantigens on regression of rous sarcomas in the chicken

Chickens of Regional Poultry Research Laboratory (RPRL) inbred line 63 regress sarcomas induced by Bryan high-titer Rous sarcoma virus to a greater extent than chickens of line 7₂, although these lines are identical for the major histocompatibility complex (MHC, B complex). They differ, however, at two independent autosomal loci, Ly-4 and Th-1, which determine surface alloantigens of partly overlapping subsets of T lymphocytes. Association of genotypes at these loci with quantitative variation in ability to regress Rous sarcomas was tested in segregating progeny derived from crosses of lines 6₃ and 7₂. In the F4 generation chickens of the Ly-4 ^a /Ly-4 ^a , Th-1 ^a /Th-1 ^a genotype (symbolized aa/aa) had significantly higher regressor ability than any of the other three double homozygous genotypes. In F5, all nine genotypes formed by combinations of homozygotes and heterozygotes were tested, and higher regressor ability was shown by the aa/aa, ab/aa, and aa/ab genotypes. These results indicate that higher regression is associated with: (1) interaction between the line 6₃ Ly-4 ^a and Th-1 ^a alleles in homozygous form; and (2) dominance x dominance interaction, in that the a allele at each locus is dominant for higher regression only within the homozygous aa genotype at the other locus.     

Genetic control of immune responses in chickens

The immune response of inbred lines of chickens to the terpolymer poly(glu⁶⁰ala³⁰tyr¹⁰) and copolymer poly(glu⁶⁰ala⁴⁰) was determined. Of six lines immunized, one (line 7) contained birds that either did not respond or were low responders to two injections of 1 mg each of the polymers in Freund's complete adjuvant. As indicated by radioimmunoelectrophoresis, low responders produced a 7S response, although the switch from 17S (high molecular weight immunoglobulin) to 7S antibody production was slower than in high-responder lines. Analysis of the distribution of responders and nonresponders in F₂ generations produced byinter se mating of F₁ hybrids of line 7 with high-responder lines, showed that immune responses were clearly determined by certain alloalleles of theB blood group locus, the major histocompatibility system in the chicken.     

Extrachromosomal Element Delta in DROSOPHILA MELANOGASTER. VIII. Inseparable Association with Sensitive Second Chromosome

The presence of delta is always accompanied by a sensitive second chromosome in Drosophila melanogaster or vice versa. The separability of delta and the chromosome line was investigated in experiments designed to eliminate delta or to suppress its multiplication for a number of generations. Cy/S^b-5 males which transmit a minute amount of delta b (retained by chromosome S^b, kills S^b/S^b and S^b/S^r zygotes) to their progeny were backcrossed for 61 generations to Cy/Pm females which carried no delta. After backcrossing 465 Cy/S^b-5 males were individually examined for retention of delta, and all were found to retain delta b in its latent state. A homozygous strain for the S^r-20B chromosome which retained a minute amount of delta r (retained by chromosome S^r, kills S^r/S^r zygotes) was obtained. 1,252 Cy/S^r-20B females derived from the homozygous strains at the 21st generation were tested individually for delta retention. All females tested were found to retain delta r in its latent state. The delta retention in S^b-5 chromosome lines isolated from S^r-Cy/S^b-5 heterozygous strains which carried delta r but not delta b was examined. The descendant Cy/S^b-5 lines from the heterozygous strains had accumulated their specific delta, delta b. These findings are consistent with those obtained in an earlier study, and lead to the conclusion that delta is associated inseparably with each specific sensitive chromosome.     

Fatness QTL on chicken chromosome 5 and interaction with sex

Quantitative trait loci (QTL) affecting fatness in male chickens were previously identified on chromosome 5 (GGA5) in a three-generation design derived from two experimental chicken lines divergently selected for abdominal fat weight. A new design, established from the same pure lines, produced 407 F2 progenies (males and females) from 4 F1-sire families. Body weight and abdominal fat were measured on the F₂ at 9 wk of age. In each sire family, selective genotyping was carried out for 48 extreme individuals for abdominal fat using seven microsatellite markers from GGA5. QTL analyses confirmed the presence of QTL for fatness on GGA5 and identified a QTL by sex interaction. By crossing one F1 sire heterozygous at the QTL with lean line dams, three recombinant backcross 1 (BC1) males were produced and their QTL genotypes were assessed in backcross 2 (BC2) progenies. These results confirmed the QTL by sex interaction identified in the F2 generation and they allow mapping of the female QTL to less than 8 Mb at the distal part of the GGA5. They also indicate that fat QTL alleles were segregating in both fat and lean lines.     

Comparisons of methods for introgressing exotic germ plasm into adapted sorghum

The incorporation of exotic germ plasm into breeding populations can broaden and diversify the genetic base of adapted genotypes. To more effectively utilize the genetic resources existing in Sorghum bicolor (L.) Moench, a rapid and efficient method of incorporating exotic genotypes into adapted populations is needed. Therefore, this study was conducted to compare the effectiveness of backcrossing to a broad-based population versus backcrossing to an inbred line for developing improved lines from adapted x exotic crosses. A wild sorghum, a cultivated landrace, and a converted sorghum line were crossed to an inbred line (CK60) and a broad-based population (KP9B). After two generations of backcrossing to the respective adapted parent, 50 F₂ lines were derived from each of the backcross generations of every mating and evaluated at three test environments. Backcrossing to an inbred line (CK60) gave fewer high-yielding segregates and generated less genetic variation than backcrossing to a population (KP9B). Also, the number of agronomically acceptable lines derived from each CK60 mating was fewer than that derived from the corresponding mating with KP9B. Overall, the use of a broad-based population as an adapted recurrent parent for introgressing exotic genotypes may provide good opportunities for developing suitable inbred lines from adapted x exotic backcrosses.Contribution no. 93-499-J from the Kansas Agricultural Experiment Station     

A USA–Africa collaborative strategy for identifying, characterizing, and developing maize germplasm with resistance to aflatoxin contamination

Aflatoxin contamination of maize by Aspergillus flavus poses serious potential economic losses in the US and health hazards to humans, particularly in West Africa. The Southern Regional Research Center of the United States Department of Agriculture, Agricultural Research Service (USDA-ARS-SRRC) and the International Institute of Tropical Agriculture (IITA) initiated a collaborative breeding project to develop maize germplasm with resistance to aflatoxin accumulation. Resistant genotypes from the US and selected inbred lines from IITA were used to generate backcrosses with 75% US germplasm and F₁ crosses with 50% IITA and 50% US germplasm. A total of 65 S₄ lines were developed from the backcross populations and 144 S₄ lines were derived from the F₁ crosses. These lines were separated into groups and screened in SRRC laboratory using a kernel-screening assay. Significant differences in aflatoxin production were detected among the lines within each group. Several promising S₄ lines with aflatoxin values significantly lower than their respective US resistant recurrent parent or their elite tropical inbred parent were selected for resistance-confirmation tests. We found pairs of S₄ lines with 75–94% common genetic backgrounds differing significantly in aflatoxin accumulation. These pairs of lines are currently being used for proteome analysis to identify resistance-associated proteins and the corresponding genes underlying resistance to aflatoxin accumulation. Following confirmation tests in the laboratory, lines with consistently low aflatoxin levels will be inoculated with A. flavus in the field in Nigeria to identify lines resistant to strains specific to both US and West Africa. Maize inbred lines with desirable agronomic traits and low levels of aflatoxin in the field would be released as sources of genes for resistance to aflatoxin production.     

Characterization of S tester lines in Brassica oleracea: polymorphism of restriction fragment length of SLG homologues and isoelectric points of S-locus glycoproteins

 Forty three S tester lines of Brassica oleracea were characterized using DNA and protein gel-blotting analyses. DNA gel-blot analysis of HindIII-digested genomic DNA with class-I and class-II SLG probes revealed that 40 lines could be classified as class-I S haplotypes while three lines could be classified as class-II S haplotypes. The band patterns in the S tester lines were highly polymorphic. Although the S tester lines typically showed two bands corresponding to SLG and SRK in the analysis with the class-I SLG probe, only one band was observed in the S ²⁴ homozygote. This band was identified as SRK, suggesting that this haplotype has no class-I SLG band. In the analysis using the class-II SLG probe, one plant yielded a different band pattern from the known class-II haplotypes, S ² , S ⁵ and S ¹⁵ . Unexpectedly, this plant was reciprocally cross-incompatible with the S ² haplotype. Therefore, it was designated as S ^2-b . We found an S ¹³ haplotype having a restriction fragment length polymorphism different from that of the S ¹³ homozygotes of the S tester line. These findings indicate that S homozygous lines with the same S specificity do not necessarily show the same band pattern in the DNA gel-blot analysis. Soluble stigma proteins of 32 S homozygotes were separated by isoelectric focusing and detected using anti-S ²² SLG antiserum. S haplotype-specific bands were detected in 27 S homozygotes but not in five S homozygotes, including the S ²⁴ homozygote. This is consistent with the observation that the S ²⁴ haplotype had no SLG band. Received: 13 July 1998 / Accepted: 29 September 1998     

Differences in red cell shape of two inbred chicken lines

Summary Comparison of two inbred chicken lines (F_x > 99.9%) revealed significant differences in shape of the red blood cells (RBC). The length-width index was lower for both sexes in IC-line (1.46) when compared to CB-line chickens (1.88). Phenotypic expression of this character in F₁ hybrids and both backcross groups corresponded to the common manifestations of the metric parameters. The index in F₁ hybrid chickens deviated from intermediate values with the dominant tendency to oval RBC. An analysis of the segregating first backcross generation chickens did not show any association between RBC shape and the genotype in the blood group systems B, C, I, and D and the IgG allotypes. The differences in RBC shape were probably not associated with the survival of RBC in the blood circulation.     

H-2-associated control of natural cytotoxicity and hybrid resistance against RBL-5

(C57B1 × DBA)F₁ hybrids were more resistant to the inoculation of 10³ Rauscher virus-induced, serially propagated RBL-5 cells than syngeneic C57Bl recipients. Resistance was linked toH-2^di in the C57Bl backcross. Spleen cells from nonimmune (C57Bl × DBA)F₁ hybrids were significantly more reactive against RBL-5 in the natural killer (NK) cytotoxicity test in vitro than were C57Bl spleen cells. In the C57Bl backcross,H-2^dH 2^b heterozygotes were more cytotoxic than theH- 2^B homozygotes. Along with RBL-5, they were also more cytotoxic to the Moloney virus-induced YAC lymphoma (of strain A origin) and to the human ALL-derived MOLT-4 line.     

Induced cytomictic diversity in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) inbred

Mutation breeding has been used for improving oligogenic and polygenic characters, disease resistance and quantitative characters including yielding ability. The cytological stability of maize inbred lines is an important consideration in view of their extensive use in genetics and plant breeding research. Investigation in Zea mays L. confirms that the migration of chromosomes is a real event that cannot be misunderstood as an artifact produced by fixation or mechanical injuries. During present investigation, we found that out of six inbred lines of Zea mays L. viz. CM-135, CM-136, CM-137, CM-138, CM-142 and CM-213 at various treatment doses of gamma irradiations viz. 200, 400 and 600 Gy, some of the plants of inbred line CM-138 at 200 Gy dose displayed characteristic cytoplasmic connections during all the stages of meiosis. Four plants from this treatment set were found to be engaged in a rare phenomenon reported as “Cytomixis”. It elucidates that in inbred of Zea mays L., induced cytomixis through gamma rays treatment may be considered to be a possible source of production of aneuploid and polyploid gametes. This phenomenon may have several applications in Zea mays L. improvement in the sense of diversity and ever yield potential.     

Precise mapping of quantitative trait loci for resistance to southern leaf blight, caused by Cochliobolus heterostrophus race O, and flowering time using advanced intercross maize lines

The intermated B73 × Mo17 (IBM) population, an advanced intercross recombinant inbred line population derived from a cross between the maize lines B73 (susceptible) and Mo17 (resistant), was evaluated in four environments for resistance to southern leaf blight (SLB) disease caused by Cochliobolus heterostrophus race O. Two environments were artificially inoculated, while two were not inoculated and consequently had substantially lower disease pressure. Four common SLB resistance quantitative trait loci (QTL) were identified in all environments, two in bin 3.04 and one each in bins 1.10 and 8.02/3. There was no significant correlation between disease resistance and days to anthesis. A direct comparison was made between SLB QTL detected in two populations, independently derived from the same parental cross: the IBM advanced intercross population and a conventional recombinant inbred line population. Several QTL for SLB resistance were detected in both populations, with the IBM providing between 5 and, in one case, 50 times greater mapping resolution.     

A three-locus model for the chicken major histocompatibility complex

The major histocompatibility complexes (B complexes) of chickens of various origins have been studied by serological and biochemical methods. TwoB complexes are of particular interest:B ^R1, a recombinant haplotype derived from theB complexes of the inbred CB and CC strains, andB ^G-B1 , theB haplotype of the G-B1 strain. TheB ^R1 haplotype differs detectably from theB ^CB haplotype only at a locus controlling the synthesis of an antigen, B-G, which (in peripheral blood) is present only on red cells. Anti-B-G sera precipitate, from¹²⁵I-labeled red cell lysates, two chains of apparent molecular weights 42,000 and 31,000 (measured under reducing conditions); the smaller is perhaps derived by proteolysis from the larger. TheB ^G-B1 haplotype differs detectably from theB ^CC haplotype only at a locus controlling the synthesis of an antigen whose tissue distribution and biochemical and biological properties are identical to those of B-G. The chicken major histocompatibility complex therefore contains at least three loci—those controlling synthesis of the B-G, and of the previously defined B and B-L antigens.The following abbreviations are used in this paper MHC major histocompatibility complex - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - MLR mixed leukocyte reaction - GVH graft-versus-host reaction     

MHC and Non-MHC genetic influences on rous sarcoma metastasis in chickens

The B ⁵/B ⁵ genotype, in Leghorns, was associated with a high degree of metastasis of Rous sarcoma virus-induced tumors, but in combination with a Leghorn-New Hampshire background markedly less metastasis occurred. Initially, four mating types were used: B ⁵/B ⁵ × B ⁵/B ⁵ chickens from the F₅ generation of the cross of Leghorn lines 6₁ and 15₁, B ²⁴/B ²⁴ × B ²⁴/B ²⁴ chickens from line UNH 105 (New Hampshires), and reciprocal crosses of B ⁵/B ⁵ × B²⁴/B²⁴ chickens. Subsequently, F₂ generation progeny of the cross of B⁵/B⁵ and B ²⁴/B ²⁴ breeders, as well as B ²⁴/B ²⁴ line UNH 105 and B ⁵/B ⁵ (6₁ × 15₁)F₂ chickens, were used. Six-week-old chickens were inoculated in the wingweb with Rous sarcoma virus. Chickens dying during a 10-week period after inoculation were necropsied and suspect metastatic lesions examined histologically. Among 234 terminal chickens from the initial four mating types the incidence of metastasis associated with B ⁵/B ⁵ Leghorns (66%) was substantially higher than for B ²⁴/B ²⁴ New Hampshires (12%) and B ⁵/B ²⁴ progeny of reciprocal Leghorn-New Hampshire crosses (19 and 24%). Subsequently, among 524 terminal hosts in the Leghorn-New Hampshire F₂ population, B genotype significantly influenced tumor dissemination. However, among 52 concurrently challenged B ⁵/B ⁵ hosts from the (6₁ × 15₁)F₂ population the incidence of metastasis (60%) was significantly higher than among 122 B ⁵/B ⁵ hosts from the Leghorn-New Hampshire F₂ population (31%), indicating a non-major histocompatibility complex genetic effect on metastasis.     

Production and propagation of fully inbred clonal lines in the Nile tilapia (Oreochromis niloticus L.).

Fully inbred clonal lines of fish are likely to be of great value in research on immunology, sex determination, quantitative genetics, and toxicology. In this study on the Nile tilapia (Oreochromis niloticus), gynogenesis or androgenesis were used to produce a first generation of completely inbred fish, from which clonal lines were established using gynogenesis, androgenesis, hormonal sex reversal and intraline crosses. The clonal nature of these lines was verified by using multilocus DNA fingerprinting and the isozyme locus ADA*. Although these lines might be expected to be monosex in nature (all-female XX or all-male YY depending on the clone), one line did contain both sexes of fish. The presence of males in this gynogenetic clonal line and data from progeny testing of these males suggested that this line was homozygous for an allele or combination of alleles at an autosomal locus or loci which caused female to male sex reversal but with limited penetrance. Outbred clonal lines were also produced by crossing between different inbred clones. J. Exp. Zool. 284:675-685, 1999.