Literature cited:
Tigchelaar, Ng, Buescher and Sistrunk (1976) suggested the possibility of an allelic relationship between the alcobaca and the nor but gave no data. Kopeliovitch, Mizrahi, Rabinowitch and Kedar (1980) reported that they found no evidence to suggest allelism between these two genes. Recently Lobo, Augustine and Hannah (1982) have claimed that the alcobaca was actually an allele at the nor locus on chromosome 10 based on results obtained from physiological studies.
In a repulsion phase cross between alcobaca and the multiple chromosome marker stock d-c-l-a-r-y-gs-ps, our results indicated that the alcobaca gene was located on chromosome 2, distally to the dwarf (d) locus with a recombination frequency of 30% (Table 1). The dihybrid segregation pattern of these two genes and the monogenic segregation of the D-d allelic pair (Table 2) clearly suggested linkage. The apparent abnormal dihybrid segregation of the alcobaca and the 4 gene pair was attributed to the phenotypic misclassification of fruit flesh color due to the influence of the lutescent gene in the background.
Further tests are being conducted to ascertain this linkage relationship by screening both chromosome 2 and 10 with suitable genetic markers.
Table 1. Linkage testing between the alcobaca (alc) locus and six other loci. (alc) is a working designation, whereby alc+ is the dominant allele, and alc the recessive allele of the.alcobaca gene.
Literature cited:
Kopeliovitch, E.Y., Y. Mizrahi, H.D. Rabinow.itch and N. Kedar. 1980 Physiology of the tomato mutant alcobaca. Physiol. Plant. 48:307-311.
Lobo, M., J.J. Augustine and L.C. Hannah. 1982. A new allele at the norlocus. Rept. Tom. Genet. Coop. 32:37-39.
Tigchelaar, E.C., T.J. Ng, R.W. Buescher and W.A. Sistrunk. 1976.- Tomato fruit ripening mutants, potential germplasm to improve quality by extending shelf life. Proc. Second Tomato Quality Workshop, Univ. of California, Davis. pp 148-158.
Table 2. Monogenic segregation pattern of the allelic pairs tested for linkage with the alcobaca locus. The Probability for di-hybrid segregation is also included for each locus.
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X^2 value P. for dihybrid
Locus (3:1) p segregation
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1. D-d
(i) 0.019 0.80 - 0.95
(ii) 0.036 0.80 - 0.95
Pooled: 0.130 0.50 - 0.80 < 0.01
Heterogeneity: 0.421 0.80 - 0.95
2. L-1
(i) 0.385 0.50 - 0.80
(ii) 2.927 0.05 - 0.20
Pooled: 0.705 0.20 - 0.50 0.80 - 0.95
Heterogeneity: 2.607 0.05 - 0.20
3. A-a
(i) 0.933 0.20 - 0.50
(ii) 0.485 0.20 - 0.50
Pooled: 1.361 0.20 - 0.50 0.80 - 0.95
Heterogeneity: 0.057 0.80 - 0.95
4. R-r
(i) 3.219 0.05 - 0.20
(ii) 1.301 0.20 - 0.50
Pooled: 4.028 0.01 - 0.05* << 0.01
Heterogeneity: 0.490- 0.20 - 0.50
5. Ps-ps
(i) 0.1445 0.50 - 0.80
(ii) 2.124 0.05 - 0.20
Pooled: 0.629 0.20 - 0.50 0.50 - 0.80
Heterogeneity: 1.639 0.20 - 0.50
6. Gs-gs
(i) 0.476 0.20 - 0.50
(ii) 0.036 0.80 - 0.95
Pooled: 0.106 0.50 - 0.80 0.20 - 0.50
Heterogeneity: 0.406 0.50 - 0.80
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