The chromosomal location of peroxidase isozymes of the wheat kernel

Summary The analysis of the individual parts of the Triticum aestivum L. kernel yields a total of 11 peroxidase isozymes: m, n, a, c, d₁, d, d₂, e, f, g and h (in order from faster to slower migration). Isozymes a, c and d are found in the endosperm (Ed) and seed coats (C), while m, n, d₁, d₂, e, f, g and h are peculiar to the embryo and scutellum (E + S). The use of the nullitetrasomic and ditellosomic series of Chinese Spring wheat allows peroxidase isozymes to be associated with specific chromosome arms. Isozymes a, c and d (Ed) are associated with chromosome arms 7D^S, 4B^L and 7A^S; whereas isozymes m, d₂, e and f are associated with chromosome arms 3D^S, 3B^L, 3D^L and 3D^L, respecitvely. Thus, the E + S isozymes are associated with homoeology group 3 and the Ed isozymes with homoeology groups 7 (a and d isozymes) or 4 (c isozymes).     

RELP markers linked to two Hessian fly-resistance genes in wheat (Triticum aestivum L.) from Triticum tauschii (coss.) Schmal

Summary Restriction fragment length polymorphism (RFLP) markers linked to genes controlling Hessian fly resistance from Triticum tauschii (Coss.) Schmal. were identified for two wheat (Triticum aestivum L.) germ plasm lines KS89WGRC3 (C3) and KS89WGRC6 (C6). Forty-six clones with loci on chromosomes of homoeologous group 3 and 28 clones on those of group 6 were surveyed for polymorphisms. Eleven and 12 clones detected T. tauschii loci in the two lines, respectively. Analysis of F₂ progenies indicated that the Hessian fly resistance gene H23 identified in C3 is linked to XksuH4 (6.9 cM) and XksuG48 (A) (15.6 cM), located on 6D. The resistance gene H24 in C6 is linked to XcnlBCD451 (5.9 cM), XcnlCD0482 (5.9 cM) and XksuG48 (B) (12.9 cM), located on 3DL.Paper No. 810 of the Cornell Plant Breeding Series     

The chromosomal location of factors determining the presence of phenolic compounds in wheat (Triticum aestivum L.)

Summary Using thin-layer chromatography and nulli-tetrasomic and ditellosomic series of Triticum aestivum L. cv. Chinese Spring, it has been possible to relate the phenolic compounds found in adult plant leaves and 12 day-old seedling leaves with the chromosomes or chromosome arms 1 B, 2 BL, 3 BL, 5 A, 6 AL, 7 B and 7 DS.     

Waxy protein deficiency and chromosomal location of coding genes in common wheat

Deficiency of the wheat waxy (Wx) proteins (Wx-A1, Wx-B1 and Wx-D1) was studied in 1,960 cultivars derived from several countries. Gel electrophoretic analyses revealed that the null allele for the Wx-A1 protein occurred frequently in Korean, Japanese and Turkish wheats but was relatively rare in cultivars from other countries and regions. About 48% of the wheats deficient for the Wx-B1 protein were from Australia and India. One Chinese cultivar lacked the WxD1 protein. While 9 Japanese cultivars were deficient in both the Wx-A1 and Wx-B1 proteins, no cultivars lacked both the Wx-A1 and Wx-D1 proteins, both the Wx-B1 and Wx-D1 proteins or all three Wx proteins. Two-dimensional gel electrophoresis revealed polymorphisms of the three Wx proteins that varied according to isoelectric points or molecular weight. The Wx-A1 gene coding the Wx-A1 protein and the Wx-B1 gene coding the Wx-B1 protein were localized in the distal regions of chromosome arms 7AS and 4AL, respectively, by deletion mapping using the deletion lines developed in the common wheat cultivar Chinese Spring.     

Diversity changes in an intensively bred wheat germplasm during the 20th century

Plant breeding may lead to narrowing genetic diversity of cultivatedcrops, thereby affecting sustained selection gains in crop improvement. A totalof 47 microsatellite primer pairs (mapped to the 21 wheat genetic linkagegroups) were assessed in 75 Nordic spring wheat cultivars bred during the20^th century to determine the variation of genetic diversity in thisgermplasm throughout this period. The number of alleles ranged from one toseven, with an average of 3.6 alleles per microsatellite marker. A dendrogramresulting from analysis of the matrix of dissimilarities using the unweightedpair-group method with arithmetic average discriminated all cultivars andrevealed clusters of accessions released both from some geographical area inthe Nordic Region and the breeding era, i.e. before and after World War II. Geneticdiversity in this wheat material increased from 1900 to 1940 and again from1960 onwards. In between these two periods there was a loss of diversity, whichcould not be explained by changes in a single genome or in one or few chromosomesets. Effects of different selection within countries are revealed by cleardifferences in frequency of some microsatellite alleles. In adition somemicrosatellite alleles were lost during the first quarter of the century whileseveral new alleles were introduced in the Nordic spring wheat material duringthe second half of the century. These results suggest that genetic diversity inNordic spring wheat was enhanced by plant breeding in the first quarter of the20^th century and following a decrease during the second quarter wasincreased again by plant breeding.     

The peroxidase isozymes of the wheat kernel: tissue and substrate specificity and their chromosomal location

Summary Peroxidase isozymes were studied in the Triticum aestivum L. kernel and in nullisomic-tetrasomic and ditelocentric combinations of Chinese Spring wheat. Analyses were carried out on different parts of dry kernels (embryo plus scutellum and endosperm) using polyacrylamide and starch gel electrophoresis, different electrophoretic buffer systems and various staining methods. The peroxidase isozymes showed a low substrate-specificity and a high tissue-specificity. The embryo plus scutellum and the endosperm always presented different peroxidase patterns. Endosperm peroxidases were associated with chromosome arms 7DS, 4BL and 7AS; whereas the embryo plus scutellum isozymes were related to chromosome arms 3AL, 3BL and 3DS. The different results obtained using various electrophoretic techniques are due to the buffer system used. All staining procedures employed revealed the same peroxidase isozymes.     

Length polymorphism and homologies of microsatellites in several Cucurbitaceae species

The objectives of this research were to assess (1) the degree of Simple Sequence Repeats (SSR) DNA length polymorphism in melon (Cucumis melo L.) and other species within the Cucurbitaceae family and (2) the possibility of utilizing SSRs flanking primers from single species to other genera or species of Cucurbitaceae. Five melon (CT/GA) _n SSRs were isolated from a genomic library. Two cucumber (Cucumis sativus L.) SSRs were detected through a search of DNA sequence databases, one contained a (CT)₈ repeat, the other a (AT)₁₃ repeat. The seven SSRs were used to test a diverse sample of Cucurbitaceae, including 8 melon, 11 cucumber, 5 squash, 1 pumpkin, and 3 watermelon genotypes. Five of the seven SSRs detected length polymorphism among the 8 melon genotypes. PCR amplification revealed between three and five length variants (alleles) for each SSR locus, with gene diversity values ranging from 0.53 to 0.75. Codominant segregation of the alleles among F₂ progeny was demonstrated for each of the five SSR loci. Four of the seven SSRs detected polymorphism among the 11 cucumber genotypes, with gene diversity values ranging between 0.18 and 0.64. Primers specific to SSRs of C. melo and C. sativus also amplified DNA extracted from genotypes belonging to other genera of the Cucurbitaceae family.     

Development of a chromosomal arm map for wheat based on RFLP markers

Summary A chromosomal arm map has been developed for common wheat (Triticum aestivum L. em. Thell.) using aneuploid stocks to locate more than 800 restriction fragments corresponding to 210 low-copy DNA clones from barley cDNA, oat cDNA, and wheat genomic libraries. The number of restriction fragments per chromosome arm correlates moderately well with relative DNA content and length of somatic chromosomes. The chromosomal arm locations of loci detected with 6 different clones support an earlier hypothesis for the occurrence of a two-step translocation (4AL to 5AL, 5AL to 7BS, and 7BS to 4AL) in the ancestral wheat genomes. In addition, 1 clone revealed the presence of a 5AL segment translocated to 4AL. Anomalies in aneuploid stocks were also observed and can be explained by intrahomoeologous recombination and polymorphisms among the stocks. We view the development of this chromosomal arm map as a complement to, rather than as a substitute for, a conventional RFLP linkage map in wheat.Paper No. 802 of the Cornell Plant Breeding Series     

Sequence variation, differential expression and chromosomal location of rice chitinase genes

Rice chitinases are encoded by a small multigene family. To clarify the overall organization of rice chitinase genes, we have isolated and characterized the genes Cht-1, Cht-2 and Cht-3. Although all the three genes encode class I chitinase, the nucleotide sequences of the coding regions of Cht-1 and Cht-3 are very similar (90%), while that of Cht-2 is clearly more divergent (78%). Only Cht-2 has a 130 by intron and encodes a C-terminal peptide sequence similar to that known to function as a vacuolar targeting signal. In 5 flanking regions of Cht-1 and Cht-3, but not of Cht-2, conserved sequences (GGCCGGCYGCCCYAG) were found. Related sequences were found also in the 5 flanking regions of another chitinase gene and a -glucanase gene which has also been reported to be stress-induced in rice. RNA blot hybridization analysis demonstrated that the stress-induced expression patterns of the Cht-1 and Cht-3 genes are similar, but quite different from that of Cht-2. However, all three genes are active in unstressed roots. By restriction fragment length polymorphism (RFLP) linkage analysis, Cht-1 and Cht-3 were mapped onto chromosome 6 and shown to be closely linked (0.8 cM). Cht-2 was mapped onto chromosome 5. All these features suggest that the expression patterns of rice class I chitinase genes may be correlated with their levels of sequence divergence and their chromosomal location.