Insensitive Genes Research Articles

In vitro expression of genes affecting whole plant phenotype ? the effect of Rht/Gai alleles on the callus culture response of wheat (Triticum aestivum L. em. Thell)

Calli were initiated from immature embryos of 12 lines of hexaploid wheat (Triticum aestivum L. em. Thell). The lines were from 3 varieties — April Bearded, Bersee and Maris Huntsman — isogenic for the reduced height/gibberellic acid insensitivity (Rht) genes — Rht1, Rht2 and Rht3 — and the ‘tall’ (rht) allele. The dwarfing genes had significant effects on the growth and morphogenesis of calli. The genes interacted with the 2,4-D in the medium and the varietal background. Calli of each line were cultured in the presence and absence of 1 mg/l of gibberellic acid (GA), but there was no interaction of the Rht genes with GA in vitro. The effect of the Rht genes is discussed in relation to their effects on cellular hormone metabolism and their involvement in previously described chromosome 4B effects in culture.

Preliminary results of a screening for GA3 response in wheats of the Gatersleben gene bank

A total of 700 wheat accessions of the Gatersleben gene bank were screened for gibberellic acid insensitivity genes (Gai) by a modified method. It was found, that 77 hexaploid and 5 tetraploid wheats were GA3-insensitive. The probable origin of theGai-genes is discussed.

A Gene for Early Maturity and Photoperiod Insensitivity in Pearl Millet1

The e1 gene was isolated by repeated backcrossing from a weak, spindly, very early maturing seedling discovered by R. F. Moore in a field of ‘Katharine’ pearl millet, Pennisetum americanum (L.) Leeke, growing in Queensland, Australia. Inbreds T23DBE and T756, carrying e1e1 developed by backcrossing the e1 gene into T23DB and T28, flowered in 45 to 55 days regardless of season planted, whereas T23DB and T28 (like most pearl millets) flowered in 75 to 85 days if planted in May and 55 to 65 days if planted in August. Thus the e1e1 gene imparts photoperiod insensitivity and makes most millets carrying it mature 10 to 40 days earlier. The e1 gene and a rapid backcrossing program make it possible to quickly create very early photoperiod‐insensitive forms of any superior pearl millet cultivar or hybrid.

A possible gene source for early, day-length neutral pigeon peas, Cajanus cajan (L.) Millsp.

Atylosia scarabaeoides Benth. and A. platycarpa Benth., close relatives of the species Cajanus cajan (L.) Millsp., were screened for photoperiodic response. Four photoperiods ranging from 12 h 45 min to 19 h were studied in three environments. A. scarabaeoides flowered freely only in the first photoperiod. A. platycarpa not only flowered early (39 to 63 days after planting) in all four photoperiods, but also exhibited a relatively constant vegetative phase up to 16 h of illumination. Cajanus cajan, in which most cultivars-if not all-exhibit a response to photoperiod, was successfully hybridized with the two Atylosia species. It is suggested that genes for earliness and insensitivity to day-length could be transferred from A. platycarpa to C. cajan.

Inheritance of insensitivity of lettuce to a surplus of exchangeable manganese in steam-sterilized soils

After steam sterilizing of certain glasshouse soils a surplus of exchangeable manganese (SEM) occurs. Great differences exist between lettuce genotypes for sensitivity to SEM. Research on the inheritance of insensitivity was carried out by intererossing five lettuce genotypes: Lactuca sativa cys. Neptune (sensitive). Plenos. Troppo and Celtuce (all insensitive) and an accession of L. scrriola (insensitive). From analysing various populations (as F1's. F2's and B1's) it appeared that different numbers of genes for insensitivity were present in the parents varying from one gene in Plenos and Troppo, two genes in L. serriola to possibly four genes in Celtuce. Genes in the three first mentioned parents were linked in repulsion phase and a chromosome map for these genes was made.

The chromosomal location of Gai 1 and Rht 1, genes for Gibberellin insensitivity and semi-dwarfism, in a derivative of Norin 10 wheat

The gene conferring gibberellin insensitivity, Gai 1, was located on chromosome 4A. This gene is associated with the semi-dwarf habit and consequently it was concluded that Rht 1 is carried by 4A. No recombination was found between Gai 1 and Gai 3, the gibberellin insensitivity gene in “Tom Thumb”-type dwarf wheats, indicating that these genes are either alternative alleles at the same locus or are closely linked.

Effect of Daylength Response on Agronomic and Quality Performance of Durum Wheat1

Durum wheat (Triticum durum Desf.) varieties grown in the United States are not adapted to the short‐day conditions of the middle latitudes (between 28°N and 28°S). Introduction of a gene or genes for daylength insensitivity could broaden the adaptability of these varieties, but the effects of insensitivity on agronomic and quality performance in northern latitudes are not well known. Fifty‐two F3 durum wheat bulks homozygous sensitive to daylength and 52 bulks homozygous insensitive to daylength were selected from 4 crosses between northern varieties and a daylength‐insensitive selection (‘Zenati’/‘Bouteille’) introduced from Israel. These 104 F3 bulks were compared for agronomic and quality performance in North Dakota in 1967 and 1968. Ten pairs of lines, near isogenic except for daylength response, were developed from three of the four crosses by selecting heterozygous plants from F3 through F6. The F6 pairs were compared in a split‐plot arrangement in four environments. Insensitive lines tended to be significantly earlier (1 to 3 days) and shorter (3 cm) than the sensitive lines. Genotype ✕ environment interactions were significant for yield. The insensitive near‐isogenic F6 lines yielded slightly more grain than the sensitive lines in two environments, five of the senstive lines yielded as much as 20 to 40% more grain than the insensitive lines in one environment, and the two response types yielded essentially alike in one environment. We conclude that durum wheats for the North Central States can be converted to the insensitive condition without loss in productivity or quality. Insensitive lines must be thoroughly tested over a wide range of temperature and daylength conditions to assure that only the most stable ones are released for commercial production.