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Lycopersicon peruvianum displays gametophytic self-incompatibility (GSI). We have isolated self-compatible (SC) tetraploids of L. peruvianum from tissue-cultured leaves and have explored the expression and inheritance of their S-related proteins. The Srelated protein profiles of styles of SC tetraploids were indistinguishable from the diploid self-incompatible (SI) explant source based on SDS-PAGE. All progeny obtained from self-fertilization of two tetraploids were SC. Cloned cDNA sequences of the S-related proteins were used to determine the inheritance of this locus in these progeny through Southern hybridization. The allelic ratio, as determined from the intensity of DNA restriction fragments, was consistent with the predicted ratio if only pollen bearing two different alleles was successful in achieving fertilization. All progeny obtained had at least one copy of each allele, and individuals fully homozygous for either allele were not found, indicating that pollen grains bearing two identical alleles were inhibited. In addition, the level of expression of the S-related proteins in the progeny correlated with the allelic dosage at the DNA level. We demonstrate that the observed self-compatibility in the tetraploids was not caused by an alteration in the expression of S-related proteins. [ABSTRACT FROM AUTHOR]

Allotetraploidization is the creation of synthetic allotetraploids. The allotetraploidization of maize can be accomplished by concentrating DPA (differential pairing affinity) factors into stocks by a recurrent selection breeding system. Selection is based on pairing configuration frequencies and altered genetic ratios that reflect DPA. Both an observed decline in the quadrivalent frequency per meiocyte from 8.10 to 7.31 and genetic data disclosing a reduction in the average frequency of recessive waxy ( wx wx) pollen from Wx Wx wx wx plants from 17.48% to 13.35%, indicate considerable progress has been made toward allotetraploidization. A simple model for the effect of DPA on chromosome pairing and genetic ratios is presented. [ABSTRACT FROM AUTHOR]

In chickpea, out of three colchicine concentrations and two treatment durations used (combinations of 0.25, 0.05, 0.025% colchicine and 4 and 6 h duration), seed treatment with 0.25% for 4 h proved to be the most effective in producing autotetraploids. Colchicine treatment on seedlings failed. The induced tetraploidy was accompanied by larger leaves, flowers, stomata, pollen grains and seeds. Mean percentage stainable pollen and podset were reduced, but some plants had relatively normal meiosis and produced as many pods as the diploid parent, indicating the potential of induced autotetraploids in chickpea improvement. [ABSTRACT FROM AUTHOR]

The genomes of the diploid wheats Triticum boeoticum and T. urartu are closely related, giving 7II in the f hybrid (TT) and 8.4 (0-14) II + 2.5 (0-7) IV in the derived amphiploid (TTTT). The genomes of the tetraploid wheats are also closely related, giving up to 7II at the polyhaploid level (AB) in the absence of the gene Ph but 14II at the tetraploid level (AABB) in the normal presence of Ph. If the amphiploid is the progenitor of the tetraploids, one or the other homoeologue (T or T) in each of the 7 homoeologous groups (the 7 potential IV) must have differentiated with respect to pairing affinity in order to account for 14II in the tetraploid. Consequently, in tetraploid X amphiploid hybrids (TTAB) carrying the Ph gene from the tetraploid, the seven differentiated chromosomes (B) would be expected to give 7I while, on the basis of their observed chiasma frequency, T, T and the less differentiated A would be expected to give 4.17I + 3.57II + 3.23III), assuming homoeologous pairing. The expected chromosomal configuration freqencies at MI (11.17I + 3.57II + 3.23III) closely fit the observed values (11.22I + 3.45II + 3.19III + 0.071IV) for such hybrids (X = 0.0046; P>0.99). Thus diploidization of the boeoticum-urartu amphiploid clearly could account for the origin of the tetraploid wheats. Furthermore, T. aestivum X amphiploid hybrids (TTABD) with and without Ph indicated that B as well as A chomosomes tended to pair with their presumed TT homologues in the absence of Ph. Other tests showed that the tetraploid wheats could not plausibly have originated from any postulated Triticum-Sitopsis (TTSS) parental combinations with or without such chromosomal differentiation. [ABSTRACT FROM AUTHOR]

Allotetraploidization is the creation of artificial allotetraploids. Allotetraploidization of maize can be achieved by restructuring a maize genome so that its chromosomes will not pair with those of the normal maize genome. The restructuring can be done by concentrating induced or naturally occurring visible and cryptic chromosome aberrations and qualitatively different genetic material into a single line by a recurrent selection type of breeding program. The basis of allotetraploidization is the presence of differential pairing affinity between normal and restructured chromosomes. Experiments demonstrate that differential pairing affinity factors occur naturally in exotic races and in standard corn belt inbred lines and that they may be readily induced by X-irradiation and chemical mutagens. [ABSTRACT FROM AUTHOR]

Two sets of diallel crosses involving seven tetraploid and five hexaploid alfalfa lines, previously selected for seed and forage yield, are studied. On the basis of combining ability and heritability estimates the following conclusion is drawn. The dominant and epistatic interactions (heterozygosity) are the major components in the expression of variability for yield and characters associated with yield in tetraploid populations. In hexaploid populations, however, there is an appreciable amount of additive variance, and the additive effect of genes along with interaction of various forms may account for the expressed variability for all the characters studied. Better genes and desirable interactions (possibly through heterozygosity) are the two essential genetic components of yield. The selection of better genes is feasible, but by itself will not produce the desired results. Future improvement may therefore depend on the utilization of heterosis and other forms of interactions. There is, in general, a very strong genetic correlation between yield and its components, and therefore, when a direct selection for yield is not feasible, the selection program may rely on a number of closely related characters. [ABSTRACT FROM AUTHOR]