A rapid screen for the detection of specific DNA sequences in plants.

We have developed a simple and quick method ("wick blot") for detecting the presence of specific DNA sequences in plants, using radiolabeled DNA probes. The method requires only small amounts of tissue, about 15-25 mg. More than a hundred samples per day can be easily extracted and blotted. It works well on various species and tissues, including leaves, embryos, and callus. The method is ideally suited for screening large numbers of putative transformants, especially populations that have not been screened by prior selection.

Gene transfer in crop improvement.

Transfer of genes between plant species has played an important role in crop improvement for many decades. Useful traits such as resistance to disease, insects, and stress have been transferred to crop varieties from noncultivated plants. Recombinant DNA methods greatly extend (even outside the plant kingdom) the sources from which genetic information can be obtained for crop improvement. Gene transfer systems based on recombinant DNA are available for several crop species and are under development for others. The concerted use of traditional and more recent methods for plant genetic manipulation will contribute to crop improvement.

A microassay for detection of DNA and RNA in small numbers of plant cells.

A microtechnique for the detection of DNA or RNA in small numbers of plant cells (1-50) has been developed using cauliflower mosaic virus (CaMV) infection of turnip as a model system. Both DNA and RNA extracted from 10 mesophyll protoplasts from CaMV-infected plants can be detected by hybridization using a radioactive probe made from cloned CaMV DNA (pCaMV10). No hybridization above background was detected in extracts of protoplasts from uninfected plants. At least 0.15 pg (11 000 molecules) of purified pCaMV10 DNA can be detected. This method is superior to existing 'macro' techniques for nucleic acid detection as smaller amounts of tissue are required and the detection is approximately 100-fold more sensitive. re]19850326 rv]19850530 ac]19850611.

Distribution of Nonstructural Variation along Three Chromosome Arms between Wheat Cultivars Chinese Spring and Cheyenne.

Metaphase I (MI) pairing of wheat homologous chromosomes is usually reduced in hybrids between cultivars relative to the parental inbred lines. Previous work suggested that this phenomenon is caused by polymorphism in nucleotide sequences (nonstructural chromosome variation) among wheat cultivars. The present work investigated the distribution of this variation along three selected chromosome arms between cultivars Chinese Spring and Cheyenne. Chinese Spring ditelosomics 3Aq, 6Ap and 6Bp were crossed with disomic substitutions of Cheyenne chromosomes 3A, 6A and 6B in Chinese Spring, respectively. The resulting F(1) plants, called substituted monotelodisomics, were crossed with the respective Chinese Spring monosomics, producing potentially "recombinant" substituted monosomics. When these "recombinant" chromosomes were combined with the parental Chinese Spring telosomes, marked reductions in mean telosome-pairing frequency were found compared with the corresponding Chinese Spring monotelodisomics. The mean pairing frequencies of the "recombinant" chromosomes showed a continuous distribution between those of the substituted and Chinese Spring monotelodisomics. The results suggest that the nonstructural variation that reduces MI pairing between chromosomes of different wheat cultivars is not localized in a specific site but distributed along each chromosome arm. Little variation was found among monotelodisomics for either the number of ring bivalents per cell or the number of univalents other than those constituting the heteromorphic pair. This implies that the reductions in MI pairing between the Cheyenne and Chinese Spring chromosomes are caused by something residing within these specific chromosomes that does not affect the pairing of the remaining Chinese Spring chromosomes in the same cell. Furthermore, the absence of parental types among the "recombinant"-substituted monotelodisomics suggests that the sequences involved in the variation studied here are capable of converting heterohomologous chromosomes to something intermediate in nature in the span of only a single generation.