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Characterization of an architectural mutant of bean (Phaseolus vulgaris, L.)
Genetic and morphological characteristics of an architectural mutant in common beans were studied. The mutant had shiny, dark green leaves, overlapping leaflets, short petioles and a reproductive terminal bud even though the line did not carry the fin gene. Branching was nearly absent resulting in a single stem vine. This is a new form of determinancy in common bean. The inheritance of the mutant was studied in crosses involving four normal parents, Oregon 91G, Minuette, 5-593, and UI 906, which represent a diversity of growth habit types. The Fâ plants had a normal phenotype, indicating that the mutant trait was recessive. Fâ segregation data fit a single recessive gene ratio and Fâ data confirmed the hypothesis that the mutant character was controlled by a single recessive gene. Tests of allelism were conducted to determine if the mutant was allelic to similar mutants. These were ol for overlapping leaflets and dgs for dark green savoy leaves. When the mutant was crossed with ol and dgs tested, all of the Fâ plants were normal. These results are consistent with the interpretation that the mutant trait was not allelic to ol and dgs. The name topiary was conferred on this mutant describing its compact and neat appearance. The gene symbol top was proposed. Because the four parental lines differ from the top line for alleles at other loci, linkage was tested for growth habit (fin), shiny leaf, cross-sectional shape of pods, striped pod (prp superscript [st]) and pod suture strings (st) with the topiary mutant. Chi-square test of independence showed no linkage between either the mutant and marker genes or among the marker genes. A phenological study of topiary revealed that long days delayed flowering an average of 15 days. In addition, the number of vegetative nodes before flowering was increased. The topiary mutant is photoperiod sensitive, but does not react in the same manner as other photoperiod sensitive beans. Whether this photoperiodic sensitivity in the mutant is independent of the topiary gene is unknown and deserves further study. The topiary mutant has potential for improving common beans. Its single stem growth habit may allow closer row spacing leading to higher planting populations and may enhance the efficiency of mechanical harvest. Pod formation at higher nodes may escape disease. Currently, the thin stems cause lodging. Development of thick and upright forms will be the subject of future studies
Genome of âCharleston Grayâ, the principal American watermelon cultivar, and genetic characterization of 1,365 accessions in the U.S. National Plant Germplasm System watermelon collection
Years of selection for desirable fruit quality traits in dessert watermelon (Citrullus lanatus) has resulted in a narrow genetic base in modern cultivars. Development of novel genomic and genetic resources offers great potential to expand genetic diversity and improve important traits in watermelon. Here, we report a high-quality genome sequence of watermelon cultivar âCharleston Grayâ, a principal American dessert watermelon, to complement the existing reference genome from â97103â, an East Asian cultivar. Comparative analyses between genomes of âCharleston Grayâ and â97103â revealed genomic variants that may underlie phenotypic differences between the two cultivars. We then genotyped 1365 watermelon plant introduction (PI) lines maintained at the U.S. National Plant Germplasm System using genotyping-by-sequencing (GBS). These PI lines were collected throughout the world and belong to three Citrullus species, C. lanatus, C. mucosospermus and C. amarus. Approximately 25 000 high-quality single nucleotide polymorphisms (SNPs) were derived from the GBS data using the âCharleston Grayâ genome as the reference. Population genomic analyses using these SNPs discovered a close relationship between C. lanatus and C. mucosospermus and identified four major groups in these two species correlated to their geographic locations. Citrullus amarus was found to have a distinct genetic makeup compared to C. lanatus and C. mucosospermus. The SNPs also enabled identification of genomic regions associated with important fruit quality and disease resistance traits through genome-wide association studies. The high-quality âCharleston Grayâ genome and the genotyping data of this large collection of watermelon accessions provide valuable resources for facilitating watermelon research, breeding and improvement