Vegetable Breeding and Genetics
Laboratory of I.L. Goldman
Genetics
Carrot and beet quality attributes such as shape, color, texture, flavor, and appearance are of primary importance to the consumer. An understanding of the nature of their genetic control is necessary to assist in the development of a greater biological knowledge base for the crop and streamline breeding efforts. To complement these efforts, Dr. Goldman used a set of recombinant inbred lines to develop a high-density restriction fragment length polymorphism map of the tomato genome and identify and characterize quantitative trait loci influencing processing traits in tomato. From a genetic point of view, tomato is the most well-characterized vegetable and thus offers the use of technologies not yet available to other crops. This work was among the first to use a well-defined set of recombinant inbred lines to dissect quantitative trait loci and may be viewed as a prelude to future molecular work with root crops such as carrot and beet.
Our research on carrot processing and disease resistance traits focused primarily on inheritance of northern root-knot nematode resistance, a major pest in carrot production throughout the US. Wang and Goldman identified two new resistance genes and unequivocally demonstrated that these two recessive genes control the reaction of host and parasite in this system. The carrot seed industry now uses these techniques and a grant from two of these companies enabled continued research on this problem. We also characterized processing carrot germplasm for field resistance to aster yellows, a serious carrot pest vectored by the aster leafhopper in the upper Midwestern United States. This work led to a better understanding of selection response to aster yellows under field conditions. In addition, Our research led to the selection of three aster yellows resistant inbred carrot inbred lines for release to the seed industry. We also investigated genotype x environment interactions for both slicing and dicing carrot production in several different planting systems in Wisconsin and developed a model for processing carrot yield optimization.
Due to the banning of synthetic red dyes as suspected carcinogens, betalain pigments found in red beet have been adopted for use as natural red food colorings. Our work focused on genetic modification of pigment concentration in beet roots and genetic characterization of improved populations. We investigated the response to selection for increased betalain pigment concentration and demonstrated that simultaneous selection for increased pigment concentration and decreased dissolved solids are incompatible possibly because biosynthesis of the pigment molecule requires sugar; thus the two objectives are in direct competition. We also investigated the nature of molecular marker frequency changes associated with this selection and identified marker-linked regions of the red beet genome that may be associated with selection for increased pigment concentration; a finding that may have implications for future selection schemes. Development of novel secondary compounds and genetic enhancement of native secondary compounds in beet and other vegetable crops as natural food additives is a targeted area of current and future research in our program. Additional research has investigated size-shape relations in cylindrical beet cultivars at varying population densities because cylindrically-shaped roots may offer greater efficiencies in processing. Finally, as few genes have been identified in red beet, our research has identified three new recessive genes: a gibberellic acid-sensitive dwarfing gene dw, a blotchy root color mutant, bl , and a gene for fasciation of the flower stem, ffs.