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- Author or Editor: I.L. Goldman x
Plants are the foundation for a significant part of human medicine and for many of the most widely used drugs designed to prevent, treat, and cure disease. Folkloric information concerning traditional remedies for disease has had inestimable value in establishing familial and cultural linkages. During the 20th century, modern medical science in the U.S. and other developed countries ushered in a new era focused on synthetic medicines. Even though many of these compounds were based on natural compounds found in plants, the drive towards synthetic pharmaceuticals created a knowledge gap concerning the health functionality of plants, crops, and food. Paralleling this development, biochemists and nutritional scientists pioneered the discovery of vitamins during the early decades of the 20th century. This research paved the way for dietary guidelines based on empirical data collected from animal feeding trials and set the stage for the current emphasis on phytonutrients. Three primary stages characterize the use of fruits and vegetable in human health. The first stage concerns the observation that many fruit and vegetable crops were originally domesticated for their medicinal properties. Making their way into the diet for this purpose, fruit and vegetable crops remained on the fringe from a culinary point of view. The second stage began when the role of vitamins became more widely understood, and fruit and vegetable plants were quickly recognized as a rich source of certain vitamins, minerals, and fiber. At this point, they became more than just an afterthought in the diet of most U.S. citizens. Cartoon icons such as Popeye made the case for the health functionality of leafy greens, while parents schooled their children on the virtues of carrots (Daucus carota), broccoli (Brassica oleracea), and green beans (Phaseolus vulgaris). This renaissance resulted in large increases in fresh fruit and vegetable consumption across the country, a trend that continues to this day. The third phase can be characterized by the recognition that fruit and vegetable crops contain compounds that have the potential to influence health beyond nutritional value. These so-called functional foods figure prominently in the dietary recommendations developed during the last decades of the 20th century. In recent years, surveys suggest nearly two-thirds of grocery shoppers purchase food specifically to reduce the risk of, or manage a specific health condition. Evidence abounds that consumers, including Baby Boomers, choose foods for specific health benefits, such as the antioxidant potential of vegetables, suggesting high levels of nutritional literacy. Clinical and in vitro data have, to some degree, supported the claims that certain foods have the potential to deter disease, however much research remains to be conducted in order to definitively answer specific dietary-based questions about food and health.
Few genes have been identified in red beet. A spontaneously occurring dwarf mutant was identified in the late 1970s and again in 1994 in several breeding populations. Mutant plants are characterized by extreme dwarfing of both root and shoot. Young leaves are narrow, thin and strap-like while older leaves are thicker and deeply veined. The shoot axis forms a compressed rosette. Neither the shoot axis nor the root axis of field-grown plants exceeds 3 cm in height. Genetic analysis of F2 and backcross populations revealed the dwarf phenotype is conditioned by a single recessive gene. Several experiments were conducted to determine if the dwarf phenotype was due to a lack of gibberellic acid (GA) production. Exogenous application of GA3 at concentrations ranging from 1 to 1000 ppm on dwarf plants a) following seeding and b) during reproductive growth revealed a linear increase in plant height. Control dwarf plants receiving a water-only treatment were 18% as tall as plants receiving regular application of 1000 ppm GA3. A wild-type phenotype during reproductive growth was recoverable following regular GA3 application.
Wisconsin Fast Plants are rapid-cycling versions of various Brassica species amenable to a variety of genetic studies due to their short life cycle and ease of handling. I have recently developed a model system using Brassica rapa L. Fast Plants for teaching the cyclical selection process known as recurrent selection in the context of a course on plant breeding. The system allows for up to three cycles of recurrent selection during a 15-week semester and enables students to gain experience in planting, selection, pollination, and seed harvest during each cycle. Fourteen cycles of replicated, recurrent mass selection for high (H) and low (L) levels of anthocyanin pigment expression in hypocotyl tissue were practiced by students in Horticulture 502 during a period of four semesters. In addition to bi-directional selection; replicated unselected (D) control populations were maintained forcomparative purposes. Over 14 cycles, highly significant gains and losses in hypocotyl pigment production were realized for H and L populations, respectively. Plants in D populations showed no directional response to random selection and therefore did not exhibit genetic drift. Plants in H populations exhibited production of anthocyanin pigment in organs other than hypocotyls, suggesting selection goals could be modified to include pigmentation of specific organs or whole plants. Results from this selection program suggest significant gains from recurrent selection can be visualized through student-based selection activities in the classroom.
Plant breeding is a process that is difficult to compress into laboratory exercises for the classroom. At the heart of plant breeding is the act of selection, a process whereby differential reproduction and survival leads to changes in gene frequency. Given the relatively short span of an academic semester, it has been difficult for students to gain experience with the practice of selection using plant materials. Nearly 15 years ago, P.H. Williams developed Wisconsin Fast Plants, a model system for teaching plant biology in a classroom setting. Wisconsin fast plants are rapid-cycling versions of various Brassica species amenable to a variety of genetic studies due to their short life cycle and ease of handling. This paper describes the development of a model system using Brassica rapa L. fast plants for teaching the cyclical selection process known as recurrent selection in the context of a course on plant breeding. The system allows for up to three cycles of recurrent selection during a single 15-week semester and enables students to gain experience in planting, selection, pollination, and seed harvest during each cycle. With appropriate trait choice, phenotypic changes resulting from selection can be visualized after just three cycles. Using the Fast Plant model, recurrent selection can be practiced successfully by students in the classroom.
Onion consumption promotes cardiovascular health by inhibiting platelet activity. Bulbs are the only onion plant organ thus far examined for antiplatelet activity. The inbred line W420B was grown in replicated field trials at four United States locations in 1994. At bulb maturity, samples from each plot were tested for antiplatelet activity using human blood plasma. The remaining portion of the bulbs from each plot was stored, vernalized, and planted in a breeding nursery in 1995. Umbels were excised from 20 randomly selected plants when >50% of the flowers had opened and tested for antiplatelet activity. Inducement of antiplatelet activity was 336% higher by onion umbels than by bulbs. This finding indicates onion umbels are a more potent source of antiplatelet activity than onion bulbs. In addition, these data suggest that onion umbels may be a richer source of bioactive organosulfur compounds in onion tissue.
The root-knot nematode (M. hapla Chitwood) poses a threat to carrot (Daucus carota L.) production in the United States. Little information is available concerning the genetic control of nematode resistance in carrot. Crosses between two inbreds, a resistant genotype (R1) and susceptible genotype (S1) identified in previous screening tests of carrot were studied in the F2 and BC1 generations to determine the heritability of resistance to the root-knot nematode. Seedlings of F2 (R1/S1), BC1S1, and BC1R1 generations were evaluated for their responses to infestation of M. hapla Chitwood based on gall number per root, gall rating per root, and root rating per root in a greenhouse experiment conducted during 1994. Narrow-sense heritabilities were calculated according to the method of Warner (1952). Narrow-sense heritability was 0.16 for resistance based on gall number, 0.88 for resistance based on gall rating, and 0.78 for resistance based on root rating. This information may be of importance to geneticists and carrot breeders for the development of nematode-resistant carrot cultivars.
The primary pigments in red beet are the betalains, which are comprised of the red-violet betacyanins and the yellow betaxanthins. Modification of betalain content and distribution in table beet has been practiced by breeders for many years, although little is known about the genetic control of these traits. The presence of dominant alleles at two linked loci (R and Y) condition production of betalain pigment in the beet plant. Red-pigmented roots are observed only in the presence of dominant alleles at the R and Y loci, while white roots are conditioned by recessive alleles at both loci and yellow roots by the genotype rrY-. A newly described gene, `blotchy' (bl), conditions a blotchy or irregular pigment patterning in either red or yellow roots. The objective of this investigation was to characterize the linkage relationships between the R and Y loci and the bl gene by evaluating segregating progenies developed from a series of matings of colored and white table beets. Segregation data indicate the bl gene is independent from R and Y and that this locus is linked to R and Y. The two-point linkage estimate between the R and Y loci pooled over eight crosses was 7.4 (1.7 cM) Linkage between R and Bl was estimated from a pooled sample of four crosses at 16.7 (10.8 cM). The most likely gene order was R-Y-Bl. These data suggest the RYBl genomic region plays a critical role in the genetic control of betalain biosynthesis in table beet.
The genetics of resistance to root-knot nematode (M. hapla Chitwood) was studied in crosses of three carrot inbred genotypes, two resistant genotypes (R1 and R2) and one susceptible genotype (S1) identified in previous screening tests. Seedlings of three parental genotypes, six F1 crosses including three reciprocal crosses, two BC1 populations, and three F2 populations were evaluated for their resistance and susceptibility to infestation of M. hapla Chitwood based on gall number per root, gall rating per root, and root rating per root in a greenhouse experiment carried out in 1994. All six F1 plants were susceptible, which indicated a lack of heterosis for resistance in these F1s. The R1 × S1 cross segregated 3 susceptible: 1 resistant in the F2, 1 susceptible: 1 resistant in the BC1R1, and did not segregate in the BC1S1. The R1 × R2 cross yielded 44 susceptible: 36 resistant seedlings in the F2 (R1R2), and 48 susceptible: 32 resistant in the reciprocal cross of R1 and R2, both of which closely fit a 9: 7 ratio (P ≤ 0.001). These results indicate these two resistant genotypes carry two different homozygous recessive genes conditioning root-knot nematode resistance. We propose a model of duplicate recessive epistasis control the reactions of host plants and nematode in these crosses.
The importance of folic acid in the human diet has been recognized in recent years by major increases in government recommended allowances. Red beet (Beta vulgaris L.) is an important vegetable source of folic acid, however little is known about the extent of variation for native folic acid content in red beet germplasm. A total of 18 red beet entries, including 11 hybrids (F1) and seven open-pollinated cultivars (OP), were evaluated for free folic acid content (FFAC) in replicated field experiments during 1993 and 1994. Significant differences among entries were detected in all studies. FFAC ranged from 3.3 to 15.2 μg·g-1 on a dry mass basis. A significant entry × year interaction was detected. Changes in rank of entries between years were minimal among F1 hybrids, while the changes in rank among OP cultivars were large. These data demonstrate significant variability among cultivated red beet germplasm sources for FFAC. Entries with high FFAC may be useful for increasing levels of this vitamin in red beet.