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Pilar Soengas, Maria Elena Cartea, Pablo Velasco, Guillermo Padilla, and Amando Ordás

The species Brassica napus includes economically important vegetable and fodder crops, such as oilseed rape, rutabaga, and leaf rape. A B. napus crop called nabicol has been grown by farmers in northwestern Spain for many years, and is an

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Pablo Velasco, Pilar Soengas, Marta Vilar, Maria Elena Cartea, and Mercedes del Rio

Glucosinolates are secondary plant metabolites that occur naturally in Brassicaceae, a plant family that has given rise to important crops such as oilseeds ( Brassica napus ) and cabbages ( Brassica oleracea ). Based on the amino acid origin of

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Pilar Soengas, Pablo Velasco, Guillermo Padilla, Amando Ordás, and Maria Elena Cartea

Brassica napus includes economically important crops such as oilseed rape, rutabaga, and leaf rape. Other vegetable forms of Brassica napus, namely nabicol and couve-nabiça, are grown in northwestern Spain and north of Portugal, respectively, and their leaves are used for human consumption and fodder. The relationship of nabicol with other Brassica napus leafy crops was studied before, but its origin remained unclear. The aims of this work were to study the genetic relationships among nabicol landraces and other B. napus crops based on microsatellites and to relate the genotypic differences with the use of the crop. The relationship among 35 Brassica napus populations representing different crops was studied based on 16 microsatellite markers. An analysis of molecular variance was performed partitioning the total variance into three components. The source of variation resulting from groups was defined considering the main use of the crop and accounted for a smaller percentage of variation than other sources of variation, proving that this division is not real. Populations clustered into seven different clusters using a similarity coefficient of 0.82. No clear association was evident between clusters and the main use of populations, suggesting genetic differences among populations could reflect differences in their origin/breeding or domestication. Spanish nabicol could have originated from a sample of couve-nabiças, and couve-nabiças could be used to improve nabicol landraces, because they have a narrow genetic basis that limits their potential for breeding.

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H. Guo, M.H. Dickson, and J.E. Hunter

Resistance to black rot caused by the bacterium Xanthomonas campestris pv. campestris was studied in Brassica oleracea, B. campestris, and B. napus. Two accessions of B. napus, PI 199947 and PI 199949, exhibited the highest resistance so far found in cultivated Brassica spp. In B. napus, the high level of resistance was conferred by one dominant gene. In B. campestris, two Chinese cabbage accessions showed quantitative inheritance for moderate levels of resistance. Resistance was transferred to B. campestris from B. napus, but a unilateral incongruity was observed for black rot and morphology, but not for stem color or bolting. The bridge line 15 was used to transfer resistance to B. oleracea.

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Weenun Bundithya and Sherry L. Kitto

Thlaspi caerulescens (Brassicaceae), known as a Zn hyperaccumulator, is able to accumulate and tolerate Zn at high concentrations in its biomass. Cell suspension cultures of Thlaspi caerulescens J et C Presl and B. napus `Westar' have been initiated to study the effect of high Zn concentrations on growth and nutrient uptake. Preliminary studies determined the optimal conditions for subculturing and maintaining cultures. Cell suspensions grew best on Murashige and Skoog medium supplemented with B5 vitamins and 1 mg 2,4-D/liter at 0.4 g/25 ml inoculation density, and with a 2-week subculture period. In an initial experiment, cell suspensions were cultured in media containing 1.96 ppm Zn (basal) or 49 ppm Zn (25x). Media and tissue samples were collected at days 0, 4, 7, 10, and 13, and their nutrient content was analyzed by ICP-AES. Thlaspi and Brassica cell suspensions grew equally well on both media. For both species, uptake patterns of Ca, K, Mg, Mn, and P were not significantly different between the two media; however, >97% of the P was taken up within 2 weeks. Zinc concentration was reduced during the first 4 days (lag phase) in the high-Zn medium, with 27% and 41% taken up by the Thlaspi and Brassica cultures, respectively. Thlaspi took up significantly less Zn than did Brassica. By day 13, Thlaspi and Brassica tissue collected from the high-Zn medium contained 10x and 32x, respectively, more Zn when compared to tissue grown on basal medium.

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Richard H. Ozminkowski Jr. and Pablo Jourdan

Brassica napus (genome aacc), a natural allotetraploid derived from hybridization between B. oleracea L. (genome cc) and B. rapa L. (genome aa), was resynthesized by somatic and sexual hybridization. Seventy-two interspecific somatic (R0) hybrids and 27 sexual (F1) hybrids were produced from the same parent plants. R0 and F1 hybrids displayed morphology that was intermediate to the species parents, but B. rapa characteristics tended to predominate. R0 hybrids with nuclear DNA content equivalent to natural B. napus were uniform for nuclear-encoded traits, whereas allotetraploid F1 hybrids were variable for traits such as morphology, flower color, and seed production. Chloroplast restriction fragment length polymorphisms (RFLPs) showed unequal segregation in the R0 population favoring the chloroplasts of B. rapa; two of the 58 R0 hybrids tested had only the B. oleracea marker and 10 contained markers of both parents. Mitochondrial RFLPs showed a similar bias among the 56 R0 hybrids tested; only four plants showed B. oleracea markers exclusively, and the remaining plants were evenly distributed between having only B. rapa markers or having combinations from both species. In contrast, sexual hybrids displayed only maternal organelle markers.

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Richard H. Ozminkowski Jr. and Pablo Jourdan

Brassica napus (genome aacc), a natural allotetraploid derived from hybridization between B. oleracea L. (genome cc) and B. rapa L. (genome aa), was synthesized by sexual and somatic interspecific hybridizations from the same parent plants to compare the two methods of combining genomes and assess the genetic consequences of bypassing the gametophytic phase before hybrid formation. Highly heterozygous species parents were first produced by intraspecific hybridization between two subspecies each of B. oleracea and B. rapa. Leaf tissue from young plants of both parental species served as a source of protoplasts for fusion; the same plants were later used for crosses. Seventy-two somatic hybrids were produced using a polyethylene glycol-mediated fusion protocol and 27 sexual hybrids were obtained by embryo rescue. Somatic hybrids were produced between one B. oleracea and two sibling B. rapa plants. Sexual hybrids were successfully produced with only one of the two B. rapa siblings. Hybrids were identified by morphology, isozyme patterns, and total DNA content. Although fertile allotetraploid somatic hybrids were obtained within 7 months after seeding parent lines, >1 year was required to produce fertile sexual hybrids.

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W. Bundithya and S.L. Kitto

Thlaspi caerulescens (Brassicaceae), known as a Zn hyper accumulator, is able to accumulate and tolerate Zn, Ni, Cu, and Cd at high concentrations in its biomass. We are examining the feasibility of using cell suspensions of T. caerulescens and B. napus to study the effect of selected heavy metals on growth and nutrient uptake. Callus was initiated by culturing seedlings on basal medium containing MS salts supplemented with MS or B5 vitamins, 1, 2, 5, or 10 mg 2,4-D/liter, and 0.7% Phytagar. Cell suspensions were initiated by transferring calli to liquid basal medium containing MS or B5 vitamins, and 1 or 2 mg 2,4-D/liter, and were incubated on a gyratory shaker at 120 rpm. Growth of suspensions inoculated at 0.2, 0.4, or 0.6 g/25 ml was monitored for 13 days. Optimal conditions required to initiate and maintain suspension cultures of T. caerulescens and B. napus include MS medium supplemented with B5 vitamins and 1 mg 2,4-D/liter, an inoculation density of 0.4 g/25 ml, and a 2-week subculture schedule.

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Kimberly A. Cochran and Craig S. Rothrock

microplot to infest the top 15 cm of soil. Brassica treatments. Brassica green manure treatments consisted of biomass of Indian mustard ( B. juncea ) ‘Fumus’ and ‘Bionute’, and canola ( B. napus ) ‘Jetton’. Rates of 700, 1400, and 4200 g·m −2 aboveground

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Dean A. Kopsell, J. Scott McElroy, Carl E. Sams, and David E. Kopsell

be amphidiploids and have haploid numbers of 17 ( B. carinata ), 18 ( B. juncea ), and 19 ( B. napus ). The genetic arrangement of the diploid and amphidiploid Brassica species is credited to the U (1935) . The diagram is referred to as the