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Zongrang Liu, Ralph Scorza, Jean-Michel Hily, Simon W. Scott, and Delano James

-dependent RNA polymerase; CaMV35S = 35S promoter of cauliflower mosaic virus; T = terminator of nopaline synthase gene; RCA intron = first intron of the arabidopsis rubisco activase ( RCA ) gene; APLPV = american plum line pattern virus; PDV = prune dwarf virus

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Denise V. Duclos* and Thomas Björkman

Cauliflower (Brassica oleracea var. italica) and Broccoli (Brassica oleracea var. botrytis) differ mainly in the stage of reproductive arrest. Cauliflower curd is an inflorescence meristem, while broccoli arrests just before anthesis. Arabidopsis studies led to the hypothesis that a mutant BoCAL allele arrested cauliflower earlier. Later, a mutant in BoAP1 was found to have similar effects. These partially redundant genes, and several identified since, are present in multiple copies in B. oleracea. Understanding their role in the arrest requires quantification of transcript abundance analysis by real-time PCR. Designing selective PCR primers is a critical first step in the process. Designs were based on alignment among the genes of interest (MADS-box genes BoCAL, BoAP1, FUL, and the non MADS-box genes LFY and TFL1) and their paralogs. The high sequence similarity (some over 95%) makes the target transcripts difficult to distinguish. Therefore, primers were designed mostly for targets in the 3'UTR region in order to gain specificity. Short amplicons, 68bp to 200bp, were required for the high PCR efficiency required to quantify these low-abundance transcripts. Primers were evaluated by conventional RT-PCR and real-time PCR. By altering temperature, Total RNA was isolated from plants that were arrested at three developmental stages, inflorescence meristem (cauliflower), floral meristem (intermediate), and floral bud (broccoli) by varying temperature. RT-PCR products were single bands of the expected size, despite the high homology between genes under study. Real-time melting curve analysis (fluorescence derivative vs. melting temperature) corroborated the presence of a single amplicon. The identity of products was confirmed by sequencing and restriction enzyme digestion.

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J. V. Davis, D. R. Earhart, A. T. Leonard, and V. A. Haby

The potential for east Texas to produce Brassica that could compete favorably with the import market exists. This study was conducted to establish optimum nitrogen and boron rates for 4 Brassica spp. grown on highly leachable east Texas soil, a Bowie series (fine-loamy, siliceous, thermic, Plinthic Paleudult). Broccoli (Brassica oleracea L. Italica, var. Green Comet), cauliflower (Brassica oleracea L. Botrytis var. White Contessa), Chinese cabbage (Brassica rapa L. Pekinensis var. Monument), and Chinese mustard (Brassica rapa L. Chinensis var. What-A-Joy) were field grown using 5 rates of N (0, 50, 100, 150, and 200 kg·ha-1) interacted with 3 rates of B (0, 1.25 and 2.5 kg·ha-1) in a complete randomized design with 3 reps. Harvested broccoli heads increased average head weight (HW), average head size (HS), and total yield (Y) for each increase of N. Cauliflower HW, HS, and Y increased up to 150 kg N ha-1. B supplementation did not statistically affect HW, HS, and Y of broccoli or cauliflower. Chinese cabbage Y increased up to 150 kg N ha-1 and produced less Y at 200 kg N ha-1 than at 50 kg N ha-1. Chinese mustard Y increased 50% for the 50 (kg·ha-1) N over no added N with additional N producing statistically equal Y. B at 1.25 (kg·ha-1) significantly increased cabbage Y, but had no effect on mustard Y.

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Warley M. Nascimento

The growing of transplants in plug cell trays is the primary method of producing brassica transplants in many countries. Seed quality is an important aspect to achieve success in transplant production. Seed size may affect seed performance, seedling growth and development of brassica transplants. Seeds of cauliflower (`Vitoria de vero') and cabbage (`Unio') from Embrapa Vegetables were used in this study. During seed conditioning, seeds were classified using round screens generating three (>1.5, 1.5-2.0, and 2.0-2.5 mm) and four (>1.5, 1.5-2.0, 2.0-2.5, and < 2.5 mm) seed size categories, for cauliflower and cabbage, respectively. The original seed lot was used as control. Seed weight increased with seed size. Seed germination (laboratory) and seedling emergence (greenhouse) were not affected by seed size. In both species, root and shoot weight, and leaf area, measured 30 days after seeding, in greenhouse conditions, increased with seed size. Also, transplants from larger seed size resulted in a significantly higher root weight, shoot weight, and leaf area relative to the original (control) seeds. The results indicate that, overall, an adequate seed conditioning improve brassica transplant quality.

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C.D. Stanley, A.A. Csizinszky, G.A. Clark, and J.W. Prevatt

Combinations ofvarious vegetable crop species grown in multiple-cropping sequences using microirrigation on a sandy soil were evaluated for production potential and changes in normal cultural management An initial fall-season fresh-market tomato crop was followed immediately by a winter-season crucifer crop (cauliflower, broccoli, or cabbage), which was followed by a spring-season cucurbit crop (cucumber, zucchini squash, or muskmelon). Studies were conducted over a 3-year period in southwestem Florida. Results showed that when cropping sequences were compared on a basis of a derived relative value index (RVI), the sequence of tomato-cauliflower-zucchini squash significantly outperformed other sequences. Several management concerns particular to the production system (crop residue removal and interference, plastic mulch deterioration and damage, and weed control) were identified and discussed. The potential savings when cropping sequences are compared to individual crop production resulted in net savings (dollar savings less additional production costs) that ranged from $565 to $1212/acre ($1396 to $2993/ha) and $614 to $1316/acre ($1516 to $3251/ha) for the 1986-87 and 1988-89 seasons, respectively.

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G. Li, A. Riaz, S. Goyal, S. Abel, and C.F. Quiros

Inheritance of three major genes involved in synthesis of aliphatic glucosinolates (GSL) was followed in segregating populations of Brassica oleracea L. generated from three crosses: broccoli × cauliflower, collard × broccoli, and collard × cauliflower. Two of these genes, GSL-PRO and GSL-ELONG, regulate sidechain length. The action of the former results in three-carbon GSL, whereas action of the latter produces four-carbon GSL. We determined that these two genes act and segregate independently from each other in B. oleracea. The double recessive genotype produces only trace amounts of aliphatic GSL. The third gene, GSL-ALK controls sidechain desaturation and, as it has been observed in Arabidopsis thaliana (L.) Heynh., we found that this gene cosegregates with a fourth gene, GSL-OH, that is responsible for sidechain hydroxylation. Elucidation of the inheritance of major genes controlling biosynthesis of GSL will allow for manipulation of these genes and facilitate development of lines with specific GSL profiles. This capability will be important for improvement of Brassica breeding lines with high content of desirable GSL, like glucoraphanin, a demonstrated precursor of anticarcinogenic compounds. Additionally, this work is the first step towards cloning the major genes of the aliphatic GSL pathway, and to use these clones in transformation strategies for further crop enhancement.

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James Nienhuis, Mary K. Slocum, Dawn A. DeVos, and Roger Muren

Genetic similarities were calculated among 89 Brassica oleracea L. genotypes, which included 62 broccolis (var. italica), 16 cauliflowers (var. botrytis), and 11 cabbages (var. capitata). These entries represented a wide range of commercially available germplasm, including open-pollinated cultivars, commercial hybrids, the inbred parents of several hybrid cultivars, and 27 entries that were provided as unknowns. Sixteen random genomic clones were used as probes in Southern hybridizations to detect restriction fragment length polymorphism (RFLP). From each of the random probes, an average of four polymorphic bands were classified as to their presence or absence for each genotype. The genetic similarity between ail pairs of genotypes was calculated. A multidimensional scaling (MDS) plot indicated that the broccoli, cauliflower, and cabbage groups were clustered with very little overlap. Within groups, genetic similarity corresponded to relationships based on available pedigree information. Comparison of banding patterns between hypothetical and actual hybrids was used to correctly identify the parents of several parent-hybrid combinations. The RFLP pattern of a hybrid and one of the parents (female) were used to predict the genotype and identity of the other parent (male).

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Steven C. Adams

Seed vigor has a very subtle effect on the productivity of greenhouses producing vegetable transplants, celery, cauliflower, lettuce, etc. and on todays highly mechanized automatic or semi-automatic transplanting operations. As greenhouse production technology moves from traditional bare root to plug/tray growing systems and as automatic and semi-automatic transplanting operations increase in number, the impact of poor seed vigor is realized.

Measures to mitigate the impact of poor seed vigor in the nursery are: Seed density grading; increased growing cycle in the nursery, hand culling or replanting. Measures to mitigate the impact of poor seed vigor in automatic transplanting operations: increase the number of people following the planter to replace poor vigor plants; use hand fed transplanters.

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Gregory S. Rogers and John J. Frett

Nicotiana transformed with the isopentenyl transferase (ipt) gene from Agrobacterium tumefaciens was fixed in 1% gluterdehyde and 4% formaldehyde for 1 h. Grids were treated with polygonal anti-IpTase antibody raised in rabbits and visualized with 10 nm protein-A-labeled colloidal gold. Initial localization was performed on Nicotiana transformed with the ipt gene under the control of the 35S promoter from cauliflower mosaic virus. Colloidal gold was found throughout the cell, including the cell wall, vacuole, and rough ER. Cell wall and vacuole labeling appears to be due to nonspecific binding and is greatly reduced by a BSA block. Colloidal gold label on rough ER provides preliminary evidence that translation occurs here rather than on free polysomes. General reaction throughout the cell indicates cytoplasmic activity of the enzyme. Future research will attempt to localize IPTase in wild-type Nicotiana and in plants transformed with the ipt gene under the control of the hsp 70 heat shock promoter.

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Brenda A. del Rosario, Robert L. Shewfelt, and Albert C. Purvis

Evidence is accumulating that mitochondria possess defense mechanisms which effectively protect component membranes from the attack by active oxygen species which are produced continuously within the organelle. This study compared the stability of microsomal (from bell pepper fruit pericarp and cauliflower florets) and mitochondrial (from bell pepper fruit pericarp) membranes against peroxidative challenge systems (cumene hydroperoxide and iron-ascorbate). Protein concentration, (i-tocopherol levels, and total lipids were observed to decrease for both membranes when challenged. The onset of peroxidation was observed to be earlier and at higher levels in microsomes than in mitochondria. These results demonstrate the increased stability of mitochondrial membrane fractions to peroxidative challenge and suggest that the level of antioxidants and not fatty acid composition is the critical factor in resistance to oxidative stress in plant mitochondria.