2003 & 2004 Publications

Stoichiometric and kinetic values of phenolics against DPPH (2,2-diphenyl-1-picrylhydrazyl) were determined for Andean purple corn (Zea mays L. ) and red sweetpotato (Ipomoea batatas). Both crops had higher antioxidant capacity and antiradical kinetics than blueberries and higher or similar anthocyanin and phenolic contents. The second-order rate constant (k2) was 1. 56, 1. 12, 0. 57, and 0. 26 (mg antiradical/mL)-1 s-1 for red sweetpotato, Trolox, purple corn, and blueberry, respectively. On the molar basis of active hydroxyl groups, k2¢ showed the same order as for k2. Corn cob and sweetpotato endodermis contributed the most in phenolic compounds and antioxidant capacity. Both crops studied can be considered as excellent novel sources of natural antioxidants for the functional food and dietary supplement markets.

This paper proposes a concept based on applying postharvest abiotic stresses to enhance the nutraceutical content of fresh fruits and vegetables. We hypothesize that select abiotic stress treatments, such as wounding, phytohormones, temperature, ultraviolet light, altered gas composition, heat shock, and water stress, among others, will affect the secondary metabolism of fresh produce and increase the synthesis of phytochemicals with nutraceutical activity or reduce the synthesis of undesirable compounds. Controlled stresses may be used as tools by the fresh produce industry to enhance the health benefit properties of fresh-cut or whole fresh produce and by the food processing and dietary supplement industries to obtain healthier processed products or enhance extractable nutraceutical yields.

An evaluation of interactive video conferencing and Web-assisted instruction to deliver a multidisciplinary course entitled Phytochemicals in Fruits and Vegetables to Improve Human Health was conducted during the spring semesters of 1999 and 2001. This course was taught by 20 instructions from 11 institutions to 49 students during spring 2001, which was an increase of 53% over spring 1999. Weekly 3-h lectures were delivered by the Trans-Texas Videoconference Network integrated with PowerPointÒor HTML slides available on the course Web site (http://phytochemicals. tamu. edu). Qualitative and quantitative data were collected through formative and summative methods. Participants expressed their satisfaction with course format and the need for technical support for interactive videoconferencing.

Several abiotic stresses, including ethylene, methyl jasmonate, temperature, light, and sounding, were tested for their ability to induce accumulation of phenolic compounds and antioxidant capacity in purple-flesh potatoes (cv. All Blue). Results indicated that temperature, ethylene, methyl jasmonate, and light treatments did not significantly affect the accumulation of phenolic compounds compared to control samples. Only tubers with low initial anthocyanin levels treated with methyl jasmonate showed ~60% anthocyanin accumulation. Wounding induced the accumulation of phenolics compounds and an increase of PAL-activity in sliced tissue compared to the control. Total phenolics increased ~60%with a parallel 85% increase in antioxidant capacity. These results show that selection of appropriate abiotic stresses can enhance the nutritional and functional value of potatoes

A mechanistic model based on synthesis and inactivation of enzymes, associated to the respiration pathway, was proposed to describe wound-induced respiration of fresh-cut produce. Carrots (Daucus carota L. ) were cut into slices, sticks, a combination of both, and shreds to obtain different wounding intensities, defined by the ratio of new area created to tissue weight (A/W). Respiration rates obtained at 10°C, showed a typical increase, a maximum peak, and a decrease until reaching steady state. A 2-phase exponential decay equation described the process, with the obtained key parameters relating to A/W. This model can be used to understand wound-induced respiration and the possible implications in produce quality changes and packaging design

The ‘Sunshine’ cultivar of vetiver (Vetiveria zizanioides (L. ) Nash, =Chrysopogon zizanioides (L. ) Roberty) was subjected to meristem tissue culture in order to produce plants that were bacteria and fungi-free. Tissue cultured (‘‘cleansed’’ or phytosanitary) vetiver was grown for five months in pots of sterilized soil, and the oil compared to non-cleansed (normal) vetiver plants grown in the same conditions except using pots of unsterilized soil. The steam distilled (24 h) oil of the roots from tissue cultured (cleansed) vetiver yielded 0. 02% clear oil compared to a 0. 35% yield of light yellow oil for the normal vetiver plants, a 17-fold smaller yield. GC/MS analyses of the oils revealed that the non-cleansed (normal) vetiver had the typical vetiver oil profile, whereas the tissue cultured (cleansed) vetiver produced large amounts of C19–C29 alkanes plus several alkanols along with typical vetiver oil compounds, but lacked presumed fungal metabolites such as b-funebrene, prezizaene, a-amorphene, and b-vetispirene. An unidentified biotic factor (apparently bacteria or fungi) appears to enhance the oil production in normal vetiver by both increasing yield and by the generation of signature oil compounds. These preliminary results of endogenous microbial transformations of plant chemistry may have broader physiological implications, especially among monocotyledons (including cereals).

Water conservation practices are critical for production and quality of watermelon (Citrullus lanatus (Thunb. ) Matsum & Nakai) in southern regions of the USA. The objective of this experiment was to determine the effect of deficit irrigation and environment on lycopene content, total soluble solids, firmness, and yield of diploid and triploid watermelon. Irrigation rates were 1. 0 evapotranspiratiion (ET), 0. 75 ET, and 0. 5 ET, which were calculated based on climatic parameters aplied to the Penman-Monteith equiation. Diploid cultivars were 'Summer Flavor 710' and 'Summer Flavor 800', and triploidcultivars were 'Summer Sweet 5244' and 'Super Seedless 7187'. To investigate if there was a consistent response in cultivars across diverse environments, three studies were conducted in remote Texas locations: Uvalde in the Wintergarden, Weslaco in the Rio Grande Valley, and Lubbock in the High Plains. To isolate the environmental effects due to weather and soil type, all experiments used similar cultural strategics (plant spacing, subsurface drip irrigation, black plastic mulch, and containerized traplsants), expcet for transplanting and harvesting dates. Deficit irrigation reducted total marketable yield by 36% at Uvalde, 30% at Lubbock, and 15% in Weslco, increasing the yield of small fruits (<5 kg). Location and irrigation rates had major influences on yield of diploid and triploid watermelon. Soluble solids content increased with deficit irrigation at 0. 5 ET rate in triploids, but not in diploids. Flesh firmness also increased in triploids compared to diploids. Fruit lycopene content increased with maturity (7 and 22 d after ripening) at ll irrigation rates and cultivars. This work across three diverse Texas locations confirms that deficit irrigation directly reduced yield, but does not reduce lycopene development and fruit quality of triploid watermelon.

'TexPrince' is being released by Texas A&M University to provide a medium chilling, commercially acceptable peach that ripens after 'Texstar' and and with or a few days after 'Juneprince' and 'TexRoyal'. This large, freestone, attractive, yellow-flesh peach ripens early June in the medium chill zones of the United States. 'TexPrince' is a replacement for 'Juneprince' where 'Juneprince' fruit inconsistently due to problems with insufficient chilling.

The Habanero pepper, a distinct cultigen of Capsicum chinense, has become increasingly popular in American markets due to its unique flavor and aroma. It is extremely pungent compared to other commonly cultivated hot peppers. This attribute restricts its culinary uses. The objective of the Habanera pepper improvement project was to breed for important flavor compounds in the absence of genes involved in capsaicin synthesis. Intensive selection in large breeding populations was carried out to identify individual plants producing fruit with good aroma and flavor and low capsaicin concentrations. An initial cross was made between a non-pungent selection of C. chinense out of PI543188 and a highly pungent, typical Habaneno pepper from Yucatan. A series of sib-selections following a single backcross of a non-pungent F2 individual to the Habanera line was carried out in field and greenhouse plantings at Weslaco. Six subsequent generations of inbreeding resulted in a highly uniform, novel variety – TAM Mild Habanero (TMH). The fruit of TMH is very similar in size and shape to the recurrent parent. Color is yellow-orange as opposed to the deep orange of the Yucatan Habanero (YH), but aroma and flavor are extremely similar. In contrast, total capsaicin concentration of TMH fruit at Weslaco averaged 154 mg·g-1 compared to 12, 704 mg·g-1 in YH. Fruit trails conducted in south Texas showed that TMH consistently matured about 10 days earlier, had significantly higher levels of beta-carotene (7. 6 mg·g-1 compared to <5 mg·g-1 in YH) and out-yield YH by 25%. These traits make TMH an ideal cultivar for Fall production in south Texas.

Embryogenic calluses of Rosa hybrida cultivar Tineke were transformed with Agrobacterium tumefaciens strain LBA4404 containing the binary vector pBIN m-gfp5-ER into which the virE/virG genes had been inserted. Visualization of GFP-expressing cells enabled visual selection of dividing, embryogenic cell clusters that were transgenic. When the Agrobacterium strain with the bifunctional fusion marker containing additional virE/virG genes was used, the number of green fluorescent calluses increased. Transformation of the GFP-expressing rose plants was confirmed by Southern blot analysis.

A new locus conditioning a pink trait in onions was identified. Unusual pink onions were found in haploid populations induced from an F1 hybrid between yellow and dark red parents and in F3 populations originating from the same cross. Segregation ratios of red to pink in F2, backcross, and F3 populations indicated that this pink trait is determined by a single recessive locus. RT-PCR was carried out to look for any differential expression of anthocyanin synthesis genes between dark red and pink F3 lines. The transcript level of anthocyanidin synthase (ANS) was significantly reduced in the pink line. To determine whether this reduced transcription is caused by other regulatory factors or by mutations in the ANS gene itself, ANS gene sequences from both dark red and pink F3 lines were compared to detect any polymorphisms. Polymorphisms were identified, and subsequently utilized as molecular markers for the selection of ANS alleles. Absolute co-segregation of the pink allele and the ANS allele from the pink line was observed in parents, F1 and F3 populations. These results indicate that reduced transcription of the ANS gene caused by mutations in a cis -acting element is likely to result in the pink trait in onions

We have identified a T-DNA insertion mutation of Arabidopsis (ecotype C24), named sto1 (salt tolerant), that results in enhanced germination on both ionic (NaCl) and nonionic (sorbito) hyperosmotic media, sto1 plants were more tolerant in vitro than wild type to Na+ and K+ both for germination and subsequent growth but were hypersensitive Li+. Postgermination growth of the sto1 plants on sorbitol was not improved. Analysis of the amino acid sequence revealed that STO1 encodes a 9-cis-epoxicarotenoid dioxygenase 9similar to 9-cis-epoxicarotenoid dioxygenase GB:AAF26356 [Phaseolus vulgaris] and to NCTED3 GB:AB020817 [Arabidopsis]), a key enzyme in the abscisic acid (ABA) biosynthetic pathway. STO1 transcript abundance with substantially reduced in mutant plants. Mutant sto1 plants were unable to accumulate ABA following native gene from the wild-type genome or supplementation of ABA to the growth medium restored the wild-type phenotype. Improved growth of sto1 mutant plants on NaCl, but not sorbitol, medium was associated with a reduction in both NaCl-induced expression of the ICK1 gene and ethylene accumulation. Osmotic adjustment of sto1 plants was substantially reduced compared to wild-type plants under conditions where sto1 plants grew faster. The sto1 mutation has revealed that reduced ABA can lead to more rapid growth during hyperionic stress by a signal pathway that apparently is at least partially independent of signals that mediate nonionic osmotic responses

Anthocyanin, one of the flavonoids, is a primary determinant of red color in onions. Inheritance studies indicate that a single gene determines the color difference between yellow and red onions. In order to establish which gene might be responsible for this color difference, full-length cDNAs of five structural genes: chalcone synthase _CHS_, flavanone 3-hydroxylase _F3H_, dihydroflavonol 4-reductase _DFR_, anthocyanidin synthase _ANS_, and flavonol synthase _FLS_ were cloned using degenerate PCR and RACE _Rapid Amplification of cDNA Ends_. RT-PCR was carried out for these five genes to examine differential expression between yellow and red colored bulbs. Accumulation of the DFR gene transcript only occurred in red onions. In F3 populations which originated from the cross between yellow and red parents, DFR transcript was detected only in red F3 lines. To design molecular markers for selection of yellow and red DFR alleles, the DFR gene was sequenced from genomic DNA isolated from both types of onions. The genomic DNA sequence revealed the DFR gene consists of six exons and five introns. A PCR-RFLP marker was designed based on 2% polymorphic nucleotide sequence of the DFR gene between yellow and red onions. The co-segregation of markers and red color were observed in F2 segregating populations, supporting the conclusion that color difference in red and yellow onions is likely to be due to the lack of an active DFR gene

Many vegetable production regions in the southwestern US are strictly regulated on water use. In addition, demand for high quality and nutritious vegetables has increased. This study was performed to explore the effects of deficit irrigation on yield, fruit quality, lycopene content, Vitamin C and sugar composition of red-fleshed diploid and triploid watermelon (Citrullus lanatus (Thumb) Matsum & Nakai) cultivars. Irrigation treatments were 1. 0, 0. 75 and 0. 5 evapotranspiration (ET) rates. Cultivars used were 'Summer Flavor 710', 'RWM 8036', 'Allsweet', 'Sugarlee', and 'SWD 7302' (diploids) and 'Summer Sweet 5244', SWT 8706', and Sugar Time', and 'Tri X Sunrise' (triploids). Total water applied through a subsurface drip system was 395, 298, and 173 mm for the 1. 0, 0. 75 and 0. 50 ET rates, respectively. Total yields were highest at 1. 0 ET (53. 9t ha-1). Triploids had a 34% higher total yield and fewer culls (2%) compared with diploid cultivars (25%). Highest yields were obtained for 'Tri X Sunrise', 'SWT 8706', and 'SWD 7302'. 'Sugar Time' had the highest soluble solids content (13. 4%) of all cultivars (ranage 9. 7-11. 0%). Triploid cultivars had firmer flesh compared to diploids (12. 0 v 9. 9. N). Lycopene content increased slightly with lmaturity (55. 8 to 60. 2 mg g-1 fw), and was significantly higher at 0. 75 ET and 1. 0 ET. Lycopene content avaraged over all treatments was 60-66 mg g-1 fw for triploids and 45 5o 80 mg g-1 fw for diploids fruits. Overall, lycopene and vitamin C content did not decrease withdeficit irrigation at 0. 75 ET. There was genetic variability for lycopene, vitamin C, and sugar composition, primarily fructose, among diploids and triloids.

A 2-year field study was conducted to determine growth, yield and bulb quality in response to stand establishment, irrigation methods, and cultivars. Containerized transplants or direct seeding were irrigated with subsurface drip (SDI) placed at 5- or 15-cm depth at water application rates of 1. 0 and 0. 5 ET. Two yellow cvs, 'TG 1015Y' and the newly developed 'Legend', and one white cv. 'Texas Early White' (TEW) were used. The initial plant population for direct seeding and transplants was 387 500 and 182 400 pl/ha, respectively. Root and shoot growth, bulb pungency pyruvic acid level), soluble solids (brix %), and the flavonoid quercetin were monitored. At harvest, bulbs were sorted by commercial size class. By mid development, transplants larger bulbs with more number of leaves and roots than direct-seeded plants. After the onset of bulbing, differences in bulb quality were measured mainly in response to stand establishment and cultivars, and minimal differences due to irrigation. At harvest, pungency was lower and brix was higher for transplants than direct seeding in both years. Pungency level ranges were 2. 8 - 3. 9 mmoles/ml (Legend), 3. 4-4. 1 (TG1015Y) and 5. 3 - 5. 7 (TEW). Transplants had 37% (200 season) and 42% (2001 season) higher total yields than direct seeding. The yield increase was greatest for the cv. "Legend'. Transplants also had large bulb sizes and higher water use efficiency than direct-seeded plants. Containerized transplants are more costly, but can provide an immediate and complete field establishment. This work demonstrated that transplanting with efficient subsurface drip systems and superior cultivars can enhance onion flavor attributes and produce uniform high-value bulb sizes, thus increasing profit potential.

Vitamin C, also known as ascorbic acid, is an important fruit quality trait in melon (Cucmis melo L. ). The purpose of this study was to identify randomly amplified polymorphic DNA (RAPD) markers associated with quantitative trait loci (QTL) for ascorbic acid content using bulked segregant analysis in an F2 population from the melon cross of ‘TAM Dulce’ (high ascorbic acid) ´ TGR1551 (low ascorbic acid). A continuous distribution for ascorbic acid content was observed in the F2 population indication quantitative inheritance for the trait. Ascorbic acid was positively correlated with sucrose % composition (r=0. 23) and negatively correlated with glucose % composition (r=-0. 39). A total of 500 random primers were used to simultaneously screen between low and high ascorbic acid bulks, and between the parents ‘TAM Dulce’ and TGR1551. Nine RAPD markers, four amplified from ‘TAM Dulce’ and five amplified from TGR 1551, were significantly associated with QTL for ascorbic acid content. Three and two QTL affecting ascorbic acid content accounted for 14% and 12% of the phenotypic variation, respectively. Of the nine markers identified, four were consistently associated with mature a melon fruit sweetness. Marker oAW06. 600 obtained from TGR1551 was associated with sucrose, sucrose % composition, and glucose % composition as well as absorbic acid. These RAPD markers associated with ascorbic acid content could be applied in selection for enhanced ascorbic acid levels in melon

We demonstrate that carrots expressing the Arabidopsis H_/Ca2_ transporter CAX1 _Cation Exchanger 1_ contained up to 50% more calcium _Ca_ than plants transformed with control vectors. The CAX1-expressing carrots were fertile, and robust plant growth was seen in the majority of the transgenic plants. CAX1-expressing carrots were crossed to a commercial carrot variety to confirm that the increased Ca accumulation was mediated by CAX1-expression, and the increased Ca content was clearly correlated with the transgene. This study suggests that modulation of ion transporters could be an important means of increasing the Ca content of agriculturally important crops. To our knowledge, this study represents the first attempts to use biotechnology to increase the Ca content of an agriculturally important crop.

A rapid and efficient method for the extraction and isolation of naringin and narirutin from citrus molasses is described. Naringin and narinutin are structurally similar glucosides present in citrus molasses. The common problem in purification of plant extracts is the large number of constituents present that are similar in nature. A flash chromatographic technique has been developed for the separation of the main flavonoid glucosides present in citrus molasses. This method is a rapid, inexpensive, technique and provides compounds with high purity that can be used for biological activity studies. The separation and yield of narirutin and naringin obtained by this method is reproducible.

We have identified a T-DNA insertation mutation of Arabidopsis (ecotype C24), named sto1 (salt tolerant), that results in enhanced germination on both ionic (NaCl) and nonionic (sorbitol hyperemic media, sto1 plants were more tolerant in vitro than wild type Na+ and K+ both for germination and subsequent growth but were hypersensitive to Li+. Postgermination growth of the sto1 plants on sorbitol was not improved. Analysis of the amino acid sequence revealed that STO1 encodes a 9-cis-epoxicarotenoid dioxygenase (similar to 9-cis-epoxicarotenoid dioxygenase GB:AA426356[Planseolus vularis] and to NCED3 GB:AB020817 [Arabidopsis]), a key enzyme in the abscisic and J(ABA) biosynthetic pathway. STO1 transcript abundance was substantially reduced in mutant plants. Mutant sto1 plants were unable to accumulate ABA following a hypersmotic stress, although their basal ABA level was only moderately altered. Either complementation of the Sto1 with the native gene from the wild-type genome or supplementation of ABA to the growth medium restored the wild-type phenotype. Improved growth of sto1 mutant plants on NaCl, but not sorbitol, medium was associated with a reduction in both NaCl-induced expression of the ICK1 gene and ethylene accumulation. Osmotic adjustment of sto1 plants was substantially reduced ABA can lead to more rapid growth during hypersonic stress by a signal pathway that apparently is at least partially independent of signals that mediate nonionic Osmotic responses.

(Sorghum bicolor) activates jasmonic acid (JA)- and salicylic acid (SA)-regulated genes, as well as genes outside known wounding and SA signaling pathways. A collection of 672 cDNAs was obtained by differential subtraction with cDNAs prepared from sorghum seedlings infested by greenbug aphids and those from uninfested seedlings. Subsequent expression profiling using DNA microarray and northern-blot analyses identified 82 transcript types from this collection responsive to greenbug feeding, methyl jasmonate (MeJA), or SA application. DNA sequencing analyses indicated that these encoded proteins functioning in direct defense, defense signaling, oxidative burst, secondary metabolism, abiotic stress, cell maintenance, and photosynthesis, as well as proteins of unknown function. In response to insect feeding, sorghum increased transcript abundance of numerous defense genes, with some SA-dependent pathogenesis-related genes responding to greenbug more strongly than to SA. In contrast, only weak induction of MeJA-regulated defense genes was observed after greenbug treatment. However, infestation tests confirmed that JA-regulated pathways were effective in plant defense against greenbugs. Activation of certain transcripts exclusively by greenbug infestation was observed, and may represent unique signal transduction events independent of JA and SA-regulated pathways. Results indicate that plants coordinately regulate defense gene expression when attacked by phloem-feeding aphids, but also suggest that aphids are able to avoid triggering activation of some otherwise potentially effective plant defensive machinery, possibly through their particular mode of feeding.