Rust disease, incited by the fungus Uromyces vignae, adversely affects production and quality of asparagus bean and other types of cowpea in many parts of the world. Genetic resistance to the rust pathogen has been identified in a few accessions, but it is difficult to efficiently transfer the resistance to a broad range of asparagus bean cultivars using traditional breeding approaches. We determined that rust resistance was controlled by a single dominant gene designated Rr1 in the cross of a highly resistant cultivar ZN016 and highly susceptible cultivar Zhijiang 282. Bulked segregant analysis was applied to an F2 population derived from these parents, and an AFLP marker (E-AAG/M-CTG), 150 bp in size, was detected in the resistant bulk. The AFLP fragment was then converted to a SCAR marker, named ABRSAAG/CTG98, and the genetic distance between the marker and the Rr1 gene was estimated to be 5.4 cM. This SCAR marker could be used effectively for MAS of Rr1 in breeding programs to develop rust-resistant asparagus bean cultivars and potentially more widely to breed rust-resistant cultivars of other types of cowpea.
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Guojing Li, Yonghua Liu, Jeffrey D. Ehlers, Zhujun Zhu, Xiaohua Wu, Baogeng Wang and Zhongfu Lu
Ana Morales-Sillero, R. Jiménez, J.E. Fernández, A. Troncoso and G. Beltrán
We report the results of a study carried out in a ‘Manzanilla de Sevilla’ olive orchard near Seville, Spain, where the influence of different fertigation treatments on oil chemical composition was considered. Four treatments were established: control (no fertilizer) and T200, T400, and T600 in which each tree, respectively, received 200, 400, or 600 g N per irrigation season of a 4N–1P–3K complex fertilizer applied daily from 1999 to 2003. Results shown here correspond to the last 2 years of the experiment, 2002 and 2003. Fruits were sampled at the beginning of ripeness at the “green” stage. Fruit water content increased with the amount of fertilizer, probably because of the increase of potassium in the pulp. Oil content was unaffected by the treatments, but oil yield increased with the fertilizer dose in 2003 as a result of the number of fruits per tree. Polyphenol content, which is related to antioxidant oil capacity, K225 (bitterness), and oxidative stability were lower in the oils made from trees receiving greater fertilizer doses. The monounsaturated fatty acid content, in particular oleic acid, decreased with increasing amounts of applied fertilizers, whereas polyunsaturated fatty acids, in particular linoleic acid, increased with it.
Paolo Benincasa, Francesco Tei and Adolfo Rosati
Wild asparagus (Asparagus acutifolius L.) is becoming an interesting niche crop for marginal areas in Europe, but little information is available regarding cultivation techniques, which differ from those of cultivated asparagus (A. officinalis). We experimented with the cultivation of wild asparagus using two different ecotypes planted at two plant densities. We measured yield and number of spears per hectare and spear quality (average weight, portion of edible part, diameter, and dry matter content). There were no significant effects of either genotype or density on the spear yield and number per hectare. No differences among treatments were found on spear quality parameters. Spear yield and number per plant decreased proportionally with increasing plant density, resulting in constant spear yield and number per hectare. Harvest efficiency was ≈1.2 kg of spears per hour of labor when the prickly evergreen vegetation was not removed before harvest and ≈3 kg per hour when the vegetation was cut and removed. In the latter case, harvest would cost approximately one-third of the gross income of the crop suggesting that the crop could easily be economically viable. Further studies are needed to assess whether cutting the vegetation affects plant vigor and longevity in the following years, but also to further study suitable techniques for crop cultivation, especially weed control.
Emad Bsoul, Rolston St. Hilaire and Dawn M. VanLeeuwen
Although bigtooth maple (Acer grandidentatum Nutt.) is an ornamental plant that might thrive in managed landscapes in arid and semiarid regions, little information on the drought tolerance of bigtooth maples appears to be available. We studied water relations, plant development, and carbon isotope composition of bigtooth maples indigenous to New Mexico, Texas, and Utah that were field-grown in New Mexico using a pot-in-pot nursery production system. Plants were maintained as well-irrigated controls or irrigated after the weight of pots decreased by 35% due to evapotranspiration. Bigtooth maples subjected to drought had more negative predawn leaf water potentials (−0.76 MPa) than the plants in the control treatment (−0.64 MPa). Drought did not affect midday leaf water potential of seed sources. Trees native to the Lost Maples State Natural Area in Vanderpool, TX (designated LMP5), had the greatest leaf area (1236 cm2) among plants from all sources, while those native to Logan Canyon in Cache County, UT (designated UW2), had among the smallest leaf area (216 cm2). Leaf area ratio (LAR) was highest in plants from LMP5 (24.23 cm2·g−1), which suggests that they have potential for more carbon assimilation than the other plants tested. Plants from LMP5 had the highest leaf area/xylem diameter ratio (135 cm−2·mm−1). This ratio was 5.8 times higher than that of UW2, which had among the lowest leaf area/xylem diameter ratios. The high leaf area/xylem diameter ratio of LMP5 plants relative to UW2 plants indicates that LMP5 plants had a larger surface area of tissues that transpire relative to those that transport water. Treatment did not affect stomatal conductance (g S) or transpiration, but g S and transpiration were positively correlated for both drought-stressed (r 2 = 0.801) and well-irrigated plants (r 2 = 0.759). Plants from New Mexico (designated DS) had the lowest transpiration rate (2.32 mmol·m−2·s−1), lowest g s (52.1 mmol·m−2·s−1), largest xylem diameter (11 mm), and had among the largest shoot dry weight (DW) and plant height. Plants did not differ either among sources or between treatments in the ratio of variable to maximal fluorescence (mean = 0.64), relative water content (averaged 57%), specific leaf weight, stem DW, root DW, and plant DW. Carbon isotope discrimination (Δ) averaged −26.53‰ and did not differ among plant sources or irrigation treatments. This suggests that Δ might not be effective in screening bigtooth maples for drought tolerance. Low transpiration rate, g S, and high shoot dry weight in DS plants and traits, such as a high LAR in plants from LMP5, suggest that plants selected from these provenances might effectively endure deficit irrigation.
Ellen Thompson, Bernadine C. Strik, John R. Clark and Chad E. Finn
The flowering morphology of the erect, thorny, primocane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars ‘Prime-Jan’ and ‘Prime-Jim’ were studied in 2005 and 2006 in Aurora, OR. Primocanes that were “soft-tipped” in early summer to 1 m were compared with untipped primocanes. In both years, soft-tipped primocanes developed two- to threefold more branches and almost twice the number of flowers as untipped canes. ‘Prime-Jan’ and ‘Prime-Jim’ began blooming on the branches of soft-tipped canes in mid-July, whereas untipped primocanes began to bloom in late July in 2005 and 2006. Within a primocane inflorescence, the terminal or distal flower was always the first to open followed by terminal flowers from axes located on the basal portion of the inflorescence. Flowers then opened acropetally within the inflorescence, with the exception of the most basal flower, which was typically the last to open. The blooming pattern within an inflorescence was similar for soft-tipped and untipped primocanes. Days from anthesis to black fruit for soft-tipped and untipped primocanes averaged 45 to 51 d in both years, depending on cultivar.
Jean-Pierre Privé, Lindsay Russell and Anita LeBlanc
Kaolin particle films are used as a means of pest control in some commercial apple orchards in the Maritime provinces; however, no studies to date have evaluated the impact of these particle films on leaf gas exchange under the region's growing conditions. Also previously unexplored is the gas exchange response of blackberry leaves to kaolin particle films and the question of whether leaf gas exchange response varies according to the leaf surface of particle film application. A study consisting of an apple field trial and a blackberry greenhouse trial was conducted during the 2005 growing season in Bouctouche, New Brunswick, Canada, with the aims of 1) characterizing the leaf temperature and gas exchange responses [net photosynthesis, stomatal conductance (g s), intercellular CO2, and transpiration] of ‘Ginger Gold’ apple [Malus ×sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] leaves to a kaolin particle film (95% kaolin clay) applied at various leaf residue densities under the province's growing conditions, 2) characterizing the leaf temperature and gas exchange responses of ‘Triple Crown’ blackberry (Rubus L. subgenus Rubus Watson) leaves to treatment of adaxial or abaxial surfaces with the kaolin particle film at various leaf residue densities, and 3) determining whether the gas exchange response of apple and blackberry leaves to the kaolin particle film varies according to leaf temperature. Leaf gas exchange measurements were taken under conditions of ambient CO2, saturated light, moderate (apple) or high (blackberry) relative humidity levels and leaf temperatures ranging from 26 to 39 °C (apple) and 15 to 41 °C (blackberry). When the particle film was applied to both the adaxial and abaxial surfaces of apple leaves at kaolin residue densities of 0.5 to 3.7 g·m−2, leaf temperature was reduced by up to 1.1 °C (P = 0.005) and g s was increased (P = 0.029) relative to leaves with trace (<0.5 g·m−2) levels of kaolin deposits. No other effects of kaolin leaf residue density on apple leaf gas exchange were found, nor were any interactions of leaf temperature × residue level (P > 0.05). When applied to a fixed area on the adaxial or abaxial surfaces of blackberry leaves at kaolin residue densities of 0.5 to 10.8 g·m−2, the particle film did not alter leaf temperature or gas exchange (P > 0.05). No interactions of leaf temperature × residue level or leaf temperature × leaf surface × residue level were found to affect blackberry leaf gas exchange (P > 0.05).
Valtcho D. Zheljazkov, Charles L. Cantrell, M. Wayne Ebelhar, Christine Coker and William B. Evans
Baikal skullcap (Scutellaria baicalensis) is an important medicinal plant with proven bioactivity. Commercially available products in the United States containing extracts or derivatives from this plant species have been shown to lack consistency of chemical composition and bioactivity. In the United States, these issues could be solved through domestic production of skullcap. The hypothesis of this study was that Baikal skullcap grown in the Mississippi climate would accumulate sufficient bioactive flavonoids, baicalin, and baicalein in the roots to justify domestic production, and that shoots of these plants might also contain the flavonoids of interest. A replicated field experiment was conducted at four locations in Mississippi (Beaumont, Crystal Springs, Stoneville, and Verona) to test the hypothesis. The concentration of the main flavonoid, baicalin, in the roots ranged from 8.1% to 15.6%, whereas the concentration of baicalein varied from 0.2% to 1.2%. The flavonoid concentrations in the roots were similar to that of commercially available skullcap roots, and to concentrations reported in the literature. Chrysin was detected in the roots from one location. Furthermore, the flavonoids apigenin, baicalein, baicalin, chrysin, and scutellarein were detected and quantified in the skullcap shoots. Overall, yields of dry roots tended to increase from southern to northern locations. This is the first report on flavonoid accumulation in Baikal skullcap roots and shoots grown in the United States. The results from this study are promising and suggest that 1) Baikal skullcap grown in Mississippi accumulates similar amounts of baicalein and baicalin to skullcap grown in other regions and can provide up to 128 kg·ha − 1 of baicalin and up to 2.32 kg·ha− 1 of baicalein; 2) flavonoid concentration in Baikal skullcap roots and shoots, yields, and mineral concentration of roots might depend on climatic and growing conditions; and 3) Baikal skullcap could be developed as a high-value crop for Mississippi and possibly other regions of the United States. Further research is needed on skullcap production methods and economic feasibility.
Ren-Huang Wang, Yu-Mei Hsu, Duane P. Bartholomew, Subbiyan Maruthasalam and Chin-Ho Lin
In Taiwan, the major yield constraint in pineapple cultivation is natural flowering, which occurs when daylengths are shorter and nights are cooler. This natural (precocious) flowering increases the cost of cultivation and reduces the percentage of fruits of marketable size. Two field experiments were conducted to evaluate the inhibitory potential of aviglycine [(S)-trans-2-amino-4-(2 aminoethoxy)-3-butenoic acid hydrochloride, AVG] on natural flowering of ‘Tainon 17’ pineapple plants during the 2003 to 2004 and 2004 to 2005 cropping seasons. In the 2003 to 2004 season, bolting in the control exceeded 80% on 2 Mar. 2004, whereas no bolting was observed in the treatments. Inhibition of bolting by aviglycine (AVG) was dependent on the concentration and frequency of application. Bolting was less than 40% when plants were treated in Nov. and Dec. 2003 with 500 mg·L−1 of AVG four times at 15-day intervals or with five applications made at 10-day intervals. For the 2004 to 2005 season, bolting of plants treated with 250 or 375 mg·L−1 AVG was delayed 4 weeks relative to the control, whereas bolting was delayed 7 weeks by four or five applications of 500 mg·L−1 of AVG applied at 10- or 15-day intervals. Both experiments showed that four to five applications of 500 mg·L−1 of AVG at 10- or 15-day intervals delayed inflorescence emergence relative to the control for the duration of the treatments. We assume control was maintained for 1 to 2 weeks after treatments stopped. Based on these results, the date AVG treatments stop can be used to estimate the duration of delay in flowering. AVG inhibits ethylene biosynthesis and has the potential to be effectively used to delay or completely control the problem of precocious flowering and associated crop losses in pineapple.
Don C. Elfving, Stephen R. Drake, A. Nathan Reed and Dwayne B. Visser
A sprayable formulation of 1-methylcyclopropene (1-MCP; AgroFresh, Spring House, PA) was applied to ‘Scarletspur Delicious’ and ‘Cameo’ apples in the orchard 1 to 3 weeks before harvest and compared in different postharvest studies with the commercial postharvest 1-MCP fruit treatment (SmartFresh; AgroFresh) and with aminoethoxyvinylglycine (AVG; ReTain; Valent BioSciences, Walnut Creek, CA). Treated apples were held in air storage for 50 to 60 d or in controlled-atmosphere storage for 120 to 125 or 215 to 225 d. With increased concentration, sprayable 1-MCP treatments were effective at controlling flesh firmness loss and internal ethylene concentration (IEC) up to 225 d of storage as well as during a 7-d poststorage shelf life simulation at room temperature. Application closer to harvest improved the effect of sprayable 1-MCP on control of flesh firmness loss and IEC. Concentrations of sprayable 1-MCP above 90 mg a.i./L produced similar fruit effects to 1-MCP. Treatment with 1-MCP showed little effect on soluble solids concentration (SSC), titratable acidity (TA), or skin or flesh color in ‘Delicious’ but slightly increased SSC and TA in ‘Cameo’ apples. AVG applied 4 weeks before commercial harvest controlled IEC nearly as well as either sprayable 1-MCP or 1-MCP during storage, but AVG-treated fruit allowed to ripen for 7 d at room temperature after storage lost much more flesh firmness regardless of storage regime. Sprayable 1-MCP also reduced starch hydrolysis, IEC and fruit drop at harvest. Sprayable 1-MCP may offer new opportunities for effective preharvest management of apple fruit condition, storability, and poststorage fruit quality.
Keith O. Fuglie
International institutions like the International Potato Center (CIP) strive to provide “global public goods” in the form of improved technologies applicable to large regions of the developing world. To identify priorities for sweetpotato improvement, CIP conducted a survey of knowledgeable scientists in developing countries to elicit their perspectives on the most important constraints facing poor and small-scale sweetpotato growers in their countries. Respondents scored productivity and other constraints according to their importance in the region or country where they worked. Mean and weighted mean scores were estimated to provide a group judgment of the most important constraints facing sweetpotato farmers in developing countries. The survey results showed that there are a few key needs facing farmers in all major sweetpotato producing areas, but there are other very important needs specific to certain regions. The needs that scored highest in all or most of the major sweetpotato producing areas in developing countries are: i) control of viruses (through varietal resistance, quality planting material, and crop management); ii) small-enterprise development for sweetpotato processing; iii) improvement in availability and quality of sweetpotato planting material; and iv) improved cultivars exhibiting high and stable yield potential. Some differences emerged, however, in priority needs of the two major centers of sweetpotato production: Additional priorities for sub-Saharan Africa include improved control of the sweetpotato weevil and cultivars with high β-carotene content to address vitamin A deficiency. For China, other top needs are: i) conservation and characterization of genetic resources; ii) prebreeding; iii) cultivars with high starch yield; and iv) new product development. The different sets of priorities reflect differences in the role of sweetpotato in the rural economy and also different capacities of the agricultural research system in these regions of the world. Compared with earlier surveys, there now seems to be a greater need for postharvest utilization research, especially in sub-Saharan Africa, partly reflecting a demand constraint due to the crop's status as an inferior food.