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  • Author or Editor: Daniel Leskovar x
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Tomato, cv. `Sunny' containerized transplants produced either with overhead (SP1) or sub (flotation) (SP2) irrigation were established in the field in fall, winter, and spring. Leaf area (LA), root volume (RV), and dry weights of shoots (SDW) and roots (RDW) were measured weekly before and after transplanting. In fall 1987, SP1 with 44 cm2 LA, 275 mg SDW, 68 mg RDW, and 0.9 ml RV at transplanting (T0) had 33% more fruit yield than SP2 transplants with 20 cm2 LA, 236 mg SDW, 62 mg RDW, and 0.6 ml RV at T0. In spring and winter 1988, SDW, RDW, and RV increased uniformly in both SP1 and SP2 plants, and yields did not differ significantly. In spring 1989, at T0, SP1 had 182 mg SDW and 7.8 shoot/root ratio (S:R) and SP2 had 92 mg SDW and 4.6 S:R, thereafter SDW and S:R ratios were not different and yields were unaffected. In fall 1989, SP1 total fruit yeild (52.3 t.ha-1) did not differ significantly from that of SP2 (47.4 t.ha-l) plants. Sub irrigated transplants may have similar fruit yields than overhead irrigated transplants provided plants are kept with minimum stress before establishment.

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Studies were conducted to evaluate growth of tomato (Lycopersicon esculentum Mill.) transplants in the field in response to age of transplants in Spring and Fall 1989. Transplants were 2 (2W), 3 (3W), 4 (4W), 5 (SW), or 6 (6W) weeks old. Drip and subseepage irrigation were used. In spring, older transplants produced more shoot and root growth up to 2 (T2) weeks after transplanting. At 3 (T3) and 4 (T4) weeks after transplanting, there were no differences between 4W, 5W, and 6W transplants. These trends were independent of irrigation systems. Total yield and early yield were similar for all transplant ages. In fall, shoot growth increased linearly with increasing transplant age at TO, but not thereafter. Chlorophyll a + b increased over time, but no treatment differences were found at T4. At planting, 2W transplants had a higher Chl a: b ratio than older transplants. This difference was reduced at T1 and T2 and became insignificant at T4. These results indicate that no improvement in yields was obtained using the traditional older transplants. Younger transplants might be used to achieve rapid seedling establishment with-minimal transplant production costs.

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`Sunny' tomato (Lycopersicon esculentum Mill.) containerized transplants were grown with the standard or conventional systems (SS) and with recently developed flotation systems (FS). Standard system and FS transplants, and direct-seeding using coated seeds were evaluated in the field for root and shoot growth and yield at Parrish, Bradenton, and Naples during fall, winter, and spring plantings. Plant growth characteristics were measured weekly before, during, and after transplanting or sowing. In the Parrish and Bradenton Fall 1987 and Bradenton Spring 1988 experiments, SS transplants had greater leaf area, root volume, shoot dry weights, and shoot: root ratios than FS transplants. During early development, the FS transplants had more lateral root growth than SS transplants, but had similar total root growth and horizontal and vertical root distribution after transplanting in the field. Transplants and direct-seeded plants allocated 72% of the total root mass in the upper 0 to 10 cm of the soil. In Fall 1987, SS transplants had between 29% and 41% more fruit yield than FS transplants at Bradenton and Parrish, respectively. In the Naples Winter 1988 and Parrish and Bradenton Fall 1989 experiments, both transplant types had similar fruit yields, but more than direct-seeded plants. Transplants grown with the flotation system are recommended for use provided that seedlings are grown and maintained with minimum hardening before establishment in the field.

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Embryogenic callus growth of sweetpotato [Ipomoea batatas (L.) Lam.] was selectively enhanced by subculture on basal callus proliferation medium modified to contain 15 mm NH4NO3. Embryogenic callus production was doubled on basal callus proliferation medium modified to contain 60 mm K+, while nonembryogenic callus production was reduced 40%. Additions of up to 40 mm NaCl to basal callus proliferation medium did not affect callus proliferation. The development of embryos from calli subculture to embryo production basal medium was unaffected by the KCl or NaCl treatments of the callus proliferation phase. However, embryo production was increased by subculturing callus from callus proliferation medium containing 20 mm NH4 + to embryo production medium containing 10 mm NH4 + Our results demonstrate that changes in mineral nutrition, in addition to growth regulator differences between callus proliferation and embryo production media, are important factors in sweetpotato somatic embryogenesis.

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Carotenoids are plant compounds that serve a variety of essential functions in the plant and have also been found to have several health-promoting activities in humans. Carotenoids found in watermelon (Citrullus lanatus) flesh are responsible for the various colors such as red, yellow and orange. Previous inheritance studies of flesh color revealed that six genes were involved in color determination. The relationship and interaction of these genes suggests that some color-determining genes may be the result of mutations on the structural genes encoding enzymes in the carotenoid biosynthesis pathway. In this study we were able to isolate and sequence six genes encoding enzymes involved in the carotenoid biosynthetic pathway, and determine their expression in different colored watermelon fruit. The cDNA was synthesized from total RNA using RACE (Rapid Amplification of cDNA ends) kit (SMART RACE cDNA Amplification Kit; Clontech, Palo Alto, Calif.). Degenerate primers were designed based on published homologous genes from other species and were used to isolate gene fragments and full-length cDNAs of phytoene synthase, phytoene desaturase, _-carotene desaturase, β-cyclase, β-carotene hydroxylase and zeaxanthin expoxidase. RT-PCR was carried out to examine any differential expression of cloned genes in white, yellow, orange and red-fleshed watermelon. All cloned enzyme-encoding genes were expressed regardless of flesh colors. These results indicate that carotenoid biosynthesis may be regulated at the post-transcriptional level. One interesting feature supports this hypothesis. In case of β-cyclase, a 229-bp leader intron was identified, and an unspliced mRNA with this leader intron existed dominantly in cDNA pool of all samples.

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Single- and double-row arrangements of a fixed population (one plant every 0.285 m2) were compared in factorial combination with two (2002) or five (2003) cultivars for effects on yield and fruit quality of bell pepper (Capsicum annuum L.). Arrangements for 2002 were S30, single rows 0.95 m apart, plants within rows 30 cm apart; D30, 1.9 m between centers of double-row beds, double rows 30 cm apart on beds, plants within rows 30 cm apart; S37.5, single rows 0.76 m apart, plants within rows 37.5 cm apart; and D37.5, 1.52 m between centers of double-row beds, double rows 24 cm apart on beds, plants within rows 37.5 cm apart. Only the S30 and D30 arrangements were used in 2003 after 2002 results showed almost no differences between S30 and S37.5 or between D30 and D37.5. Choice of cultivar was more critical in Texas, where `X3R Wizard' consistently outperformed `King Arthur', than in Oklahoma. Single rows resulted in more full-season total marketable fruit weight than double rows in three experiments out of four, primarily as a result of an increased weight of U.S. No. 1 fruit with single rows. Average weight per marketable fruit was consistently unaffected by plant arrangement. Single rows also resulted in a greater full-season weight of sunburned fruit than double rows in two experiments out of four. Cultivar × plant arrangement interactions were not evident in Oklahoma and never involved full-season marketable fruit weights at either location in either year. Given the tested population, a single-row arrangement is likely to result in increased full-season production of U.S. No. 1 bell pepper fruit compared with a double-row arrangement, despite an increased potential for sunburned fruit with single rows.

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The Texas Agricultural Experiment Station/Texas A&M University announces the release of two new open-pollinated cultivars of long chile. The first, `TAM Ben Villalon,'(TBV) is a long green chile/Anaheim type, while the second, `TAM Valley Hot,' (TVH) is a large cayenne type. Both cultivars have complex pedigrees involving TAES potyvirus resistant germplasm developed by Ben Villalon. Consequently, they exhibit resistance to some strains of tobacco etch virus when mechanically inoculated. In addition, TBV exhibits resistance to several strains of pepper mottle virus. These new cultivars out-yielded their comparable commercial cultivars, `Sonora,' and `Mesilla', when grown with drip irrigation at Weslaco and Uvalde, Texas. TBV yielded 16,632 kg/ha of green pods, compared to 14,228 kg/ha for `Sonora.' Both cultivars had similar capsaicin concentrations of 30–40 ppm on a fresh-weight basis. TBV pods are significantly heavier than those of `Sonora' due to thicker flesh. It should be useful for the green chile processing and fresh market industries. TBV may also be dried at the red stage to produce chile powder, which is very similar in quality to that of `NM 6-4.' TVH pods are not significantly different from `Mesilla' for size or weight, but contain significantly more capsaicin (670 vs. 320 ppm) when grown at Weslaco. TVH should be well-suited to the cayenne mash industry for hot sauce production due to its high heat level. Both cultivars will be distributed through commercial seed companies after receiving approval for Plant Variety Protection Patents.

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Lysimeters are used to measure real-time water use during the growing season. By relating the water use of a specific crop to a well-watered reference crop, such as alfalfa or grass, crop coefficients (Kc) can be developed to assist in predicting accurate crop needs using available meteorological data. Reference evapotranspiration can be obtained from several weather networks; however, without crop coefficients for specific crops, this information is only useful for grass. Three weighing lysimeters, consisting of undisturbed 1.5 m × 2.0 m area by 2.2-m depth cores of soil, comprise the Texas A&M Research and Extension Center–Uvalde lysimeter facility. Two lysimeters, weighing around 15,000 kg, have been placed beneath a linear LEPA irrigation system and used in field production. A third lysimeter measures reference ET values (ETo) and is located in a grassed area near the field lysimeters irrigated by subsurface drip irrigation system. Spinach was grown in one of the two crop lysimeters while onion was grown in the second lysimeter. Daily water use was measured on 5-min intervals. Results show the possibility of saving ≈61 to 74 million m3 of water per year in the irrigated farms of the Edwards aquifer region if proper irrigation management techniques are implemented in conjunction with the newly developed crop coefficients. Crop water requirements, Kc determination, and comparison to existing FAO Kc values will be discussed.

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A two-year experiment was conducted to determine yield, water use efficiency, and leaf quality responses to deficit irrigation and plant population of spinach (Spinacia oleracea L.). Three irrigation regimes were imposed with a center pivot system, 100%, 75%, and 50% crop evapotranspiration rates (ETc). Spinach seeds were planted on 11 Nov. 2003 at three plant populations: 494 (P-1), 618 (P-2), and 741 (P-3) thousand seeds/ha on cvs. DMC 16 and ASR 157, and on 15 Oct. 2004 at four plant populations: 655, 815, 988, and 1149 thousand seeds/ha on cv. DMC 16. Harvests were done on 3 Mar. 2004 and 26 Jan. 2005. In the first season, marketable yield was not reduced by deficit irrigation, but water use efficiency was significantly higher for 50% ETc compared to 100% ETc. The cv. DMC 16 had a significantly lower percentage of stem weight than ASR 157 (8.3 vs. 16.4%). The cv. ASR 157 had an excess of stem weight at 100% and 75% ETc compared to 50% ETc at P-1, but similar at P-2 and P-3. The cv. DMC 16 had a trend of reduced stem weight for P3 at 50% ETc. In the second season, marketable yield was reduced by deficit irrigation. However, water use efficiency was significantly higher for 50% ETc compared to 100% ETc, but similar to 75% ETc. Deficit irrigation also decreased the percentage of stem weight. Despite a slight increase in the percentage of of yellow leaves, but not in percentage of of stem weight, marketable yield and water use efficiency were significantly higher at 1149 thousand seeds/ha. This study showed that deficit irrigation in combination with increased plant population has the potential to increase yield and water savings, without adversely affecting leaf quality.

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Globe artichoke is typically grown in Mediterranean and coastal areas. Because of the high profitability as a specialty crop, demand to develop production systems optimized for other semiarid and water-limited regions is rising. Field experiments were conducted over three seasons (2008–09, 2010–11, and 2011–12) in southwest Texas to investigate plant growth, physiology, and yield of artichoke grown as an annual system. Three strategies were evaluated: planting configuration (single and double lines per bed), plasticulture (bare soil and black plastic mulch), and cultivars differing in maturity (‘Imperial Star’, early; ‘Green Globe Improved’, late). Each fall, transplants were established in the field at 2.03 m between rows and 0.90 m between plants (single line) or 4.06 m between rows and 0.90 m between plants (double line). In both cultivars, black plastic mulch enhanced plant growth (leaf number, plant height and width) and increased early yield; however, its effect on total yield and yield components was not consistent. Single line per bed significantly increased head number of jumbo and large size per plant as compared with double line in the 2009 season. Chlorophyll index was unaffected by either planting configuration or plastic mulch. Comparing cultivars, ‘Green Globe Improved’ had lower marketable yield but bigger head size than ‘Imperial Star’ in one and two seasons, respectively. Our results indicate that single line with black plastic mulch can be recommended to improve earliness and water savings as compared with the bare soil system for annual artichoke production.

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