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  • Author or Editor: Carl E. Motsenbocker x
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Field and greenhouse studies examined the fruit detachment force (FDF) and fruit and pedicel characteristics of two lines of tabasco pepper (Capsicum frutescens L.) at several stages of maturity. The detachment force of red-mature `McIlhenny Select' fruit at the calyx-fruit detachment area was lower than that of less mature fruit stages. The force required to detach red-mature Hard Pick (HP) tabasco fruit was higher than that of redmature `McIlhenny Select' fruit in the field and greenhouse. The fruit detachment force of red field-grown HP fruit was higher, and in the greenhouse was lower, than that of green or breaker fruit. HP fruit of all maturity stages, except red-mature, separated similarly to `McIlhenny Select' fruit with little or no fruit tissue attached to the calyx. Fruit detachment force was not correlated with any fruit or pedicel characteristics studied.

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Pepperoncini pepper (Capsicum annuum var. annuum L. `Golden Greek') was grown at in-row spacings of 7.5, 15, 22.5, 30, and 45 cm to determine the effect of plant population on growth and fruit yield in a 2-year field study. In 1992, pepper plants grown at the 15-cm in-row spacing had the lowest plant, stem, and leaf dry weights, while plants at the lowest density (45-cm spacing) had the highest plant, leaf, and stem dry weights and the largest leaf area (LA). Of plants grown at the 7.5-cm spacing, the total yield and fruit count per hectare were higher than at the other spacings; however, fruit yield per plant was lowest. In 1993, the lowest plant and leaf dry weights and LA and highest LA index (LAI) were from plants at the 7.5-cm in-row spacing. Plants at the 45-cm spacing had the highest plant and leaf dry weight and LA and the lowest LAI. Pepper plants grown at the narrowest spacing produced the lowest early and total fruit yield per plant but the most fruit per hectare. In general, plants grown at the narrowest spacings produced the smallest plant, leaf, and stem biomass but resulted in the highest fruit yields and counts per hectare and the lowest fruit yields per plant.

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`McIlhenny Select' (easy detachment) and `Hard Pick' are two lines of tabasco pepper (Capsicum frutescens L.) that differ in the fruit detachment characteristics. Cellulase (Cx) and polygalacturonase (PG) activity, extracted from the fruit abscission zone, correlated inversely with the force needed to separate the fruit from the pedicel. A trend of higher Cx and PG is associated with the lower detachment force in the McIlhenny Select line. Differences in the fruit cell wall protein profile between both lines occurred during ripening. Two bands of 23 kDa and 40 kDa were higher in `McIlhenny Select'. A band of approximately 30 kDa was higher in `Hard Pick', while a band of ≈70 kDa increased in both lines. Isolation and characterization of these bands as well as Cx and PG is needed to understand the factors affecting fruit detachment in tabasco pepper.

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Two tabasco pepper (Capsicum frutescens L.) lines were previously identified that differ in fruit detachment characteristics. Ethephon treatment (1000 μl/L) to intact tabasco fruit 29 days after anthesis (green-mature) enhanced ripening as indicated by fruit coloration in both lines. `McIlhenny Select' fruit, which normally separate readily at the red-mature stage, however, had a quicker ripening response compared to `Hard Pick' fruit. Ethephon increased cellulase activity in the fruit tissue of both tabasco lines compared to the untreated control, and there was a trend of higher cellulase activity in `McIlhenny Select' compared to `Hard Pick'. Differences in ripening and enzyme activity in response to ethylene generators indicate that the two tabasco lines are suitable material to investigate the physiological processes involved in pepper fruit ripening.

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Red-mature Tabasco (Capsicum frutescens) fruit (`McIlhenny Select') normally separate easily at the junction of the fruit and receptacle or calyx. Differences in fruit detachment force (FDF) between two lines, one that separates readily (`McIlhenny Select') and one that does not (`Hard Pick'), have been reported previously (Motsenbocker et al., 1995). In this study, enzyme activity from the detachment area was analyzed by viscosity reduction. The reaction mixture was 0.3% pectin in 20 mm NaAc, pH 5.5, for polygalacturonase (PG) and 0.6% carboxymethyl cellulose (CMC) in 20 mm NaPO4, pH 6.0, for cellulase. Preliminary data indicated that PG and cellulase enzyme activity increased during fruit ripening in both lines. Only cellulase activity, however, correlated with FDF. In addition, the activity of both enzymes was higher in the `McIlhenny Select' line than the `Hard Pick' line at the orange and red-mature stages.

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Field and greenhouse studies were conducted to examine fruit detachment force and plant parameters of two strains of Tabasco (Capsicum frutescens) at different stages of maturity. The detachment force of mature red `McIlhenny Select' at the fruit-receptacle detachment area was less than that of breaker and mature green fruit. `McIlhenny Select' separated cleanly at all stages of maturity. A wild type Tabasco strain `HP' did not abscise at the red mature stage; fruit detachment force was greater than that of `McIlhenny Select'. The detachment force of mature green and breaker `HP' fruit were similar to those of `McIlhenny Select' at the same stage of maturity. Fruit weight, length, and width of the two tabasco strains were not different. The utility of the `McIlhenny Select' and `HP' strains for physiological studies of pepper fruit abscission will be discussed.

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Tomato is an important vegetable crop in Louisiana for small- to large-scale growers. Growers often use protected cultivation with structures, such as greenhouses, in order to take advantage of higher prices early in the season and increase profits through increased tomato yield and quality. A negative aspect of greenhouse use is the high investment and production costs associated with these structures. High tunnels, or simple greenhouse-like structures, have been used to protect crops from cold temperature in northern states, as they often provide benefits similar to greenhouses with considerably lower cost. Very little research has been conducted on the use of high tunnels for crops in the southern states. High tunnels in combination with row covers were evaluated for field cultivation of spring season fresh market tomato in Louisiana. The studies were set up in a randomized complete-block design with three replications. Tomatoes were transplanted into single rows on four-row raised beds covered with black plastic mulch on 1.2-m centers on 13 Mar. 2004. Row covers were installed immediately after transplanting and removed on 3 May. Plants were harvested for 6 weeks starting 12 May 2004. Both high tunnels and row covers significantly increased minimum and maximum air temperatures at a 15-cm height compared to the black plastic mulch control. Early yield was highest with the tunnel treatment without row cover compared to tunnel with row cover and similar to row cover alone or the control. There were no differences in total marketable yield between treatments. Research results from 2 years will be presented.

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Cayenne pepper fruit adhere tightly to the calyx/receptacle, increasing the cost of hand harvest and restricting mechanical harvest. Eight (8) cayenne pepper genotypes were selected from field observations to characterize fruit detachment forces(FDFs) and examine potential relationships between FDF and other fruit parameters. A preliminary greenhouse experiment revealed two genotypes with consistently lower FDFs and two with consistently higher FDFs over several progressive harvest. A field experiment confirmed these characteristics. No correlation between any fruit parameter and FDF was found to be consistent over the genotypes studied.

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Two genotypes of cayenne pepper, Capsicum annuun, have been previously identified which differ significantly in ease of fruit detachment force. Both greenhouse- and field-grown plants of these genotypes, Cajun1-9027 and Cap-9004, were investigated for differences in cell type or organization where the fruit and receptacle join. Scanning electron microscopy revealed that mature fruit of genotype Cajun1-9027, which does not separate, exhibits a distinct region of sclerified cells that extend from the periphery of the fruit into the receptacle for at least 15 cell layers. In contrast, mature fruit of the more readily detachable genotype, Cap-9004, had fewer sclerified cells at the point of detachment. Neither genotype exhibits a well-defined abscission zone prior to, or at, maturity. Interpretation of histochemical staining of fruit-receptacle sections following ethylene treatment at different fruit developmental stages will be discussed.

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Field experiments were conducted to assess how sweetpotato [Ipomoea batatas (L.) Lam.] clones interfere with weeds and how clones tolerate weed interference. Eleven clones with architecturally different canopies were evaluated for yield, canopy surface area and dry mass, weed dry mass, and light interception at ground level. A 2-fold difference in ground area covered by canopy surface area was observed among the eleven clones 42 days after planting, and a 3-fold difference in canopy dry mass at harvest. Yields were reduced from 14% to 68% by weed interference. The yields of high-yielding clones, `Beauregard', `Excel', L87-125, `Regal', `Centennial', and W-274, were reduced to a significantly greater extent by weeds than were yields of the other five clones. No differences were observed between clones for weed suppression as measured by weed dry mass at harvest and ground light interception. Short-internode and long-internode clones had similar competitive abilities. Yield of high-yielding clones was impacted more by weed interference than was that of low-yielding clones.

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