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Abstract

Increasing the P rates from 0 to 20 ppm increased shoot and crown fresh and dry weight, plant height, and fleshy root and bud production in 10-week-old asparagus (Asparagus officinalis L.) seedlings. Increasing K rates from 0 to 200 ppm decreased the production of fleshy roots relative to buds. Shoot production progressively increased as N rates increased from 100 to 200 ppm in conjunction with P rates increasing from 10 to 20 ppm. The partitioning of dry weight into crowns predominated over that partitioned into shoots in any combination of N rate from 0 to 200 ppm, and P rate from 0 to 20 ppm. With P rates held constant at 0 to 20 ppm, however, increasing the N rates from 0 to 200 ppm tended to reduce the partitioning rate into crowns and enhanced partitioning into the shoots. Nutrient solutions containing at least 20 ppm P and 100 ppm N and K are recommended in vermiculite-perlite-peat media natively low in NPK.

Open Access

‘Mountain Crown’ is a fresh-market plum tomato F 1 hybrid ( Solanum lycopersicum L.) developed by crossing NC 30P × NC 1 Plum. It is resistant to verticillium wilt ( Verticillium dahliae Kleb) (race 1) ( Ve/Ve gene), fusarium wilt ( Fusarium

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Lycopersicon pennellii accession LA 1277 was crossed to tomato (L. esculentum) and the F1 was backcrossed to tomato. Self-pollinated seed was saved from backcross plants and seedlings derived were inoculated with Fusarium oxysporum Schlecht f.sp. radicus-lycopersici Jarvis and Shoemaker, the causal agent of Fusarium crown and root rot (FCRR). Seed was saved from resistant plants that were self-pollinated and screened until homozygous resistance was verified five generations after the backcross. Three homozygous lines were crossed to Fla. 7547, a tomato breeding line susceptible to FCRR but resistant to Fusarium wilt races 1, 2, and 3. Subsequently, backcrosses were made to each parent and F2 seed were obtained. The three homozygous FCRR-resistant lines were also crossed to Ohio 89-1, which has a dominant gene for FCRR resistance presently being used in breeding programs. F2 seed were obtained from these crosses. These generations were inoculated with the FCRR pathogen. The resistant parents, F1, and backcross to the resistant parents were all healthy. The backcross to the susceptible parent and the F2 segregated healthy to susceptible plants in 1:1 and 3:1 ratios, respectively. Thus, the resistance from LA 1277 was inherited as a single dominant gene. This gene was different than the gene from Ohio 89-1 because susceptible segregants were detected in the F2 generation derived from the two resistant sources.

Free access

table beet quality and yield is Rhizoctonia root and crown rot caused by the fungus Rhizoctonia solani Kühn (Abawi et al., 1986; Natti, 1953 ; Pethybridge et al., 2018 ), which renders table beet roots unmarketable. Currently, there are few chemical

Open Access

Excessive cutting pressure (CP) early in the lifespan of an asparagus (Asparagus officinalis L.) plantation may weaken and reduce yields and quality. The objective of this research was to determine how increasing CP affects yield, quality, and survival of spring-harvested and summer-forced asparagus. `Jersey Gem' asparagus was harvested for 4 years (1999–2002) in spring or summer-forced on 1 Aug. using the following CP (weeks/year from 1st to 4th years, respectively): 2, 3, 4, 6 (low), 3, 4, 5, 7 (medium), and 4, 5, 8, 10 (high). In all harvest years, as CP increased, marketable number and weight increased. Yield in spring harvest seasons significantly increased with each increase in CP. In summer, yield significantly increased only when high CP was used with equivalent yields at low and medium CP. With summer forcing, there were 48% and 55% fewer large spears at medium and high CP, respectively, compared to the same CP used during spring harvest seasons. Stands tended to decrease with CP from 1997 to 2003, but these differences were not significant and not severe enough to kill the plants. Yearly root fructose concentrations (RFC) with all CP increased yearly from 1999 to 2001 and plateaued from 2002 to 2003. From 1999 to 2002, RFC increased 53%, 27%, 13%, and 13% in unharvested control, low, medium, and high CP, respectively, indicating that with a greater CP, RFC decreased. RFC in summer-forced asparagus was significantly less than spring-harvested in 83% of all sample months. RFC in spring-harvested asparagus was similar to unharvested asparagus in February, March, April, November, and December; however, in all other sample months, spring-harvested RFC was significantly lower than unharvested control plants. The highest CP scheme is appropriate for spring-harvested asparagus based on greatest marketable yields and acceptable cull losses. For summer-forced asparagus, the lowest CP scheme is more appropriate based on acceptable marketable yields and to avoid undue plant stress verified by unacceptably large cull losses mostly attributed to spindly spear size and lower RFC.

Free access

Abstract

Increasing the concentration of sucrose in media containing 5 μm ancymidol increased rooting, with about 95% rooting of two asparagus (Asparagus officinalis L.) selections (Guelph-97, ‘Jersey Centennial’) obtained with 7% sucrose. In the absence of ancymidol, there was no evidence that increased sucrose concentration increased rooting. The increased rooting was not due to an osmotic effect, since the replacement of sucrose by an equimolar concentration of mannitol did not improve rooting. Chemical names used; 1-naphthaleneacetic acid (NAA), N-(2-furanylmethyl)-1H-purin-6-amine (kinetin), and α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol).

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1 Professor of Vegetable Crops. Florida Agr. Expt. Sta. Journal Series no. R-00261. Rhubarb crown divisions provided by Nourse Farms, South Deerfield, Mass., and `Victoria' seedlings by Hunsader Farms, Bradenton

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The estimate of the photosynthetic response to temperature is important for accurate growth predictions in process-based models designed to respond to broad variation in environmental conditions. Several studies have attempted to decipher the temperature and mesophyll response functions for use in the widely used Farquhar et al. (1980) biochemically based photosynthesis model. Unfortunately, published values of Rubisco kinetic properties (Kc and Ko) differ among species. To compound the problem, the methodology used to estimate Kc and Ko has not been consistent. We compared the variation in carbon gain estimates of a whole tree by incorporating the different temperature parameter estimates of Bernacchi et al. (2001, 2003) and Medlyn et al. (2002) into a three-dimensional biological process-based model. In addition, we also investigated the contribution of mesophyll conductance by incorporating Rubisco enzyme kinetics parameters reported by Bernacchi et al. (2002). Temperature parameters substantially influenced our whole tree carbon gain estimates. The variation among model estimates of aboveground net carbon gain was ≈11% for 3-year-old red maple saplings. Variation was even greater when mesophyll conductance was incorporated. The different parameter estimates, if not validated at the whole plant scale, can introduce inaccuracies and exacerbate carbon gain estimates of single plants, stands of plants, and entire ecosystems.

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