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Four sweetpotato breeding lines were tested for their sodium tolerance in sand culture. All plants were grown in the greenhouse in sterilized sand and watered daily with a modified half-Hoagland solution (N: K-1:2:4). Four sodium levels (0, 35, 70, and 105 ppm) were applied to the breeding lines in a split-plot design with four replications. Soil leachate was collected every 2 days and was measured for P, Na concentration, and electrical conductivity. Plants were grown for 60 days. Preliminary results from analysis of soil leachate showed an increase in EC as sodium concentration increased 5 days after treatments were initiated. Potassium and Na concentration varied with each breeding line tested. Storage root fresh and dry weight were significantly affected by Na levels (i.e., lines tested were tolerant ≤70 ppm Na).
Abstract
Controlled-environment agriculture gives the greenhouse manager freedom to take advantage of opportunities which are unavailable in open-field agriculture. To take full advantage of this flexibility, a greenhouse manager must be prepared to be responsive to current crop production and market conditions. In this study, the problem of managing greenhouse crops for either maximum production or profit of operation is examined, particularly the question of when to terminate a given crop and to plant new seedlings. The effects on production of dividing the greenhouse to permit crops at different stages of maturity to be grown simultaneously are considered. The annual price fluctuation and its effect on crop scheduling decisions is discussed. A formal mathematical model for crop production is not needed in order to formulate an objective decision making method, rather one may make use of current and past production data to make crop management decisions. A decision-making guideline (an algorithm) based on some simple observations from the definition of a maximum is presented and used throughout as a guide for management.
Bean golden mosaic virus (BGMV) is a devastating disease of common bean (Phaseolus vulgaris L.) in tropical America. The disease is effectively controlled by combinations of genetic resistances. The most widely deployed source of resistance to BGMV is a recessive gene (bgm-1) derived from the dry bean landrace cultivar Garrapato (Mexico) that conditions a nonmosaic partial resistance response to the pathogen. To expedite introgression of partial resistance into snap bean for southern Florida and other susceptible dry bean market classes for the Caribbean and Central American regions, a RAPD marker tightly linked to bgm-1 has been identified. Two contrasting DNA bulks, one consisting of five BGMV-resistant and the other five susceptible F6 recombinant inbred lines, were used to screen for polymorphic fragments amplified by 300 decamer primers in the polymerase chain reaction. RAPDs generated between the bulks were analyzed across F2 populations segregating for the marker and the gene. One codominant RAPD marker (R2570/530) tightly linked to the recessive resistance gene bgm-1 was found. The 530-base pair (bp) fragment was linked in repulsion with bgm-1 and the other 570-bp fragment was linked in coupling. No recombinants between R2570/530 and bgm-1 were observed among 91 F2 progeny from one dry bean population, and there were two recombinants (4.2 cM) observed among 48 F2 progeny combined across four snap bean populations. Assays of R2570/530 across susceptible germplasm and lines likely to have the `Garrapato'-derived partial resistance to BGMV have revealed that the codominant marker is gene-pool nonspecific and maintains its original linkage orientation with the recessive bgm-1 gene through numerous meioses. The codominant marker is useful for rapidly introgressing partial resistance to BGMV into susceptible germplasm.