Quantitative trait loci controlling sulfur containing amino acids, methionine and cysteine, in soybean seeds.

Soybean [Glycine max (L.) Merr.] is the single largest source of protein in animal feed. However, a major limitation of soy proteins is their deficiency in sulfur-containing amino acids, methionine (Met) and cysteine (Cys). The objective of this study was to identify quantitative trait loci (QTL) associated with Met and Cys concentration in soybean seed. To achieve this objective, 101 F(6)-derived recombinant inbred lines (RIL) from a population developed from a cross of N87-984-16 x TN93-99 were used. Ground soybean seed samples were analyzed for Met and Cys concentration using a near infrared spectroscopy instrument. Data were analyzed using SAS software and QTL Cartographer. RIL differed (P<0.01) in Met and Cys concentrations, with a range of 5.1-7.3 (g kg(-1) seed dry weight) for Cys and 4.4-8.8 (g kg(-1) seed dry weight) for Met. Heritability estimates on an entry mean basis were 0.14 and 0.57 for Cys and Met, respectively. A total of 94 polymorphic simple sequence repeat molecular genetic markers were screened in the RIL. Single factor ANOVA was used to identify candidate QTL, which were confirmed by composite interval mapping using QTL Cartographer. Four QTL linked to molecular markers Satt235, Satt252, Satt427 and Satt436 distributed on three molecular linkage groups (MLG) D1a, F and G were associated with Cys and three QTL linked to molecular markers Satt252, Satt564 and Satt590 distributed on MLG F, G and M were associated with Met concentration in soybean seed. QTL associated with Met and Cys in soybean seed will provide important information to breeders targeting improvements in the nutritional quality of soybean.

Seed quality QTL in a prominent soybean population.

Soybean [Glycine max (L.) Merr.] is a versatile crop due to its multitude of uses as a high protein meal and vegetable oil. Soybean seed traits such as seed protein and oil concentration and seed size are important quantitative traits. The objective of this study was to identify representative protein, oil, and seed size quantitative trait loci (QTL) in soybean. A recombinant inbred line (RIL) population consisting of 131 F6-derived lines was created from two prominent ancestors of North American soybeans ('Essex' and 'Williams') and the RILs were grown in six environments. One hundred simple sequence repeat (SSR) markers spaced throughout the genome were mapped in this population. There were a total of four protein, six oil, and seven seed size QTL found in this population. The QTL found in this study may assist breeders in marker-assisted selection (MAS) to retain current positive QTL in modern soybeans while simultaneously pyramiding additional QTL from new germplasm.

Osmotic dehydration of apple slices using a sucrose/CaCl2 combination to control spoilage caused by Botrytis cinerea, Colletotrichum acutatum, and Penicillium expansum.

The efficacy of sucrose combined with CaCl2 during osmotic dehydration (OD) was tested for the control of Botrytis cinerea, Colletotrichum acutatum, and Penicillium expansum growth on lightly processed apple slices. The objective of this work was to determine whether the addition of CaCl2 in the osmotic solutions would limit the proliferation of fungal decay organisms. Slices were submitted to OD for 1 h at 25 degrees C in solutions containing 5 to 65% sucrose. Calcium chloride was added to a similar set of sucrose solutions at 0 to 8%. Control slices were made of untreated slices, and slices were processed in water. The mass ratio of the slices did not vary when fruit pieces were processed in solutions containing 5 to 65% sucrose. These slices showed a high susceptibility to spoilage compared to the control slices not submitted to OD: a significant twofold and 60% increase in decay area caused by B. cinerea and P. expansum, respectively, was observed when slices were processed in 50% sucrose/0% CaCl2; C. acutatum showed a significant 50% increase in decay area when slices were processed in 20% sucrose/0% CaCl2. Calcium uptake was significantly increased when slices were processed in CaCl2 solutions, and the highest Ca content was observed when processed in 8% CaCl2, reaching 40 times that of the control slices processed in water. Calcium-treated slices were less susceptible to spoilage by all three pathogens, and the most effective combination in reducing apple slice spoilage was 20 to 30% sucrose combined with 2% CaCl2.

Influence of metam sodium on the dissipation and residual biological activity of the herbicides EPTC and pebulate in surface soil under black plastic mulch.

Metam sodium is a potential replacement for methyl bromide, which is used to control soil pests. Metam sodium rapidly breaks down in the soil to form methylisothiocyanate (MITC). Dissipation of the herbicides EPTC and pebulate in a silt loam soil under plastic mulch in the absence and presence of metam sodium was examined in field experiments in 1998 and 1999 at Knoxville, Tennessee. EPTC half-life (DT(50)) was 9 d, but when applied in conjunction with metam sodium DT(50) increased to 22 d. Similarly, average pebulate DT(50) was 8 d and increased to 23 d when applied in conjunction with metam sodium. This increase in herbicide DT(50) with the addition of metam sodium is thought to be due to a reduction in soil microorganisms that degrade EPTC and pebulate. EPTC applied with metam sodium injured tomato plants and reduced total crop yield more than EPTC, pebulate, or pebulate with metam sodium. The increased tomato injury may have been related to the greater and prolonged activity of EPTC and slower EPTC dissipation in the presence of metam sodium or MITC.

Variability of Three Isolates of Botrytis cinerea Affects the Inhibitory Effects of Calcium on this Fungus.

ABSTRACT Botrytis cinerea is an economically important pathogen. Epidemiological studies are difficult because of the genetic variability within this species. The objectives of this work were to study the variability and to compare the inhibitory effects of Ca on three isolates of B. cinerea from decayed apple (B) and grape (C and C77:4). Among these isolates, B had the least radial growth but had a sporulation rate 40% higher than that of both C77:4 and C. In situ, isolate C incited the largest decay area in the fruit of two of four apple cultivars examined and had the highest polygalacturonase activity in vitro. Maximum mycelial growth was reached with CaCl(2) at 1 g liter(-1) for isolates B and C77:4 and at 4 g liter(-1) for isolate C. Calcium (CaCl(2)) inhibited polygalacturonase activity at 1 g liter(-1) for C and C77:4 and at 16 g liter(-1) for B. Calcium infiltration reduced decay caused by all three isolates by three to five times. Mycelial DNA analysis showed that 42% of the character loci scored were polymorphic and the greatest similarities were found between B and C77:4. These results support the evidence that the biological and statistical variability in research can be affected by the B. cinerea isolate selected. Despite this variation, Ca treatment of apples reduced decay caused by all three Botrytis cinerea isolates.

Gene encoding polygalacturonase inhibitor in apple fruit is developmentally regulated and activated by wounding and fungal infection.

A cDNA encoding polygalacturonase-inhibiting protein (PGIP) from mature apple fruit has been cloned and characterized. The open reading frame encodes a polypeptide of 330 amino acids, in which 24 amino acids at the N-terminus comprise the signal peptide. Apple PGIP contains 10 imperfect leucine-rich repeat sequence motifs averaging 24 amino acids in length. In addition to the 1.3 kb PGIP transcript, the cloned cDNA also hybridized to RNA molecules with sizes of 3.2 and 5.0 kb. Genomic DNA analysis revealed that the apple PGIP probably belongs to a small family of genes. PGIP transcript levels varied in fruit collected at different maturities, suggesting the gene is developmentally regulated. Very high PGIP transcript levels were detected in decayed areas and the tissue adjacent to the inoculation sites of Penicillium expansum and Botrytis cinerea. However, no increase in the amount of PGIP transcript in tissue distant from the decayed region was observed. Wounding on fruit also induced PGIP gene expression but to a much lessser extent when compared with decayed areas. After storage at 0 degrees C for 1 month, the abundance of PGIP transcript in ripe fruit was substantially increased. The PGIP gene in immature and ripe fruit was rapidly up-regulated by fungal infections, while in stored fruit the induction was very limited and concurred with an increase of fruit susceptibility to fungal colonization. Since PGIP gene expression is regulated by fruit development and responds to wounding, fungal infection and cold storage, these observations suggest that apple PGIP may have multiple roles during fruit development and stress response.

Polygalacturonase produced in apple tissue decayed by Botrytis cinerea.

An exo-polygalacturonase with an isoelectric point of 4.6 and an apparent molecular weight of 45 kDa was isolated from apple tissue decayed by Botrytis cinerea. This isozyme had a similar isoelectric point, optimum pH, and mode of action as an isozyme produced in liquid culture by B. cinerea. The enzyme produced in the decayed tissue was less sensitive to lower pH and less inhibited by CaCl2, MgCl2, or NaCl than the enzyme produced in culture. Such changes in the properties of the enzyme produced in infected tissue could have been essential for the pathogen's successful colonization of the host tissue. Among the cations studied, calcium was the best inhibitor of PG activity.

Influence of low temperature preincubation on somatic embryogenesis and ethylene emanation from orchardgrass leaves.

The objectives of this study were to determine the effects of low temperature (4 degrees C) preincubation on somatic embryogenesis from orchardgrass (Dactylis glomerata L.) leaf cultures and to relate these effects to ethylene emanation during the preincubation and incubation periods. Experiments were also conducted with an ethylene biosynthesis inhibitor aminooxyacetic acid (AOA). Segments from the innermost two leaves were cultured on SH medium with 30 micromoles dicamba at 4 degrees C for 1 to 7 d before transfer to 21 degrees C. Results from a paired design showed that the embryogenic response of leaf segments preincubated at 4 degrees C was equal or superior to nonpreincubated leaves at all time periods. Ethylene emanation was decreased during the low temperature incubation. Transfer of leaf segments from 4 degrees C to 21 degrees C was accompanied by a burst of ethylene which rose to control levels within 30 min. AOA at 20 and 40 micromoles decreased ethylene emanation but did not stimulate the embryogenic response. We conclude that the stimulation of somatic embryogenesis by low temperature is probably due to factors other than suppression of ethylene biosynthesis.

Effect of 1-Aminocyclopropane-1-carboxylic acid and aminoethoxyvinylglycine on ethylene emanation and somatic embryogenesis from orchardgrass leaf cultures.

Ethylene emanation rates were assessed from leaf tissues of an embryogenic seed plant (Cycle 0) and regeneration cycle plants selected for enhanced embryogenesis (Cycles I, II and IV). In all experiments, ethylene was assessed from the basal 1 cm portion of the innermost leaf. Ethylene emanation was five-fold higher in Cycle II and Cycle IV plants than in Cycle 0 and nonembryogenic (NE) seed plants. After two days culture on Schenk and Hildebrandt medium containing 30 µM dicamba (SH-30), ethylene emanation from Cycle 0 and Cycle II leaf sections increased by 55-fold. Culture of leaf explants for 30 days on SH-30 containing 1 mM 1-aminocyclopropane-1-carboxylic acid (ACC) reduced the embryogenic response by 99%. Treatment of leaf explants with 1 mM aminoethoxyvinylglycine (AVG) reduced ethylene emanation but did not affect embryogenesis. The data indicate that ethylene mediated by ACC may hinder the embryogenic response from orchardgrass leaf cultures.

Inhibition of somatic embryogenesis in orchardgrass by endogenous cytokinins.

Endogenous indoleacetic acid (IAA) and cytokinin concentrations were measured by high performance liquid chromatography in leaf sections of an orchardgrass (Dactylis glomerata L.) genotype which exhibited a high capacity for somatic embryogenesis in vitro and in two genotypes that did not exhibit this capacity. The nonembryogenic genotypes contained 3- to 4-fold higher concentrations of zeatin, zeatin riboside, dihydrozeatin, dihydrozeatin riboside, and total cytokinins than the embryogenic genotype. There were no significant differences in IAA concentrations between genotypes. Cytokinin concentrations between basal and distal sections of embryogenic genotype were not different, but the IAA concentration was significantly greater in basal sections. Somatic embryogenesis was inhibited in the embryogenic genotype by 0.001 micromolar exogenously added zeatin.

Net photosynthetic rate of sour cherry (Prunus cerasus L. 'Montmorency') during the growing season with particular reference to fruiting.

Diurnal and seasonal net photosynthetic rates (Pn) of sour cherry were determined. Leaf Pn was not significantly affected by shoot excision. Under constant environmental conditions (PFD, 1200 µmol m(-2) s(-1); temp. 25; relative humidity, 80-90%) there was no significant diurnal fluctuation in Pn for individual leaves. However, there was a pronounced fluctuation in Pn for whole trees measured under constant temperature but natural variation in sunlight from sunrise to sunset. Maximum Pn occurred before solar noon, remained constant for 1-2 hr, then declined. Photosynthetic rate of recently expanded leaves fluctuated through out the season but, in general, was greatest in the spring as leaves expanded, reached a peak, remained stable for several weeks, then gradually declined. The Pn of leaves on terminal shoots was not significantly different from the Pn of leaves on spurs of the same physiological age. The presence of fruit did not have a consistent effect on the Pn of sour cherry leaves.

Net photosynthetic rate of sour cherry (Prunus cerasus L. 'Montmorency') during the growing season with particular reference to fruiting.

Diurnal and seasonal net photosynthetic rates (Pn) of sour cherry were determined. Leaf Pn was not significantly affected by shoot excision. Under constant environmental conditions (PFD, 1200 µmol m(-2)s(-1); temp. 25; relative humidity, 80-90%) there was no significant diurnal fluctuation in Pn for individual leaves. However, there was a pronounced fluctuation in Pn for whole trees measured under constant temperature but natural variation in sunlight from sunrise to sunset. Maximum Pn occurred before solar noon, remained constant for 1-2 hr, then declined. Photosynthetic rate of recently expanded leaves fluctuated through out the season but, in general, was greatest in the spring as leaves expanded, reached a peak, remained stable for several weeks, then gradually declined. The Pn of leaves on terminal shoots was not significantly different from the Pn of leaves on spurs of the same physiological age. The presence of fruit did not have a consistent effect on the Pn of sour cherry leaves.