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1.
Alex Beharav Dalia Lewinsohn Aleš Lebeda Eviatar Nevo 《Genetic Resources and Crop Evolution》2006,53(3):467-474
A total of 1027 genotypes of wild Lactuca spp. (L. serriola, L. saligna, and L. aculeata), originating from Israel, Jordan, East Turkey, Armenia, Kazakhstan, China, and various other countries in Europe were screened
for resistance to the lettuce downy mildew (Bremia lactucae Regel). The genotypes of L. serriola (N = 962); L. saligna (N = 43); and L. aculeata (N = 22) were tested at the seedling stage with two isolates of B. lactucae (race Bl-21 and Isr-74) isolated from cultivated lettuce in Italy and Israel, respectively. Altogether, the isolates possess
virulence against 17 out of 20 Dm genes/R-factors composing the established differential set of lettuce lines/varieties. They could therefore be used for preliminary
detection of the presence of new resistance factors. A total of 83 and three genotypes of L. serriola and L. saligna, respectively, were resistant to infection by each of the two isolates alone as well as to the infection by a mix of the
two isolates. These genotypes probably carry previously unknown resistance, and therefore could be suitable for exploitation
by breeders and further detailed research. The wild progenitor of lettuce, L. serriola, and related species harbor significant untapped genetic resources for lettuce improvement. 相似文献
2.
Tietel Z Lewinsohn E Fallik E Porat R 《Journal of agricultural and food chemistry》2011,59(21):11779-11785
To elucidate the roles of ethanol fermentation metabolism in causing off-flavors, 'Mor' mandarins were exposed to anaerobic atmospheres for 0, 2, 4, 7, and 10 days to gradually increase juice ethanol and acetaldehyde levels through enhanced fermentation. Exposure to anaerobic atmosphere caused progressive decline in fruit sensory quality, from nearly "good" to "very bad", because of decreased typical mandarin flavor and increased sensation of 'musty' and 'ethanol' off-flavors. GC-MS analysis revealed significant (p ≤ 0.05) increases in the contents of 12 aroma volatiles, including the ethanol fermentation metabolites ethanol and acetaldehyde, and several fatty acid and amino acid catabolism derivates, 7 of which were ethyl esters, which suggests that they were esterification products of ethanol and acyl-CoA's derived from fatty acid and amino acid catabolism. These de novo synthesized anaerobiosis-regulated ethyl esters impart 'pungent', 'ethereal', 'waxy', 'musty', and 'fruity' notes. Overall, these results suggest that besides the direct effects of ethanol and acetaldehyde, downstream ethanol esterification products may also be involved in causing off-flavor sensation in mandarins. 相似文献
3.
Frydman A Weisshaus O Huhman DV Sumner LW Bar-Peled M Lewinsohn E Fluhr R Gressel J Eyal Y 《Journal of agricultural and food chemistry》2005,53(25):9708-9712
Neohesperidin dihydrochalcone (NHDC) is a seminatural, safe, low-calorie sweetener, bitterness blocker, and flavor enhancer with unique properties and applications for the food, beverage, pharmaceutical, and animal feed industries. Current production is limited by the availability of the substrate neohesperidin, a flavonoid that accumulates to significant levels only in the inedible bitter citrus species. We propose a process to convert hesperidin, a tasteless flavonoid extracted from orange peels that are abundant byproducts of the vast orange juice industry, into neohesperidin using metabolic engineering and biotransformation via three steps: (i) extraction of hesperidin from orange peels, (ii) hydrolysis of sugar moieties, and (iii) biotransformation of hesperidin hydrolysis products into neohesperidin. We overcame the current technological bottleneck in biotransformation of hesperidin hydrolysis products into neohesperidin using metabolically engineered plant cell cultures expressing a recombinant flavanone-7-O-glucoside-2-O-rhamnosyltransferase. A small-scale production experiment established the feasibility of the proposed process. 相似文献
4.
5.
Ninio R Lewinsohn E Mizrahi Y Sitrit Y 《Journal of agricultural and food chemistry》2003,51(3):797-801
The columnar cactus Cereus peruvianus (L.) Miller, Cactaceae (koubo), is grown commercially in Israel. The unripe fruits are green, and the color changes to violet and then to red when the fruit is fully ripe. The content of soluble sugars was found to increase 5-fold during ripening. Glucose and fructose were the main sugars accumulated in the fruit pulp, and each increased from 0.5 to 5.5 g/100 g fresh weight during ripening. The polysaccharides content decreased during ripening from 1.4 to 0.4 g/100 g fresh weight. The titratable acidity decreased and the pH increased during ripening. The major organic acid found in the fruit was malic acid, which decreased from 0.75 g/100 g fresh weight at the mature green stage to 0.355 g/100 g fresh weight in ripe fruits. Citric, succinic, and oxalic acids were found in concentrations lower than 0.07 g/100 g fresh weight. Prominent accumulation of aroma volatiles occurred toward the end of the ripening process. The main volatile found in the ripe fruit was linalool, reaching concentrations of 1.5-3.5 microg/g fresh weight. 相似文献
6.
The variation and distribution of virulent phenotypes ofBremia lactucae Regel, the causal agent of lettuce downy mildew, were studied during 2002–2003 in lettuce fields (Lactuca sativa) in Israel. A total of 21 isolates ofB. lactucae were collected from nine locations in three regions of Israel: Galilee, the Coastal Plain, and the Shefela. The isolates
were examined for the presence of 21 virulence factors (v-factors) and their combinations with differential sets of lettuce
lines/varieties. There were clear differences in v-factors, and a broad diversity of v-phenotypes among the isolates was found.
Although 17 different v-phenotypes and 20 v-factors were detected, a composite of similar v-phenotypes generally occurred
between isolates within the three regions. They differed mostly in the presence or absence of only a few v-factors. The Coastal
Plain region averaged the highest virulence complexity (0.63), significantly different from that of the Shefela (0.45) and
of Galilee (0.4). Comparison of the IsraeliB. lactucae isolates that were tested in this study with data of other countries showed that factor v18, which did not occur in the Israeli
populations, was detected only in Czech and German pathogen populations.
http://www.phytoparasitica.org posting Dec. 21, 2006. 相似文献
7.
Racheli Ninio Efraim Lewinsohn Yosef Mizrahi Yaron Sitrit 《Postharvest Biology and Technology》2003,30(3):273-280
Cereus peruvianus (L.) Miller (koubo, also known as apple cactus) is a new fruit crop in Israel. When the fruit reach full maturity, they tend to crack due to uncoordinated growth of the different fruit tissues. This phenomenon normally causes heavy fruit losses, as much as 90% of the total yield. To prevent this problem, fruit are usually harvested before they reach full ripening, i.e. at the violet stage, a practice that effectively prevents cracking, but also reduces the overall quality of the marketed fruit. In order to establish optimal harvesting protocols and storage conditions, we characterized fruit ripening under storage, comparing purple-harvested fruit, stored fruit (purple and red-ripe) and tree-ripened red-split fruit. Organoleptic tests indicated that the overall flavor increased concomitantly with the development of the red peel color. During ripening, the pH slightly increased, while titratable acidity and the content of malic acid decreased. These changes were more marked in stored than in tree-ripened fruit. The levels of polysaccharides, glucose and fructose did not change significantly during storage. The content of linalool and linalool derivatives increased dramatically during storage, being much higher than that of cracked tree-ripened fruit. Our results indicated that the overall quality of the fruit increased during storage as expressed by color change, decreased acidity and enhanced levels of aroma compounds, while the content of carbohydrates was practically unaffected. 相似文献
8.
Tadmor Y Fridman E Gur A Larkov O Lastochkin E Ravid U Zamir D Lewinsohn E 《Journal of agricultural and food chemistry》2002,50(7):2005-2009
Vegetable cultivation favored the inclusion of pleasant aromas in the produce, whereas unpleasant aromas were selected against. Introgression lines, generated by hybridization of a cultivated tomato (Lycopersicon esculentum) to its wild relative L. pennellii, were used to map quantitative trait loci (QTL) that influence tomato aroma. A marked undesirable flavor was detected by taste panelists in L. pennellii fruits and was related to an introgressed segment from the short arm of chromosome 8. Analysis of the ripe fruits' volatiles of chromosome 8 introgressed lines revealed an up to 60-fold increase in the levels of 2-phenylethanol and phenylacetaldehyde, as compared to the cultivated tomato. This effect was associated with a 10 cM segment originating from the wild species. Although 2-phenylethanol and phenylacetaldehyde have favorable contribution to tomato aroma when present at low levels, phenylacetaldehyde has a nauseating objectionable aroma when present in levels >0.005 ppm. The loss of the ability to produce high levels of phenylacetaldehyde contributed to the development of desirable aroma of the cultivated tomato. The findings provide a genetic explanation for one of the aroma changes that occurred during the domestication of the tomato. 相似文献
9.
Holland D Larkov O Bar-Ya'akov I Bar E Zax A Brandeis E Ravid U Lewinsohn E 《Journal of agricultural and food chemistry》2005,53(18):7198-7203
Apple (Malus domestica Borkh.) cultivars differ in their aroma and composition of volatile acetates in their fruit flesh and peel. Cv. Fuji flesh contains substantial levels of 2-methyl butyl acetate (fruity banana-like odor), while the flesh of cv. Granny Smith apples lacks this compound. Granny Smith apples accumulate mainly hexyl acetate (apple-pear odor) in their peel. Feeding experiments indicated that Fuji apples were able to convert hexanol and 2-methyl butanol to their respective acetate derivatives in vivo, while Granny Smith apples could only convert exogenous hexanol to hexyl acetate. Differential substrate specificities of the in vitro acetyl-CoA:alcohol acetyl transferase (AAT) activities were also detected among cultivars. In Granny Smith apples, the AAT activity was detected only in the peel, and its specificity was almost exclusively restricted to hexanol and cis-3-hexenol. In Fuji apples, the AAT activity was detected in both peel and flesh and apparently accepted a broader range of alcohols as substrates than the Granny Smith enzyme activity. Our data strongly suggest that different AAT activities are operational in apple tissues and cultivars and that these differences contribute to the variation observed in the accumulation of volatile acetates. 相似文献
10.
Recruitment, migration, growth, longevity and reproduction of Penaeus (Melicertus) japonicus Bate along the south-east coast of the Mediterranean were investigated.Relative population density, measured by catch per unit effort and average body length of the population were used in studying the recruitment, migration and growth of the various age groups.The reproductive state of the females was examined using three parameters: (1) gonado somatic index (ovary weight/total weight); (2) average diameter of ova; (3) morphological appearance of the ova according to a three stage scale.The results showed that P. japonicus migrates from inshore waters to the open sea during its benthic life cycle.Penaeus japonicus is distributed only on sandy substrate. It is suggested that the width of the longshore sandy strip determines the duration of the migration and hence the longevity and maximal growth of the individuals. Rate of migration might be accelerated by increasing density of young age groups near the shore. The estimated life span of each age group is 28–29 months. The maximal average body length of the population is 17 cm for males and 20 cm for females.Penaeus japonicus reproduce from April to November. This period corresponds to the appearance of a new age group about one kilometer offshore.The morphological appearance of the ova, average ovum diameter in each ovary and the female gonado-somatic index (GSI) are related to each other and can serve as a maturation index.Mature females are characterized by body length > 14 cm, GSI > 0.085 and average ovum diameter > 296 μ. 相似文献