Browsing by Subject "Physiologie"

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    Physiological mechanisms and growth responses of sweet potato subjected to salinity
    (2023) Mondal, Shimul; Asch, Folkard
    For the development of salt-tolerant sweet potato varieties, either through breeding or biotechnology, an appropriate salinity screening tool is necessary for the identification of tolerant or sensitive genotype. Our overall objectives for this study were to develop a suitable, reliable and rapid salinity screening tool in view of salt tolerance mechanism in sweet potato under salinity. To better understand the tolerance mechanisms; leaf level ion uptake and distribution patterns by transpirational water loss and leaf level ROS scavenging antioxidant enzyme activities were evaluated under salinity. Additionally, different ion extraction methods were tested which will contribute to the development of reliable salinity screening tool in sweet potato genotypes. All the experiments were conducted in the greenhouse and VPD (vapor pressure deficit) chambers of the Hans-Rutenberg Institute of Tropical Agricultural Sciences, University of Hohenheim, Germany, in a hydroponic system. Twelve genotypes of sweet potato were collected from Bangladesh Agricultural Research Institute (BARI) and used to evaluate salt thresholds with salt tolerance mechanisms for a wide range of salinity levels (0, 50, 100, and 150 mM NaCl). First, genotypic thresholds were determined for 12 sweet potato genotypes exposed to salinity, whereupon it was found that 75 mM root zone salinity (NaCl) was the threshold for sweet potato. The genotypic threshold was estimated from the dry matter accumulation that began to decrease under the influence of salinity. It was found that genotypic thresholds were negatively linearly correlated with the difference between tissue K content at 75 mM NaCl and tissue K content at controlled salinity in the root zone. This information is very important for identifying the salt tolerant and sensitive genotype of sweet potato. Second, the uptake and distribution of Na, K, and Cl ions by transpiration, across different-aged leaves, were studied to better understand the mechanisms of salt tolerance in sweet potato. Two different sweet potato genotypes were subjected to salt stress of 0 and 50 mM NaCl in artificially dry (VPD 2.27 kPa) and humid (VPD 0.76 kPa) chambers. We found that cumulative water loss per unit leaf area was twice as high at a VPD of 2.27 kPa, but Na uptake remained the same. No relationship was observed between water loss from individual leaves and Na or Cl uptake. About 30% more Na was distributed in the petioles of salt tolerant genotype compared to leaf blades, while the opposite was observed in salt sensitive sweet potato genotype and VPD had no effect on Na distribution. Third, the activities of ROS scavenging antioxidant enzymes were evaluated with respect to different leaf age, in two different genotypes of sweet potato under 100 mM salinity. In general, antioxidant enzymes in sweet potato do not respond to salt stress but are altered by the effects of leaf position, leaf age, duration of stress, and genotype. No effect of Na on antioxidant enzyme activities was found under salt stress in sweet potato leaves. However, the significant positive correlation between K concentration and the level of SOD (super oxide dismutase) in older leaves suggests that SOD contributes to the maintenance of a high K concentration to protect photosynthetic activity. In summary, this study shows that sweet potato responds differently to salinity depending on the genotype, and that the threshold beyond which yield decreases is 75 mM NaCl. Genotypic threshold strongly linked to high tissue K content under increasing salinity that suggests a salt tolerance mechanisms in sweet potato. Salt-tolerant sweet potatoes distribute significant amounts of Na and K in their petioles. Young leaves of the tolerant genotype contain more K under salt stress. GR and positive relationship between K concentration and SOD in salt tolerant genotypes indicate some tolerance mechanisms. So, a screening tool is proposed for sweet potato based on the genotypic ability to maintain high tissue K levels under increasing salinity level.
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    Physiologische und genetische Einflüsse auf die Qualität von Schweinefleisch aus baden-württembergischen Gebrauchskreuzungen
    (2012) Fecke, Anna; Weiler, Ulrike
    What genotypes, basing on the genetic lines supplied by German Genetic, guarantees both a high-value carcass and excellent pork quality and high eating quality and also how the criteria of fertility, weight development and yield at slaughter, relate to the criteria of pork quality. 10 genotypes were studied. Therefore the sows crossbred represent typically genotypes in Baden-Württemberg as well as the Leicoma hybrid sows. These sows were bred at the LSZ Boxberg with Pietrain and Duroc boars. The sows of the LW*(LC*DL) had the highest fertility rate. The boar lines showed no influence on either the birth weight or fertility parameters. The boar line, however, did reflect a highly significant influence on the daily gain in all further production periods (Duroc vs. Pietrain: suckling +8%; rearing +3,8%; fattening +6,5%).The offspring from the sows LW*(LC*DL) had the greatest daily gain in the suckling period and had a higher weaning weight (+6%, p<0.05) than the offspring from the LW*(SH*DL), which achieved the lowest overall weaning weight. On analyzing the relationship between the development weights in the various production periods and the birth weight, it was obvious that the birth weight provides a significant positive influence on the performance in every production period, except for rearing. Indeed, in the rearing period the animals with a high birth weight tended to show low daily gains, whereas the piglets with a low birth weight were able to partially compensate for the early growth deficit during this period. The Pietrain offspring had more lean meat content than the Duroc offspring. The dissection in Trial #2 shows that the Pietrain offspring had 3.3% more ham content and 4.0% more of the valuable cuts. The Duroc offspring had less lean meat content in the belly (-4.2%, Gruber Formula), more back fat (+13.7%), more leaf fat (+14.6%), and 12.5% more corrected fat area than the Pietrain offspring. The offspring of the sows LC*LW had a significantly shorter carcass than the offspring of the other sows. The offspring from the 50% Leicoma sows showed the greatest corrected fat area. The offspring from the sows LW*(LC*DL) had 17.1% less corrected fat area. The correlation analysis resulted in the established relationships. Especially of a practical interest, is the close relationship between lean meat content (FOM) and the pork underbelly (Gruber Formula) (r=0.92; n=240; p<0.001). For nearly every parameter the results of the pork quality grading under practical conditions (Trial #1) tended toward improved values for the pigs with Duroc genes, which showed a significantly lower drip loss. The influence of the sows on pork quality parameters was negligible. Besides these parameters, some carcasses were also characterized with PSE qualities (pH1<5.8; conductivity 24hr p.m.>8.0mS/cm). In Trial #1, based on the pH-readings at the slaughterhouse, almost no carcasses (0.15%) were identified with PSE, whereas the conductivity measurements in ham, 5.79% of the carcasses were identified as PSE. In Trial #2, 15.0% of the animals were PSE based on pH1 or conductivity measurements in the loin and ham. There were 5 carcasses which have PSE after both measurements in loin and ham. In the histochemical analysis of the muscle fiber classification the only difference between the boar lines was found in the percentage of red fibers. The eating quality tests revealed an influence from the boar line. In general, all genotypes produced a high quality lean meat content according to the market requirements. As to expectation the improved pork quality of the Duroc breed was justified by the best eating quality, an improved water-holding capacity and a higher intramuscular fat content. An acceptable overall pork quality can be achieved by pairing the offspring from the Pietrain*LW*(LC*DL). The offspring with some Schwäbisch-Hall genes have an opportunity to establish a regional market. However, their performance was not convincing because in fertility, in daily gain, and even in pork quality they attained below average values. Nevertheless, an optimal pork quality can be achieved more efficiently with other genotypes. On establishing predicting criteria, the percentage of PSE of the pork carcasses is quite positive. The superiority of the 24hr p.m. conductivity value for the drip loss predict is evident here. The measurement of the conductivity subsume the effects of slaughtering and cooling and is more appropriate than the pH1 value, especially, for the incoming inspection in the deboning area as well as for quality assurance.