scholarly journals Sources of Tyrosine in Genotypes of Solanum tuberosum L. Differing in Capacity to Produce Melanin Pigments

1994 ◽  
Vol 119 (4) ◽  
pp. 770-774 ◽  
Author(s):  
Robert P. Sabba ◽  
Bill B. Dean

Potato tubers (Solanum tuberosum) of genotypes that vary in resistance to dark pigment formation when damaged, characteristic of the physiological disorder blackspot, were assayed for free tyrosine. The tubers were also assayed for relative levels of chorismate mutase and proteinase activities, which can regulate free tyrosine levels. The susceptibility of potato tubers to blackspot was shown to be correlated to the amount of free tyrosine by third order regression (R = 0.88). Tyrosine was found to be a limiting factor in pigment development. Chorismate mutase activity (CMI and CMII) was not correlated to blackspot susceptibility of the genotypes studied. Proteinase activities of Atlantic, TXA 763-5, Ranger Russet, Russet Burbank, and Lemhi Russet tuber protein extracts measured with synthetic substrates correlated with blackspot susceptibility. This suggests that the high free tyrosine levels associated with blackspot susceptibility may be due to high levels of proteinase activity in the tuber, rather than tyrosine synthesis.


1966 ◽  
Vol 21 (9) ◽  
pp. 879-888 ◽  
Author(s):  
Volkmar Loeschcke ◽  
Hermann Stegemann

Up to 25 proteins have been found in the sap of potato tubers by polyacrylamid electrophoresis. The mode of preparation and concentration of the plant material was investigated as well as the pretreatment of the polyacrylamid gel to avoid undue retardation of the migrating bands.Sulfite was the most active inhibitor of sap-browning compared with ascorbic acid and cysteine. which did not influence the protein pattern except for one line. The juice had to be dialyzed or filtered through Sephadex G 25 to remove an unkown acidic material which interferes with the more acidic proteins and causes spreading and diffusing of bands. Proteins were concentrated by means of Carbowax MW 20000. For best results ionic contaminations inherent in the gels was removed by electrophoresis before applying the proteins or dyes. Very few proteins were affected by decreasing the pore size of the gel. Ammonium sulfate (40% saturation) precipitated mainly those proteins which are similar in electrophoretic behavior to the albumin- and transferrinregion of human plasma.



Plant Biology ◽  
2002 ◽  
Vol 4 (1) ◽  
pp. 77-85 ◽  
Author(s):  
M.-L. Fauconnier ◽  
J. Rojas-Beltrán ◽  
J. Delcarte ◽  
F. Dejaeghere ◽  
M. Marlier ◽  
...  


2000 ◽  
Vol 26 (3) ◽  
pp. 153-160 ◽  
Author(s):  
Yosuke MURATA ◽  
Kevin F. YAPTENCO ◽  
Tomohiro NOGUCHI ◽  
Toshiro SUZUKI ◽  
Hiroaki SATO ◽  
...  


2003 ◽  
Vol 43 (6) ◽  
pp. 631 ◽  
Author(s):  
L. A. Sparrow ◽  
K. S. R. Chapman

Thirteen field trials were conducted on ferrosols and tenosols in Tasmania to assess the response of potatoes (Solanum tuberosum L., cv. Russet Burbank) to basal (up to 250 kg/ha) and topdressed (up to 100 kg/ha) nitrogen fertiliser. Economic yield responses to basal nitrogen were obtained at 9 sites. Topdressing did not increase yield compared with equivalent rates of basal nitrogen, and often failed to compensate for a lack of nitrogen applied at planting. This lack of response may reflect the inability of the potato crop to make use of nitrogen applied during tuber bulking. Nitrogen fertiliser decreased tuber specific gravity at several sites. The effects of nitrogen on misshapen tubers, bruising susceptibility, crisp colour and hollow heart were inconsistent and often of no practical importance. However, at 2 sites, nitrogen fertiliser increased yields of misshapen tubers at the expense of processing tuber yields. At 1 of these sites, nitrogen topdressing decreased the yield of misshapen tubers. Otherwise, topdressing had similar effects on tuber quality to those of basal nitrogen. Growers should fertilise with nitrogen to optimise their yields. Optimum rates were greater in paddocks that had been continuously cropped for more than 10 years (average rate 193 kg/ha), than in those that had been in pasture (average rate 48 kg/ha).



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