Methanol extracts of vine latex of four cultivars of sweetpotato [Ipomoea batatas (L.) Lam.] were analyzed for their chemical phenolic composition by reversed-phase HPLC. Major components were identified as hexadecyl, octadecyl, and eicosyl p-coumarates by an evaluation of data from UV spectra, hydrolysis, synthesis, and GC/MS of their trimethylsilyl derivatives. Both Zand E-isomers of the phenolic acid were found, with the latter predominating. Trace quantities of hexadecyl (Z)-and (E)-ferulates were also identified in ester concentrates. Levels of octadecyl (E)-p-coumarate ranged from 0.7% fresh weight in cv. Resisto to almost 2% in cv. Jewel, while the hexadecyl ester levels were only V* to V3 these values. Levels of the Z-esters were Vio to V20 of the levels of the corresponding E-isomers. Levels of the esters in cv. Jewel sweetpotato root latex were 2-10-fold the levels in the vine latex, while the ratio of E-esters to Z-esters was found to be 7-14-fold. The concentration of Z-esters among the sweetpotato cultivars tested correlated closely with the leaf feeding index for the sweetpotato weevil (Cylas formicarius) (R2: C20 = 0.96; Cis = 0.98; Cíe = 0.71). The results indicate a possible relationship between latex chemistry and insect resistance that might be exploited via plant breeding.

Bluish fluorescent and phenolic components were produced in cassava roots in response to cutinjury, and in relation to physiological deterioration and microbial deterioration. The former proved to consist of five coumarin components, the main three of whichwere scopoletin, scopolin and esculin, and the other two were scopoletin-and esculetin-containing conjugates. A main component of the latter was (+)-catechin. Some enzymes pertaining to the production of the secondary metabolites such as acid invertase, phenylalanine ammonialyase and peroxidase were formed in cut-injured tissue and in non-infected tissue adjacent to the soft-rotten part. Cassava roots easily deteriorate during storage soon after harvest, and the deteriorative nature is classified into physiological (or primary) deterioration and microbial (or secondary) deterioration.1~4) The former involves brownish discoloration (so called vascular streaking) in the intervening part between the outermost and inner parts of parenchymatous tissue, and the latter is characterized by light brownish discoloration of the soft-rotten part and by blue-black pigmentation of the xylem vessels or extensive discoloration, light greyblack, of the non-rotten tissue adjacent to the rotten part. Such deterioration in cassava after harvest lowers the food quality and is a serious problem for a number of the people in tropical regions for whomcassava roots are the main staple. Therefore, the Tropical Products Institute

When cassava (Mauihet escadeta Crantz) root was cut into blocks and incubated under laboratory conditions, the blocks showed more widespread and more even symptoms of physiological deterioration than those under natural conditins. Thus, the tissue block system has potental for bio- (12)(13)(14). The deterioration consists of two types. The first is physiological deterioration characterized by internal root discoloration. The second is microbial deterioration caused largely by a wound pathogen (1). The mechanism and cause of the deterioration, however, have not yet been elucidated thoroughly.Under natural conditions, the roots show rather local and spotted deterioration symptoms and that has hindered biochemical studies. In the present study, we cut the cassava root into blocks and incubated them under laboratory conditions. The blocks showed more widespread and more even physiological deterioration symptoms than those under natural conditions, indicating the potential for biochemical study of deterioration.Cassava is a cyanogenic plant and contains linamarin (isobu-tyronitrile-i-r-glucoside) as a main component (2). In this paper,we investigated the changes in cyanide content and linamarase (linamarin fl-D-glucoside glucohydrolase; EC 3.2.1.21) activity

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