Anthocyanin decolorisation and its role in lychee pericarp browning

Mature red lychee fruit were stored at 3 different temperature and relative humidity regimes. Total anthocyanin concentration, pigment distribution, pH of the pericarp homogenate, Hunter a values (redness index), and visual colour were measured as a function of pericarp weight loss. Pericarp colour rapidly deteriorated during both ambient and high temperature storage, resulting in a uniform browning of the pericarp surface. The degree of tissue browning was proportional to the rate of pericarp desiccation. Although anthocyanin degradation occurred concurrently with tissue browning, visual colour and Hunter a values were not consistent with total anthocyanin concentration. Instead, a more significant correlation was seen between Hunter a values and the pH of the pericarp homogenate. Pericarp colour could be altered by external pH. Acidification of whole fruit increased pericarp redness, whereas alkaline treatment caused discoloration. Both colour responses occurred independently of anthocyanin synthesis and degradation and were completely reversible. These results question the current theory that browning is due to anthocyanin degradation. No evidence of browning was observed in the anthocyanin-containing mesocarp, and acidification of already brown tissue significantly increased pericarp redness independently of anthocyanin synthesis. We believe that anthocyanin pigments were progressively decolorised during ambient storage, possibly due to changes in pericarp pH. Once colourless, independent tissue browning became visual and was enhanced.

Dissemination of New Technology in a Farming Systems Research and Extension Programme: Diffusion of Rice Varieties in an Area with Poor Production Potential

SummaryThe diffusion of rice varieties introduced into an area with poor production potential and problems of soil degradation was studied in a farming systems research and extension programme. Two rice varieties, BW. 272–3 and At. 85–1 were identified as appropriate for the area and efforts made to transfer the experimental results to the farmers. BW. 272–3 was widely adopted by farmers in the lower, intermediate and upper areas of the recommendation domain but adoption of At. 85–1 was confined to the intermediate and upper areas. Adoption of rice varieties was mainly governed by the characteristics that allowed a variety to perform well under adverse conditions and by the farm gate price it could command, which depended on grain pericarp colour.Difusión de nuevas variedades de arroz

Linkage between brown planthopper resistance and morphological characters in rice

SummaryLinkage was detected between brown planthopper resistance and anthocyanin or nonanthocyanin pigmentation in rice cultivars. The crossover values were: 21·9–37% for leaf sheath, 31% for junctura, 41% for auricle, 12·5–40% for ligule, 14·32–1% for leaf tip and margin, 19·7–37% for stigma, 19·7–36% for apiculus and 46·7% for pericarp colour. Genes governing resistance and black hull colour or glabrousness of leaf blade assorted independently. The genes identified and designated for brown planthopper resistance and pigmentation have been tentatively proposed to linkage groups II, IV and V.