Minerals are believed to be essential for human health and also have an effect on fruit development and quality. However minerals can’t be created by living things, only coming directly from the diet.  

Apple, one of the staple fruits worldwide, is a good resource of mineral nutrients. So far, there are few reports on the evaluation of fruit mineral content in apple germplasm resources, and little is known about genetic basis of mineral accumulation in apple fruit.  

In order to understand the genetic variation for calcium (Ca) and zinc (Zn) accumulation in apple fruit germplasm, LIAO Liao, supervised by Prof. HAN Yuepeng from Wuhan Botanical Garden of the Chinese Academy of Sciences, assessed Ca and Zn content in mature fruits of 417 apple germplasm (378 cultivars and 39 wild relatives) by Flame Atomic Absorption Spectrometry (FAAS). 

A wild genetic variation for fruit Ca and Zn accumulation in apple germaplsm was uncovered. The content of Ca between the varieties reached 23 fold, while the Zn was as high as 95 times. The average concentration of Ca was quite similar between cultivated and wild fruits.

By contrast, the average concentration of Zn in wild fruits was significantly higher than that in cultivated fruits, which could be attributed to an indirect result of artificial selection on fruit quality during the process of apple domestication. Apple fruits from different geographical origins showed no significant difference in the Zn and Ca concentration.  

Both Ca and Zn concentrions in apple fruit were the highest in the early stages of fruit growth, and decreased significantly in fruit expanding stage. During the late stages of fruit development, Ca concentration showed a slight decrease trend, whilst Zn displayed different patterns of variation. 

This  is the first study to provide a large-scale survey of Ca and Zn concentrations in apple germplasm that  is helpful for future research on genetic basis and breeding of apple in terms of fruit mineral nutrition. 

This work was supported by the National Natural Science Foundation of China, and the results have been published in Journal of the Science of Food and Agriculture entitled “Assessment of calcium and zinc accumulation in cultivated and wild apples”. 

Range and distribution of the concentrations of Ca and Zn in mature fruits (Image by LIAO Liao) 

Changes in the Ca and Zn concentration in fruits of different cultivars of apple (Image by LIAO Liao)