Sunday, August 27, 2017

Genes bring apple history into focus

DNA orbit animatedWe all know that apples are from Kazakhstan. But today, gene resequencing techniques are telling us more about the long voyage of the apple from the wilds of the Tien Shen mountains to the U-Pick orchard.

In particular, the modern European-style apple is a cross between the original Kazakh apple, Malus sieversii, and the European crab apple, M. sylvestris.

A study of 117 modern varieties plots the influence of 24 apple species on today's domesticated apples. In a nutshell, according to the authors,

During the domestication process, cultivated apples retained the large fruit size from M. sieversii, gained the firm texture and appetizing flavor from the hybridization with M. sylvestris, and continued to be bred into larger and firmer fruit with better flavor and aroma.

Again, we already know that flavor is largely about striking the right balance between sweet and tart. The researchers found the genes for these traits in modern domesticated apples: sweet from the Asian sieversii and tart from the European sylvestris.

Over time, human preference had selected for these genes.

Of that process, the authors say,

Crop domestication is an artificial selection process, fostering co-dependence between human and crop plants. This process often includes an initial phase of unconscious selection by farmers for several thousand years, followed by a subsequent breeding phase of intentional selection of favorable traits by breeders.

Naibin Duan, Yang Bai, Honghe Sun, Nan Wang, Yumin Ma, Mingjun Li, Xin Wang, Chen Jiao, Noah Legall, Linyong Mao, Sibao Wan, Kun Wang, Tianming He, Shouqian Feng, Zongying Zhang, Zhiquan Mao, Xiang Shen, Xiaoliu Chen, Yuanmao Jiang, Shujing Wu, Chengmiao Yin, Shunfeng Ge, Long Yang, Shenghui Jiang, Haifeng Xu, Jingxuan Liu, Deyun Wang, Changzhi Qu, Yicheng Wang, Weifang Zuo, Li Xiang, Chang Liu, Daoyuan Zhang, Yuan Gao, Yimin Xu, Kenong Xu, Thomas Chao, Gennaro Fazio, Huairui Shu, Gan-Yuan Zhong, Lailiang Cheng, Zhangjun Fei, and Xuesen Chen. 2017. "Genome re-sequencing reveals the history of apple and supports a two-stage model for fruit enlargement" Nature Communications 8, 249 doi:10.1038/s41467-017-00336-7.

Image: Zephyris at the English language Wikipedia. GFDL  from Wikimedia Commons.

1 comment:

  1. Great article.

    I feel that our various North American crabs have already made some genetic contributions. For example - the Hewe's (Virginia) Crab. See the article at https://www.smithsonianmag.com/science-nature/apples-of-your-eye-71328777/ where it says "Thus emerged,for instance, the small Hewes’ Crab, possibly a cross between an apple of European stock and the crab apple, native to Virginia."

    The researchers in this article indicate that our N.A. crabs might have even more to contribute - "In addition to M. sieversii in Xinjiang, six other species in distinct habitats, such as M. ioensis and M. angustifolia in North America and M. baccata in East Asia, were also identified with homogeneous genetic background, which gave rise to other hybrid species and possess tremendous value in apple breeding practices (Supplementary Fig. 3). "

    I know that the native crabs and wild hybrids where I live in Ohio are as tough as nails. Very disease resistant and bear a crop every year.

    Let us hope that DNA research will identify the markers for the most desired traits. Then massive amounts of small seedlings can be grown and DNA tested and evaluated quickly for further development.

    I fear that the Chinese are way ahead of us on this.

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