Organic food is the development trend of food in the world today. China's green food is a kind of food with pollution-free, safety, high-quality and nutritious properties, similar to organic food in the international market. The Chinese government has paid attention to the sustainable development of agro-ecosystems under the pressures of population growth and agricultural expansion since the 1980s and began to develop a green food industry in 1990. After the development of about two decades, now the Chinese green food industry has already entered a fast-growth stage. It has reached a considerable scale and is expanding rapidly. The share of green food in the global market is continuously increasing and a two-tier certification system has been established. However, green food's further development is still facing some difficulties and problems. This paper mainly analyzes those problems and discusses reasonable solutions. Specifically, this paper first gives a detailed introduction to green food and the green food industry in China, and then analyzes the major problems impeding the further development of green food industry, such as unreasonable product structure and enterprise structure, incomplete market system and backward certification system. Finally, suggestions on product structure, enterprise structure, publicity, market, certification system and governmental policies are put forward.

BackgroundThe intramuscular fat content (IMF) refers to the amount of fat within muscles, including the sum of phospholipids mainly found in cell membranes, triglycerides and cholesterol, and is determined both by hyperplasia and hypertrophy of adipocyte during the development of pigs. The IMF content is an important economic trait that is genetically controlled by multiple genes. The Laiwu pig is an indigenous fatty pig breed distributed in North China, characterized by excessively higher level of IMF content (9%~12%), therefore, is suitable for the identification of genes controlling IMF variations. To identify genes underlying IMF deposition, we performed genome-wide transcriptome and methylome analyses on longissimus dorsi (LD) muscle in Laiwu pigs across four developmental stages.ResultsA total of 22,524 expressed genes were detected and 1158 differentially expressed genes (DEGs) were hierarchically clustered in the LD muscle over four developmental stages from 60 d to 400 d. These genes were significantly clustered into four temporal expression profiles, and genes participating in fat cell differentiation and lipid biosynthesis processes were identified. From 120 d to 240 d, the period with the maximum IMF deposition rate, the lipid biosynthesis related genes (FOSL1, FAM213B and G0S2), transcription factors (TFs) (EGR1, KLF5, SREBF2, TP53 and TWIST1) and enriched pathways (steroid biosynthesis and fatty acid biosynthesis) were revealed; and fat biosynthesis relevant genes showing differences in DNA methylation in gene body or intergenic region were detected, such as FASN, PVALB, ID2, SH3PXD2B and EGR1.ConclusionsThis study provides a comprehensive landscape of transcriptome of the LD muscle in Laiwu pigs ranging from 60 to 400 days old, and methylome of the LD muscle in 120 d and 240 d Laiwu pigs. A set of candidate genes and TFs involved in fat biosynthesis process were identified, which were probably responsible for IMF deposition. The results from this study would provide a reference for the identification of genes controlling IMF variation, and for exploring molecular mechanisms underlying IMF deposition in pigs.Electronic supplementary materialThe online version of this article (10.1186/s12864-017-4201-9) contains supplementary material, which is available to authorized users.

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