Turning Potatoes into a Staple Grain: Variety Selection Comes First
To make the potato a staple grain, whether it is turned into steamed buns and noodles on the dining table, or into reserve grain and emergency grain in the national grain depots, the potato must first be "transformed" into potato flour. So, can all potatoes be processed into potato flour? What kind of potato can be "ground to pieces" for national food security? To find out, our reporter interviewed Jin Liping, chief expert of the National Potato Industry Technology System and a researcher at the Institute of Vegetables, Chinese Academy of Agricultural Sciences.
Potato Flour
Currently Only a Few Varieties Can Be Used for Potato Flour Processing
Using fresh potatoes as raw material, through cleaning, peeling, sorting, slicing, rinsing, pre-cooking, cooling, steaming, mashing and other processes, then dehydrating and drying, the resulting fine granular, flake-like or powdery products are collectively called potato flour.
The state is promoting the strategy of making the potato a staple grain, turning the little potato into a staple food on the dining table. This involves not only using potato flour to make steamed buns, noodles and comprehensive utilization products, but is also a choice based on the potato's high yield, the nutritional value of potato flour, and its easy storage. However, not all potatoes can be used for potato flour processing; currently only a few varieties produce potatoes that can be used for potato flour processing. At present, varieties dedicated to fried food processing and potato flour processing are still dominated by introduced foreign varieties. In particular, the varieties grown on a large scale in North China for food processing and potato flour processing raw material production are basically the introduced foreign varieties "Shepody" and "Atlantic." These two varieties have excellent processing quality, but because they require large amounts of water, fertilizer and pesticides, their planting cost is high, the suitable areas are small, and their disease resistance is poor, making them difficult for ordinary farmers to grow successfully.
Specialized Varieties
The vast majority used in production are fresh-eating table potato varieties, which are hard pressed to meet the needs of staple-grain development
Potato varieties differ markedly in tuber dry matter content, tuber flesh color, eye depth, reducing sugar content, solanine content, polyphenol oxidase content and so on, all of which affect the processing quality of potato flour. Varieties with high dry matter content give a high flour yield; white tuber flesh gives potato flour a light color; many and deep eyes give a low output rate; high reducing sugar content and polyphenol oxidase content darken the color of the potato flour; and high solanine content makes detoxification difficult and the process complicated. Therefore, producing potato flour requires selecting varieties with shallow eyes, good tuber shape, white tuber flesh, low reducing sugar content and low solanine content. In addition to the above requirements for potato flour processing varieties, staple-grain varieties should also be rich in protein, vitamin C, carotene and other beneficial substances and nutritional quality indicators.
As of 2013, China had bred more than 430 new varieties, of which more than 200 new varieties were selected and approved since 2001, mainly including fresh-eating table potato types, starch processing types, fried food processing types and specialty types, with considerable improvement in yield, quality, disease resistance and appearance traits, but only 5-8 potato flour processing varieties. The vast majority applied on a large scale in production are fresh-eating table potato varieties, which are hard pressed to meet production and staple-grain processing needs.
Variety Breeding
Domestic breeding lacks high-quality parents; 50% of the varieties bred so far come from 7 parents
The potato is a tetraploid, vegetatively propagated crop, so germplasm innovation and variety breeding take a very long time; breeding one new variety takes 10-13 years. For a long time China's potato processing industry was underdeveloped, and potato breeding took high yield and disease resistance as its main goals, resulting in a single type of bred varieties and a severe shortage of various specialized varieties.
The lack of superior germplasm resources has long been the main limiting factor in China's potato variety breeding. Due to the lack of long-term stable support, resource research and improvement have lagged, and research on mining and utilizing favorable genes in related resources is still at an early stage. Breeding lacks high-quality parents; 50% of the varieties bred so far come from 7 parents, and very few breakthrough superior varieties have been bred. Internationally, nearly 230 wild species and primitive cultivated species, with more than 7,000 local varieties in total, are conserved; at present China has conserved only more than 3,000 resources in a few research institutions, among which there are large numbers of duplicate resources. Seriously insufficient scientific and technological investment has led to China's potato breeding technology lagging behind, being unsystematic and inefficient, and has further constrained the carrying out of basic and public-welfare research such as germplasm innovation and breeding technology innovation.
Virus-Free Seed Potatoes
At present the coverage rate of high-quality seed potatoes is only about 35%, and most farmers use their own retained seed potatoes
Specialized varieties, like ordinary varieties, must undergo virus removal to restore the variety's characteristics and produce virus-free seed potatoes before they can be used in production, and only when matched with high-quality and efficient production technology can a relatively high yield be obtained. Because genetic linkage is difficult to break and for other reasons, generally high-quality processing specialized varieties have poor disease resistance, so in production high-quality virus-free seed potatoes must be used for high yield to have a foundation.
At present, virus-free seed potato production has spread across more than 20 provinces, municipalities and autonomous regions nationwide. According to incomplete statistics, in 2014 the production capacity of pre-elite seed potatoes (microtubers) had reached 4.5 billion, with actual production of about 2 billion, but the current coverage rate of high-quality seed potatoes is only about 35%, and most farmers are still using their own retained seed potatoes.
The reason is that the existing seed potato production system lacks planning, and investment is mostly concentrated in the labor-intensive, energy-consuming links of tissue culture and pre-elite seed potato production, while insufficient attention is paid to base construction, standardized production technology systems and quality control technology research and development in the field seed potato production link. As a result, microtuber production capacity is large while the seed potato production capacity actually used for commercial potato production is insufficient, causing virus-free seed potatoes to be of poor quality and high price.
To accelerate the promotion of virus-free seed potatoes, there is an urgent need to speed up the formulation of a potato seed industry plan, build a potato seed industry system with clear division of labor, smooth circulation, high quality and high efficiency; strengthen the building of enterprise-based propagation and marketing systems to enhance the supply capacity of high-quality seed potatoes; establish third-party quality inspection and testing service institutions to ensure seed potato quality; and strengthen technical training to expand potato farmers' awareness of high-quality seed potatoes.
Resistance to Late Blight
Breeding disease-resistant varieties is like a race between breeders and the changing physiological races of the late blight pathogen
Late blight is the most important disease harming China's potato production. It occurs year-round in the Northeast and Southwest, the main potato-producing areas, and also frequently occurs in parts of the Northwest and North China, seriously affecting the yield and quality of potato production. Breeding and planting disease-resistant varieties is the most economical, most effective and simplest method of controlling potato late blight, but late blight resistance is very complex, and the physiological races of the pathogen change frequently. Newly emerging physiological races cause many disease-resistant varieties, even newly released disease-resistant varieties, to lose resistance and suffer sharp yield reductions. Therefore, breeding disease-resistant varieties is like a race between breeders and the changing physiological races of the late blight pathogen. With deeper research into late blight resistance and the application of molecular biology techniques in conventional breeding, more potato varieties with better and more durable resistance to late blight will be bred and applied in production.
Making the potato a staple grain means working hard on deep processing of potatoes; fresh eating is only a small part, and producing potatoes that can be processed into potato flour is the core of staple-grain development. A few days ago, the reporter visited the Xisen Potato Industry Group, whose R&D base is located in Yanqing, Beijing.
In Xisen's production workshop, the reporter saw workers under a 40-power microscope stripping shoot tips into the nutrient medium in test tubes. This process is called shoot-tip virus elimination, and it is a key step affecting potato yield before propagation. In the storage workshop, little potatoes the size of a one-yuan coin were piled in wooden boxes; these are called pre-elite seed potatoes and will undergo field planting trials. Xisen Potato Industry Group is the enterprise supporting the National Potato Engineering Technology Research Center. It has built a virus-free potato microtuber rapid propagation base in Yanqing, Beijing, with an annual output of 420 million virus-free microtubers, and has built a 300,000-mu field seed potato breeding base. It is a potato production and processing enterprise whose breeding level and production capacity are among the leading in the country. Chairman Liang Xisen told the reporter that Xisen currently has 18 varieties with independent intellectual property rights, among which "Xisen No. 3" and "Xisen No. 4" have already passed variety approval, while "Xisen No. 5," "Xisen No. 6" and "Xisen No. 7" are undergoing regional trials and are applying for a "birth certificate."
It is understood that the potato varieties used in most parts of China at present are varieties such as "Atlantic," "Shepody" and "Dutch potato" introduced from abroad in the 1980s. These varieties have gradually been phased out abroad and also show variety degeneration in China. Kong Haiming, a technical staff member of the Xisen Group, said that the "Atlantic" variety is large and prone to hollow heart, and "Xisen No. 5" has solved this problem well, while "Xisen No. 3" and "Xisen No. 4," mainly used for fresh eating, are more outstanding in yield than the "Dutch potato."
Having shifted from real estate to agriculture, Liang Xisen has been "burning money" on breeding new varieties for 10 years. When the variety resources reached a certain scale, he again and again called on the state to switch varieties. "If our country's seed potatoes could use better varieties, it would be a revolutionary change for the entire industry." Liang Xisen said he was very excited about the staple-grain strategy for potatoes just announced by the Ministry of Agriculture, but he always worried that the public might misunderstand potato staple-grain development, thinking that staple-grain development means eating fresh potatoes. He told the reporter that from the perspective of the national food security strategy, deep processing of potatoes is where the significance of promoting staple-grain development lies, and that the potato flour processing industry requires unified planting, unified management and unified processing using varieties suitable for processing into potato flour, which is very difficult to accomplish in smallholder family production.