Seed banks for rice

We recently sounded the alarm in Water Matters that the world is threatened by rising rice prices. The eyes of more than half of humanity are turning to the grain’s seed banks, especially the richest one, operated in the Philippines by the International Rice Research Institute.

Disappearing rice paddies

Historic rice varieties, both seeded Oryza sativa and African O. glaberrima, are being displaced from agriculture by newer cultivars. More than one farmer is changing his production profile from rice to other crops. Plenty of people are also giving up farming to seek their fortunes in the cities.

Even worse off are wild relatives of rice (e.g., Leersia blizzard and Zizania ostraca), threatened by habitat loss and, in places, extermination as living reservoirs of pests and pathogens of cultivated forms of rice. The importance of certain CWR, especially Porteresia coarctata, is increasing in the era of modern climate change and habitat loss, as they are donors of invaluable salinity resistance genes [1, 2, 3, 4].

Does it work? Don’t correct it unless…

The common method of accumulating rice gene resources remains the storage of seeds in seed banks under moderately low temperatures (+2°C to -20°C), and at the same time moderately low humidity (on the order of 6-7 percent of the initial moisture content of fresh weight). Seeds banked in this way have to be renewed every dozen years or so by sowing under controlled conditions and then harvesting the progeny seeds. This entails the risk of the disappearance of some alleles due to the random nature of inheritance, and, above all, the loss of a significant proportion of seeds and seedlings under the pressure of pathogens, herbivores and the action of abiotic factors (droughts, hailstorms).

Meanwhile, a number of species and varieties require quite different methods of long-term storage. Conversely, even ordinary specimens can be banked almost indefinitely (that is, without the need for refreshing by sowing and with no discernible loss of viability after thousands of years) using more expensive, more technically sophisticated methods. Simply drying them more powerfully and then freezing them in liquid nitrogen would suffice. Or, instead of seeds, collect in vitro cultures that can be passaged or frozen in one way or another [1, 2, 3, 4].

Reserves – time for a comeback?

Among the wild relatives of rice, there is no shortage of species for which it would be advisable to create protected areas (reserves and national parks), possibly cultivation in a kind of botanical gardens (field gene banks). This is especially true of genera and species:

1. not setting seeds at all or setting them sporadically, multiplying only or mainly vegetatively (many Leersia fezes, Oryza longistaminata, O. neocaledonica, O. granulata, O. meyeriana);
2. producing, as befits angiosperms, recalcitrant seeds that die when dried – so they cannot be stored in low humidity or frozen after drying, e.g.: Porteresia coarctata;
3. not flowering under seed bank conditions(Oryza schlechteri, Hastings River reed Potamophila parvifolia , and Zizaniopsis at IRRI);
4. requiring specific conditions, e.g.: shade with permeable, fresh soil as forest species (albeit the previously mentioned Oryza granulata and O. meyeriana). [1, 2, 3, 4]

Unnecessary twins

More than 780,000 samples of cultivated rice and their CWRs are now deposited in seed banks in more than 40 countries. Unfortunately, a significant and, even worse, an unknown number of them are duplicates. The number of samples therefore does not correspond to the number of historical cultivars and wild rice cousins. Thus, space and funds are wasted maintaining the same variety in multiple locations, while leaving dozens of other cultivars and CWRs at the mercy of fate.

The most important, because the richest rice seed banks in the world, are those managed by the CGIAR (Consultative Group for International Agricultural Research), while physical seed is stored in the largest international banks: International Rice Research Institute (IRRI, O. sativa) and AfricaRice (African rice O. glaberrima). Also, CIAT (International Center for Tropical Agriculture) has collections of rice and its relatives for Latin American countries.

As you can easily guess, an impressive stock of local breeds, historical cultivars and wild rice relatives is being collected by the People’s Republic of China’s national seed bank: CAAS. The analogous institutions of the United States and the Russian Federation are also quite resourceful. But even the richest gene bank won’t help when a tsunami of thermonuclear fire hits, vaporizing both the resources themselves and the scientists who study them [1, 2, 3, 4].

In the article I used, among others:

1. https://www.irri.org
2. https://www.africarice.org
3. https://www.ifpri.org/partnership/international-center-tropical-agriculture-ciat/
4. https://caas.cn/en/Newsroom/ResearchUpdate/02dbb70ec5a84fabac4b87b3224be5cc.htm