Genetics of abiotic stress tolerance

Published on December 1, 2013   50 min

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Hello. My name's Mark Tester, and I've been asked to talk about the genetics of abiotic stress tolerance. I work primarily on salinity tolerance, so the focus will be on that. However, of course, I'll try to allow people to think more broadly and to consider how the work that we're doing on salinity tolerance could be applied to studies on drought tolerance, low temperature tolerance, high temperature tolerance, and all those other abiotic stresses that impinge on the plant's daily life.
The context for a lot of work on abiotic stress tolerance of plants is the requirement to increase food production. This increase is required in ways that are much greater than previously. In this slide, there's an analysis of the global cereal production over the last 50 years, in blue, and you can see that empirically, it is observed to be linear, with an average increase of about 32 million tons a year. If we are to meet the FAO's requirement for an increased food production of 70% by 2050, we need to increase this annual increase, if you're still with me, from 32 million tons a year to 44 million tons sustained over the next 40 years. That's increasing the rate of annual increase of food production that's been going 50 years by 38%. This is a very, very tall order, and requires significant innovations. One of the areas in which we need to innovate is to increase yield stability, which we'll discuss on the next slide.
So we need to increase the food supply. There are only modest opportunities left to increase the area under cultivation. There's, I think, also only a modest theoretical chance to increase the yield potential. That's a little more arguable, but I think it's a generalization that has a fair bit of validity. What we need to be able to do is increase what is termed the yield stability, increase the ability of plants to maintain their growth under less-than-optimal conditions relative to optimal conditions, so increase their ability to maintain yield when there is a low supply of water, a high amount of salinity in the subsoil, increasing the ability of plants to use nitrogen more efficiently. To do this, and to do this at a rate described in the previous slide, we need a serious innovation. We need to use the tools of plant science and agronomy. We need to be able to have innovation in modern plant breeding, such as provided by quantitative genetics and genomics. And we probably also need to use the tools of genetic modification. The graph on this slide shows three different varieties of wheat grown at different sites in Australia from relatively well- watered on the right too much less well- watered on the left of the slide, and it's showing here three different varieties. The one in green is better able to maintain its yield as you go to lower water supply sites compared to the other two varieties, in particular the one in red, where there's a big decrease in yield. What we're wanting to do is find the genes that are in such as that green variety, which are better able to help the plant maintain growth under the low water conditions and thus contribute to what we would term this yield stability.
My work mainly focus on salinity, and this can be used for this lecture as a model for abiotic stress tolerance and the use of genetics to try to address abiotic stress tolerance. Salinity is actually quite a good area of research to choose because it is widespread. It's present in semi-arid, dryland agriculture. It's particularly widespread in irrigated systems, where globally, perhaps 20% of the land area is affected, and that area is increasing. This is particular pertinent given that approximately 1/3 of the calories produced in crops are produced in these unsustainable, irrigated systems in which salinity is a very important issue. Of course, salinity is also increasing because of seawater ingress in many otherwise highly productive coastal areas. The deltas of some of the world's major rivers are examples of this. The Mekong River is the picture in the top right-hand slide, showing abandoned rice fields in the delta of the Mekong River in Vietnam. Salinity can be addressed by both management, agronomic solutions, but also genetics, and genetics can be a significant contributor in irrigated systems, but in dryland systems, it's the only option for trying to increase yields in areas with high amounts of subsoil salinity and no water to try to move that salinity out of the system. Another reason salinity's quite a good report is because the tolerance mechanisms which are slowly being elucidated are probably going to be largely universal. Salinity tolerance genes discovered in a dryland wheat system, for example, may well be likely to have some level of contribution in a wide range of other areas globally, irrigated rice, irrigated wheat, and so on. So I think a lot of the mechanisms can be applied over a wide part of the planet, and this is in contrast to many other stresses, in particular, drought, where some adaptations that will help plants grow well under one type of low water can, in effect be deleterious, detrimental, to growth in another type of drought. There's no such thing as drought per se. There's different types of droughts, and sometimes, often, in fact, these different types of droughts require quite distinct physiological adaptations to try to help plants maintain growth. So drought is much more complex than salinity. So benefits of investment in salinity research are quite likely to be delivered globally.

Genetics of abiotic stress tolerance

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