Improve water use through genetics
By Thinus Louw: Agronomist - Free State Business Unit
Global agricultural production has to grow by an astronomical 70% average by 2050 to feed an increasing world population. Reaching this challenging goal will require an enormous effort, for various reasons. To make matters worse, this 70% growth in agricultural production will have to be achieved despite several factors that would make it more difficult. Firstly, there is the negative impact of global warming on agricultural production. The influence of the expected increases in temperature on a warm, dry area is substantial. Secondly, there is increasing pressure on agriculture due to the fact that it consumes so much water, and thirdly there is the influence of growing fertilizer costs on the profitability of agricultural production.
Given this background, we have to consider how and where improved genetics can contribute towards the attainment of this objective. It is generally accepted that plant breeding was responsible for one of the largest, if not the largest, contribution to increased agricultural production during the last few years. For the purpose of this discussion, we will focus on the potential influence of improved genetics on the more efficient use of water and plant nutrients.
Experts in this field agree that improving the resistance of plants to drought stress with the use of genetics is very difficult and expensive. But it can be done! The same goes for the improvement of the plant's ability to use plant nutrients, especially nitrogen, more effectively. It is relatively simple in the case of RR or BT genes, as plants would either have this trait or not. It is different when breeding for plants that can withstand moisture stress more effectively, as there are thresholds. In other words, a plant cannot live without water and/or nitrogen. Remember, the aim is not for plants to survive under stress conditions, but for them to produce! This, of course, is of the utmost importance to thoroughly understand the mechanisms of plant stress before any progress can be made. One of these effects, for example, is that the genes involved in the resistance to moisture and nutrient stress have an inhibiting effect on the production of ethylene. When the plant produces ethylene, it's going into a stressed state.
Germplasms with the ability to handle the mentioned stress conditions well are the building blocks of any progress in this field. This germplasm descends from plants with specific inherent traits which allow them to not only produce better under stress conditions than conventional cultivars, but also to produce the same as conventional cultivars during favourable conditions. This germplasm is available to the seed industry in South Africa. It is interesting that there is a fair degree of synergism when breeding/selecting plants with the mentioned traits. Therefore the tendency is that plants that use water more effectively are also inclined to use nitrogen more efficiently. The reason for this phenomenon is evident: it is all about the ability of the plant to handle stress.
Certain physical traits are associated with plants that perform well under drought stress conditions. Some of these traits are:
- Lapse of time between the appearance of the beard and pollen fall. The trend is that plants under the mentioned stress conditions will perform better if pollen fall happens sooner after the appearance of the beard.
- A stronger tendency towards multiple cobs is another trait which indicates a better ability to handle stress.
- The so-called Staygreen trait is also associated with plants that can better handle this stress.
- A maize plant with a smaller tassel has further advantages over a plant with a larger tassel.
- Plants that are more resistant to this stress also tend to flower faster than plants that are less resistant. Plants that flower faster can, for example, reduce the negative effect of a mid-summer drought. Evidently this and other traits can sometimes also have a negative effect on production.
- It is interesting that plants that tend to curl their leaves sooner under moisture stress conditions are often seen as plants that can limit moisture losses and will therefore survive longer than other plants. The reverse is actually true: there is a trend that plants who do not curl their leaves as easily will perform better under said conditions. The explanation for this is actually logical. It is no use for the plant to only survive if it doesn't produce. It is better for the plant's leaves to stay open for as long as possible and produce as much as possible.
- Maize plants that fill the cobs with kernels quickly after pollination, especially at the ends of the cob, handle stress conditions much for effectively than maize that tend to fill the cobs more slowly.
- Lastly, the root system also plays an important role in the handling of stress. A deep, aggressively growing root system is naturally preferable to a shallow, slow growing system.
Even though genetics is not within Omnia’s field of expertise, we can still contribute in the following ways:
- Because we often work with experts in other disciplines such as the seed industry, we will be able to give our clients limited advise, or refer them to experts who can assist them regarding the choice of adapted cultivars.
- Most of Omnia's field personnel have good knowledge regarding the choice of crops in a specific area, the optimal planting time of different crops, as well as the best practices for soil preparation. All of the mentioned factors have an influence on the optimal use of water and nutrients.
- Obviously a balanced fertilizer programme will have a large impact on the efficient use of water and nutrients by the plant. Over and above the influence of the total rate of every nutrient applied, other facets of the fertilizer programme such as the timing of application, where the fertilizer is placed, specific product, etc. also have a large influence.
Agriculture and especially plant breeders, are facing an enormous challenge. We are confident that this challenge will be met. SIMMYT, who supplies improved germplasms to the seed industry, estimates an advantage of up to $1.5 billion if, just in Africa, current cultivars are replaced by 2016 with better drought resistant ones. Success in this field is therefore non-negotiable.