5 minute read
Climate crisis: New strategies to manage fruit production
Fruit production is becoming increasingly important the South African agriculture. Recent estimates by the Buro for Food and Agriculture Policy indicate that the area under high value export fruits and nuts has expanded by 130 000 hectares over the past decade and that export volumes may grow a further 30% by 2031, suggesting that the gross production value could reach R53 billion by 2031, in nominal terms. In addition, the value of citrus and subtropical crops currently stands at R34 billion but by 2031, citrus alone is expected to reach R40 billion.
Mariana Purnell CONTRIBUTOR
Apart from the known infrastructure problems like ports, roads and irrigation schemes that will impact the horticulture industry going forward, the impact of climate change is an unknown factor.
However, there are many challenges for worldwide agriculture. By 2050 we will need to produce 60 to 100% more food. The US anticipates that its fresh fruit imports will rise by 45% as the land available for farming shrinks. The pressure is on to improve productivity or use marginal land.
Adapting production systems to be resilient against extreme climates and adverse environmental conditions is a growing priority. The focus has now turned to a range of climate smart solutions, including biotechnology innovations that allow scientists to explore the potential of science to minimise the impacts of climate change.
At a recent Croplife seminar, Chris Dardick, Lead Scientist at the US Department of Agriculture, explained the approach of the Agricultural Research Service (USDA-ARS) to both climate change and improved environmental stewardship in order to reduce environmental impacts of agricultural systems and enhance the ability of farmers to secure fruit supplies in the future.
Biotechnology strategies are focused on improving both the productivity and the production practices, as well as their sustainability with regard to chemical and water inputs and the climate response of orchard systems. But there are numerous challenges for fruit crop genetic improvement. Fruit trees are large, perennial, propagated vegetatively and slow growing. They have very particular environmental needs, are also subject to dormancy which is cold induced and have high water requirements. Despite the fruit being highly perishable, consumers expect beautiful, blemish-free products regardless of the important role played by chemical inputs as well as storage and shipping.
Plant architecture has become a critical feature of fruit and nut tree sustainability as it affects the productivity of the system and the environment. The now established technique of training branches allows for better light capture due to improved light penetration, which improves the fruit quality as a result of enhanced colouration.
In peach and apple orchards, for example, the trees are pruned into a plant wall rather than free-standing trees and managed through labour intensive practices to optimize light capture and fruit quality. The light penetration is important for the fruit as it impacts the efficiency of the trees in terms of transportating water and nutrients.
Other horticultural issues are transpiration and water use efficiency, access to water and nutrients as well as tolerance to drought and flooding. Typically, the top of the tree is grafted onto a special root stock, bred for its ability to access water and nutrients and also tolerate flooding.
From an economic standpoint there are also benefits as there is much higher productivity on less land with fewer chemical inputs.
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According to Dardick, they are also introducing specific traits that influence plant architecture into various crops. The loss of the TAC1 gene leads to upright, compact plant architecture suited for high density planting in plum, tomato and peach production. The loss of LAZY1 gene in plums has led to low growing trees that can be managed from the ground. A gene called DRO 1 regulates the lateral root angle and enables the development of a much deeper root system in plums.
Fruit crops require a period of dormancy which is typically cold induced. Climate change is causing changes in the climate zones where fruit can be grown. Altered plant hardiness zones and production ranges result in reduced chilling and increased abiotic stress. It also exacerbates spring frost. Research is thus focusing on manipulating plant dormancy and bloom.
Scientists have found that the EVG locus controls dormancy onset in peaches. They have successfully manipulated the gene that represses flowering at low range temperatures in plums to alter dormancy and bloom time.
The fastest growing agricultural sector in the US is vertical farming where crops are produced in a controlled environment. These agricultural operations have thus far focused on leafy greens and vegetables, with companies like AeroFarms, Bowery, Plenty and Toshiba taking the lead. But scientists are now turning to techniques to adapt fruit trees for indoor farming under controlled environments. Through flowering controlled by temperature, research on plums has already shown the potential for smaller tree size, continual flowering and setting fruit all year round as well as no dormancy requirement.
The advantage of these indoor fully controlled farms is that there are little or no chemical inputs - they do not use pesticides and are highly productive. The downside is that they are very energy intensive. But, he argues, what this development shows is that biotechnology can be used to dramatically change the way we grow and produce some of these crops in a more environmentally sustainable manner.
In addition to the various applications to deliver climate resilient crops, research is also targeting marginal soils - previously unsuitable landscapes that are not really usable and have a negative environmental footprint. Following the rehabilitation of coal mines, rootstocks are now available to support fruit trees in such areas.
Apple rootstocks were developed from wild apple species growing in marginal land with poor nutrient conditions, specifically for use on such mining sites. By using a combination of soil amendment strategies and genetics they now have productive orchards on previously unused lands. Similarly, it has been found that apple rootstock ability to uptake heavy metals is genetic. Research will now focus on identifying rootstocks that do not take up heavy metals or do so very inefficiently to be incorporated into new approaches.
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