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Conserving crop wild relatives key to enhanced productivity

Wednesday October 16 2019

A basket of fruits.

A basket of fruits. Better crop yields to an extent depends on among other factors the use of crop wild relatives to improve the quality of crops we grow. FILE PHOTO | NMG 

BRIAN OKINDA
By BRIAN OKINDA
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From climate change, land degradation, soil destitution, pest and disease outbreaks, to genetic erosion –where the limited gene pool of an endangered species diminishes due to its procreative individuals dying away before reproducing, agricultural productivity and food production continue to face a sustained onslaught of challenges.

Researchers at the Intergovernmental Panel on Climate Change (IPCC) painted a grim picture of this situation, warning that agricultural production and crop yields could decline by two per cent every decade as at the same time demand for agricultural produce for food purposes increases by approximately 14 per cent due to negative impacts of climate change.

Even severe forecasts of this are expected beyond the 2050, according to the IPCC scientists.

And worsening the situation, the rapidly increasing human population in the coming years will, simultaneously, require that global food production increases by up to 70 per cent.

This will lead to an increase in demand for crop production to guarantee food security for the growing population.

Not only do yields need to increase significantly but crops themselves, by the same token, need to progressively develop more resilience to the changing conditions.

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Plant breeders turned to the mostly unexploited gene pool of genetic diversity within crop wild relatives (CWRs) as these are key to tackling the seemingly looming catastrophe.

These wild species of the tamed plants we grow are a genetic treasure trove of diversity for developing the desirable qualities such as resilience and robustness that our tamed plants require to survive and thrive.

They essentially are wild plants related to crops of socioeconomic value, such as human food crops as well as livestock forage and fodder plants, as well as relatives of plants we use for medicinal, forestry, industrial and ornamental purposes.

These plants are a source of genes for addressing different stresses in the plants as well as address other breeding goals including increased crop yield and quality improvement, according to Céline Termote, a scientist at Bioversity International.

They contain a rich supply of resistance genes for both biotic and abiotic plant stresses and are mainly made up of both crop ancestors and other interrelated species, which have been used to improve crops for years.

“From these, farmers are able to get quality seeds for crop cultivation and also livestock due to the prospect of breeding enhanced varieties from agro-biodiversity. Nutritive food security is ensured, the farm ecosystem and soils are revitilised, farmers get access to varied highly tolerant crops for cultivation, and hence are cushioned against crop failures, and their intercultivation time and again control pests and diseases and addresses effects of climate change,” she says.

Transferring these traits including disease resistance from the CWRs to our modern-day domesticated breeds, is normally done using traditional breeding methodologies as well as molecular approaches, which entail cloning genes from wild species and transferring them into the targeted crop’s cultivated background.

FOOD SECURITY FOR THE GROWING POPULATION

There are also newer technologies for gene-editing that allow scientists and breeders to understand the genetic diversity of alleles and their disease or drought resistance characteristics in wild species.

These are then edited in the existing alleles of the target plant’s genome so that the plant acquires the resistance qualities of the wild crops as well.

Genes from wild plants have even at times been known to provide their neighbouring cultivated plants with resistance against pests and diseases and improved tolerance to abiotic stresses, including salinity and drought, through natural cross pollination, when they happen to grow next to each other.

This explains why some knowledgeable farmers sometimes accept the presence of specific wild crops on their farms because they understand the value of these wild plants in providing beneficial traits to their domesticated crops.

This introgression of drought or disease tolerance alleles from the cultivated crop’s wild relatives which are adapted to extreme environments, into the domesticated progenies, is held as potentially an economically viable approach to enhance crop productivity and consequently ensure food security for the fast growing human population under increasingly duress settings.

However, in the whole situation, an inconsistency arises in that, while crop yields have in the past several years been somewhat satisfactory globally, continued introduction of new varieties and mismanagement of the environment are now posing a threat to the indigenous landraces and their CWRs, which are the basis of the said satisfactory yields and success.

CWRs are threatened by factors including effects of habitat destruction, nutrient enrichment and climate change which are adversely impacting on these wild plant species.

And better crop yields in this age, to an extent depends on among other factors, the use of these CWRs to improve the qualities of the crops we grow.

These challenges are in turn gradually yet negatively affecting the way we are able to produce agricultural food in sustainable ways.

This leads to our hope of food security becoming more dependent on extensive resources found in nature, and which are themselves at the same time being exhausted.

While CWRs can improve drought resilience in crops, due to climate change, these genetic resources may themselves be under threat of extinction in the wild, especially due to human activities and climate change.

Their conservation guarantees an availability of the diversity needed to meet the demands of agricultural production under the unpredictably changing climatic conditions, according to Joseph Ireri, a principal scientist at the Plant Genetic Resource Centre, which is based at Kenya Agricultural and Livestock Research Organisation’s (Kalro) Genetic Resources Research Institute (GeRRI).

Scientists are now calling for protection of the Plant Genetic Resources (PGR), in which falls the CWRs, as they have an important role to play in ensuring food and nutrition security.

CONSERVATION EFFORTS

These PGRs have for ages provided the foundation for crop improvement ever since the advent of agriculture.

They are important sources for developing new and improved varieties and their loss could eliminate a key source of plant diversity and tolerance.

“The first step required to improve CWRs’ conservation is to identify which CWR taxon requires enhanced protection and the conditions to which it should be conserved against –pests, diseases, or adverse climate changes,” says Mr Ireri.

This can be done through creation of a CWR checklist and inventory, which consists of names of different taxa and their establishment within any geographical region.

Once the priority CWR has been identified for any geographical area of study it is then necessary to carry out a ‘gap analyses.

This is a process whereby the extent of current conservation efforts for priority taxa are examined and decisions made as to where further conservation efforts are necessary to ensure the long-term persistence of populations and the genetic diversity within them, using both in-situ and ex-situ conservation approaches.

In the in-situ approach, Mr Ireri says these wild plants are let to grow within their natural settings, such as is the case in specific conservation areas including in Marsabit.

Methodologies for in-situ conservation are genetic reserve conservation and on-farm conservation.

“In the ex-situ approach, the plants are collected and stored in seed-banks, gene-banks and this approach entails cryogenic preservation of the vegetative material. Then there is also the arboretum or botanical gardens method of conservation in which endangered plant species are cultivated to maintain and preserve plant and biological diversity,” Mr Ireri says.

However, ex-situ’s shortcoming is that preserved agro-biodiversity seldom develops adaptive mechanisms towards the changing conditions.

The country, he mentions, is keen on these CWRs’ conservation and agriculture biodiversity, as there are a number of seed and gene-banks already set up and a list of up to 29 identified crops, including millet, sorghum, beans and a variety of nuts, currently under the programme.

The in-situ and ex-situ approaches, he adds, complement each other. All the CWRs cannot be conserved in the gene-banks and hence why the in-situ approach is important.

CWRs are usually released for enhanced breeding purposes in the instances of severe pest, disease and drought outbreaks which necessitate improving the domesticated varieties to enhance their resilience towards these conditions.