Editing IPCC:AR6/WGII/Chapter-5 (section)

==== 5.4.4.3 Cultivar improvements ====

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As stated in AR5, cultivar improvements are one effective countermeasure against climate change ( [[#Porter--2014|Porter et al., 2014]] ; [[#Challinor--2016|Challinor et al., 2016]] ; [[#Atlin--2017|Atlin et al., 2017]] ). Plant breeding biotechnology for climate change adaptation draws upon modern biotechnology and conventional breeding, with the latter often assisted by genomics and molecular markers. Plant breeding biotechnology will contribute to adaptation for large-scale producers ( ''high confidence'' ). However, in addition to inconsistencies in meeting farmer expectations, a variety of socioeconomic and political variables strongly influence, and limit, uptake of climate-resilient crops ( [[#Acevedo--2020|Acevedo et al., 2020]] ; [[#Rhoné--2020|Rhoné et al., 2020]] ).

Genome sequencing significantly increases the rate and accuracy for identifying genes of agronomic traits that are relevant to climate change, including adaptation to stress from pests and disease, temperature and water extremes ( ''high confidence'' ) ( [[#Brozynska--2016|Brozynska et al., 2016]] ; [[#Scheben--2016|Scheben et al., 2016]] ; [[#Voss-Fels--2016|Voss-Fels and Snowdon, 2016]] ). Access to this information where it is needed and in practical timeframes, as well as the expertise to use it, will limit the sharing of benefits by the most vulnerable groups and countries ( ''high agreement'' , ''limited evidence'' ) ( [[#Heinemann--2018|Heinemann et al., 2018]] ).

Genetic improvements for climate change adaptation using modern biotechnology have not reliably translated into the field ( [[#Hu--2014|Hu and Xiong, 2014]] ; [[#Nuccio--2018|Nuccio et al., 2018]] ; [[#Napier--2019|Napier et al., 2019]] ), but good progress has been made by conventional breeding. Desirable traits that adapt plants to environmental stress are inherited as a complex of genes, each of which makes a small contribution to the trait ( [[#Negin--2017|Negin and Moshelion, 2017]] ). Adaptation by conventional breeding requires making rapid incremental changes in the best germplasm to keep pace with the environment ( [[#Millet--2016|Millet et al., 2016]] ; [[#Atlin--2017|Atlin et al., 2017]] ; [[#Cobb--2019|Cobb et al., 2019]] ). Further improvements would be difficult without ''in situ'' and ''ex situ'' conservation of plant genetic resources to maintain critical germplasm for breeding ( [[#Dempewolf--2014|Dempewolf et al., 2014]] ; [[#Castañeda-Álvarez--2016|Castañeda-Álvarez et al., 2016]] ).

Despite the advances in sequencing, phenotyping remains a significant bottleneck ( [[#Ghanem--2015|Ghanem et al., 2015]] ; [[#Negin--2017|Negin and Moshelion, 2017]] ; [[#Araus--2018|Araus and Kefauver, 2018]] ); the emergence of high-throughput phenotyping platforms may reduce this bottleneck in future. Emerging modern biotechnology such as gene/genome editing may in the future increase the ability to better translate genetic improvements into the field ''(medium agreement'' , ''limited evidence)'' ( [[#Puchta--2017|Puchta, 2017]] ; [[#Yamamoto--2018|Yamamoto et al., 2018]] ; [[#Friedrichs--2019|Friedrichs et al., 2019]] ; [[#Kawall--2019|Kawall, 2019]] ; [[#Zhang--2019b|Zhang et al., 2019b]] ).

Other breeding approaches assisted by genomics have been making steady gains in introducing traits that adapt crops to climate change ( ''high confidence'' ). DNA sequence information is used to identify markers of desirable traits that can be enriched in breeding programmes, as well as to quantify the genetic variability in species ( [[#Gepts--2014|Gepts, 2014]] ; [[#Brozynska--2016|Brozynska et al., 2016]] ; [[#Voss-Fels--2016|Voss-Fels and Snowdon, 2016]] ). However, breeding for smallholder farmers and the stresses caused by climate change are unlikely to be addressed by the private sector and will require more public investment and adjusting to the local social-ecological system ( [[#Glover--2014|Glover, 2014]] ; [[#Heinemann--2014|Heinemann et al., 2014]] ; [[#Acevedo--2020|Acevedo et al., 2020]] ). Modern biotechnology has not demonstrated the scale neutrality needed to serve smallholder-dominated agroecosystems, due to a combination of the kinds of traits and restrictions that come from the predominant intellectual property rights instruments used in their commercialisation, as well as the focus on a small number of major crop species ( ''medium confidence)'' ( [[#Fischer--2016|Fischer, 2016]] ; [[#Montenegro%20de%20Wit--2020|Montenegro de Wit et al., 2020]] ).

Globally, there is a notable lack of programmes aimed specifically at breeding for climate resilience in fruits and vegetables, although there have been calls to begin this process ( [[#Kole--2015|Kole et al., 2015]] ). Breeding for climate resilience in vegetables has great potential given the range of crop species available. Tolerance to abiotic stress is reasonably advanced in pulses ( [[#Araújo--2015|Araújo et al., 2015]] ; [[#Varshney--2018|Varshney et al., 2018]] ), but examples of translation to commercial cultivars are still limited ( [[#Varshney--2018|Varshney et al., 2018]] ; [[#Varshney--2019|Varshney et al., 2019]] ). The infrastructure for germplasm collection, maintenance, testing and breeding lags behind that of major crops (partly because of the large number of species involved) ( [[#Keatinge--2016|Keatinge et al., 2016]] ; [[#Atlin--2017|Atlin et al., 2017]] ).

Participatory plant breeding (PPB) facilitates interaction between Indigenous and local knowledge systems and scientific research and can be an effective adaptation strategy in generating varieties well adapted to the socio-ecological context and climate hazards ( ''high confidence'' ) (Table 5.5, Westengen and Brysting, 2014; [[#Humphries--2015|Humphries et al., 2015]] ; [[#Anderson--2016|Anderson et al., 2016]] ; [[#Migliorini--2016|Migliorini et al., 2016]] ; [[#Leitão--2019|Leitão et al., 2019]] ; [[#Ceccarelli--2020|Ceccarelli and Grando, 2020]] ; [[#Singh--2020|Singh et al., 2020]] ).

'''Table 5.5 |''' PPB as cultivar improvement adaptation method.

{| class="wikitable"
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! '''Region'''

! '''Crop(s) used for breeding'''

! '''Results'''

|-
| West Africa

| Sorghum and pearl millet

| * Released sorghum and millet varieties which were selected for climate variability (e.g., drought), low soil fertility, pest and disease resistance, gendered preferences for processing, and nutrition ( [[#Camacho-Henriquez--2015|Camacho-Henriquez et al., 2015]] ; [[#Weltzien--2019|Weltzien et al., 2019]] ).
* Farmers who adopted these varieties increased yield, income and food security, alongside increased technical knowledge of plant breeding, and increased breeders’ understanding of local farmers’ varietal requirements ( [[#Trouche--2016|Trouche et al., 2016]] ).
* Joint learning with scientists led to increased genetic gain both in terms of operational scale and focused breeding for diverse farmer priorities ( [[#Weltzien--2019|Weltzien et al., 2019]] ).

|-
| South America (Andes)

| Potato

| * PPB with Indigenous Quechua and Aymara farmers resulted in potato varieties with traits from wild relatives, with yield stability, higher yields under low input use and disease resistance under climate change impacts such as increased hail or frost events and upward expansion of pests and diseases ( [[#Camacho-Henriquez--2015|Camacho-Henriquez et al., 2015]] ; [[#Scurrah--2019|Scurrah et al., 2019]] ).

|-
| Asia (southwest China)

| Maize

| * PPB done primarily with women farmers, led to 1500 landraces safeguarded, 12 farmer-preferred varieties released and 30 landraces released, bred for improved yield (15–20% increases), drought resistance, taste, market potential and other priority traits ( [[#Song--2019|Song et al., 2019]] ).
* Studies suggest PPB improved farmer knowledge, income and access to resilient seeds, and strengthened institutions such as women-led farmer cooperatives and Farmers’ Seed Network of China ( [[#Song--2019|Song et al., 2019]] ).

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