Drought-stress found leading to natural selection in rice

Saakshi Bangera, DY Patil School of Biotechnology and Bioinformatics

Global climate change, one of the most critical environmental challenges today, continues to jeopardize the agricultural industry of India. Cultivation of tolerant crops is a need of the hour to meet the increasing demands of the country. One of the ways out of this rabbit-hole has been proposed to be Plant breeding via natural selection. As we all know, natural selection allows plant adaptation to stress at its genome level. Thus, we can develop strategies to manipulate the genome to deliver stronger yields.

Natural selection has been observed in various crops according to their geographical location and environment. A study involving drought-tolerant rice crops across South Asia, specifically – India, Bangladesh and Nepal has recently been carried out by Santosh Kumar et al. In the study, plant traits and genotypes were further linked with the environmental conditions to observe the influence of these traits on the yield. 

This study, more precisely – the breeding program, was conducted at the International Rice Research Institute (IRRI). A strategy of direct selection for yield under drought stress was followed. After developing the drought-tolerant varieties, they are now being cultivated in drought-prone regions of the above-mentioned countries. It was reviewed that the factors affecting soil moisture hold a sound responsibility in affecting the relationships between plant traits and yield. In drought-prone areas, atmospheric status has a strong effect along with moisture in the soil. This and many other observations made it important to distinguish atmospheric conditions when correlating traits with the crop yield. 

An assumption made in this analysis was that dimensions of the flag-leaf (penultimate leaf) and stomatal density along with the surrounding conditions affect rice traits. 

Results:

• Effect on flag length and width

Flag leaves were reliably observed to be longer in crops growing under drought stress. Rainfall, soil pH, phosphorus content, and bulk density were correlated with length, while maximum temperature, potassium content, and water retention were correlated with width. Interestingly, minimum temperature showed an opposite connection with the length and width of the flag-leaf. In summary, flag-leaf length was affected by the atmosphere, and flag-leaf width was affected by the soil’s properties

• Effect on stomatal density

In drought-breeding lines, low stomatal densities were observed as compared to drought-susceptible lines. When comparing across trail sites, the stomata-width was influenced by the drought conditions. Plants growing in environments with low soil moisture and high transpiration rate showed low stomatal density.

• Correlation between leaf traits and grain yield

The effect of this correlation varied with trial sites. In South Asia, flag-leaf length showed a positive relationship with crop yield. The relationship between grain yield and stomatal density was negative.  The leaf traits in the drought-breeding lines were observed to be remarkably stable.

Our take from this

As we know about the stability of physiological traits, this knowledge can be used as an advantage with respect to yield. With the correct use of understanding of the environmental correlation with the soil, we can improve the effectiveness of breeding. There is immense potential in this field for further improvement, to tackle the climate-related problems faced by agro-industry. After characterizing the physiological traits, our knowledge of plant adaptations can be greatly enhanced by conducting genome analysis. Further, desirable alleles could be adopted for crop breeding.

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Source:

1. Santosh Kumar, Santosh Tripathi, Suresh Prasad Singh, Archana Prasad, Fahamida Akter, Md Abu Syed, Jyothi Badri, Sankar Prasad Das, Rudra Bhattarai, Mignon A Natividad, Marinell Quintana, Challa Venkateshwarlu, Anitha Raman, Shailesh Yadav, Shravan K Singh, Padmini Swain, A Anandan, Ram Baran Yadav, Nimai P Mandal, S B Verulkar, Arvind Kumar, Amelia Henry, Rice breeding for yield under drought has selected for longer flag leaves and lower stomatal density, Journal of Experimental Botany, Volume 72, Issue 13, 22 June 2021, Pages 4981–4992, https://doi.org/10.1093/jxb/erab160
2. Henry R. J., Nevo E, Exploring natural selection to guide breeding for agriculture, Plant Biotechnology J, volume 12, issue 6, P655-662(2014) DOI: https://doi.org/10.1111/pbi.12215

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About the Author: Saakshi Bangera is currently pursuing MSc in Biotechnology from DY Patil School of Biotechnology and Bioinformatics. I don’t have a specific area of interest yet, because I believe there’s still a lot left to learn. Although I do wish to explore toxicology and food biotechnology. I am quite passionate about Biotechnology and I aim to grab every opportunity I come across.