Biochemical Parameters Allow The Identification Of Tolerant Genotypes Of Buffel Grass (Cenchrus ciliaris L.) To Drought And Heat Stress

Arid and semi-arid ecosystems occupy vast regions in many countries in the world. In these regions, edaphic and climatic conditions impose important restrictions on agriculture. Particularly in Argentina, cattle breeding activity is carried out in the northwest of the country in an area that covers 10 million hectares where arid and semi-arid environments predominate.

The native grasslands in the region generate a scarce supply of fodder. In addition, they are often irrationally exploited, supporting high grazing pressure that causes environmental deterioration. To increase forage production, recover degraded paddocks, and allow the recovery of natural pastures, subtropical species have been implanted. Buffelgrass (Cenchrus ciliaris L.) is one of the introduced species most used in these environments, and several studies have shown its usefulness in increasing forage production in both quantity and quality, relieving grazing pressure on native species and favoring restoration and conservation of natural prairies.

Nevertheless, extreme climatic events such as severe drought and high temperatures have become more frequent in the last decade, causing serious problems in this region by damaging the production of pastures. Buffelgrass has been affected too. The National Institute of Agricultural Technology (INTA) has an active collection of Cenchrus ciliaris L., and its Institute of Physiology and Plant Genetic Resources (IFRGV) conducts a breeding program to increase tolerance to abiotic stress in this plant species. Cenchrus ciliaris L. is an apomictic species, with asexual reproduction by seed, which implies negligible natural variability.

The research group that leads the breeding program has three different sexual genotypes which are used in directed crosses to generate genetic recombination and variability. Moreover, induced mutations, anther culture, and in vitro regeneration are also performed. As in any breeding program, the tasks of phenotyping and molecular characterization are constantly carried out. Comparative trials are also developed in growth chambers under controlled conditions and in environmental tests to evaluate the genotypes response to different abiotic stress.

In this context, one of the objectives of the program is to find biochemical parameters associated with tolerance to abiotic stress due to drought and heat, to be used as a rapid and easy tool for the characterization and identification of tolerant genotypes. We focus our studies on the oxidative metabolism that changes in plants when adverse growth conditions occur. Biochemical signals and defense responses are generated, which play a very important role in adaptation and survival to adverse environmental conditions. Therefore, it is of interest to evaluate the oxidative damage and to understand the antioxidant response associated with tolerance to abiotic stress in Cenchrus ciliaris L. genotypes.

Of all the measured biochemical parameters, the oxidative damage quantified by the content of malondialdehyde (MDA content), the total reducing power quantified by the ferric reduces the ability of plasma technique (FRAP value), and the enzymatic activities catalase and superoxide dismutase (CAT and SOD activities) showed contrasting responses between tolerant and susceptible genotypes when drought and heat stress conditions were imposed. These results were confirmed later in environmental trials. These biochemical parameters could be used to identify tolerant genotypes in Cenchrus ciliaris L. breeding program, and they can be studied to be implemented with the same purpose in other plant species.