Agrobacterium tumefaciens–mediated transformation of three groundnut (Arachis hypogae L.) genotypes from Southern and Eastern Africa

ABSTRACT

Groundnut or peanut (Arachis hypogae L.) is one of the principal economic oilseed legumes and is largely cultivated in tropical, subtropical and warm temperate regions of the world. It is an upright or prostrate annual plant. Groundnut contributes significantly to household food security and cash income through the sale of the seeds and also provides a valuable source of proteins, fats, energy and minerals. Developing countries account for nearly 95% of the world production. Groundnut production in African countries has been fluctuating greatly over the last decade. This has been attributed to biotic and abiotic constraints. Pests and diseases that are major biotic factors can lead to yield losses as high as 100% resulting in total crop failure. Traditional plant breeding methods used to improve the crop are time consuming, expensive and involve transfer of unwanted traits along with the desired ones. Besides they are limited to the existing narrow gene pool within compatible groundnut genotypes. Recent advances in biotechnology offer alternative tools such as genetic engineering through which genes that confer some of these traits can be isolated, cloned and introduced into important crops. Genetic transformation protocols are both genotype and species dependent and specific protocols need to be developed for every plant species and sometimes even each genotype. Development of a good transformation protocol for African groundnuts will provide a platform for further genetic improvement for traits such as drought, pest and disease resistance and biofortification. Transformability of three groundnut genotypes; ICGV90704, ICGV12991 and JL24 was assessed using cotyledon explants from mature seeds infected with four Agrobacterium tumefaciens strains AGL0, EHA 105, C58 and LBA 4404 containing a standard binary vector with a GUS reporter gene. The transformation efficiency (TE) expressed as a % of PCR positive shoots out of the total number of shoots infected, of groundnut variety ICGV90704 was 1.33% with strain EHA105, 0.81% with strain AGLO and 0.39% with strain LBA4404. Variety ICGV12991 recorded a TE of 1.11% with strain AGLO, 0.59% with strain C58 and 0.53% with strain LBA4404. Variety JL24 had a TE of 1.03% with strain AGLO and 0.99% with strain C58. ANOVA between and within the three varieties at the explant producing shoots, total shoots in S1, total shoots in S2 and total shoots in RIM showed strain LBA4404 to be more efficient followed by AGLO and EHA105. The least efficient strain was C58. Groundnut variety ICGV 90704 was found to be the most amenable to transformation. It is concluded that cotyledons can be used as explants in the transformation of African groundnuts.