Introgression and evaluation of glyphosate tolerance gene EPSPS into the Indian soybean (Glycine max L.) variety JS9560 through marker assisted backcross breeding

Abstract

Weeds are becoming increasingly prevalent, which poses a serious threat to soybean production in India and results in significant yield losses. Developing herbicide-tolerant soybean cultivars, when coupled with a lack of novel herbicides, increases the herbicidal spectrum and reduces crop phytotoxicity, making it an efficient weed management method. Currently, no Indian soybean is herbicide-tolerant, and no study on the development of herbicide-tolerant soybeans has been executed in India. Introgression of an herbicide-tolerant gene into the genetic background of popular Indian soybean is an effective strategy to develop novel soybean cultivars. Therefore, the molecular marker-assisted backcross breeding (MABB) approach was adopted in the current study for the genetic introgression of a glyphosate-tolerant gene, EPSPS, to develop herbicide-tolerant soybean. The introgression of the glyphosate-tolerant gene, EPSPS, from an American herbicide-tolerant soybean variety (S14-9017GT) into the genetic background of the elite popular Indian soybean variety, JS 9560 (the recurrent parent), was done using MABB. Foreground selection was done using the EPSPS gene-linked Simple Sequence Repeat (SSR) marker EPSPS2, and background selection was performed using 124 genome-wide SSR markers polymorphic between S14-9017GT and JS 9560. Selection of glyphosate-Tolerant lines in each generation until BC2F2 was carried out to improve the recovery of the recurrent parent genome (RPG). About 38 BC2F2 plants were developed and found to recover 94.35 to 98.77% of the recurrent parent genome. The improved BC2F2 population was evaluated for herbicide tolerant using glyphosate spray (3 ml/litre), and it was found that fourteen (14) BC2F2 plants were homozygous (EPSPS/EPSPS) for the glyphosate Tolerant trait, in which P-11-09 is showing the highest recurrent parent genome recovery (98.77%). Selfing of positive BC2F2 plants resulted in 583 BC2F3 population. Phenotypic selection for agronomic traits in the Tolerant BC2F3 generation was carried out, and it was recorded that the performance of BC2F3 plants was like that of the recurrent parent, JS 9560. Overall, the study showed that the glyphosate-tolerant EPSPS allele was successfully introgressed into the genetic background of the popular soybean variety JS 9560, resulting in the development of herbicide-tolerant (HT) BC2F3 lines. This is the first study on the breeding of herbicide-tolerant soybeans in India. The superior plants developed will be tested in further breeding programs to develop soybean cultivars with glyphosate tolerant in India.