**6. Conclusions**

*Legume Crops - Prospects, Production and Uses*

the phytate found in soybean meal [151].

**5.2 Genetic engineering efforts**

in soybean seed.

breeding efforts to improve protein quality have involved identifying quantitative trait loci (QTL) that are associated with the amino acid content [139]. QTLs are regions of DNA that are associated with a particular trait and allow breeders to select for particular cultivars that have the trait of interest [140]. The composition of soybean seed oil primarily includes linolenic, steric, palmitic, linoleic, and oleic acid [141]. There have been breeding attempts mainly to increase oleic acid in soybean seed while keeping linolenic acid relatively low, due to respective human health impacts [141, 142]. Lastly, soluble sugar levels, specifically sucrose content, has also been an area of interest in soybean breeding [135]. While sucrose is the main sugar found in soybean, fructose and glucose are also present but in trace amounts [143]. Similar to protein content, multiple QTLs have been identified associated with high sucrose [144]. Sucrose is a desirable seed composition trait due to soy food flavor improvement for human consumption [144]. Overall, conventional breeding has been used to improve protein quality, oil content, and sucrose content

While soybean does have numerous profitable seed traits, it also contains several unfavorable traits that include trypsin inhibitors (TIs), indigestible carbohydrates, and phytate [145, 146]. There are two trypsin inhibitors found in soybean, the Kunitz and Bowman-Birk trypsin inhibitor, and they are antinutritional factors due to their ability to interfere with protein digestibility and reduce the health of animals that are fed soybean meal containing these proteins [147, 148]. Currently, processors can heat the soybean meal in order to inactivate the trypsin inhibitors, but this step is costly [149]. Due to TIs negatively affecting animal health and increased cost for inactivation, more breeding efforts are being made to develop low-TI soybean lines [150]. Indigestible carbohydrates, raffinose and stachyose, that are found in soybean seed are also a target for soybean breeding since they can cause flatulence and diarrhea when consumed [144]. There has been progress made in lowering these carbohydrates, which include identifying QTLs associated with raffinose and stachyose [144]. Lastly, while phytate is an antinutritional factor found in soybean, there is not a lot of work being done anymore to breed low phytate soybean lines since phytase supplements are an effective, inexpensive way to reduce

Genetic engineering involves the process of artificially and intentionally manipulating the DNA of an organism with the purpose of modifying that organism [152]. Some of the methods used to transform plants include *Agrobacterium*, electroporating plant protoplasts, and microparticle bombardment [153]. One relatively new field within genetic engineering is gene editing which involves using clustered regularly interspaced short palindromic repeats or CRISPR/Cas9 system [154]. Genetic engineering works by introducing a gene from one organism into another organism so that it can now express that gene product or by causing frameshifts or deletions to knockout a particular gene in an organism [152]. CRISPR/Cas9 has been gaining a lot of attention due to its promising ability to efficiently and effectively improve agronomic traits in crops [155, 156]. Genetic engineering in soybean was first successfully accomplished in the 1990s [157]. Since this time, genetic engineering has been used frequently in soybean with about 90.7 million hectares of genetically modified/GM soybean being planted in 2014 [157]. Most of this genetic engineering has been done to create Roundup Ready soybean that is resistant to glyphosate herbicides [158]. Roundup Ready soybean is prevalent because it allows growers to spray herbicides to kill any weeds in the field while not killing the soybean [158]. Genetic engineering has been used

**38**

Soybean is an essential crop that is grown globally due to its various and diverse uses. Given its importance, there are many pre-growing practices to prepare the field for the growing season, including tillage, pre-plant fertilization, and monitoring soil pH. Many agronomic aspects must be considered during growing season to ensure successful soybean growth including crop rotations, double cropping, cover crops, irrigation, row spacing, plant density, and post-emergence fertilization. Additionally, integrated pest management involving the use of pesticides, resistant soybean cultivars, and cultural practices are vital to control the numerous pests of soybean. While soybean is highly used in livestock feed due to its high protein content, it's methionine deficiency and presence of antinutritional factors still present problems that need to be solved. Soybean versatility is represented by the many uses in human consumption, biofuels, and other industrial uses. Traditional and conventional breeders have been working to increase protein and oil content, while eliminating antinutritional factors. Genetic engineering and gene editing show promise to help improve soybean by introducing genes to improve protein and oil quality and knocking out genes to remove antinutritional factors.

### **Acknowledgements**

The authors would like to acknowledge Virginia Tech's Open Access Subvention Fund for funding the publishing fee.
