As David versus Goliath battles go it is hard to imagine a more uneven fight than the one about to play out in front of the US supreme court between Vernon Hugh Bowman and Monsanto.

On the one side is Bowman, a single 75-year-old Indiana soybean farmer who is still tending the same acres of land as his father before him in rural south-western Indiana. On the other is a gigantic multibillion dollar agricultural business famed for its zealous protection of its commercial rights.

Not that Bowman sees it that way. "I really don't consider it as David and Goliath. I don't think of it in those terms. I think of it in terms of right and wrong," Bowman told The Guardian in an interview.

Either way, in the next few weeks Bowman and Monsanto's opposing legal teams will face off in front of America's most powerful legal body, weighing in on a case that deals with one of the most fundamental questions of modern industrial farming: who controls the rights to the seeds planted in the ground.

The legal saga revolves around Monsanto's aggressive protection of its soybean known as Roundup Ready, which have been genetically engineered to be resistant to its Roundup herbicide or its generic equivalents. When Bowman – or thousands of other farmers just like him – plant Monsanto's seeds in the ground they are obliged to only harvest the resulting crop, not keep any of it back for planting the next year. So each season, the farmer has to buy new Monsanto seeds to plant.

However, farmers are able to buy excess soybeans from local grain elevators, many of which are likely to be Roundup Ready due to the huge dominance Monsanto has in the market. Indeed in Indiana it is believed more than 90% of soybeans for sale as "commodity seeds" could be such beans, each containing the genes Monsanto developed.

Bowman, who has farmed the same stretch of land for most of the past four decades and grew up on a farm, ended up on Monsanto's radar for using such seeds – bought from a local grain elevator, rather than Monsanto – for year after year and replanting part of each crop. He did not do so for his main crop of soybeans, but rather for a smaller "second late season planting" usually planted on a field that had just been harvested for wheat. "We have always had the right to go to an elevator, buy some 'junk grain' and use it for seed if you desire," Bowman said.

To put it mildly, Monsanto disagrees. The firm insists that it maintains patent rights on its genetically modified seeds even if sold by a third party with no restrictions put on its use – even if the seeds are actually only descendants of the original Monsanto seeds. To that end it sued Bowman, eventually winning a legal settlement of some $84,456 (£53,500) against him for infringing the firm's patent rights. Monsanto says that if it allowed Bowman to keep replanting his seeds it would undermine its business model, endangering the expensive research that it uses to produce advanced agricultural products.

On a website the firm set up to highlight its arguments in the case, Monsanto insists a Bowman victory at the supreme court could "jeopardize some of the most innovative biotechnology research in the country" in industries that range from farming to medicine. It says protecting patent rights fully is vital to preserve a commercial incentive to develop and refine new products.

But Bowman has numerous supporters who believe his case could help reform aspects of commercial farming – that is now dominated by huge corporations rather than small or family-run business – to vital reforms. Bowman's legal team intends to argue that the case could open the industry to greater anti-trust scrutiny, arguing that large corporation's vice-like grip on farming and control of seeds needs to be loosened. "It opens up these transactions (buying seeds) to greater anti-trust scrutiny by the Department of Justice. Right now they are sheltered by patent trust protection," said Bowman's lawyer Mark Walters.

Campaign groups are also eager to back the case. This coming Tuesday, farming campaign groups the Center for Food Safety and Save Our Seeds will release a joint report examining the modern seeds industry. The organizations are enthusiastic backers of Bowman's cause. Debbie Barker, a program director for SOS, said a Bowman victory at the supreme court could nudge the industry towards opening up and treating seeds as a common resource, not a fiercely fought-over commercial battleground. "It would help with wider reforms," Barker said. SOS believes Monsanto and other major firms are less concerned with protecting interests in research than in their lucrative business model. After all, just three firms now control more than 50% of the global seed market.

Yet, despite the vast sums of money involved in modern farming, it is ironically Bowman's own lack of cash that has seen the case end up at the supreme court. Monsanto has a long record of reaching settlements with commercially pressured farmers it targets for patent infringements. But when the firm sued Bowman, he was already bankrupt after an unrelated land deal went wrong. Thus, he had little to lose. "I made up my mind to fight it until I could not fight it anymore," he said. "I thought: I am not going to play dead."