I’ve never had great luck growing broccoli. In the past, I’ve lost a lot of it to flea beetles. Lately, though, I think more extreme weather events and earlier, warmer springs have been to blame. Despite my best attempts to plant early and choose varieties that can handle my local climate, I nearly always end up with broccoli quickly bolting to seed.
We’ve long known that broccoli and broccoli relatives like cabbage, kale and cauliflower perform best in the cool temperatures of the early spring and fall months. So, what exactly can be done to succeed with broccoli despite shorter periods of cool weather and warmer temperatures overall?
As it happens, a group of plant scientists may be a little closer to working that out.
In late 2022, researchers from Cornell University’s School of Integrative Plant Science and Zhejiang University’s College of Agriculture and Biotechnology published the results of a new study in the journal Molecular Horticulture. Together, they examined the effects of high temperatures on a Brassica oleracea cultivar known as Green Harmony F1.
They grew three sets of broccoli plants, exposing each to specific temperatures—60.8, 71.6 and 82.4 degrees F, respectively. The broccoli grown at the coolest temperature developed normal flower heads.
As for the broccoli plants grown at the two higher temps? At 71.6 degrees F, the plants’ floral crowns became deformed and, at 82.4 degrees F, they looked a lot more like cauliflower than broccoli. The researchers then examined floral specimens from each group at the genetic level in order to understand the mechanics behind the broccoli plants’ responses to heat.
By applying whole-genome sequencing to the broccoli samples, the researchers were able to locate the section of genetic code in which genes associated with abnormal floral development are either expressed or suppressed. According to a Cornell University news release, “They found that abnormal flower development in broccoli was regulated by sets of floral development cessation-associated genes (FCGs).”
In other words? The broccoli’s makeup included genetic elements which can affect normal floral development. The researchers determined that, in the presence of high heat, a process called DNA methylation—during which some genes are actively switched on or off—plays an important role in the formation of those abnormal, cauliflower-like flowers.
After chemically preventing the methylation process from taking place, the researchers were able to grow normal broccoli flower heads—even in high heat conditions.
“Once we understand the mechanism better, we should be able to devise ways to develop a new biotechnology, a molecular genetics approach to suppress DNA methylation, in order to breed crops to grow in much warmer temperatures and in wider regions,” said co-author Dr. Susheng Gan via the Cornell University news release.
Although Gan and her colleagues suspect that their findings could be applied to other crops, additional study will be needed. If they are able to prevent other crop abnormalities even in the face of higher temperatures, their findings could be the basis for a new breed of heat-resistant—or at least more heat-resilient—crops.
And that could mean no more bolting broccoli when things get hot.