How about getting the ultimate taste of summer – fresh, mouth-watering Ontario peaches – two weeks earlier than normal, and with even better colour, taste and texture?
That’s what U of G plant breeder Jay Subramanian is aiming for.
As part of the Department of Plant Agriculture, Subramanian is using molecular genetics to pinpoint favourable traits in stone fruits – specifically peach and plum – and incorporate them into superior fruit that meets the desires of producers and consumers.
One of the desirable traits in peaches is early maturity.
“We are looking to combine the best elements of a peach into a variety that will be ready for harvest sooner,” he says.
Subramanian’s goal is to make top-notch Ontario peaches available earlier in the summer so they hit the market at the same time as imported peaches, so consumers can support local farmers for the entirety of peach season.
His new early fruiting variety, the Veeblush, became available to orchards five years ago and is already in high demand among Niagara peach growers. With two new early varieties in the pipeline this year and as many as six by 2025, Subramanian’s vision for an Ontario-centric peach market is within reach, and much sooner thanks to his research.
Here’s the science behind it. By streamlining the genetic selection process, Subramanian is able to more quickly determine the genes that result in differences in peach fruit development. His more refined process of molecular breeding reduced the time necessary to perfect fruit from 25-30 years all the way down to 10 or 12.
He first uses a technique called a genome-wide association study (GWAS) to sequence the approximate 30,000 genes within the peach genome. In Subramanian’s research programs, more than 350 different individual peach types are sequenced.
From there, he’s able to zero in on mutations varying from plant to plant by sorting the genome into a Manhattan plot, a type of bar graph resembling a city skyline. Each bar represents a variation of a gene called a single nucleotide polymorphism (SNP). These SNPs are responsible for differences in peach fruit traits.
The next step of the process involves determining the significance of each SNP, or in other words, which gene variations correspond to the traits producers and consumers want most in a peach.
Once the desired genetic mutations are identified, the breeding process can be streamlined. A typical hybridization involving 50,000 pollinations will result in a little less than 3,000 seeds. Before Subramanian’s method, all 3,000 seeds would need to be raised to seedlings then to mature fruiting trees to identify the early fruiting breeds possessing the best looking and tasting fruits.
Now, breeders can simply run what’s called a polymerase chain reaction (PCR) on a leaf from each seedling, a process that amplifies a small sample of DNA into an amount large enough to be studied in detail.
From the PCR, the small handful of plants carrying the early fruiting gene along with other desirable traits associated with taste and colour can be identified. By raising these plants only, the genetic selection process is reduced from the 10 years it takes to raise a fruiting tree to the few months it takes a seed to become a seedling.
“This saves producers a lot of time and space,” says Subramanian. “If you were to plant and raise 5,000 peach trees you would need 20 acres and 10-plus years, whereas the hand-selected group of seedlings would likely only require one row, and you could be sure they all have the traits you want.”
What’s more, researchers can also determine which peach varieties will be most resistant to certain diseases through molecular breeding.
Specifically, Subramanian’s next project is working to reduce the spread of black knot disease, the most devastating fungal disease affecting all plum varieties. By sequencing RNA – the molecule responsible for regulating and expressing genes – Subramanian is looking for disease resistance markers, or sequences in the RNA that correlate to lower susceptibility to diseases like black knot. He also hopes to extend peach shelf life through genetic selection via RNA sequencing.
“By identifying small mutations that have a huge impact, we can get closer to perfecting Ontario peaches,” says Subramanian.
This research was performed in collaboration with researchers at the Vineland Research and Innovation Centre. Funding was provided by the Ontario Tender Fruit Producers Marketing Board, the Niagara Peninsula Fruit and Vegetable Growers’ Association, the Ontario Ministry of Agriculture, Food and Rural Affairs and the Innovation Superclusters Initiative.