Researchers are looking for a solution to stop pollen abortion in female kiwifruit plants.
Orchardists will no longer have to plant 10% or more of their vines as non-fruiting males to assist with fertilisation if the three-year Otago University-Plant and Food Research project succeeds.
They have got nearly $1 million from the Government’s Endeavour Fund to determine the cause of pollen abortion.
Dr Lynette Brownfield, a lecturer at Otago University’s biochemistry department, said crops such as grapes initially relied on male and female plants for fertilisation but breeding selection over thousands of years meant they evolved to no longer need male plants.
Unlike grapes, kiwifruit have not evolved or endured selection pressure, meaning they have remained dioecious.
So orchardists plant non-fruiting males and employ beekeepers to put hives in orchards to complete the pollination and fertility cycle.
Kiwifruit do not produce nectar so bees are reluctant pollinators while extensive protection means airborne pollination is not an option.
Flowers on female kiwifruit plants initiate pollen development but the pollen is aborted before maturity.
The flowers on the male plant start forming female organs but they are also aborted early.
Brownfield hopes to use knowledge acquired from genetic and molecular research into plant fertility to try to stop the abortion with the focus on female plants.
“The aim of the project is to really understand the cause of this abortion, that maybe something has not developed as it should happen, such as a protein not being turned on.”
By monitoring gene expression from the plants Brownfield hopes to get a hint at what is happening genetically before it happens, which could provide a solution.
Having females that produce pollen in orchards means the male plants could be removed and growers would no longer need to manage bees for pollination thus reducing costs, increasing yields and improving land-use efficiency.
Another part of the project will look at what male plants contribute to kiwifruit production.
Traditionally, breeders have focused on female production traits to improve productivity, fruit size and quality but Brownfield said it has been more difficult to determine what males contribute.
That knowledge could potentially lead to breeding new varieties or for traits such as the volume of pollen expelled, fruit size, productivity and quality.
Using gene markers breeders can select for desired production attributes.
“Potentially, using this knowledge for breeding means selecting offspring from parents that both have great quality fruit.”
A hermaphrodite kiwifruit has been bred but is not yet commercially viable.
Meanwhile, researchers at the North China University of Science and Technology’s life sciences school say the fact today’s kiwifruit have as much vitamin C as an orange is caused by the fruit’s ancestors spontaneously duplicating its DNA.
They have determined that this happened in two separate events 50 to 57 million and 18-20m years ago.
In a report published in the journal iScience, study author and agricultural plant scientist XinyinWang said it was caused by a polyploidy event, in which thousands of extra gene copies were produced over night.
“These extra copies may greatly elevate the robustness of the plant, providing opportunities for natural selection to prune and rewire its biological system over time.”
Kiwifruit shares a common ancestor with coffee and grapes and XinyinWang and his team of scientists compared the genomes of all three plants and found the kiwifruit genome often contains four or five copies of a gene in areas where coffee and grapes have only one.
Those extra genes in the kiwifruit include biological instructions for creating and recycling vitamin C.
XinyinWang said that helps kiwifruit evolve by aiding growth and resistance to damage. In contrast coffee’s evolution was to produce caffeine and grape its purple pigment to protect the plant from extreme temperatures.
