A tedious and unpredictable process
Updated 15 Jun 2015, 1:29am
PHOTO: Mango breeder Ken Rayner using tweezers to pick male flowers from a mango tree on his orchard, 30 kilometres west of Katherine. (Daniel Fitzgerald)
Cross-pollinating mango trees by hand is a delicate, time consuming process with little guarantee of success.
00:00 AUDIO: Ken Rayner says he is one of only a few people cross-pollinating mangoes by hand (ABC Rural)
For mango breeder Ken Rayner, after spending most of his working life doing various jobs on cattle stations across the Northern Territory, it is a work of passion.
Mr Rayner has been cross-pollinating mango trees, with the aim of creating new varieties, for about the past 30 years and believes he is one of only a few in Australia working by hand.
Mango trees across the Top End have started to flower over the past few weeks, which means he has had to move quickly with his work while the trees are in bloom.
It is one in about 20,000 that you get [the characteristics] you want, so it is pretty tedious.
Katherine mango breeder, Ken Rayner
When ABC Rural visited his orchard about 30 kilometres west of Katherine, Mr Rayner had been picking individual flowers from his mango trees since early morning.
"I've picked off a section of a mango flower panicle, I am going to take male flowers off the panicle so I can use those as a pollen source for cross breeding," he said.
Using magnified glasses and a pair of tweezers, the work of picking off the tiny flowers, which are only a couple of millimetres wide, needed to be done at the precise time when the pollen had opened.
"Some trees you won't get pollen off them until such time as they are ready themselves," he said.
"Some trees won't open their male pollen until 10 or 11 o'clock in the morning, others open very early."
Once Mr Rayner had carefully picked off a few dozen male flowers and placed them in a padded box, he left them in the shade until the female flowers were ready.
PHOTO: Ken Rayner carefully picks the male flowers from a mango panicle for cross pollination. (Daniel Fitzgerald)
Then, holding the male flower in his tweezers, Mr Rayner delicately rubbed it against the female flower on the parent tree he wished to cross pollinate with.
"You take the male pollen up and you rub it across the stigma three or four times, so the pollen is deposited on the tip of the stigma," he said.
"The pollen being so small you can't see if it is successful or not until such time as you get a result of growing fruit."
Mr Rayner usually repeated this process about 50 times a day during flowering.
"It is one in about 20,000 that you get [the characteristics] you want, so it is pretty tedious," he said.
"But sometimes you do get them to click and then you go back and re-pollinate into that line, use that female parent again and again.
"There are that many genes and chromosomes in a mango, all the crosses you do into the one tree from a male parent will not necessarily be the same."
PHOTO: A plastic cap is left of a pollinated flower for several days to prevent bees from interfering with Ken Rayner's hand pollination. (Daniel Fitzgerald)
From successful pollination of a flower, which produces a fruit to be planted, hopefully with the right characteristics, the development of a line of mango trees still takes a long time.
"It is usually 25 years to go from pollination to the person doing the work to get anything out of it," Mr Rayner said.
Mr Rayner said the long lead time on producing and developing new varieties of mangoes meant market expectations could often be ahead of mango varieties in commercial production.
Though he has been told he is wasting his time with hand cross-pollination, Mr Rayner said he was having some success.
"I now have two fruit varieties which will be on the market within the next couple of years," he said.
"That is being commercialised by a southern firm and is going quite well.
"Probably in another two years we will have a reasonably good supply for the commercial market.
"So that is satisfying."