Avoid disease pressure

It's up to growers to prolong the usefulness of new chickpea varieties


Cropping
NSW Department of Primary Industries plant pathologist, Kevin Moore, says to get any sort of longevity out of new chickpea varieties, growers need to farm smarter, because ascochyta has a knack for resistance.

NSW Department of Primary Industries plant pathologist, Kevin Moore, says to get any sort of longevity out of new chickpea varieties, growers need to farm smarter, because ascochyta has a knack for resistance.

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Unnecessary exposure to high pathogen loads threatens new chickpea varieties, including PBA Seamer.

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The chickpea industry’s latest variety, PBA Seamer, launched at last year’s AgQuip, is already being put under unnecessary disease pressure which could accelerate how quickly it succumbs to the ascochyta pathogen.

However, growers can slow this development if they’re smart about how they they farm, NSW Department of Primary Industries plant pathologist, Kevin Moore, told the audience at the Grains Research and Development Corporation (GRDC) Commonwealth Bank AgQuip breakfast information session last month.

With the 2017 northern crop at close to one million hectares, and with an estimated yield of 1.5 tonnes a hectare, at a price of $850/t, the value of the crop is just over $1.1 billion, he said.

“Now if the ascochyta gets away on you, and it only reduces yield by 20 per cent – and it can do that very quickly with a single rainfall event – that’s going to cost the industry $230 million,” Mr Moore said.

He said if a producer was applying four ascochyta fungicides at $15/ha each, for a total cost of $60/ha, they will get back $195/ha.

“That’s a pretty good return on investment,” he said, reminding farmers of the importance of having a plan in place.

However, the ascochyta situation was constantly changing.

“Flippa lasted 11 years, HatTrick seven years – how long have we got with Seamer?” Mr Moore said.

In July, multiple ascochyta infections in Seamer were discovered on a property on the eastern Darling Downs in Queensland.

He said the Seamer was planted into a paddock which in the previous year had grown HatTrick – which is now susceptible to ascochyta – and didn’t apply any fungicides.

“So this Seama is getting hammered by ascochyta and that is putting pressure on this variety, so I’m suggesting to you people, look after these great new chickpea varieties that you are helping develop and farm sensibly,” he said.

Plant breeders and pathologists keep track of the extent of ascochyta’s ability to overcome chickpea resistance in the latest varieties at the Tamworth Centre for Crop Improvement.

This occurs in trials, which includes two series.

One contains plants that get inocculated with ascochyta and gets no fungicide, and one that contains the same varieties, but doesn’t get innoculated, and receives regular applications of fungicide.

What the trials show is the ascochyta pathogen’s rate of adaptation to new varieties – and it is not good news.

“Normally, as you go from 1984 varieties to 2016 (varieties), these plots should get greener and greener,” Mr Moore said.

“Last year, Flipper should have been greener than Yorker, but not quite as green as HatTrick.

“However, Yorker was greener, which meant the pathogen had adapted to Flipper.

“And it’s not just Flippa. They have also identified high levels of susceptibility in Kyabra.”

The centre has monitored the pathogen’s adaptation to new varieties since 1998, when it first caused widespread damage to the chickpea crop.

Mr Moore explained that when HatTrick was released in 2009, the pathogen isolates that infected Kyabra only had a limited effect on HatTrick because the pathogen had not yet adapted to it.

“HatTrick wasn’t released until 2009, but you can see this isolate I got from Yallaroi in 2014 is doing a fair bit of damage to HatTrick,” Mr Moore said, as he explained a photo of chickpea plants with ascochyta infection.

“And this one, that I got from Graman in 2016, it’s also doing some damage, so the (pathogen) isolates that were collected before HatTrick was released are infecting HatTrick, but not causing a lot of damage.”

“However, the isolates that I’ve collected after HatTrick was released, in other words after the pathogen population had been exposed to the variety, are causing damage.”

This was well demonstrated in trials at Tamworth during the two wettest years of the past 20 years – 2010 and 2016.

“The 2010 year (pathogen isolate) and the 2016 year (isolate) caused 100pc yield loss,” he said.

In 2010, where the trial didn’t put any foliar fungicides on HatTrick, ascochyta only took 30pc of the yield. Last year, it took about 98pc. 

He said this was because the pathogen had adapted to HatTrick.

“And it’s not just in our trials. It’s appearing in peoples’ paddocks,” he said.

As an example he said in a paddock at Graman, which had a strip that missed one of seven sprays, the yield was 0.5t/ha, which was a significant reduction from the bulk of the paddock that got all seven sprays and produced 3.3t/ha.

“So missing that one spray resulted in a 75pc yield loss, which meant it only returned the farmer $400/ha, compared to the rest of the paddock, which at $800/t was $2500/ha,” he said.

“It wasn’t just that he missed the spray – it was when he missed it (when the crop was going from vegetative to reproductive).”

“The pathogen is changing, we’ve got a problem with varietal purity in our industry and we believe that as plants go from the vegetative to the reproductive phase their susceptibility to ascochyta increases.”

He said, therefore, growers needed to be smart about how they farmed, and make sure they plan their management to prevent diseases overcoming the resistance traits of new varieties.

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