Rootstock ‘SR1’

New Avocado rootstock in New Zealand

SR1 is the rootstock recovered from an ‘escaped’ avocado tree that was the sole survivor from a block of Hass trees grafted to unknown seedling rootstocks planted near Whangarei around 1987. Up until 2002/03 reasonable crops were produced. However, from 2002 to 2008 the block declined severely due to waterlogging and Phytophthora infection despite intensive remedial actions. During this period the SR1 “mother” tree was noted to be the only tree which showed no signs of decline and consistently producing crops, despite being at the bottom of the block and only 10-15m from a swampy area.

Survival trial
In 2009 all the original trees had died except the mother tree which was then cut off below the graft union to retrieve and clone the rootstock. Once enough propagation material had been produced, a “killing field” trial was established in March 2011 on the original Phytophthora infested site. The purpose of this trial was to test survivability of SR1 compared to other industry rootstock varieties and no attempt was made to control rootrot. The trial consisted of 8 trees each on 5 different rootstocks grafted with Hass, planted in a random design. Rootstocks used were:- SR1, Dusa, Duke 7, Reed and Zutano. Nine years after the trial planting, Hass on SR1 and Dusa are the only survivors in the ‘killing field’, with SR1 appearing stronger and healthier than Dusa.

Production trial
Because productivity is vital to the success of any avocado planting, a production trial was also established in 2013 to compare the performance of Hass grafted to SR1 with other commercially available rootstocks which were established in a NZ Avocado Industry trial the same year. The site was also originally a commercial avocado block which was established in 1988. Despite early productivity, the block slowly declined due to Phythophthora and poor soil aeration. Before replanting with the new rootstocks, the old avocado trees were felled and mulched in situ, then the soil was deep ripped and humped and hollowed. The new plantings were made at 6 X 3 metres and under drip irrigation. Other rootstocks used were Zutano, Duke 7, AIC 1, AIC 3, Velvick, Dusa and Bounty. The entire block was planted with 11% pollinizer cultivars and managed homogenously and using best practice techniques.

Comparative production
‘SPW Avocados Ltd’, the owners of the avocado rootstock SR1, were granted a PVR for the stock, on 5 December 2019.

In New Zealand, SR1 is available exclusively from Lynwood Avocado Nursey.

A contract has recently been signed with Flemings Nursery of Queensland, Australia and grafted tissue is currently in quarantine in Melbourne.

For more information:
Stephen Wade

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