Plants – Fruit – Avocado
Plant Patent
2001-10-25
2004-11-09
Bell, Kent (Department: 1661)
Plants
Fruit
Avocado
Plant Patent
active
PP015309
ABSTRACT:
Botanical classification:
Persea americana
Mill.
BACKGROUND OF THE INVENTION
The present invention generally relates to avocado trees. More particularly, the present invention relates to a new and distinct variety of avocado tree,
Persea americana,
with significantly improved resistance to root rot.
A tree or seedling rootstock was discovered in an avocado orchard heavily infested with root rot, caused by
Phytophthora cinnamoni
at Westfalia Estate, South Africa. Most trees in that orchard died of root rot, however, the tree of the present invention was one of the few survivors and looked very healthy.
In the Westfalia nursery, an asexual reproduction of the tree rootstock was made by taking a bud bearing stick from a rootstock shoot and grafting onto a nurse seedling in the nursery. The grafted wood was subsequently rooted following standard procedures for producing clonal avocado trees. The trees were grafted with the scion ‘Hass’ in the nursery and planted in field trials in which the tree always showed the same superior resistance to root rot as the original seedling. The clones or propagules of the tree have been found to be identical to the original seedling in all distinguishing characteristics.
A Simple Sequence Repeat (SSR) DNA fingerprinting technique was performed on avocado leaves of various varieties, including the ‘Merensky 2’. Three samples from the same cultivar were used. Aside from leaves of the ‘Merensky 2’, three other rootstock selections from the Westfalia nursery, ‘Edranol’, ‘Ettinger’, ‘Fuerte’, and ‘Duke 7’ were used. Total genomic DNA was isolated from the leaf samples using 2% CTAB and chloroform:isoamylalcohol (24:1). The SSR primers were: A1E11, A4F08, A7G04, of which the A7G04 primer was found not useful and the A1E11 primer most useful in clearly distinguishing the cultivars, except two of the rootstocks from the Westfalia nursery. No variation could be found between the different samples from the same cultivar. It was concluded that two of the cultivars from the Westfalia nursery were identical. However, there were differences found between the ‘Merensky 2’ and the other varieties, and very clear differences found between the ‘Merensky 2’ and the ‘Duke 7’ variety.
In California, the ‘Merensky 2’ avocado trees have been planted and grown at the “University of California South Coast Field Station”, in Irvine, Calif.
SUMMARY OF THE INVENTION
The invention relates to a new and distinct variety of an avocado tree having many characteristics similar to that of ‘Duke 7’. The invention is characterized by superior resistance to root rot, such as that caused by
Phytophthora cinnamoni
, as compared to ‘Duke 7’. The fruit of the present invention has been found to be slightly larger than that of ‘Duke 7’, and also has a better taste than that of ‘Duke 7’.
An additional report characteristic of ‘Merensky 2’ is its affect on the bearing of the ‘Hass’ avocado. ‘Hass’ grafted onto the instant cultivar bears more fruits than ‘Hass’ grown on ‘Duke 7’.
REFERENCES:
patent: PP12439 (2002-03-01), Krome et al.
UPOV ROM GTITM Computer Database, GTI JOUVE Retrieval Software 2002/05, citation(s) for Latas, Merensky, ‘Merensky 2’, and ‘Dusa’.*
Anon. Avocado Important Commercial cultivars Cultivar: Edranol ARC—Institute for Tropical and Subtropical Crops Http:/www.arc.agric.za/institutes/itsc/main/avocado/edranol.htm.*
List of publications http://www.kypros.org/ARI/hopubl1.html pg. 2.*
AvoResearch vol. 1, Issue May 2, 2001 California Avocado Commission.*
Westfalia Nursery: Avocado & Mango Young Trees for Export; Reasearch and Development http://www.westfalianursery.co/za/resdev.htm.*
Ettinger http://www.ucavo.ucr.edu/AvocadoWebSite% . . . vocadoVarieties/VarietyLisa/Ettinger.html.*
Edranol http://www.ucavo.ucr.edu/AvocadoWebSite% . . . vocadoVarieties/VarietyLisa/Edranol.html.*
Fuerte http://www.ucavo.ucr.edu/AvocadoWebSite% . . . vocadoVarieties/VarietyLisa/Fuerte.html.*
Menge, J.A. Screening and Evaluation of New Rootstocks with Resistance toPhytophthora cinnamomihttp://www.avocado.org/static/growerres/symposium/19mengeroot.php.
Bell Kent
Borrowman Aaron T.
Haas W C
Kelly Lowry & Kelly, LLP
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