The evaluation of resistance to shothole, leaf rust and fruit tree red spider mite in elite domestic plum hybrids in Latvia
2013
Grāvīte, I. | Kaufmane, E.
The aim of this study was to select hardy plum hybrids suitable for sustainable growing, which can be registered as cultivars. In Latvia the most important diseases and pests causing significant yield decreases of Prunus domestica are shothole (Stigmina carpophila), leaf rust (Tranzschelia spp.) and fruit tree red spider mite (Panonychus ulmi). Elite plum hybrids from a Latvian-Swedish common breeding program were evaluated in natural field conditions at the Latvia State Institute of Fruit-Growing to select the most resistant genotypes to these diseases and pests. The incidence of pests and disease severity were evaluated on eight to nine-year-old plum trees. Evaluation of 16 hybrids began in 2007. After the winters of 2009/2010 when temperatures fell below -28°C, and 2010/2011 when fluctuations of temperature were from 0+/-3°C in January to -24°C in February; evaluation was continued on the eight most winter-hardy hybrids. The fruit tree red spider mite evaluations were made in spring on the abaxial surface of new leaves. Leaf damage caused by the most important diseases, shothole and leaf rust was rated on a 5-point scale. Hybrid trees differed significantly in resistance to leaf rust. Hybrids 1432B1 and BPr6511 had significantly less rust damage than the other trees. As the only registered acaricide in Latvia is a phosphor-organic compound which is not effective against red spider mite, it was necessary to select plum hybrids high resistance to this pest. Hybrids BPr8932, 1228C and 1658K had the lowest infestations of red spider mite. BPr6511 and 1658K exhibited the least shothole damage. Plum hybrids BPr6511 and 1658K were the most resistant to the complex of important diseases and pests evaluated.
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