Articles
BREEDING FOR ROSETTE RESISTANCE IN BLACKBERRY
Article number
505_40
Pages
313 – 318
Language
Abstract
Rosette, incited by Cercosporella rubi (Wint) Plakidas, is a serious disease of most erect blackberries (Rubus spp.) and probably the most limiting factor in blackberry production in the southern United States.
The tetraploid cultivar Humble has been reported variously as immune or tolerant to rosette.
A breeding program was initiated at Poplarville, Miss. with the objective of breeding thornless 4X cultivars with rosette resistance derived from ‘Humble’. A productive rosette resistant plant (MSUS29) was identified from the cross ‘Humble’ X ‘Brazos’. MSUS29 was backcrossed to standard cultivars and thornless cultivars.
An elite thornless selection (MSUS119) was identified from crosses with the thornless cultivar Navaho.
The most recent crosses were made between selections with ‘Humble’ as the source of rosette resistance and ‘Arapaho’ or MSUS119 as the source of thornlessness.
It is a challenge to select rosette resistant plants because we have not been able to develop a reliable screening procedure using artificial inoculation with C. rubi and all seedlings are screened in the field using natural infection.
To determine the propensity of ‘Humble’, ‘Brazos’, and ‘Rosborough’ to transmit rosette resistance, we studied its heritability (h2) in blackberry.
Only ‘Humble’ transmitted enough resistance to be usable as a parent.
Although the h2 of resistance (0.48) was fairly high, low variability among parents other than ‘Humble’ would suggest little progress from mass selection in these cultivars.
We evaluated the effect of rosette on ripening date, yield, and berry weight.
Berries ripened about the same time and weighed about the same when grown at rosette-free or disease endemic locations.
A significant clone X location interaction for yield was caused by reduced fruit set on plants where rosette was endemic.
The tetraploid cultivar Humble has been reported variously as immune or tolerant to rosette.
A breeding program was initiated at Poplarville, Miss. with the objective of breeding thornless 4X cultivars with rosette resistance derived from ‘Humble’. A productive rosette resistant plant (MSUS29) was identified from the cross ‘Humble’ X ‘Brazos’. MSUS29 was backcrossed to standard cultivars and thornless cultivars.
An elite thornless selection (MSUS119) was identified from crosses with the thornless cultivar Navaho.
The most recent crosses were made between selections with ‘Humble’ as the source of rosette resistance and ‘Arapaho’ or MSUS119 as the source of thornlessness.
It is a challenge to select rosette resistant plants because we have not been able to develop a reliable screening procedure using artificial inoculation with C. rubi and all seedlings are screened in the field using natural infection.
To determine the propensity of ‘Humble’, ‘Brazos’, and ‘Rosborough’ to transmit rosette resistance, we studied its heritability (h2) in blackberry.
Only ‘Humble’ transmitted enough resistance to be usable as a parent.
Although the h2 of resistance (0.48) was fairly high, low variability among parents other than ‘Humble’ would suggest little progress from mass selection in these cultivars.
We evaluated the effect of rosette on ripening date, yield, and berry weight.
Berries ripened about the same time and weighed about the same when grown at rosette-free or disease endemic locations.
A significant clone X location interaction for yield was caused by reduced fruit set on plants where rosette was endemic.
Publication
Authors
C. L. Gupton
Keywords
Rubus spp., Cercosporella rubi, double blossom, heritability of rosette resistance, rosette effects on blackberry
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