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Abstract

Twenty-three strawberry cultivars, naturally infected with Diplocarpon earliana (Ell. & Ev.) Wolf, ranged from resistant in cultivars such as ‘Earlibelle’, ‘Albritton’ and ‘Empire’ to very susceptible in the cultivars ‘Redglow’, ‘Jerseybelle’ and ‘Vesper’. In general, leaf scorch resistance ratings were similar to those for the same cultivars tested elsewhere.

In 14 progenies from crosses involving 9 cultivars a larger % of seedlings were rated resistant from selfed resistant (R) parents than from selfed susceptible (S) or intermediate (I) parents, or from crosses involving these parents.

Open Access

`Blake's Pride' has been released jointly by USDA and The Ohio State Univ. as a new fire blight-resistant cultivar. The original seedling tree was selected in 1977 at the Ohio Agricultural Research and Development Center in Wooster by R.C. Blake and T. van der Zwet from a cross of US 446 × US 505, performed in 1965 by H.J. Brooks, and was tested under the original seedling number, OHUS 66131-021. The fruit of `Blake's Pride' is pyriform to round-pyriform in shape, and is moderate in size, averaging ≈2.75″ to 3″ in diameter, and 3.25″ in height. The stem is short, medium in thickness, and upright. Skin undercolor is yellow, the finish is glossy, and 20% to 30% of the fruit surface is covered with a smooth, light tan russet. Harvest maturity occurs about 3 weeks after `Bartlett', and the fruit will store in air storage for at least 3 months without core breakdown or superficial scald. The flesh texture is moderately fine, juicy, and buttery. Grit cells are moderately small and occur primarily around the core and in a thin layer under the skin, similar to `Bartlett'. The flavor is subacid and aromatic. The tree is moderate in vigor on `Bartlett' seedling rootstock, and upright-spreading in habit. Yield has been moderate to moderately high. Fire blight infections are rare, and extend no further than 1-year-old growth. Artificial blossom inoculations indicate a moderate degree of resistance of blossoms to fire blight infection. Resistance of `Blake's Pride' to both shoot and blossom infection is much greater than that of `Bartlett'.

Free access

Abstract

Of 20 cultivars of pear (Pyrus spp.) evaluated for their degree of resistance to fire blight, caused by Erwinia amylovora (Burr.) Windslow et al., following 6 years of epiphytotic conditions, 9 were rated as resistant: (in descending order) ‘Magness’, ‘Moonglow’, ‘El Dorado’, ‘Cornice’, ‘Maxine’, ‘Mac’, ‘Dawn’, ‘Duchess d’Angouleme’, and ‘Kieffer’. Small plots of trees, sufficient to determine very susceptible cultivars, are not adequate to evaluate resistant cultivars.

Open Access

Abstract

‘Hull Thornless’ (Rubus sp., is a vigorous and productive thornless blackberry cultivar with firm, sweet, fruit. It is named for the late John W. (Jack) Hull, formerly of the University of Maryland, the University of Arkansas, and the U.S. Department of Agriculture, who spent most of his life breeding blackberries and raspberries. ‘Hull Thornless’ is the fifth in a series of tetraploid, genetically thornless blackberry hybrids developed by the USDA and cooperating agencies (4). It is adapted principally to USDA Plant Hardiness Zones 6-8.

Open Access

Abstract

No consistent trend towards increased inbreeding has existed within the U.S. Department of Agriculture pear breeding program over 17 years of crosses based on the mean inbreeding coefficient and the percentage of non-inbred progenies. Selections did not tend to be more or less inbred than the population of all seedings. There was consistent, but small, trend towards a reduction in seedling vigor with increased levels of inbreeding as measured by 5th year stem diameter. A significant positive, but small, association between increased inbreeding and improved flavor, grit, and texture were observed, even after correction for the effects of parental values for these characters. Limited inbreeding does not adversely affect improvement of fruit quality and appears to be of some benefit in facilitating selection of favorable alleles.

Open Access