Abstract
Various pear species bloom at different times during the spring. Pyrus calleryana Decaisne is one of the earliest and P. communis L. is one of the latest blooming species. In 1975 there were 34 days between the earliest and latest blooming clones. When species or selections with different bloom times were crossed, two generations were needed to bring the bloom time of the progeny to the bloom time of the later blooming parent. The bloom of any given progeny occurred within only 4 to 5 days. No seedling in a progeny flowered later than the later blooming parent. Discovery of late blooming germplasm is essential for the development of late blooming types of pears.
The pear tree ( Pyrus spp.) is a temperate-climate fruit species, and its cultivation in subtropical regions was made possible by hybrid cultivars obtained from the cross Pyrus communis × Pyrus pyrifolia ( Curi et al., 2017 ). This cross
costs and enhance the sustainability of the pear industry. The programs seek to combine resistance from Pyrus ussuriensis Maxim, P. pyrifolia (Burm.) Nakai, and from landraces of P. communis L. ( Bell, 2013 ; Bell and Puterka, 2004 ; Braniste et
Pears belong to the family Rosaceae, subfamily Maloideae, and genus Pyrus . According to Challice and Westwood (1973) , the most important pear species are distributed in five main groups: European species ( P. communis , P. cordata Desv., and
Abstract
During the early 1900s, several plant exploration trips to the Orient were made to collect Pyrus species from Japan, China, Korea, and Manchuria to search for resistance to fire blight [Erwinia amylovora (Burr.) Winsl. et al.]. Following numerous inoculations in various tree tissues, Reimer (15) reported the four most important species, ranked in descending order of blight resistance, as follows: P. ussuriensis Maxim, P. calleryana Deche, P. betulaefolia Bunge, and P. pyrifolia (Burn.) f. Nak. Pyrus ussuriensis and P. pyrifolia were used in earlier breeding programs and are the parent species of many oriental cultivars. However, their textures and flavors have not been accepted by most Americans. P. calleryana also has been used in the USD A pear breeding program, and selections of the 3rd backcross generation appear useful only for resistance.
. communis may provide a pathway for developing new fruits with desirable traits for both growers and consumers. Fruits of Pyrus and Aronia hybrids may be large and sweet, while still maintaining the high levels of health-promoting compounds present in
Pear psyllids are a serious insect pest of the cultivated European pear ( Pyrus communis L.) in the production regions of North America and Europe. In North America, Cacopsylla pyricola (Förster) is the only psyllid pest of pears, whereas in
Pear psyllids ( Cacopsylla spp., Hemiptera: Psyllidae) are major pests of European pear ( Pyrus communis L.) in orchards in most temperate regions where the crop is grown ( Berrada et al., 1995 ; Westigard et al., 1970 ). In North America, the
Explants of three rootstock selections Pyrus calleryana Dcne `Oregon Pear Rootstock (OPR) 157', P. betulifolia Bunge `OPR 260', and P. communis L. `Old Home' × `Farmingdale 230' (`OH × F 230') were initiated from forced branches of field-grown trees. `OPR 260' and `OH × F 230' shoots cultured on Cheng medium with IBA proliferated better than those on NAA. NAA and IBA at concentrations >0.5 μm inhibited shoot multiplication. Overall, the best micropropagation medium for `OPR 260' and `OH × F 230' was Cheng medium with 8 μm BA and 0.5 μm IBA. Shoot multiplication of `OPR 157' was best on 8 μm BA and better on low NAA (0.5 μm) or no auxin than on IBA. `OH × F 230' rooted easily (>80%) with all IBA and NAA treatments. The best rooting treatment (42.9%) for `OPR 260' was 10 μm IBA in darkness for 1 week; for `OPR 157' (23.9%), it was a 15-second dip in 10 mm NAA. Only rooted plantlets survived 4 weeks of greenhouse acclimatization. Chemical names used: N6-benzyladenine (BA); indole-3-butyric acid (IBA); napthaleneacetic acid (NAA).
The genus Pyrus (pears) consists of important fruit trees, and ≈20 primary species are generally accepted by most taxonomists ( Challice and Westwood, 1973 ). Based on their geographic distribution, Pyrus species are divided into oriental and