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Olfa Zarrouk, Yolanda Gogorcena, Maria Angeles Moreno, and Jorge Pinochet

Trials were established at Aula Dei Experimental Station (EEAD-CSIC, Zaragoza, Spain) to assess graft compatibility between peach cultivars [Prunus persica (L.) Batsch] and new Prunus spp. rootstocks or selections. Peach cvs. `Catherina' and `Tebana' and nectarine cvs. `Big Top' and `Summergrand' were grafted on peach seedlings, plum rootstocks, almond × peach hybrids, and other interspecific rootstocks. Part of the evaluated material belongs to the EEAD-CSIC selection program, which has showed good adaptation to Mediterranean growing conditions. Other rootstocks such as Bruce, Evrica, Hiawatha, Ishtara, Tetra, and Krymsk-1 have been recently introduced in Spain. A peach and a plum source, GF 677 and Adesoto 101, respectively, were used as compatible reference rootstocks. Both are widely used for peach and nectarine production in the Mediterranean area.

Open access

E.N. Ashworth, J.A. Anderson, G.A. Davis, and G.W. Lightner

Abstract

Ice formation was initiated between –0.6° and –2.6°C in mature Prunus persica (L.) Batsch trees growing in the field. Trees supercooled very little. Ice formation was initiated at several locations in the tree and subsequently spread throughout. The release of the latent heat of fusion following ice formation in the tissue maintained tissue temperatures 1° to 3° above air temperature for several hours and mitigated the tissue's response to ambient temperatures.

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Ke Cao, Lirong Wang, Gengrui Zhu, Weichao Fang, Chenwen Chen, and Pei Zhao

, 1977 ). Different levels of RKN resistance have been observed in Prunus species and the corresponding resistance ( R ) genes used for rootstock breeding ( Esmenjaud et al., 1997 ). The Myrobalan plum clone P.2175 is highly resistant to all tested RKN

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W.R. Okie, G.L. Reighard, T.G. Beckman, A.P. Nyczepir, C.C. Reilly, E.I. Zehr, W.C. Newall Jr., and D.W. Cain

Long-term field trials of a wide range of peach [Prunus persica (L.) Batsch] germplasm on two peach tree short-life (PTSL) sites revealed marked differences in survival among lines. Generally, cuttings and seedlings of a given line performed similarly, as did ungrafted seedlings and their counterparts grafted to a commercial cultivar. No apparent relationship existed between a line's chilling requirement and survival. B594520-9 survived best in Georgia and South Carolina, providing significantly greater longevity than Lovell, the standard rootstock for use on PTSL sites. B594520-9 is derived from root-knot-nematode-resistant parentage, and progeny of surviving seedlings have demonstrated root-knot resistance similar to Nemaguard seedlings.

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F.A. Bliss and Ali A. Almehdi

Seedlings of Prunus mahaleb are often used as rootstocks for sweet cherry (P. avium) scion cultivars in commercial orchards. While they are desirable based on ease of propagation and economical production of nursery stock, seedlings may be variable resulting in nonuniform compound trees, and they are susceptible to several important diseases. Seedling sources have shown substantial variability for population uniformity of plant growth, and reaction to crown gall, powdery mildew and Phytophthora root rot. Segregating families also vary for pollen fertility, inbreeding response and control of scion growth. Multiple screening for favorable trait combinations is underway to develop improved sources of cherry rootstocks.

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H. Yaegaki, M. Miyake, T. Haji, and M. Yamaguchi

Pollen fertility and inheritance patterns of male sterility were analyzed in various cultivars and selections of Japanese apricot (Prunus mume Sieb. et Zucc.). Male sterility segregated differently in two types of crosses. In pairings of male-sterile and male-fertile parents, progenies were either all male-fertile, all male-sterile, or mixed. Crossing two male-fertile plants resulted in offspring that were either all male-fertile or mixed. Male sterility in Japanese apricot appears to be of the gene-cytoplasmic type. The genotypes of 10 cultivars and three selections are determined.

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J.D Norton, B.R. Abrahams, G. E. Boyhan, and Hongwen Huang

Forty eight cultivars, species, and their progeny including Prunus americana P. angustifolia, P. cerasifera P. munsoniona, P. salicina, P. simoni, and P. triflora were evaluated for resistance to Xylella fastidiosa based on percent of scalded leaves and tree longevity. Observations indicate that resistance is heritable and controlled by recessive genes. Further, X. fastidiosa transmission was evaluated in plum and peach by chip and slip budding. Transmission as measured by enzyme-linked immunoabsorbant assay indicated that chip budding resulted in a higher level of transmission over slip budding in plum but not in peach. Neither Lovell nor Nemaguard rootstock had an effect on transmission.

Open access

Dan E. Parfitt and S. Ganeshan

Abstract

Seven assays (hanging-drop slide and agar-plate germination, acetocarmine, three tetrazolium-based stains, and Alexander’s staining procedures) were used to estimate pollen viability in Prunus armeniaca L., P. avium L., P. dulcis Webb, P. persica (L.) Batsch, and P. salicina Lindl. The two in vitro germination tests (hanging-drop and agar-plate) were the most reliable and were highly correlated (r = 0.96). The pollen staining procedures were not reliable or consistent and were not positively correlated with the in vitro assays. Acetocarmine and Alexander’s stains stained dead pollen.

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Mark Rieger

Root and shoot characteristics related to drought tolerance were studied for Prunus persica, P. andersonii, P. besseyi, P. maritima, P. subcordata, and P. tomentosa. In general, shoot characteristics were more closely associated with drought adaptation than root characteristics across species. The most xeric species, andersonii, had the most xerophytic leaf morphology, highest rates of leaf gas exchange, high root length/leaf area and root weight/leaf area ratios, but had root length and hydraulic conductivity similar to that of more mesic species. Water use efficiency (WUE) increased as water potentials (ψ) dropped to -3.0 to -4.0 Mpa during a 5-7 day drought for the xeric andersonii and subcordata. However, after an initial increase, WUE decreased with declining ψ in the other 4 species, indicating that carboxylation was affected by stress in the -1.5 to -3.0 range of ψ for besseyi, maritima, persica and tomentosa. CO2 assimilation (A) decreased linearly with ψ during drought in all species, but the ψ at which A reached zero was not well correlated with drought adaptation. Root hydraulic conductivity was similar for all species, indicating a lack of importance of this parameter for drought tolerance. The data suggest that introduction of xerophytic shoot characteristics into commercial cultivars of Prunus would improve drought tolerance to a greater extent than using drought tolerant species as rootstocks.

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R. Tao, H. Yamane, H. Sassa, H. Mori, H. Murayama, T.M. Gradziel, A.M. Dandekar, and A. Sugiura

Stylar proteins of four Prunus species, P. avium, P. dulcis, P. mume, and P. salicina, were surveyed by 2D-PAGE combined with immunoblot and N-terminal amino acid sequence analyses to identify S-proteins associated with gametophytic SI in the Prunus. All four S-allelic products tested for P. dulcis could be identified in the highly basic zone of the gel. These S-proteins had Mr of about 28–30 kDa and reacted with the anti-S4 -serum prepared from Japanese pear (Pyrus serotina). Two of six S-allelic products tested for P. avium could be also identified in the 2D-PAGE profiles, with roughly the same pI and Mr as those of S-proteins of P. dulcis. Putative S-proteins for P. mume and P. salicina were found in the same area of 2D-PAGE as the area where S-proteins of P. avium and P. dulcis were located. N-terminal amino acid sequence analysis of these proteins revealed that they were similar to S-RNases reported previously.