Breeding for resistance: breeding for Plum pox virus resistant apricots (Prunus armeniaca L.) in Spain

Plum pox virus , Dideron type (PPV-D), was first detected in Spain in 1984. Since then, it has spread among Japanese plum trees and apricot trees has been extremely rapid in the main producing areas. In Spain, breeding for resistance was the only efficient method for controlling the disease on apricot. Two breeding programmes are currently producing new hybrids resistant to the disease. The main problem encountered by both programmes is the difficult procedure needed for screening the trait that delays the programmes. Nevertheless, more than 8000 seedlings have been produced, two new varieties have been released and several advanced selections are under study. The procedure for screening sharka resistance has varied by techniques and cultivars used which has resulted in different hypotheses about inheritance of the trait. Additionally, several studies on mapping and molecular markers in progress could provide markers for molecular assisted selection that can increase the breeding efficiency.     

Breeding for resistance: conventional breeding for Plum pox virus resistant apricots (Prunus armeniaca L.) in Greece

A large apricot breeding programme has been conducted at NAGREF-Pomology Institute, Naoussa-Greece, for the control of sharka disease, since 1989. Ten apricot cultivars of North American origin: 'Stark Early Orange', 'Stella', 'NJA2', 'Sunglo', 'Veecot', 'Harlayne', 'Henderson', 'Goldrich', 'Orangered' and 'Early Blush', selected for their resistance to the highly virulent local strain of Plum pox virus (PPV)-M (Marcus), have been used as parents in crosses with quality cultivars, mainly with the local cv. Bebecou, from 1989 to 2003. Approximately 7000 hybrids have been created. Resistance to PPV was the main criterion of selection. Most hybrids have been subjected to artificial inoculation by PPV-M and examined for symptom expression for more than five years. Indexing to GF-305, as well as laboratory diagnostic tests, have been applied. The genetic analysis showed that: (1) 50% of the hybrids inherited resistance to PPV in the families where cvs. Stark Early Orange, NJA2, Sunglo, Veecot and Harlayne were used as a parent, and (2) 100% of the hybrids inherited resistance to PPV in the families where cv. Stella was one of the parents. Resistance to PPV appears to be under simple genetic control involving one gene locus. Promising apricot selections resistant to PPV-M have been released.     

Breeding for resistance: breeding for Plum pox virus resistant apricots (Prunus armeniaca L.) in the Czech Republic

Plum pox virus (PPV) causes serious damage in apricots grown in the Czech Republic and other countries where it is present. To study PPV resistance in apricot, three backcrosses between apricot cultivars or selection resistant to PPV and apricot cultivars or selections susceptible to PPV ('LE-3218' × 'Stark Early Orange', 'LE-3241' × 'Vestar' and 'LE-3246' × 'Vestar') were performed. The seedlings were repeatedly inoculated with PPV-M strain by an infected chip. The resistance of the plants was evaluated by visual inspection for symptoms and ELISA in three consecutive growth periods. The Chi-square (χ²) test was used to analyse the data. It was found that two independent dominant complementary genes conditioned PPV resistance in apricot in the case of the backcrosses. The mode of inheritance for resistance to PPV in cv. Harlayne was determined from F1 progenies. Resistance to PPV in 'Harlayne' was controlled by three independent complementary dominant genes. This knowledge will help us in effective planning of apricot breeding programmes.     

Breeding for resistance: breeding for resistance to Plum pox virus in Italy

Plum pox virus (PPV) resistance in apricot and peach in Italy has been researched in several Italian institutions, including the Institutes for Fruit Tree Culture and Plant Pathology in Rome, which are assessing resistance, and the Universities of Bari, Bologna and Milan, examining breeding techniques, both by cross-breeding and genetic transformation approaches. A reliable protocol for resistance assessment has been set up, in which biological indexing, ELISA and PCR techniques are used. No source of resistance has yet been found in peach. Hybridization with Prunus davidiana could be investigated given the promising results obtained within the INRA programme in France. Almost 6000 apricot seedlings from controlled crosses between resistant parents have been investigated in search of possible molecular markers, but no positive results have been obtained so far, probably due the fact that resistance to both D and M strains is sought. The transformation of cultivars has proven difficult in apricot where the regeneration step is particularly critical, while in peach a reliable regeneration protocol still remains to be set up.     

从德国虞美人花卉中检测到李痘病毒

虞美人(ＰａｐａｖｅｒｒｂｏｅａｓＬ.)为罂粟科的常见栽培花卉植物。采集自世博会德国园的虞美人(ＰａｐａｖｅｒｒｂｏｅａｓＬ.)病株,表现明显的细花叶症状,具有典型的病毒病症状。因而我们采用电镜负染,生物接种实验,初步认为侵染德国虞美人引起花叶的病原为李痘病毒(Ｐｌ     

Hosts and symptoms of Plum pox virus: ornamental and wild Prunus species

Several ornamental and wild Prunus species have been identified as natural and/or experimental hosts for Plum pox virus (PPV). The significance of natural vs. experimental hosts, graft or bud-transmitted infections vs. aphid-transmitted infections in ornamental or wild Prunus hosts, and their relevance in the field situation, are not clearly understood. However, since PPV is aphid-transmitted, any host in the field or nursery serves as a potential reservoir and source of inoculum and must be monitored and controlled in any PPV eradication or management programme.