CSG 15 Research and Development Final Project Report (Not to Be Used for LINK Projects)
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MINISTRY OF AGRICULTURE, FISHERIES AND FOOD CSG 15 Research and Development Final Project Report (Not to be used for LINK projects) Two hard copies of this form should be returned to: Research Policy and International Division, Final Reports Unit MAFF, Area 6/01 1A Page Street, London SW1P 4PQ An electronic version should be e-mailed to [email protected] Project title Genetic improvement of resistance to pests and diseases, tree habit and fruit quality in apple and pear MAFF project code HH1016STF Contractor organisation Horticulture Research International and location East Malling West Malling, Kent ME19 6BJ Total MAFF project costs £ 833,256 Project start date 01/04/97 Project end date 31/03/00 Executive summary (maximum 2 sides A4) The project has the following objectives: · to identify in apple and pear sources of resistance to economically important pests and diseases for which no breeding lines have yet been developed · to elucidate in apple inheritance of other agronomically describable trees and fruit characters · to raise selections of apple and pear with desirable combinations of commercial characters · to identify genotypically good parents in apple and pear · to resolve the incompatibility genotype of ‘Meridian’ and of 50 other apple cultivars. Some 3,500 apple selections of normal habit and 300 pear selections were planted out for assessment by the Apple and Pear Breeding Club, along with 700 columnar selections. Some 34,000 seedlings were screened for resistance to scab in the glasshouse, and the survivors planted in an unsprayed seedling nursery, together with 3,500 seedlings combining mildew resistance genes. About 25,000 seedlings not carrying disease resistance were planted in the sprayed nursery. Approximately 45,000 apple flowers and 10,000 pear flowers were hand-pollinated to raise progenies for genetic studies or for screening. The progeny ‘Elise Rathke’ (weeping) x ‘Pink Pearl’ segregated for weeping habit, indicating this character is controlled by a major gene. Progenies were raised of two ‘low ethylene’ apple selections. The pears ‘Comice’ (quince compatible) and ‘Williams’ (quince incompatible) were intercrossed. CSG 15 (Rev. 12/99) 1 Project Genetic improvement of resistance to pests and diseases, MAFF HH1016STF title tree habit and fruit quality in apple and pear project code Segregation for pink flesh in the progeny ‘Falstaff’ x ‘Pink Pearl’ indicated this novel character is controlled by a dominant gene. However, the progeny ‘Telamon’ x ‘Pink Pearl’ failed to segregate, indicating linkage of the gene for pink flesh with the incompatibility locus, S. This was confirmed later by showing that the incompatibility ribonuclease for S3 cosegregated with pink flesh in the former progeny. Using AFLPs, bands differentiating DNA bulked variously for apetaly, columnar habit, purple pigmentation, woolly apple aphid resistance and mildew resistance were detected. In the case of mildew resistance, these bands have been tested for cosegregation with phenotype. Four markers were found for Pl-w, one of which has been cloned and sequenced for conversion to a SCAR marker. A range of pear genotypes was screened in the glasshouse for response to the pear bedstraw aphid, but some inconsistencies with the reported literature were noted. Six apple selections that may have resistance to apple sawfly were moved to an infestation plot. The apple genebank catalogue was updated to incorporate notes explaining the potential use of most of the accessions. An effort was made to obtain donors of all Malus genes in the literature. By analysing stylar ribonucleases, it was possible to assign incompatibility genotypes to 50 apple cultivars. Analysis of the new cultivar ‘Meridian’ revealed only one allele, S5. Use of primers showed that the second allele, S9, was present, even though it was not functional. The genotype of ‘Meridian’ o o can thus be indicated at S5S9 , where S9 represents a stylar mutation. Analysis of a progeny of ‘Northern Spy’ segregating for resistance to woolly apple aphid indicated that the S locus is not linked with the resistance gene, despite previous reports. Twenty-nine papers describing this work were published or submitted and 30 presentations made to growers or conferences. The progress in the development of breeding lines and markers opens up opportunities for developing marker-assisted selection for apple, to improve the efficiency of the selection process. A CSG7 has been submitted to MAFF envisaging work on marker conversion, identification of new markers, development of high throughput screening, testing multiplexing and implementation of marker-assisted selection. Various selections from previous projects that had been passed to the Apple and Pear Breeding Club for evaluation or development performed well. The scab-resistant apple cultivar ‘Saturn’ and the Cox- type ‘Meridian’ were released to growers via the Apple and Pear Research Council. Selections E11- 20 and E88-9 look promising in trial and 20 more apple selections and two pear scion selections were chosen for trialling. The rootstocks AR86-1-20 and AR86-1-25, resistant to woolly apple aphid and crown rot and of similar vigour to MM106, are candidates for release. Five more rootstock selections performed well in trial – AR680-2, AR801-11, AR835-11, AR839-9 and AR852-3. CSG 15 (1/00) 2 Project Genetic improvement of resistance to pests and diseases, MAFF HH1016STF title tree habit and fruit quality in apple and pear project code Scientific report (maximum 20 sides A4) BACKGROUND The UK produces some 300,000 tonnes of apple and pears per annum, worth £100M at wholesale prices. For supermarket sales, fruit must be attractive with good flavour and texture and long shelf- life, and novel features are desirable. In addition, growers need reliable cropping, resistance to pests and diseases, easily managed tree form and, for main crop varieties, good storage performance. Rootstocks are needed to dwarf trees to a manageable size and these rootstocks should be easy to propagate, resistant to soil-borne pests and diseases, well anchored and free from suckers, and should induce precocious and reliable cropping. HRI-East Malling has identified donors for most, but not all, desirable characters and has developed appropriate breeding lines. In many cases, the genetic control of the characters has been resolved. In some cases, linked molecular markers have been identified, that in future could allow marker- assisted selection. The project aims to develop breeding lines and genetic information, including markers, that can be exploited for the benefit of the industry via the complementary breeding programme funded by the Apple and Pear Breeding Club. OBJECTIVES (I) To identify in apple and pear sources of resistance to economically important pests and diseases for which no breeding lines have yet been developed, especially apple sawfly, pear bedstraw aphid and pear psylla. (II) To elucidate in apple inheritance of other agronomically desirable tree and fruit characters such as dwarfing habit and low ethylene production, including novel ones such as weeping habit and red flesh, by identifying sources of these characters, if necessary, determining the genetic control and, if appropriate, detecting genetic markers. (III) To raise seedlings of apple and pear with desirable combinations of commercial characters, including sufficient resistance to scab and mildew so that 70% fewer fungicide sprays are needed to apple than for existing cultivars. (IV) To identify genotypically good parents in apple and pear and to accelerate seedling selection. (V) To resolve the incompatibility genotype of ‘Meridian’ and of 50 apple cultivars from the National Fruit Collections at Brogdale (year 3 only). METHODS AND RESULTS General Frequent contacts were maintained with the APRC Breeding and Varietal Development Committee and grower organisations such as the East Kent Fruit Society to help ensure the programme responded to the needs of the industry. An open day was held on 1 October 1998 to explain to growers and advisors the process of apple and pear breeding, from the strategic research funded by MAFF through nearer-market work funded by the Apple and Pear Breeding Club. CSG 15 (1/00) 3 Project Genetic improvement of resistance to pests and diseases, MAFF HH1016S title tree habit and fruit quality in apple and pear project code TF Advanced selections Replicated trials of about 30 selections of columnar habit were assessed in all three years. Spring frosts hampered drastically reduced crops in 1997, but in 1998 SA544-28, -39 and -48 (‘Falstaff’ x ‘Obelisk’) were shortlisted. However, texture was disappointing in 1999, perhaps because we misjudged harvest date, and parts of the trial were retained for a further year. Initial assessment, seedlings and crossing In the fruit assessment plots, the progeny ‘Falstaff’ x ‘Pink Pearl’ (pink flesh) segregated for pink flesh, potentially a useful novel character, indicating this character is controlled by a dominant gene for which ‘Pink Pearl’ is heterozygous. However, the progeny ‘Telamon’ x ‘Pink Pearl’ failed to segregate, raising the possibility of linkage with the incompatibility locus as described later. Other columnar progenies were evaluated for fruit quality and disease resistance. On the fruit assessment plots, over 3 years, some 3,500 apple selections of normal habit, worked on M9, were planted as cordons for assessment by the Apple and Pear Breeding Club, along with 325 pear selections on Quince C. About 700 columnar selections, worked on M26, were planted out. Some 34,000 seedlings were screened over the 3 years for resistance to scab in the glasshouse and resistant survivors were planted out into an unsprayed nursery plot. Around 3,500 seedlings were raised combining different mildew resistant genes for the identification and development of molecular markers. About 25,000 seedlings, not carrying scab or mildew resistance, were raised and planted in the sprayed nursery. The progeny ‘Elise Rathke’ (weeping) and ‘Pink Pearl’ (pink flesh) segregated for weeping habit, suggesting this character is controlled by a single gene, ‘Elise Rathke’ being heterozygous.