pear
TRANSCRIPT
Assignment on breeding of pearCourse title : Breeding of fruit crops
Course No : FSC 506
Submitted by:Pawan NagarM.SC.(Horti.) fruit scienceReg. No :04-2690-2015
pearBotanical Name :- Pyrus communis LFamily:- RosaceaeOrigin:- EuropeChromosome No.:- 2n = 51(Triploid)
Introduction
Pyrus communis, known as the European pear or common pear, is a species of pear native to central and eastern Europe and southwest Asia.
It is one of the most important fruits of temperate regions, being the species from which most orchard pear cultivars grown in Europe, North America, and Australia have been developed.
Related Species:- Pyrus pyrifolia Pyrus pashia Pyrus serotina Pyrus salicifolia
Ploidy levels in Pear
1.Triploid (2n = 51)
2. Tetraploids (2n = 68)
3. Hexaploid (2n = 102)
Genetic Resources
The commercial genotypes most commonly found today are diploids although there are triploids (2n=51) and even tetraploids.
Commercial triploid cultivars produce little good pollen, so that cropping in an orchard requires at least two intercompatible cultivars.
The tetraploids have aroused interest because of their extra large fruit and leaves although generally, they yield poorly (Zielinski and Thompson 1967).
Different cultivar of PearBlake's Pride pear Packham's Triumph pear
Clairgeau pearLouise Bonne of Jersey pear
Varieties of Pear
Eight varieties of pears, from left to right, Bartlett, two Red Bartlett varieties, Anjou, Bosc, Comice, Concorde, and Seckel.
Breeding objectives
Improvement of fruit quality.
Addition to climate adaption, disease resistance is very important in some regions.
Early bearing and consistent cropping are important.
Adequate disease and pest resistance.
Important to develop rootstocks that induce similar size control and precocity in the scion cultivar as Quince A but that are more compactable winter hardy, and disease resistant.
Floral biology
1. Pear blossoms are white, rarely pinkish, and born in umbel like Corymb.
2. The flower consist of five petals and sepals and 20-30 stamens with anther that usually red.
3. Styles vary from 2-5 and are free but closely constricted at the base.
4. The ovary has 5 locules with 2 ovules per locule with a maximum seed set obtain of ten.
Breeding system
Incompatibility and sterility
Polyploidy
Mutation
Hybridization and mating designs
Parental selection, progeny testing, and progeny size
Mutation breeding
Irradiation (X-rays) has been used to increase the frequency of mutations in fruit trees . Several kinds of mutations have been identified after irradiation in P. communis including bloom time, blossom color, ripening time, fruit color and growth habit .
In P. pyrifolia mutations have been induced that effected disease resistance and self-compatibility.
At least five European and four Japanese pears have been developed through mutation breeding.
Biotechnology
Cell and tissue culture
Somaclonal variability and
genetic improvement
Transformation
Breeding for specific tree and production characters
1. Growth habit
2. Precocity
3. Self incompatibility
4. Parthenocarpy
5. Productivity
Fruit character 1. Fruit quality
2. Flavour
3. Texture
4. Skin colour
5. Russets
6. Flesh colour
7. Fruit size
8. Fruit shape
9. Ripening Season
10.Storage quality
11.Processing quality
Achievement and Prospects Scion cultivars
Centuries of selection have resulted in the development of several broadly adapted cultivars of high quality, including Bartlett, Anjou, Comice, Bosc, Nijisseiki and Housi, that are successfully grown in many part of the world.
Improve cold hardiness.
To reduce management cost and shorten time to bearing, pears are being grown on dwarfing rootstocks.
High density planting.
Development of disease and pest resistant cultivars.
Resistance to Biotic and Abiotic
The resistance genes to fire blight have yet to be identified, researchers have long known the sources of resistance and began the breeding for fire blight resistance at Geneva in New York State, Harrow Station in Canada and Angers in France in the 1980.
The release of such partially resistance or tolerant cultivars such as ‘Harrow Sweet’, ‘ ‘Harrow Crisp’, ‘Blake’s Pride’, ‘Aida’ and ‘Boheme’.
