Abstract
Pollen viability and germination capability in three pear cultivars viz. Pathernakh, Punjab Beauty and Shinseiki were investigated up to 12 weeks (3 months) stored at different temperatures i.e. room temperature, refrigerator (40oC), freezer (-20oC) and liquid N (-120oC). Viability was tested in 2 per cent acetocarmine solution whereas, for in Vitro pollen germination pollen grains were germinated in 10 percent sucrose solution at weekly intervals. The pollen viability and in Vitro germination percentages of the genotypes were significantly affected by storage temperatures. The pooled data for a period of two years revealed that average viability varied from 40.68% (Shinseiki) to 48.75% (Patharnakh) whereas, germination percentage varied from 34.93% (Shinseiki) to 42.81% (Patharnakh) among the cultivars under study. Pollen stored at low temperature (-120oC and -20oC) showed better viability and germination percentage as compared to pollen stored at room temperature and 4 oC. The cultivar Patharnakh had maximum viability and germination percentage when pollen were stored at -20 (67.40% and 59.62%, rsespectively) and -196? (68.06% and 61.83%, respectively), followed by Punjab Beauty and Shinseiki. The results indicate that pollen collected and stored at sub-zero temperatures from early blooming pear varieties can be stored for very long period without any appreciable loss of viability and germination and can be used along the whole blooming season for hybridization programmes by fruit breeders even at distant places for the development of new strains so as to widen the genetic base and create variability in pear.
Highlights
Pear is one of the most important temperate fruits of the world next to apple
The results indicate that pollen collected and stored at sub-zero temperatures from early blooming pear varieties can be stored for very long period without any appreciable loss of viability and germination and can be used along the whole blooming season for hybridization programmes by fruit breeders even at distant places for the development of new strains so as to widen the genetic base and create variability in pear
It is quite obvious that staining tests are not a reliable measure of pollen viability as compared to in-vitro pollen germination tests
Summary
Pear is one of the most important temperate fruits of the world next to apple. Total world pear production reached 19.5 million metric tons in 2006 (FAOSTAT 2007) ranking second after apple, among global production of deciduous fruit tree species. In India the annual pear production is 1.76 lakh metric tons from an area of 38600 ha (Anonymous, 2006). In Punjab, it ranked 4th among fruit crops in terms of area after citrus, guava and mango and occupies an area of 2598 ha with an annual production of 58,643 mt (Aulakh & Gill, 2010). Cryopreservation is an effective method of long-term pollen storage. Under these conditions all metabolic processes in the biological systems, including pollen are virtually arrested, permitting maintenance of viability. Cryogenic pollen storage permits maintenance of pollen viability for several decades but storage beyond 3-5 years has not been reported in many species
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