Exploring storage protocols for yam (Dioscorea spp.) pollen genebanking

Abstract

Implementation of pollen genebanks allows the conservation of plant genetic resources at the haploid level, pollen genetic manipulations, scheduling of hybrid seed production and improvement of breeding efficiency. To establish pollen storage protocols for various genotypes of West African yams, laboratory experiments were conducted on fresh pollen and pollen stored under various conditions at the Genetic Resources Unit International Institute of Tropical Agriculture Ibadan, Nigeria (IITA). The storage treatments examined were air-dried storage, freeze-drying followed by storage in liquid nitrogen and hermetic cold storage without previous drying ("wet-cold" storage). Pollen maintained under dry conditions (dry-air and freeze-dried) maintained aceto-carmine stainability up to 400 days but drastically lost germination capacity, most notably under dry-air storage. But pollen samples maintained at "wet-cold" conditions under −80°C retained germination capacity after 2 years. The results provide evidence to suggest recalcitrance of yam pollen grains in view of poor pollen survival with drying. Therefore, the "wet-cold" storage procedure appears to be the most promising method for the sustainable implementation of yam pollen genebanks. Pollen storage protocols for active and base collections were proposed, based on these findings.

First report of a successful development of yam hybrids (Dioscorea alataL.) from lyophilized and long-term stored pollens

“…Our study observed a 45% decrease in pollen germination from fresh pollens to one-year lyophilized pollens. Daniel et al, [44] also observed a sharp decrease in pollen germination of yam species after cryo-preservation. They recommended that wet-cold storage (hermetic cold storage without previous drying) is a superior method for long-term pollen viability compared to air-dried storage and freeze-drying.…”

“…However, the success rates vary according to the plant species. Many studies have reported in vitro germination of preserved pollens of yam using different techniques [20,23,24,[42][43][44]. For instance, Mondo et al, [20] achieved 26.4-59.7% in vitro germination in D. alata.…”

“…Treatment 1 with 48 h drying appeared superior to Treatment 2 with 72 h drying. The low efficacy of T2 may be attributed to the reduced moisture content due to longer drying period [44].…”

First Report of a Successful Development of Yam Hybrids (Dioscorea alata L.) from Lyophilized and Long-Term Stored Pollens

“…However, the success rates vary according to the plant species. Many studies have reported in vitro germination of preserved pollens of yam using different techniques [20,23,24,[42][43][44]. For instance, Mondo et al [20] achieved 26.4%-59.7% in vitro germination in D. alata.…”

Genetic Mechanisms for Hybrid Breeding in Vegetable Crops

“…Alexander et al [ 51 ] also claimed that Capsicum pollen could retain its viability and fertility for more than 42 months under cryopreservation. Pollen samples of yam retained their germination capacity even after 2 years when subjected to “wet-cold” conditions at −80 °C [ 52 ]. In cucurbits, pollen tube growth in watermelon was observed to be highest at 35 °C and lowest at 15 °C [ 53 ].…”