Effects of Temperature and Humidity Conditions during Storage on in vitro Pollen Germinability of Lychee (Litchi chinensis Sonn.)

Abstract

Pollen of ‘Bengal’ and ‘Chakrapat’ lychee was stored under various temperature and humidity conditions supposing the storage conditions can be duplicated easily by private orchads. During the storage under refrigerator temperature (5ºC) with 30% RH (relative humidity) condition, the ‘Chakrapat’ pollen which had 65% pre-storage germination (PSG) indicated slowly decreasing germination to 40% within 8 weeks. The germination decreased more rapidly when the pollen was stored under room temperature (20ºC) with 50% RH condition. Whereas the pollen stored under drier condition (RH < 10%) at 5 or 20ºC showed moderate decrease to 35% germination within one week, although no subsequent reduction within 8 weeks was observed. Deep-freezer temperature (-40ºC) storage for one month showed high germination which was similar to PSG for both cultivars. ‘Chakrapat’ pollen (60% PSG) showed 30% germination after one-year storage under the temperature of freezer (-10ºC) or deep-freezer (-40ºC) condition. Lower PSG (< 50%) pollen showed larger reduction in germination than higher PSG (≥60%) pollen when freezed or refrigerated during storage. Temperature of deep-freezer (-40ºC) was optimal for several-week storage. As a practical method, however, temperature of 5ºC with 30% RH seemed to be facilitative. In order to store pollen for one year, temperatures -10 and -40ºC are most recommendable.