Effect of temperature on pollen germination and pollen tube growth of four cultivars of mango (Mangifera indica L.)

Summary

The effect of a constant (10, 15, 20 or 25°C) or a diurnal maximum/minimum (15/5, 20/10, 25/15 or 30/20°C) incubation temperature on in vitro pollen germination and pollen tube growth in the pistils of two poly-embryonic (‘Kensington’ and ‘Nam Dok Mai’), and two mono-embryonic (‘Irwin’ and ‘Sensation’) mango cultivars was studied. In in vitro experiments where pollen was incubated in a liquid germination medium for 24 h in darkness, little difference was found between pollen germination of mono- and poly-embryonic cultivars. Averaged over the four cultivars, 53.9% of pollen germinated at 10°C, this increased to 76.2% when the incubation temperature was increased to 15°C, thereafter up to 25°C the percentage germination remained stable but germination decreased slightly to 68.2% at 30°C. Similarly, there was no difference in percent germination between cultivars when pollen was incubated under diurnal temperature regimes. Mean pollen germination of all four cultivars was 52.3% at 15/5°C and pollen germination increased by 10% when the temperature was raised to 30/20°C. When self-pollinated flowers were incubated for 24 h on a semi-solid agar medium at 10°C, pollen tube growth of the four cultivars was retarded and no pollen tubes reached the ovaries. As the temperature was increased from 15 to 25°C, the mean number of pollen tubes in ovaries increased from 0.04 to 0.25. At 30°C, the mean number of pollen tubes that entered ovaries decreased to 0.04. After incubation under diurnal temperature regimes, the mean number of pollen tubes in ovaries of all four cultivars at 15/5°C was 0.23 and increased to 0.42 when the temperature increased to 30/20°C. At each incubation temperature, there were significant differences in pollen tube growth between cultivars, but there were no differences between the temperature response of pollen from mono- and poly-embryonic cultivars.