Evaluating Self-Pollination Methods: Their Impact on Nut Set and Nutlet Abscission in Macadamia

Area of Science:

• Horticultural Science
• Plant Breeding
• Reproductive Biology

Background:

• Nut set is crucial for macadamia yield and orchard profitability.
• Pollination is a critical factor influencing nut set.
• Macadamia cultivars exhibit varying degrees of self- and cross-pollination.

Purpose of the Study:

• To investigate nut setting and nutlet abscission in macadamia cultivars under controlled self-pollination.
• To assess the effectiveness of different self-pollination methods (autogamy, geitonogamy) compared to open-pollination.
• To identify macadamia cultivars with desirable self-pollination traits for breeding purposes.

Main Methods:

• Four macadamia cultivars ('HAES 791', 'HAES 741', 'HAES 344', 'A16') were studied.
• Controlled self-pollination was achieved through autogamy (AG), geitonogamy 1 (GG1), and geitonogamy 2 (GG2).
• Results were compared against open-pollination (OP).

Main Results:

• 'HAES 741' and 'HAES 791' were identified as partially self-fertile; 'HAES 344' and 'A16' were self-infertile.
• Open-pollination resulted in significantly higher nut set than all self-pollination methods.
• Nut set under self-pollination ranged from 3.7-6.5% of open-pollination levels in self-fertile cultivars.

Conclusions:

• Partially self-fertile macadamia cultivars can achieve adequate yields with reduced reliance on external pollinators.
• No significant differences in nut set or abscission were found among the tested self-pollination methods.
• Understanding self-pollination is key for macadamia breeding programs aiming to enhance yield and profitability.