|ZHANG, LU - Oklahoma State University|
|BEEDE, ROBERT - University Of California, Davis|
|FERGUSON, LOUISE - University Of California, Davis|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2019
Publication Date: 11/1/2019
Citation: Zhang, L., Banuelos, G.S., Wallis, C.M., Beede, R.H., Ferguson, L. 2019. Dust interferes with pollen-stigma interaction and fruit set in pistachio Pistacia vera cv. Kerman. HortScience. 54(11):1967-1971. https://doi.org/10.21273/HORTSCI14330-19.
Interpretive Summary: Spring mowing in pistachio orchards creates dust that may interfere with pollination and negatively affect nut yields. Mixtures of dust and pollen were applied to pistachio flowers, and dust was observed to damage both pollen viability and stigma quality. Furthermore, GA3, an important flowering hormone, was triggered by dust treatments resulting in empty nutshells or blanks at harvest. This result demonstrates that pistachio growers should take actions to minimize dust caused by mowing to gain increases in nut yields.
Technical Abstract: Springtime flail mowing of row middles for weed control in California pistachio (Pistacia vera L.) orchards blows dust into the leafless canopy if it occurs during bloom. The effect of dust on pistachio pollination and fruit set is unknown. Rachises were bagged pre-bloom and hand-pollinated with pollen and dust mixtures at 1:0, 1:1, 1:4, 1:16 and 0:1 volume/volume ratios on five successive days. The 2016 and 2017 trials demonstrated that dust damaged both pollen viability and stigma quality, particularly if contaminated with herbicide residues (GlyStar® Plus and Treevix®). Decreased yield was a function of decreased fruit set, increased embryo abortion and/or parthenocarpy and a lower split nut percentage. The GA3 content in flowers of both the pollen and dust treatments was significantly higher than in non-pollinated flowers, suggesting dust stimulated parthenocarpy, resulting in empty nutshells, “blanks” at harvest.