Identification of the profile of endogenous cytokinin-like compounds during different plant growth stages and their effects on flower bud abscission in pistachio (Pistacia vera L.)

Abstract

Alternate bearing is a significant economic problem that affects fruit producers, consumers and the economy of a country. Concentrations of cytokinin (CK)-like compounds in different tissues of pistachio trees (Pistacia vera ‘Uzun’) were measured to elucidate the relationship between endogenous CKs and flower bud abscission (alternate bearing). Identification and quantification of CK-like compounds of the Z, DHZ and iP types from different physiological stages and tissues were performed using high-performance liquid chromatography–electrospray ionisation–tandem mass spectrometry (HPLCESI-MS/MS) techniques. Five to seven different CK-like compounds were detected, respectively. Isopentenyl adenine riboside (iPR) and trans-zeatin-O-glucoside (t-ZOG) were the main isoprenoid CKs, as the dominant conjugates in all the analysed organs of pistachio trees. The leaves and shoots of ‘On’-year trees had significantly higher CK contents than those of ‘Off’-year trees on all the sampling dates. Interestingly, the relatively high CK activity was recorded before flower bud abscission in the fractions corresponding to iPR and t-ZOG, while this activity dropped considerably during the flower bud abscission period (55 DAFB). Consequently, the strong negative correlation between CK concentration and bud abscission could be the first indication of the role of CK-like compounds in this unique phenomenon in the ‘Uzun’ pistachio cultivar. It was concluded that CKs could have an important role in the alternate bearing in pistachio.

Transcriptomic Analysis of the Pistacia vera (L.) Fruits Enable the Identification of Genes and Hormone-Related Gene Linked to Inflorescence Bud Abscission

“…This finds support two recent qualitative analysis conducted by Gündeşli, 2020 [ 54 ] and Gündeşli et al, 2020 [ 55 ] showing an increase in gibberellins and a decrease in auxins levels in pistachio “ON” organs possibly linked to initial embryo development and an evident correlation with flower bud abscission. It is also noticeable that auxin exerts inhibitory effects on the cytokinin pathway and signaling mechanisms, as reported in different studies [ 55 , 56 ].…”

“…This can be assumed as a sign of competition between pistachio fruits and inflorescence buds during the “ON” and “OFF” season and indicate the strength of the fruit. Many studies have shown that cytokinin availability is related to plant sink strength under stress [ 56 , 57 , 58 ]. A possible explanation is that cytokinin may increase the sink capacity by intensifying cell proliferation or regulating sucrolytic enzymes’ activity gaining more photo-assimilates, as demonstrated in grapevine ( Vitis vinifera L.) [ 58 ].…”

Transcriptome and targeted hormone metabolome reveal the molecular mechanisms of flower abscission in camellia

“…Cytokinins are involved in the control of cell division and growth, while ethylene is hypothesized to mediate the effects of CTK on abscission ( Gundesli et al., 2020 ). Cytokinins influence apical dominance, axillary bud formation, and leaf withering in addition to their primary roles in cell proliferation and differentiation.…”