Regulation of Spraying 6-BA in the Late Jointing Stage on the Fertile Floret Development and Grain Setting in Winter Wheat

Abstract

Wheat yield is largely determined by the grains per spike, which in turn is related to the fertile floret development prior to anthesis. The aim of this study was to assess the physiological mechanism of exogenous 6-benzylaminopurine (6-BA) on fertile floret development and grain setting characteristics by foliar application in winter wheat. Field experiments were conducted during the 2016–2017 and 2017–2018 growing seasons in China. Two foliar spraying applications with water (S0) and 6-BA (S1) were applied to a large-spike variety (V1) and a multiple-spike variety (V2) 25 days after jointing. At anthesis, spike dry weight and soluble sugar, sucrose, auxin, and cytokinin were all positively correlated with the number of fertile florets and grains per spike. During the abortion stage of fertile florets, 6-BA application compared to the control reduced the auxin content, increased the cytokinin content and spike dry matter and transported more soluble sugar and sucrose from the non-spike organs to the spike. Exogenous 6-BA application increased the number of fertile florets (~1.84 to ~2.50) and number of grains (~2.83 to ~3.51) by primarily suppressing the number of degenerated and aborted florets. The results provide important evidence that 6-BA application has a positive effect on floret fertility and grain setting, which lead to a further increase in grain yield.

A ‘wiring diagram’ for sink strength traits impacting wheat yield potential

“…However, there is a negative correlation between auxin concentration and the number of fertile florets at the abortion stage. Adding exogenous 6-benzylaminopurine (6-BA, a synthetic CK) during the abortion phase increased the CK level, reduced the auxin level, decreased the number of floret abortions, and increased spike dry weight ( Li et al , 2019 ). Thus, increasing CK levels in spikes during the floret abortion phase results in increased grain number, for example, by decreasing cytokinin oxidase activity that catalyses the degradation of CK ( Bartrina et al , 2011 ; Zhang et al , 2011 ).…”

“…cytokinin oxidase/dehydrogenase, CKX)] enzymes. The grain sink strength of the spike meristem could therefore be enhanced by altering CK homeostasis through the up-regulation or down-regulation of these enzymes, respectively, to coordinate growth and floret fertility ( Li et al , 2019 ). While there has been speculation on a possible trade-off between fruiting efficiency and spike dry weight at anthesis (see above; Link 10, Fig.…”

“…In addition, there is a clear indication that accumulation of abscisic acid (ABA) in developing grains of maize can result in grain abortion ( Wang et al , 2002 ). In addition, CKs during the grain abortion phase have been identified as playing a potentially relevant role in increasing sink strength ( Zalewski et al , 2010 ; Li et al , 2019 ). In summary, pinpointing the plant hormone signals underlying grain abortion and their genetic control in wheat may allow the development of genotypes with a less conservative strategy for determination of grain number.…”

Spraying exogenous hormones alleviate impact of weak-light on yield by improving leaf carbon and nitrogen metabolism in fresh waxy maize

“…Exogenous application of 6-BA effectively alleviated the adverse effects of waterlogging on maize by increasing the leaf area index and chlorophyll content, reducing the MDA content, maintaining the stability of chloroplast ultrastructure (Ren et al, 2017), and reducing the ABA content (Hu et al, 2022). Exogenous 6-BA application during the fertile florets abortion stage of wheat increased the number of florets and number of grains by primarily suppressing the number of degenerated and aborted florets, which result in a further increase in grain yield (Li et al, 2019). Yuan et al (2014) reported that soaking maize seeds by 6-BA could alleviate the physiological damage under drought stress.…”