Knockdown of an inflorescence meristem‐specific cytokinin oxidase – OsCKX2 in rice reduces yield penalty under salinity stress condition

Abstract

Cytokinins play a significant role in determining grain yield in plants. Cytokinin oxidases catalyse irreversible degradation of cytokinins and hence modulate cellular cytokinin levels. Here, we studied the role of an inflorescence meristem-specific rice cytokinin oxidase - OsCKX2 - in reducing yield penalty under salinity stress conditions. We utilized an RNAi-based approach to study the function of OsCKX2 in maintaining grain yield under salinity stress condition. Ultra-performance liquid chromatography-based estimation revealed a significant increase in cytokinins in the inflorescence meristem of OsCKX2-knockdown plants. To determine if there exists a correlation between OsCKX2 levels and yield under salinity stress condition, we assessed the growth, physiology and grain yield of OsCKX2-knockdown plants vis-à-vis the wild type. OsCKX2-knockdown plants showed better vegetative growth, higher relative water content and photosynthetic efficiency and reduced electrolyte leakage as compared with the wild type under salinity stress. Importantly, we found a negative correlation between OsCKX2 expression and plant productivity as evident by assessment of agronomical parameters such as panicle branching, filled grains per plant and harvest index both under control and salinity stress conditions. These results suggest that OsCKX2, via controlling cytokinin levels, regulates floral primordial activity modulating rice grain yield under normal as well as abiotic stress conditions.

Phytohormonal cross-talk modulate Bipolaris sorokiniana (Scc.)interaction with Zea mays

“…Oxidase activity is induced upon the elevated stress condition on plant (Joshi et al, 2018). As expected, uniconizole treatment to maize seedlings increased oxidase activity till 72 hour which later became normal as control.…”

Deployment of cold tolerance loci from Oryza sativa ssp. Japonica cv. ‘Nipponbare’ in a high‐yielding Indica rice cultivar ‘93‐11’

“…Because high tolerance to abiotic stress has been shown to cause yield penalty under normal conditions due to a growth–tolerance trade‐off (Deng et al., ; Joshi et al., ), we further investigated several yield‐related traits for 93‐11( qCTS11.1&2 NP ) in the field under normal cultivation conditions. Compared with ‘93‐11’, the cold‐tolerant 93‐11( qCTS11.1&2 NP ) line showed no significant differences with respect to panicle number per plant, spikelet number per panicle, seed setting rate, 1,000‐grain weight and total grain yield per plant (Figure b), indicating that introgression of qCTS11.1 and qCTS11.2 does not impose a yield penalty.…”

“…Crop breeding aims to balance stress tolerance with yield, and QTL pyramiding may impact growth fitness due to linkage drag or/and tolerance–growth trade‐offs (Deng et al., ; Joshi et al., ). In this study, pyramiding the qCTS11.1 and qCTS11.2 QTLs from Japonica rice enhanced the cold tolerance of an Indica cultivar with no negative effects on grain yield when grown in the field under normal conditions.…”

“…Because high tolerance to abiotic stress has been shown to cause yield penalty under normal conditions due to a growth-tolerance trade-off (Deng et al, 2017;Joshi et al, 2017), we further investigated several yield-related traits for 93-11(qCTS11.1&2 NP ) in the field under normal cultivation conditions. Compared with '93- we identified a total of seven loci associated with cold tolerance in a Japonica rice cultivar, six of which were previously reported to be associated with seedling cold tolerance in other Japonica cultivars (Andaya & Tai, 2006;Han et al, 2007;Ranawakea et al, 2014;Ma et al, 2015;Mao et al, 2015; Table 1), suggesting a conserved mechanism of cold tolerance in Japonica rice subspecies.…”

“…Crop breeding aims to balance stress tolerance with yield, and QTL pyramiding may impact growth fitness due to linkage drag or/and tolerance-growth trade-offs (Deng et al, 2017;Joshi et al, 2017). In this study, pyramiding the qCTS11.1 and qCTS11.…”