Investigating the tipping point of crop productivity induced by changing climatic variables

The effect of climate patterns on rice productivity in Pakistan: an application of Driscoll and Kraay estimator

This study assesses climate change impact on rice productivity in 28 top rice-producing districts in Pakistan. Driscoll and Kraay estimation is applied on panel data from 1981 to 2019. The cross-sectional dependency test results reveals that climatic factors such as rainfall, humidity, and temperature have correlation issue in different selected regions. The study observes that temperature, rice productivity, and rainfall have inverted U-shape relationship. Rice productivity response is quadratic instead of linear towards average rainfall and temperature during the particular cultivation time, comprising of harvesting, flowering, and planting. The coefficient of temperature during planting time is positive and significant, while the square of temperature during planting time is negative and significant. Temperature during flowering and harvesting time is significant and positive, while the square of temperature during flowering and harvesting time is negative and significant. Rain fall during planting and flowering time are positive and significant; besides that, fertilizer usage stimulates and humidity hinders rice productivity in selected districts of Pakistan. Our empirical results considered the issues of spatial dependency, serial correlation, and heterogeneity.

Interactive effects of tropospheric ozone and blast disease (Magnaporthe oryzae) on different rice genotypes

Rising tropospheric ozone concentrations can cause rice yield losses and necessitate the breeding of ozone-tolerant rice varieties. However, ozone tolerance should not compromise the resistance to important biotic stresses such as the rice blast disease. Therefore, we investigated the interactive effects of ozone and rice blast disease on nine different rice varieties in an experiment testing an ozone treatment, blast inoculation, and their interaction. Plants were exposed to an ozone concentration of 100 ppb for 7 h per day or ambient air throughout the growth period. Half of the plants were simultaneously infected with rice blast inoculum. Grain yield was significantly reduced in the blast treatment (17%) and ozone treatment (37%), while the combination of both stresses did not further decrease grain yields compared to ozone alone. Similar trends occurred for physiological traits such as vegetation indices, normalized difference vegetation index (NDVI), photochemical reflectance index (PRI), Lichtenthaler index 2 (Lic2), and anthocyanin reflectance index 1 (ARI1), as well as stomatal conductance and lipid peroxidation. Ozone exposure mitigated the formation of visible blast symptoms, while blast inoculation did not significantly affect visible ozone symptoms. Although different genotypes showed contrasting responses to the two types of stresses, no systematic pattern was observed regarding synergies or trade-offs under the two types of stresses. Therefore, we conclude that despite the similarities in physiological stress responses to ozone and blast, the tolerance to these stresses does not appear to be genetically linked in rice.