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Due to climatic changes, rice crop is affected by moisture deficit stress and pathogens. Tissue water limitation besides reducing growth rates, also renders the crop susceptible to the infection by Xanthomonas oryzae pv. oryzae (Xoo) that causes bacterial leaf blight. Independently, both drought adaptation and Xoo resistance have been extensively studied. Though the cross-talk between drought and Xoo stress responses have been explored from individual stress studies, examining the combinatorial stress response is limited in rice. Recently published combined stress studies showed that under the combined stress, maintenance of carbon assimilation is hindered and such response is regulated by overlapping cellular mechanisms that are different from either of the individual stresses. Several receptors, MAP kinases, transcription factors, and ribosomal proteins, are predicted for playing a role in cellular homeostasis and protects cells from combined stress effects. Here we provide a critical analysis of these aspects using information from the recently published combined stress literature. This review is useful for researchers to comprehend combinatorial stress response of rice plants to drought and Xoo.

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Background The unprecedented drought and frequent occurrence of pathogen infection in rice is becoming more due to climate change. Simultaneous occurrence of stresses lead to more crop loss. To cope up multiple stresses, the durable resistant cultivars needs to be developed, by identifying relevant genes from combined biotic and abiotic stress exposed plants. Results We studied the effect of drought stress, bacterial leaf blight disease causing Xanthomonas oryzae pv. oryzae (Xoo) pathogen infection and combined stress in contrasting BPT5204 and TN1 rice genotypes. Mild drought stress increased Xoo infection irrespective of the genotype. To identify relevant genes that could be used to develop multi-stress tolerant rice, RNA sequencing from individual drought, pathogen and combined stresses in contrasting genotypes has been developed. Many important genes are identified from resistant genotype and diverse group of genes are differentially expressed in contrasting genotypes under combined stress. Further, a meta-analysis from individual drought and Xoo pathogen stress from public domain data sets narrowed- down candidate differentially expressed genes. Many translation associated genes are differentially expressed suggesting their extra-ribosomal function in multi-stress adaptation. Overexpression of many of these genes showed their relevance in improving stress tolerance in rice by different scientific groups. In combined stress, many downregulated genes also showed their relevance in stress adaptation when they were over-expressed. Conclusions Our study identifies many important genes, which can be used as molecular markers and targets for genetic manipulation to develop durable resistant rice cultivars. Strategies should be developed to activate downregulated genes, to improve multi-stress tolerance in plants.

A field experiment was conducted during four consecutive winter seasons from 2013-14 to 2016-17 at Patna, Bihar under sandy clay loam soil. The trial on potato was laid out in randomized block design with four replications with objective to develop nutrient omission plot technique in potato. The highest plant height and number of shoot per plant were recorded under 150% recommended dose of fertilizer of NPK. The range of dry matter content in potato tuber varied from 16.1 to 17.7% on dry weight basis. The maximum yield of smallest tuber (0-25g) was recorded under 150% recommended dose of fertilizer of NPK, which was at par to all the nutritional treatments and significantly superior over absolute control plot. The maximum yield of medium, large and very large size tuber was recorded under 150% recommended dose of fertilizer of NPK. However, 150% recommended dose of fertilizers of NPK recorded about 13% higher net return over 100% recommended dose of fertilizers of NPK. The maximum yield reduction was observed in the omitted plot without nitrogen among other nutrients like phosphorus and potassium. Hence, nitrogen was one of the most limiting nutrients for tuber yield of potato.