Discovery of potential protein biomarkers associated with sugarcane white leaf disease susceptibility using a comparative proteomic approach

Sugarcane white leaf disease (SCWLD) is caused by phytoplasma, a serious sugarcane phytoplasma pathogen, which causes significant decreases in crop yield and sugar quality. The identification of proteins involved in the defense mechanism against SCWLD phytoplasma may help towards the development of varieties resistant to SCWLD. We investigated the proteomes of four sugarcane varieties with different levels of susceptibility to SCWLD phytoplasma infection, namely K88-92 and K95-84 (high), KK3 (moderate), and UT1 (low) by quantitative label-free nano-liquid chromatography-tandem mass spectrometry (nano LC-MS/MS). A total of 248 proteins were identified and compared among the four sugarcane varieties. Two potential candidate protein biomarkers for reduced susceptibility to SCWLD phytoplasma were identified as proteins detected only in UT1. The functions of these proteins are associated with protein folding, metal ion binding, and oxidoreductase. The candidate biomarkers could be useful for further study of the sugarcane defense mechanism against SCWLD phytoplasma, and in molecular and conventional breeding strategies for variety improvement.

Gene Co-Expression Analysis Reveals Transcriptome Divergence between Wild and Cultivated Sugarcane under Drought Stress

Drought is the main abiotic stress that constrains sugarcane growth and production. To understand the molecular mechanisms that govern drought stress, we performed a comprehensive comparative analysis of physiological changes and transcriptome dynamics related to drought stress of highly drought-resistant (ROC22, cultivated genotype) and weakly drought-resistant (Badila, wild genotype) sugarcane, in a time-course experiment (0 h, 4 h, 8 h, 16 h and 32 h). Physiological examination reviewed that ROC22, which shows superior drought tolerance relative to Badila, has high performance photosynthesis and better anti-oxidation defenses under drought conditions. The time series dataset enabled the identification of important hubs and connections of gene expression networks. We identified 36,956 differentially expressed genes (DEGs) in response to drought stress. Of these, 15,871 DEGs were shared by the two genotypes, and 16,662 and 4423 DEGs were unique to ROC22 and Badila, respectively. Abscisic acid (ABA)-activated signaling pathway, response to water deprivation, response to salt stress and photosynthesis-related processes showed significant enrichment in the two genotypes under drought stress. At 4 h of drought stress, ROC22 had earlier stress signal transduction and specific up-regulation of the processes response to ABA, L-proline biosynthesis and MAPK signaling pathway–plant than Badila. WGCNA analysis used to compile a gene regulatory network for ROC22 and Badila leaves exposed to drought stress revealed important candidate genes, including several classical transcription factors: NAC87, JAMYB, bHLH84, NAC21/22, HOX24 and MYB102, which are related to some antioxidants and trehalose, and other genes. These results provide new insights and resources for future research and cultivation of drought-tolerant sugarcane varieties.

Performance of High Yielding Promising Sugarcane Variety for Western Zone of Tamilnadu

Sugarcane is an important commercial crop cultivated in over 23,000 ha in Erode district of TamilNadu state. Attempts were made by researchers and extension workers to improve the productivity of sugarcane by adopting high yielding varieties and improved production technologies. The on-farm trials were conducted during Kharif 2017 and 2018 in five farmers’ field to assess the performance of high yielding promising sugarcane varieties suitable for Western Zone of TamilNadu. The varieties selected for trial were Co 86032 and Co 0212. The study revealed that Co 0212 recorded more number of productive tillers per plant (10.4), intermodal length (14.51 cm), stem girth (11.22) and individual cane weight (1.511 kg) which was superiorly higher than the existing variety Co 86032. Similarly Co 0212 recorded the yield of 127.5 ton / ha during 2017 which was 17.24 per cent higher yield than the existing variety and 138.86 ton / ha recorded and 30.68 per cent yield advantage was noticed in the ratoon crop. The highest benefit cost ratio of 2.44 was recorded in Co 0212 in ratoon crop and 2.05 in first crop where as 1.73 and 1.86 BCR observed in Co 86032 in first and ratoon crop respectively. Considering the above facts, Co 0212 would be identified as a better alternate variety suitable for the Western Zone of TamilNadu

Differential Protein Expression Analysis of Two Sugarcane Varieties in Response to Diazotrophic Plant Growth-Promoting Endophyte Enterobacter roggenkampii ED5

Plant endophytic bacteria have many vital roles in plant growth promotion (PGP), such as nitrogen (N) fixation and resistance to biotic and abiotic stresses. In this study, the seedlings of sugarcane varieties B8 (requires a low concentration of nitrogen for growth) and GT11 (requires a high concentration of nitrogen for growth) were inoculated with endophytic diazotroph Enterobacter roggenkampii ED5, which exhibits multiple PGP traits, isolated from sugarcane roots. The results showed that the inoculation with E. roggenkampii ED5 promoted the growth of plant significantly in both sugarcane varieties. 15N detection at 60 days post-inoculation proved that the inoculation with strain ED5 increased the total nitrogen concentration in the leaf and root than control in both sugarcane varieties, which was higher in B8. Biochemical parameters and phytohormones in leaf were analyzed at 30 and 60 days after the inoculation. The results showed that the inoculation with E. roggenkampii ED5 improved the activities of superoxide dismutase (SOD), catalase (CAT), NADH-glutamate dehydrogenase (NADH-GDH), glutamine synthetase (GS), and endo-β-1,4-glucanase, and the contents of proline and indole acetic acid (IAA) in leaf, and it was generally more significant in B8 than in GT11. Tandem Mass Tags (TMT) labeling and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to perform comparative proteomic analysis in the sugarcane leaves at 30 days after inoculation with strain ED5. A total of 27,508 proteins were detected, and 378 differentially expressed proteins (DEPs) were found in the treated sugarcane variety B8 (BE) as compared to control (BC), of which 244 were upregulated and 134 were downregulated. In contrast, a total of 177 DEPs were identified in the treated sugarcane variety GT11 (GE) as compared to control (GC), of which 103 were upregulated and 74 were downregulated. The DEPs were associated with nitrogen metabolism, photosynthesis, starch, sucrose metabolism, response to oxidative stress, hydrolase activity, oxidative phosphorylation, glutathione metabolism, phenylpropanoid metabolic process, and response to stresses in Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) database. To the best of our knowledge, this is the first proteomic approach to investigate the molecular basis of the interaction between N-fixing endophytic strain E. roggenkampii ED5 and sugarcane.

DIFFERENTIAL EFFECT OF SALINITY ON GROWTH, NUTRIENT CONCENTRATION AND CHLOROPHYLL IN SUGARCANE VARIETIES MEX 69-290 AND CP 72-2086

Sugarcane (Saccharum spp. hybrids) is moderately sensitive to salinity and the effects on plant performance vary according to stress level and genotype. This study aimed to evaluate the effect of salt stress induced by application of different NaCl levels in the irrigation solution on plant height, indirect index of chlorophylls (SPAD), and macronutrients concentration (N, P, K, Ca, Mg and S) and Na in leaves of two sugarcane varieties: CP 72-2086 and Mex 69-290. The experiment was set in a completely randomized design with a 2×5 factorial arrangement. The study factors were sugarcane variety (CP 72-2086 and Mex 69-290) and NaCl concentration (0.0, 71.8, 143.6, 215.4 and 282.7 mM NaCl). Salinity as a single factor negatively affected plant height, SPAD units and N and P concentration in leaves; Ca concentrations increased, while K, Mg and S remained unaffected by the tested NaCl levels. Mex 69-290 grew higher and concentrated greater levels of N and K. Interactions of factors showed that salinity reduced growth in both varieties, but this reduction was more pronounced in CP 72-2086. SPAD units were also significantly reduced by salinity in both varieties. Concentrations of N and P in leaves decreased in both varieties in response to NaCl, while those of K and Ca increased in Mex 69-290. Concentration of Na was higher in Mex 69-290 which exhibited better performance than CP 72-2086. Sodium concentrations in leaves increased in direct relation to the tested NaCl concentrations. Mex 69-290 reached higher concentrations of Na in leave tissues but displayed better health than CP 72-2086. Thus, the variety Mex 69-290 showed more efficient Na-tolerance mechanisms related to Ca and K concentrations, and an indirect chlorophyll index better than CP 72-2086.

Sugarcane Ratooning Ability: Research Status, Shortcomings, and Prospects

Sugarcane is an important sugar crop and it can be subjected to ratooning for several years. The advantages of ratooning include quality improvement, efficiency enhancement, and reduced costs and energy use. The genotype, environment, cultivation management, and harvesting technology affect the productivity and longevity of ratoon cane, with the genetic basis being the most critical factor. However, the majority of research has been focused on only limited genotypes, and a few studies have evaluated up to 100 sugarcane germplasm resources. They mainly focus on the comparison among different genotypes or among plant cane, different selection strategies for the first and second ratoon crops, together with screening indicators for the selection of stronger ratooning ability. In this paper, previous studies are reviewed in order to analyze the importance of sugarcane ratooning, the indicative traits used to evaluate ratooning ability, the major factors influencing the productivity and longevity of ratooning, the genetic basis of variation in ratooning ability, and the underlying mechanisms. Furthermore, the shortcomings of the existing research on sugarcane ratooning are highlighted. We then discuss the focus of future ratoon sugarcane research and the technical methods that will shorten the selection cycle and increase the genetic gain of ratooning ability, particularly the development of linked markers. This review is expected to provide a reference for understanding the mechanisms underlying the formation of ratooning ability and for breeding sugarcane varieties with a strong ratooning ability.

Simulating the impact of climate change on sugarcane production in Punjab

The present study was performed at three diverse agro-climatic zones of Indian Punjab. A validated DSSAT-CANEGRO model was used to simulate the response of different climate change scenarios on cane yield of four sugarcane varieties (CoPb 91, CoJ 88, Co 118 and Co 238) for each zone. Results described that elevated and lowered minimum temperature upto 3.0°C may alter cane yield by -17.9 to 18.0 per cent. Similarly, ±3.0°C altered maximum temperature may change the cane yield by -17.6 to 17.5 per cent. The sugarcane yield may be decreased by 2.4 to 14.4 per cent, 3.3 to 17.6% and 0.3 to15.4 per cent with 2.5 to 15 per cent reduced solar radiation and increase in the same unit may enhance the yield by 1.9 to 9.0 per cent, 1.3 to 13.6 per cent and 2.0 to 12.3 per cent at Faridkot, Gurdaspur and Kapurthala, respectively. A±30 mm rainfall may change the cane yield by 9.2 to 18.0 % similarly, rise and fall in CO2 by 5 to 30 ppm was able to increase and decrease the cane yield by 2.4- 22.6 and 3.5 - 27.8 per cent, at different regions. This study confirmed that for sugarcane cultivation in Punjab CoPb 91 should be preferred. However, CoJ 88 and Co 238 may suffer cane yield loss of 7.8 and 9.9 per cent respectively.