A B S T R A C TVirus infection can result in the alteration of physiological, biochemical and metabolic processes within plants leading to symptom development. Banana bunchy top virus (BBTV) is one of the most destructive viral diseases in Tropical Asia, Pacific Indian Oceania (PIO) regions and Africa leading to 100% yield loss in banana and plantains. Though molecular characterization and their diversity were studied in depth in recent years, information on physiological and biochemical changes during banana-BBTV interaction is still not convincingly explained. Therefore, the present investigation was conducted to find out the quantifiable changes in physiological and biochemical parameters such as proteins, pigment and carbohydrate content, phenolic compounds, polyphenol oxidase (PPO), peroxidase (POX), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT) and superoxide dismutase (SOD) activities in leaves of banana cultivars Grand Nain (AAA) and Virupakshi (AAB). The amount of carbohydrate contents, phenolic compounds, PPO, POX, APX, GPX, CAT were significantly higher in BBTV infected leaves of both the cultivars over the healthy, whereas total protein content, pigments and SOD activity showed an opposite trend. Overall the results suggest that BBTV infection induces significant changes in enzyme levels leading to irreversible symptom development. Further studies would lead to identification of biochemical markers for studying plant-virus compatible and incompatible interactions.

The Salt Overly Sensitive (SOS) pathway is a crucial ion homeostasis process in crop plants trafficking excess Na+ ions for elimination/sequestration. The SOS pathway genes SOS1 (Na+/H+ antiporter), SOS2 (CIPK), and SOS3 (CBL) associated with ion homeostasis were isolated and characterized in the sugarcane clone Co 85019. The isolated genes had a coding region of 1086, 904, and 636 bp, respectively. A nucleotide blast analysis of the isolated SOS gene sequences showed strong similarity with previous genes found to be involved in the active functioning of the SOS pathway for ion homeostasis conferring salinity tolerance in sugarcane. The analysis of tissue specific gene expression of the identified SOS genes revealed a significant linear increase in the leaves under the first 96 h of salt stress (2.5‐ to 21.6‐fold) in the tolerant genotype Co 85019, while the expression in the roots showed a linear increase up to 48 h and thereafter a gradual decline. The expression of SOS genes in the susceptible genotype (Co 97010) was significantly lower than in the tolerant genotype. Tissue ion content analysis also revealed a differential accumulation of Na+ and K+ ions in the contrasting sugarcane genotypes (Co 85019 and Co 97010) and this corroborates the varied expressions of SOS genes between the tolerant and susceptible varieties under salinity. Genome‐wide analysis of identified SOS family genes showed the homologs in Saccharum complex members, Sorghum bicolor and Zea mays, and this verifies a close genetic similarity among these genera.

The comparative responses of photosynthesis, growth, dry matter accumulation leaf water (< l ) and osmotic (S) potentials were investigated in contrasting genotypes of sugarcane. Photosynthetic rate, transpiration rate and < l did not differ significantly among genotypes in the formative stage of crop growth (60-150 days of crop age). Leaf < l showed consistent difference among the clones due to salinity treatment. During grand growth stage (150-240 days of crop age), the photosynthetic rate, transpiration rate (t) and < l decreased due to salinity treatment. Dry biomass accumulation was severely affected and biomass allocation towards stem reduced drastically in sensitive types. The reduction in ultimate sink size as revealed by cane length and stem biomass was in accordance with the tolerance potential of the clones.

Collection HIGHLIGHTS Sugarcane hybrids with improved IWUE have greater scope in sugarcane agriculture as irrigation water is getting scarce.  Among sugarcane hybrids, Co 8371 registered high mean water productivity of 4.18 kg m -3 , followed by Co 85019(3.92 kg m -3 ), while in I 2 , six hybrids had significantly higher water productivity (Co 85019, Co 0212, Co 86249, Co 10026, Co 0218 and Co V92102) above 4 kg m -3 .  Deficit irrigation scheduling (irrigation at recommended interval, with 50% crop evapotranspiration replacement) appears to be far more useful than reducing frequency as well as quantity of irrigation water alone. Hybrid mean water productivity was 3.2, 2.7, and 2.1 kg m -3 in I 0 , I 1 , and I 2 , respectively.ABSTRACT. The escalating deficit rainfall scenario in India indicates that drought is a recurrent phenomenon associated with tropical sugarcane farming, and the availability of irrigation water for sugarcane cultivation will be much less in coming years. To meet the challenge of limited and costly water supply, tropical sugarcane growers will have to find ways of increasing the efficiency of irrigation to maintain high cane yields. More efficient irrigation systems, accurate irrigation scheduling, and the right choice of sugarcane hybrids are potential means of increasing irrigation water use efficiency (IWUE), water productivity (WP), and global water security. With the objective of optimizing irrigation water use, a field experiment evaluating the physiological efficiency of commercial sugarcane hybrids for WP in a sandy clay soil under water-limited conditions was conducted during 2016-2017 at the ICAR-Sugarcane Breeding Institute in Coimbatore, India. The replicated field experiment was laid out in split-plot design with three irrigation levels as the main plot and 33 sugarcane hybrids as subplots. The prevailing climatic conditions during the experiment represented a tropical wet and dry climate, with the wet season lasting from October to December due to the northeast monsoon. The results showed that full irrigation at recommended intervals with 100% crop evapotranspiration (ET) replacement (I 0 ) produced significantly higher cane yield than deficit irrigation at recommended intervals with 50% crop ET replacement (I 1 ) and skipping alternate irrigations with 50% crop ET replacement (I 2 ). The deficit irrigation treatments (I 1 and I 2 ) had declines in cane yield of 41.2% and 56.4%, respectively. IWUE was similar in I 0 and I 1 , while I 2 had reduced IWUE by 23%. WP was significantly influenced by irrigation level; reduction in irrigation water reduced WP by 17.5% and 36.3% in I 1 and I 2 compared to I 0 . Among sugarcane hybrids, Co 85019, Co 13006, Co 10026, Co 99004, CoLk 8102, Co 86249, Co 8371, Co 94008, and Co 95020 yielded higher than the genotypic mean under both deficit irrigation treatments, suggesting their usefulness in deficit irrigation strategies. Sugarcane hybrids with high WP can play a pivotal role in sustaining sugarcane productivity and can reduce the larg...