Transcriptome and Metabolome Analyses Reveal an Insight of Chlorophyll, Photosynthesis, Metal Ion and Phenylpropanoids Related Pathways in Sugarcane Ratoon Chlorosis

BackgroundRatoon sugarcane (Saccharum officinarum) is susceptible to chlorosis, significantly reducing production. The molecular mechanism underlying this phenomenon remains unknown. We analyzed the transcriptome and metabolome of chlorotic and non-chlorotic sugarcane leaves from the same field to gain insight into the symptom. ResultsThe agronomic traits, like plant height, leaf number, stalk nod number, and tiller number, declined in chlorotic sugarcane. The chlorophyll content in chlorosis leaves was significantly lower than non-chlorotic leaves. A total of 11,776 differentially expressed genes (DEGs) were discovered in transcriptome analysis. In the KEGG enriched chlorophyll metabolism pathway, sixteen DEGs were found, eleven of which were down-regulated. Two photosynthesis pathways were also enriched, with 32 genes downregulated and four genes upregulated. Among the 81 enriched GO biological processes, there were four categories related to metal ion homeostasis and three related to metal ion transport. Approximately 400 metabolites were identified in metabolome analysis. The thirteen classified differentially expressed metabolites (DEMs) were found all down-regulated. The phenylpropanoid biosynthesis pathway was enriched in DEGs and DEMs, indicating phenylpropanoids' vital role in chlorosis. ConclusionsAccording to our study, chlorophyll production, metal ion metabolism, photosynthesis, and some secondary metabolites of the phenylpropanoid biosynthesis pathway, were considerably altered in chlorotic ratoon sugarcane. Our finding revealed the relation between chlorosis and these pathways, which would further the understanding of the mechanism of ratoon sugarcane chlorosis.

Potassium and Water-Deficient Conditions Influence the Growth, Yield and Quality of Ratoon Sugarcane (Saccharum officinarum L.) in a Semi-Arid Agroecosystem

Groundwater and soil potassium deficiencies are present in northern India. Sugarcane is a vital crop in the Indian Punjab; it is grown on approximately 91,000 hectares with an average yield of 80 tonnes ha−1 and a sugar recovery rate of 9.59%. The role of potassium (K) fertilizer under both sufficient and deficient irrigation in ratoon sugarcane crops is not well documented. We conducted a split-plot ratoon cane experiment during 2020–2021 at the Gurdaspur Regional Research Station of Punjab Agricultural University, India, on K-deficient soils. Main treatments were fully irrigated (I1) and water stressed (I0) conditions, with sub-treatments reflecting K fertilizer application rates of 0 (M1), 67 (M2), 133 (M3), and 200 (M4) kg K ha−1. The ratoon sugarcane performance was assessed in terms of growth, productivity, sugar quality and incidence of key insect pests. At harvest, trends in the growth and yield parameters in I1 were improved over the I0 treatment, with cane height (+12.2%), diameter (+3.3%), number of internodes (+5.4%), biomass yield (+7.6%) and cane yield (+5.9%) all higher, although little significant difference was observed between treatments. Ratoon cane yield under irrigation was 57.1 tonnes ha−1; in water-stressed conditions, it was 54.7 tonnes ha−1. In terms of sugarcane quality parameters, measured 12 months after harvesting the initial seed crop, values of Brix (+3.6%), pol (+3.9%), commercial cane sugar percentage (+4.0%) and extractable sugar percentage (+2.8%) were all higher in the irrigated treatments than the water-stressed plot. Irrigated treatments also had a significantly lower incidence of two key insect pests: top borer (Scirpophaga excerptalis) was reduced by 18.5% and stalk borer (Chilo auricilius) by 21.7%. The M3 and M4 treatments resulted in the highest cane yield and lowest incidence of insect pests compared to other K-fertilizer treatments. Economic return on K-fertilizer application increased with increasing fertilizer dosage. Under the potassium-deficient water-stressed conditions of the region of north India, a fertilizer application rate of 133 kg K ha−1 is recommended to improve ratoon sugarcane growth, yield, and quality parameters and economic returns for sugarcane farmers.

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.

Yield and Quality of Ratoon Sugarcane Are Improved by Applying Potassium under Irrigation to Potassium Deficient Soils

The current study was carried out at the experimental farm of Rana Sugars Ltd., Buttar Seviyan, Amritsar, Punjab, India, to identify methods to improve the yield and quality of ratoon sugarcane in potassium-deficient soils. The treatments comprised two levels of irrigation, resulting in plants which either received sufficient water (I1) or were water-stressed (I2), and four rates of potassium (K) application: 0 (K1), 40 (K2), 80 (K3) and 120 (K4) kg K2O ha−1. The results showed that the irrigation levels did not influence crop parameters significantly, although all parameters presented higher values for I1-treated plots. Compared to the K1 (i.e., 0 kg ha−1 K fertiliser applied) treatment, the K2, K3 and K4 treatments yielded 11.16, 37.9 and 40.7%, respectively, higher millable canes and 1.25, 5.62 and 13.13% more nodes per plant, respectively. At 280 days after harvest of the first (plant) crop, the I1 treatment provided ratoons which were up to 15.58% higher than those obtained with the I2 treatment, with cane girths up to 7.69% wider and yields up to 7.29% higher than those observed with the I2 treatment. While the number of nodes per plant did not differ significantly between treatments, there were significant differences in other parameters. Quality parameters (with the exception of extraction percentage) were significantly enhanced by the K3 treatment. The benefit-to-cost ratio (B/C) was higher for the I1 treatment than for the I2, due to a reduced productivity associated with the I2 treatment. At both irrigation levels, the K3 treatment resulted in the highest quality parameters. K1-, K2- and K4-treated plots presented more instances of insect infestations than plots receiving the K3 treatment. Relative to the K3 plots, infestation by the early shoot borer (Chilo infuscatellus) was 18.2, 6.0 and 12.2% higher, respectively, in plots that underwent the K1, K2 and K4 treatments, while infestation by the top borer (Scirpophaga excerptalis) was 21.2, 9.21 and 14.0% higher, and that by the stalk borer (Chilo auricilius) was 10.7, 0 and 8.10% higher. Not all infestation differences between treatments were significant. Our research demonstrates that growing sugarcane in potassium-deficient soils with applications of 80 kg K2O ha−1 under irrigation should be recommended to increase yield and quality while minimising insect infestation and to implement sustainable ratoon sugarcane production.

Wireworms in Florida Sugarcane

Wireworms, the larval stage of a click beetle, often cause severe damage to numerous crops in Florida. At least twelve species of wireworms have been found in southern Florida, but only the corn wireworm, Melanotus communis, is considered to cause significant economic damage to sugarcane. Since M. communis is the important wireworm species, the rest of this document will pertain to this species. Generally, wireworms are a pest of newly planted sugarcane and only rarely a pest in ratoon sugarcane. More studies are needed, but the current information suggests substantial percentages (e.g. 40% or more) of wireworms could be killed by flooding but, in general, the flood duration had to be at least 4 to 5 weeks at water temperatures above 24 °C. Soil insecticides are generally used in newly planted sugarcane for wireworm control. Insecticides are not used for wireworm control in ratoon sugarcane. Pheromone traps are untested in Florida sugarcane for click beetles but have an important function in for both mass trapping and monitoring in other agricultural systems.