Interspecific Hybrids Of Saccharum Research Articles

Effect of survey farmers’ knowledge and practices on the yield of sugarcane in Pakistan

Sugarcane (Saccharum interspecific hybrids) yield is greatly affected by different pests in Pakistan. A total of three hundred and thirty-six (336) volunteer sugarcane farmers were interviewed and their fields inspected. Major pests were noted as; rat (Bandicota bengalensis), termites (Heterotermes indicola), borer (Bissetia steniellus), and leafhopper (Pyrilla perpusilla). These occurred in single and combined status in sugarcane fields. Most (147/336) of the sugarcane farmers mentioned four types of pests in their fields. In general 200/336 of the sugarcane farmers had applied pesticides in single and combined forms in their fields, they achieved a maximum average yield of 80 t ha−1. The number of farmers who applied malathion was 36/336. They achieved an average yield of 105.5 kg ha−1. Only one sugarcane farmer applied regent and furadon in combined form and obtained an average yield of 92.6 kg ha−1 in their field. Linear regression showed a significant relationship between average sugarcane yield and pest infestation (R2 = 0.9689) as well as pesticide application (R2 = 0.9128) in the area investigated. In total 299 out of the 336 sugarcane farmers were small size landholders up to 2 ha. A limited number (35/336) of the farmers visited the public agricultural extension department for information and application techniques of pesticides against pests. It will be fruitful if the public and private agricultural extension departments start awareness programmes on pest infestation among sugarcane farmers and train them to practice recommended pesticide applications in their sugarcane fields.

Florida Crop/Pest Profile: Sugarcane

Sugarcane (Saccharum interspecific hybrids) is the main source of sugar in the world. It is grown in more than 90 countries in tropical and subtropical regions. Cultivation techniques and production challenges vary by location. This document discusses character- istics of the sugarcane crop and pests affecting its production in Florida, which is the largest producer of sugarcane in the United States

Registration of ‘Ho 05‐961’ sugarcane

Abstract‘Ho 05‐961’ (Reg. no. CV‐207, PI 699490) sugarcane (interspecific hybrids of Saccharum spp.) was evaluated and selected by scientists at the USDA‐ARS, working cooperatively with the Louisiana State University Agricultural Center and the American Sugar Cane League, Inc. It was released to growers in Louisiana in 2012. The cultivar was tested across the crop cycle (plant cane and first and second ratoons) at 11 farm locations and compared with HoCP 96‐540, the most widely grown cultivar in Louisiana at that time. The sucrose yield (Mg ha−1) of Ho 05‐961 was equivalent to HoCP 96‐540. Ho 05‐961 had sucrose content significantly higher for each crop, indicating moderately early maturity. The cultivar is moderately resistant to smut, brown rust, and leaf scald. HoCP 05‐961 is moderately susceptible to sugarcane mosaic caused by Sorghum mosaic virus and orange rust. It is moderately resistant to the sugarcane borer, Diatraea saccharalis F., and moderately responsive to glyphosate ripener. The high sucrose content of Ho 05‐961 makes it a useful addition to current commercial sugarcane cultivars available for Louisiana.

Eight Species of Poaceae Are Hosting Different Genetic and Pathogenic Strains of Sugarcane Mosaic Virus in the Everglades Agricultural Area.

Sugarcane mosaic virus (SCMV) was detected by reverse transcription polymerase chain reaction in eight different species of the Poaceae family in the Everglades Agricultural Area (EAA) of south Florida: broadleaf signalgrass (Urochloa platyphylla), Columbus grass (Sorghum almum), goosegrass (Eleusine indica), maize (Zea mays), sorghum (Sorghum bicolor), St. Augustine grass (Stenotaphrum secundatum), southern crabgrass (Digitaria ciliaris), and sugarcane (Saccharum interspecific hybrids). Based on their coat protein (CP) gene sequence, 62 isolates of SCMV from Florida and 29 worldwide isolates representing the known genetic diversity of this virus were distributed into eight major phylogenetic groups. SCMV isolates infecting Columbus grass, maize, and sorghum in Florida formed a unique group, whereas virus isolates infecting sugarcane in the United States (Florida and Louisiana) clustered with isolates from other countries. Based on the entire genome coding region, SCMV isolates infecting sugarcane in Florida were closest to virus isolates infecting sorghum species or St. Augustine grass. Virus isolates from Columbus grass, St. Augustine grass, and sugarcane showed different virulence patterns after mechanical inoculation of Columbus grass, St. Augustine grass, and sugarcane plants, thus proving that these isolates were different pathogenic strains. Sugarcane was symptomless and tested negative for SCMV by tissue blot immunoassay after inoculation with crude sap from SCMV-infected Columbus grass, indicating that Columbus grass was not a reservoir for SCMV infecting sugarcane in the EAA. Close CP sequence identity between isolates of SCMV from Columbus grass, maize, and sorghum suggested that the same virus strain was naturally spreading between these three plants in south Florida.

First report of Sugarcane Streak Mosaic Virus (SCSMV) infecting sugarcane in Côte d'Ivoire.

Sugarcane streak mosaic virus (SCSMV; Poaceavirus; Potiviridae) is the causal agent of streak mosaic disease of sugarcane (Saccharum interspecific hybrids), a major industrial crop that is widely cultivated in tropical and subtropical regions for sugar and ethanol production. was first reported by Hall et al. (1998) from quarantined germplasm material exhibiting mosaic symptoms imported from Pakistan into the USA. Subsequently, the virus was also reported to occur in most of the Asian countries like Bangladesh, India, Indonesia, Iran, Sri Lanka, Thailand, Vietnam and China (Chatenet et al. 2005; Hema et al. 2008, Kasemsin et al. 2016, Putra et al. 2014, Xu et al. 2010, Moradi et al. 2015; Moradi et al. 2018, Zhang et al. 2018). Until now, there is no report of SCSMV outside the Asian continent. From February to October 2018, sugarcane plants exhibiting symptoms such as irregular yellow and green mosaic, interveinal chlorotic specks, and streaks were observed in Bafing (Borotou-Koro), Marahoué (Zuénoula) and Tchologo (Ferkéssédougou) regions of Côte d'Ivoire (Fig. 1a). Varieties under large-scale commercial cultivation such as R570, R579, SP711406, Co997, Co449, M1176/77, M2593/92, M2580/95, and M1400/86 were all symptomatic. A total of 94 sugarcane leaf samples were collected from these regions and, among those, 82 showed disease symptoms and 12 were symptomless. Samples were first tested for the presence of sugarcane mosaic virus (SCMV), which causes mosaic a disease that is already present in Africa. Serological tests with infected sap using a Double Antibody Sandwich (DAS)- Enzyme Linked Immuno Sorbent Assay (ELISA) kit (DSMZ, RT-0166, Braunschweig, Germany) were negative for SCMV and no amplification product was obtained by RT-PCR using primers specific to the coat protein (CP) gene of SCMV (Putra et al. 2003). The 82 symptomatic leaves tested positive by DAS-ELISA with SCSMV antiserum (polyclonal antibodies were graciously provided by Prof. Hema M. of the Sri Venkateswara University, Tirupati, AP, India), whereas the 12 symptomless samples tested negative. To confirm these results, virus free greenhouse-grown sugarcane varieties Co997 and M1176/77, were mechanically inoculated with 10 sap extracts from 10 SCSMV-infected sugarcane leaf samples. Sap was also extracted from DAS-ELISA negative sugarcane leaves and used as negative control. For sap preparation, leaves were homogenized with a mortar in 2 mL of phosphate buffer 0.01 M pH 7.2 (ratio 1:10). Fifteen 4-week-old plants per variety were inoculated separately with each sap. All inoculated plants exhibited streak mosaic symptoms 13 days post-inoculation (fig. 1b), and the presence of SCSMV in the inoculated plants was confirmed by DAS-ELISA. Total RNA was extracted from four symptomatic leaf samples, one symptomless and one DAS-ELISA positive sample using TRIzol reagent (Invitrogen, Carlsbad, CA, USA). cDNA was synthesized using M-MLV Reverse Transcriptase (Promega, Cat.No.M1705, Madison, WI, USA) following the manufacturer's instructions. A 690-nucleotide fragment of the CP gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with primers SCSMV-F690 and SCSMV-R690 (Viswanathan et al. 2008). All primers were synthesized by Eurogentec (Seraing, Belgium). Aliquots of RT-PCR products (5 μl) were analyzed by electrophoresis on 1.2 % (w/v) agarose gel, stained with ethidium bromide and visualized on a UV transilluminator (Fig. 2). An amplification product of the expected size was obtained for all five symptomatic or DAS ELISA positive but not for the symptomless sample. Two RT-PCR products were sequenced and deposited in GenBank under accession Nos. LR594547 and LR594582. These partial CP gene sequences shared highest nucleotide identity with two isolates of SCSMV from India in GenBank: 91% with JN315855 and 90% with EF655859, thus confirming that SCSMV was occurring in sugarcane in Côte d'Ivoire. To our knowledge, this is the first report of natural infection of sugarcane by SCSMV in Africa. Streak mosaic is a serious threat to the entire sugar industry in West Africa and needs further investigations as it may affect sugarcane yields and impact local economies. Our findings further illustrate the need to develop virus-free germplasm for local, national, and international distribution of sugarcane.

Viral Metagenomic-Based Screening of Sugarcane from Florida Reveals Occurrence of Six Sugarcane-Infecting Viruses and High Prevalence of Sugarcane yellow leaf virus.

A viral metagenomics study of the sugarcane virome in Florida was carried out in 2013 to 2014 to analyze occurrence of known and potentially new viruses. In total, 214 sugarcane leaf samples were collected from different commercial sugarcane (Saccharum interspecific hybrids) fields in Florida and from other Saccharum and related species taken from two local germplasm collections. Virion-associated nucleic acids (VANA) metagenomics was used for detection and identification of viruses present within the collected leaf samples. VANA sequence reads were obtained for 204 leaf samples and all four previously reported sugarcane viruses occurring in Florida were detected: Sugarcane yellow leaf virus (SCYLV, 150 infected samples out of 204), Sugarcane mosaic virus (1 of 204), Sugarcane mild mosaic virus (13 of 204), and Sugarcane bacilliform virus (54 of 204). High prevalence of SCYLV in Florida commercial fields and germplasm collections was confirmed by reverse-transcription polymerase chain reaction. Sequence analyses revealed the presence of SCYLV isolates belonging to two different phylogenetic clades (I and II), including a new genotype of this virus. This viral metagenomics approach also resulted in the detection of a new sugarcane-infecting mastrevirus (recently described and named Sugarcane striate virus), and two potential new viruses in the genera Chrysovirus and Umbravirus.

Registration of ‘HoCP 04‐838’ Sugarcane

‘HoCP 04‐838’ (Reg. No. CV‐181, PI 687221) sugarcane (interspecific hybrids of Saccharum spp.) was selected and evaluated by scientists at the USDA–ARS, working cooperatively with the Louisiana State University Agricultural Center, and the American Sugarcane League, Inc., from a cross between the female parent ‘HoCP 85‐845’ and the male parent ‘LCP 85‐384’. It was released to growers in Louisiana in May 2011. Yields from three crops (plant, first ratoon, and second ratoon) at 12 farm locations compared well with HoCP 96‐540, the most widely grown cultivar in Louisiana during that time. The plant‐cane sucrose yield (Mg ha−1) of HoCP 04‐838 was equivalent to HoCP 96‐540, and cane yield was significantly higher than HoCP 96‐540. HoCP 04‐838 is earlier maturing than HoCP 96‐540 but not as early as ‘HoCP 00‐950’, the high sucrose standard cultivar. Mature stalk cold tolerance was similar to LCP 85‐384, the cold tolerance standard. HoCP 04‐838 is resistant to smut, mosaic caused by Sorghum mosaic virus, brown rust, and ratoon stunt. HoCP 04‐838 is moderately resistant to leaf scald and is susceptible to Sugarcane yellow leaf virus. It is resistant to sugarcane borer. HoCP 04‐838's high yield potential and cold tolerance make it a useful addition to existing commercial sugarcane cultivars in Louisiana.

Florida Crop/Pest Profile: Sugarcane

Sugarcane (Saccharum interspecific hybrids) is the main source of sugar in the world. It is grown in more than 90 countries in tropical and subtropical regions. Cultivation techniques and production challenges vary by location (Rott 2017; Rott 2018). This 19-page document discusses characteristics of the sugarcane crop and pests affecting its production in Florida, which is the largest producer of sugarcane in the United States. Written by P. Rott, D. C. Odero, J. M. Beuzelin, R. N. Raid, M. VanWeelden, S. Swanson, and M. Mossler, and published by the UF/IFAS Agronomy Department, revised May 2018. https://edis.ifas.ufl.edu/pi207

Turning a Blind Eye to Ratoon Stunting Disease of Sugarcane in Australia.

The Australian sugar industry has never pursued genetic resistance to ratoon stunting disease (RSD), despite it being widely considered to be one of the most important diseases of sugarcane (Saccharum interspecific hybrids). This is because of a prevailing view that the disease is economically managed, and that no further action needs to take place. However, there is a range of epidemiological evidence that suggests that RSD is having a more significant impact than what is generally recognized. This review traces the factors that have led to an industry stance that is apparently without any scientific justification, and which has tended to downplay the significance of RSD on Australian sugarcane productivity, and thus has led to significant lost production. The consequences of this position are that RSD may be influencing broad but poorly explained issues such as commercial ratooning performance of existing varieties and the "yield decline" that has been subject to much scrutiny, if not much success in resolving the issue. Based on the available information, this review calls on the Australian sugar industry to prioritize selection for RSD resistance in the plant improvement program.

Molecular Detection of Diverse Leifsonia Strains Associated With Sugarcane.

Leifsonia xyli subsp. xyli, causal agent of ratoon stunting disease (RSD) of sugarcane (Saccharum interspecific hybrids), is the most well-known member of the Microbacteriaceae genus Leifsonia. However, the presence of other Leifsonia strains associated with sugarcane has not been reported. A total of 697 Australian and 40 Indonesian sugarcane fields were screened by leaf sheath biopsy (LSB) PCR using primers specific for L. xyli subsp. xyli, in addition to primers designed to amplify DNA from other members of the genus Leifsonia. While L. xyli subsp. xyli was detected in 126 fields, a total of 37 distinct and novel Leifsonia and non-Leifsonia strains were detected in 116 fields. Representatives of these strains were also detected in multiple samples of expressed xylem sap. Sequencing and phylogenetic analyses demonstrated the presence of a broad complex of novel Leifsonia strains, in addition to strains closely related to the recently erected Cnuibacter genus. Attempts to isolate Leifsonia strains were unsuccessful; however, one strain related to Cnuibacter was recovered from expressed xylem sap. Among the genetically diverse lineages discovered, identical genotypes were present in multiple sugarcane varieties growing in disparate regions in different years, strongly suggesting an ongoing association with sugarcane. The epidemiological significance of these strains is unknown, but there is evidence that they can interfere with serological and microscopic RSD diagnostics, and there is the potential that they may represent new and distinct pathologies of sugarcane.

Efficient Diagnosis of Ratoon Stunting Disease of Sugarcane by Quantitative PCR on Pooled Leaf Sheath Biopsies.

Ratoon stunting disease (RSD), caused by the bacterium Leifsonia xyli subsp. xyli, is arguably one of the most devastating diseases of sugarcane. Four diagnostic techniques were compared for 100 fields of sugarcane (Saccharum interspecific hybrids) of unknown infection status. These were quantitative polymerase chain reaction on pooled leaf sheath biopsies (LSB-qPCR), conventional PCR on the same templates (LSB-PCR), evaporative-binding enzyme immunoassay (EB-EIA) coupled with phase contrast microscopy (PCM) on expressed xylem sap from the same fields, and conventional PCR on the same xylem sap samples. LSB-qPCR and LSB-PCR detected the causal agent in 27 and 18 fields, respectively, whereas, from samples of expressed xylem sap from the same fields, conventional PCR identified 12 infections and EB-EIA/PCM detected L. xyli subsp. xyli in 3 fields. The sensitivities of qPCR and PCR were approximately 103 and 104 CFU ml-1, respectively, determined from plate counts of a dilution series. Tests were conducted on a further 139 LSB samples from across the Australian industry, with qPCR and PCR diagnosing RSD in 31 and 25 fields, respectively. Using qPCR and PCR on LSB samples, RSD was diagnosed in a range of cultivars throughout the year, and qPCR and PCR could detect L. xyli subsp. xyli in sugarcane ranging from 3 months to greater than 1 year old.

Reduced tillage planting and the long-term effect on soil-borne disease and yield of sugarcane (Saccharum inter-specific hybrid) in Queensland, Australia

Pachymetra is a major root disease of sugarcane causing yield and economic loss in the Australian sugar industry, with planting of resistant cultivars being the control strategy practiced by the industry. To adopt reduced tillage and not be affected by soil compaction in the old inter-row it is necessary to re-plant into the old crop row. The hypothesis was: would reduced tillage and planting in the old crop row in conjunction with rotation of resistant and susceptible cultivars minimise the effect of this soil borne disease on crop yield? To facilitate the adoption of reduced tillage in the Australian sugar industry randomized block field experiments were undertaken on Alfisols, near Tully, north Queensland and Bundaberg, south Queensland, Australia comparing reduced tillage with conventional cultivation for planting sugarcane Results showed that, providing Pachymetra resistant cultivars were used, there was no yield reduction with reduced tillage. Levels of Pachymetra remained close to the threshold of 40,000 spores per kilogram of soil under the resistant cultivar but increased under the susceptible cultivar as the crop cycle progressed. Planting a resistant cultivar after a susceptible cultivar or vice versa did not affect cane yield. Over a crop cycle of a plant and three ratoons at Bundaberg the average yields of the susceptible and resistant cultivars were 114 and 89t/ha, respectively, an increase of 28% with the resistant cultivar. Similarly at Tully the average yield for the resistant and susceptible cultivar was 75 and 69t/ha, a 9% increase in yield with the resistant cultivar.Earthworm numbers recovered quicker under reduced tillage compared with conventional tillage suggesting that in the medium to long-term soil health will benefit by the adoption of reduced tillage for planting sugarcane. Reduced tillage did not affect the population of Pratylenchus zeae and increased the number of Rotylenchus nematodes under stool sprayout compared with all other tillage treatments.It is concluded that sugarcane cultivars are available that allow the adoption of reduced tillage in Pachymetra areas without compromising yield.

Isomaltulose is actively metabolized in plant cells.

Isomaltulose is a structural isomer of sucrose (Suc). It has been widely used as a nonmetabolized sugar in physiological studies aimed at better understanding the regulatory roles and transport of sugars in plants. It is increasingly used as a nutritional human food, with some beneficial properties including low glycemic index and acariogenicity. Cloning of genes for Suc isomerases opened the way for direct commercial production in plants. The understanding that plants lack catabolic capabilities for isomaltulose indicated a possibility of enhanced yields relative to Suc. However, this understanding was based primarily on the treatment of intact cells with exogenous isomaltulose. Here, we show that sugarcane (Saccharum interspecific hybrids), like other tested plants, does not readily import or catabolize extracellular isomaltulose. However, among intracellular enzymes, cytosolic Suc synthase (in the breakage direction) and vacuolar soluble acid invertase (SAI) substantially catabolize isomaltulose. From kinetic studies, the specificity constant of SAI for isomaltulose is about 10% of that for Suc. Activity varied against other Suc isomers, with V(max) for leucrose about 6-fold that for Suc. SAI activities from other plant species varied substantially in substrate specificity against Suc and its isomers. Therefore, in physiological studies, the blanket notion of Suc isomers including isomaltulose as nonmetabolized sugars must be discarded. For example, lysis of a few cells may result in the substantial hydrolysis of exogenous isomaltulose, with profound downstream signal effects. In plant biotechnology, different V(max) and V(max)/K(m) ratios for Suc isomers may yet be exploited, in combination with appropriate developmental expression and compartmentation, for enhanced sugar yields.

Microbial communities in sugarcane field soils with and without a sugarcane cropping history

Microbial communities in rhizosphere soil from sugarcane (Saccharum inter-specific hybrids) and bulk soil were compared at paired field sites with and without a sugarcane cropping history to determine whether monoculture affects soil microbial community composition. Differences were evaluated for culturable microorganisms and functional diversity indicated by community level physiological profiles (CLPP). Qualitative differences in rhizosphere bacterial communities were detected between sites with no sugarcane cropping history (Nsite) and sites with a long-term sugarcane cropping history (Lsite). More fluorescent pseudomonads were detected in Nsite than Lsite rhizosphere soil at two of three sites, and Actinobacteria were more numerous in Nsite than Lsite rhizosphere soil at one site. Fusarial fungi were more numerous in Nsite than Lsite rhizosphere soils. Bacteria were more numerous in rhizosphere soil compared to bulk soil. Total bacterial, pseudomonad, and Actinobacteria population densities were greater in bulk soil from an Nsite compared to an Lsite. CLPP distinguished bulk from rhizosphere soil at one of two sites and Nsite and Lsite rhizosphere soils at two of four sites. Site affected CLPP similarity more than cropping history. The results demonstrated that sugarcane monoculture can affect the composition of the microbial community in field soil. The findings have possible implications for reduced yields associated with sugarcane monoculture.

Effect of conversion of sugarcane plantation to forest and pasture on soil carbon in Hawaii

It is well known that land use change can affect soil C storage of terrestrial ecosystems either by altering the biotic processes involved in carbon cycling or by altering abiotic processes such as carbon adsorption on soil minerals. Relatively few studies, however, have examined the dynamics of soil C pools after conversion of farmland to forest or pasture. We selected three pairs of secondary forests and pastures that originated from the same abandoned sugarcane (interspecific hybrids of Saccharum spp.) land in the wet tropics of Hawaii to examine whether forest or pasture converted from farmland is more effective in sequestering C in soils. We compared the soil C pool, soil chemistry, and stable C isotope ratios between the forests and pastures. We found that total soil C was greater (P < 0.01) in forests than in the pastures 22 years after land conversion. The percentages of SOC4 in the pastures were significantly higher than in the secondary forests in both soil layers. The percentages of SOC3 in the pastures were lower than in the secondary forests in both soil layers. The net SOC3 increase in the forest soils at 0–10 and 10–25 cm was 28.6 ± 5.6 and 43.9 ± 3.2 Mg ha−1 while net SOC4 increase in pasture soils at these respective depths was 18.8 ± 2.2 and 26.1 ± 2.7 Mg ha−1. We found that the net increases of SOC3 in both soil layers in the forest were greater (P < 0.01) than the net increases of SOC4 in the respective soil layers in the pasture. Aluminum saturation was greater (P < 0.01) in the forests than the pastures in both soil layers. There was no difference in oxalate extractable Fe concentration between the forests and the pastures but oxalate extractable Al concentration in both soil layers was greater (P < 0.05) in forests than the pastures. Our findings indicated that reforestation of abandoned sugarcane farmland in Hawaii is more effective in soil C increase and stabilization than conversion to pasture.

Sugarcane Postharvest Residue Management in a Temperate Climate

Full retention of sugarcane (interspecific hybrids of Saccharum spp.) postharvest residue may reduce ratoon crop yields. The objective of this study was to determine the effects of different residue removal timings and methods on sugarcane yield. A two‐factor (timing and method) experiment was conducted on both clay and silt loam soils in southeastern Louisiana. Removal timings consisted of the following physiological stages: predormancy, complete dormancy, intermediate dormancy, and postdormancy. Removal methods consisted of partial removal from the row top by mechanical means, complete removal by burning, and no removal (control) applied to first, second, and third ratoons. Sugar yields following burning at predormancy (6800 kg ha−1), complete dormancy (6610 kg ha−1), and mechanical removal at predormancy (6500 kg ha−1) were greater than the control (6190 kg ha−1) for all ratoons. Burning at postdormancy decreased sugar yields by 440 kg ha−1 relative to the control. Ratoons responded similarly to the residue management practices evaluated, and effects were consistent on both clay and silt loam soils. Results show that the residue generated during the green‐cane harvesting of sugarcane in Louisiana should be removed from harvested fields as soon after harvest as possible to ensure optimum yields of subsequent ratoon crops.

Influence of Nonoptimal Ripener Applications and Postharvest Residue Retention on Sugarcane Second Ratoon Yields

Retention of sugarcane (interspecific hybrids of Saccharum spp.) postharvest residue and certain glyphosate ripener application regimes may independently reduce yields of the subsequent ratoon crop in wet climates. The objective of this experiment was to determine the effects of ripener application and ripener treatment to harvest intervals (THI) on yields of the treated first ratoon, and the combined effects of these treatments and postharvest residue retention on the subsequent second ratoon. Whole plots consisted of either a nontreated control or 0.21 kg a.e. ha−1 glyphosate applied to the first ratoon of cultivar LCP 85–384. Split‐plots consisted of THI of 40, 50, and 60 d for all plots. Split‐split plot treatments consisted of partial removal of postharvest residue or complete retention for second ratoon. Averaged across all THIs for the first ratoon, glyphosate increased sucrose yield by 300 kg ha−1 compared with the control. The 60 d THI reduced second ratoon cane and sucrose yields by 5.4 Mg ha−1 and 900 kg ha−1, respectively, compared with the means of the 40 and 50 THI and sucrose yields by 300 kg ha−1 compared with the control. Full residue retention reduced second ratoon cane and sucrose yield by 2.3 Mg ha−1 and 300 kg ha−1, respectively, compared with partial removal. Residue retention and glyphosate application were not negatively synergistic. Producers should remove postharvest residue from the row top and harvest ripener‐treated cane at a THI of 40 to 50 d to maximize sucrose yields in the first ratoon while also preventing yield losses in the subsequent second ratoon.

Viruses causing mosaic disease in sugarcane and their genetic diversity in southern China

A survey of cultivated hybrid sugarcane (Saccharum inter-specific hybrid) and noble sugarcane (Saccharum officinarum) in southern China for the presence of Sugarcane mosaic virus (SCMV), Sorghum mosaic virus (SrMV) and Sugarcane streak mosaic virus (SCSMV) was conducted by RT-PCR from the years 2003 to 2006. SCMV and SrMV, but not SCSMV, were found. A high incidence of SCMV and SrMV coinfection was revealed in both hybrid and noble sugarcanes. All coinfected plants showed mosaic symptom, whereas plants infected with a single virus were symptomatic or asymptomatic. It appears that virus mixtures are more virulent than single infections. The nucleotide sequences of the coat protein (CP) gene of 33 SCMV and 10 SrMV isolates from this study were compared to those of CP genes of SCMV and SrMV reported in GenBank. One hundred and seventy-three SCMV isolates, with the exception of MDB and Abaca strains, can be grouped into five groups, which include three previously known groups, the sugarcane (SCE), maize (MZ), and Thailand groups, and two newly identified groups, the noble sugarcane (NSCE) and Brazil groups. Twenty-two SrMV isolates were divided into two groups, HS (hybrid sugarcane) and NS (noble sugarcane) groups. Five out of eight SrMV hybrid isolates belonged to the HS group, and two SrMV noble isolates and three hybrid isolates were within the NS group. Interestingly, the three hybrid isolates within the NS group were isolated from hybrid sugarcane co-infected with SCMV. This indicates that SCMV helps the NS group SrMV to infect hybrid sugarcane.

Relationship Between Sugarcane Rust Severity and Soil Properties In Louisiana

ABSTRACT The extent of spatial and temporal variability of sugarcane rust (Puccinia melanocephala) infestation was related to variation in soil properties in five commercial fields of sugarcane (interspecific hybrids of Saccharum spp., cv. LCP 85-384) in southern Louisiana. Sugarcane fields were grid-soil sampled at several intensities and rust ratings were collected at each point over 6 to 7 weeks. Soil properties exhibited significant variability (coefficients of variation = 9 to 70.1%) and were spatially correlated in 39 of 40 cases with a range of spatial correlation varying from 39 to 201 m. Rust ratings were spatially correlated in 32 of 33 cases, with a range varying from 29 to 241 m. Rust ratings were correlated with several soil properties, most notably soil phosphorus (r = 0.40 to 0.81) and soil sulfur (r = 0.36 to 0.68). Multiple linear regression analysis resulted in coefficients of determination that ranged from 0.22 to 0.73, and discriminant analysis further improved the overall predictive ability of rust models. Finally, contour plots of soil properties and rust levels clearly suggested a link between these two parameters. These combined data suggest that sugarcane growers that apply fertilizer in excess of plant requirements will increase the incidence and severity of rust infestations in their fields.

Allelopathic, Autotoxic, and Hormetic Effects of Postharvest Sugarcane Residue

With green sugarcane (interspecific hybrids of Saccharum spp.) harvesting, 6 to 24 Mg ha−1 of postharvest residue is deposited on the field surface covering the sugarcane stubble that must reemerge for several ratoon crops. The objectives of this research were to: (i) determine if postharvest residue possesses allelopathic, autotoxic, and hormetic properties; (ii) determine the interaction of soil type with possible autotoxic effects; and (iii) identify a reliable indicator species. Extract concentrations consisted of 0, 0.1, 10, 25, and 100% of the original solution of a 1:28 tissue to water extract. The higher concentrations of residue extracts exhibited autotoxicity by delaying early leaf development. The lower extract concentration of 10% increased sugarcane bud germination by 45% compared with the control, indicating hormetic effects. Allelopathic activity on tall morninglory (Ipomoea hederacea Jacq.) was more pronounced on a light soil; germination and radical length were reduced by all concentrations by an average of 42% and 8 mm, respectively, compared with the control. Seedling dry weights were reduced by an average of 10 mg by the 10, 25, and 100% extract concentrations relative to the control. On the heavy soil, only the 100% concentration reduced radical length and weight by 5 mm and 4 mg, respectively, relative to the control. Extract effects on oat (Avena nuda L.), rye (Secale cereale L.), and tomato (Lycopersicon esculentum Mill.) showed poor correlation with effects on sugarcane. Chemical analysis by gas chromatography/mass spectrotometry indicated the extract contained benzoic acid. Further studies are needed to establish the impact of benzoic acid in natural settings.