EFFECTS OF SUGARCANE YELLOW LEAF VIRUS INFECTION ON SUGARCANE YIELD AND ROOT SYSTEM DEVELOPMENT
By
A.C.M. VASCONCELOS1, M.C. GONÇALVES2, L.R. PINTO1, M.G.A. LANDELL1 and D. PERECIN3
1Centro de Cana/Instituto Agronômico (IAC)
Rodovia Anel Viário, km 321. CEP 14032-800, Ribeirão Preto, SP, Brazil
2Centro de Sanidade Vegetal, Instituto Biológico
3Departamento de Ciência Exatas/Faculdade de Ciências Agrárias e Veterinárias/UNESP
E-mail: [email protected]
KEYWORDS: Breeding, Sugarcane, Yellow Leaf Syndrome, Yellow Leaf.
Abstract
Sugarcane yellow leaf disease causes significant yield losses in susceptible sugarcane varieties. In Brazil, YLS was not recognised as an economically important disease until the early 1990s when the drastic epidemics of the disease occurred in variety SP71-6163. Since then, breeders began to take into account its occurrence during the selection stages and its effects on vegetative development. The objective of the present work was to evaluate the effects of the Sugarcane yellow leaf virus (SCYLV), the causal agent of yellow leaf on sugarcane yield and root system development. The experiment was conducted in Ribeirão Preto, SP, Brazil, on Typic Hapludox soil, in variety IAC89-2135 during the plant cane cycle. SCYLV diagnosis was assayed by DAS-ELISA and RT-PCR for discrimination between infected and uninfected plants. The infected plants showed significant reduction of root dry weight and fresh weight of the above ground plant parts and an increase in Brix and sucrose content in the stalks. Although infected plants maintained the root system vertical architecture, root dry weight was reduced and negatively correlated with fresh weight and stalk number, showing that alterations in root and vascular systems may constitute important effects caused by SCYLV infection.
Introduction
Sugarcane yellow leaf syndrome (YLS) has been associated with significant yields losses in susceptible sugarcane varieties. Symptoms of YLS have been attributed to many causes, both biotic and abiotic. With the determination that sugarcane yellow leaf virus (SCYLV) caused the YLS symptoms in Brazil, the disease is called sugarcane yellow leaf (Vega et al., 1997; Maia et al., 2000).
In Brazil, yield losses from 20% to 30% due to yellow leaf were reported in the variety SP71-6163 in the early 1990s (Vega et al., 1997). The full extent of SCYLV effect in Brazilian commercial varieties is not known, but the virus became endemic in the main cultivated areas; thus, there was a need for the development of resistance in the sugarcane breeding programs.
In the Agronomic Institute of Campinas (IAC) sugarcane breeding program, the main traits evaluated during selection of cultivars are productivity, sucrose content and disease resistance. The variety IAC89-2135 showed favourable characteristics, and superiority compared to other commercial varieties until 1998, when the first symptoms of SCYLV were found causing decline in the yield.
The present work was performed to investigate the effects of the SCYLV infection on variety IAC89-2135 root system development and its relationship with the yield.
Materials and methods
Field study was conducted in Ribeirão Preto, São Paulo state, Brazil, on variety IAC 89-2135 planted in February 1999 in Typic Hapludox soil. Field measurements were 100 m wide by 50 m long, with 1.4 m between sugarcane rows.
Nine months after planting, samples were randomly taken from 5 places where plants showed SCYLV symptoms, and from other 5 places from symptomless plants. Stalks were counted in 1 m row, cut and fresh weighed.
Ten stalks from each sample were taken for the analysis of brix (%), fibre and sucrose content (SC). In each sampling location, the roots were quantified from 3 depths: 0 to 20 cm, 20 to 40 cm and 40 to 60 cm.
The trenches were dug under the cane row for extraction of soil monoliths with roots, measuring 150 cm, in the traverse sense to the line, and 20 cm longitudinal to the line. The roots were washed, dried at 70oC, for 48 hours, and sifted to separate vegetable impurity for subsequent weighing.
Treatments were compared by the variance analysis (F statistics) and Tukey test to detect differences among averages. Linear regression was done, separately between root dry weight and above ground plant part attributes for each treatment (healthy or infected).
To confirm if the observed symptoms were caused by SCYLV, sugarcane leaves from plants showing the same symptoms as those used for fresh weight and root dry weight evaluations as well as plants without symptoms were randomly collected and tested by DAS-ELISA using SCYLV-specific polyclonal antisera (Scagliusi and Lockhart, 2000). SCYLV infection was also assayed by RT-PCR with specific primer pair P1f/P2r (Gonçalves et al., 2002) based on the coat protein coding region of SCYLV.
Results and discussion
Among the five characteristics used to evaluate the effect of SCYLV on sugarcane yield, the stalk number and fibre content showed no significant differences between infected and uninfected sugarcane plants. However, significant differences were observed for fresh weight, Brix and sucrose content (Table 1).
Table 1—Sugarcane yield measurements of SCYLV infected and uninfected plants, at nine months after planting (immature plants).
Trials Fresh weight kg/m2 Stalk number per metre oBrix Fibre (%) Sucrose content (%) Uninfected plants 8.00 a* 13.80 a 9.18 b 8.61 a 3.10 b Infected plants 4.70 b 11.20 a 10.52 a 10.00 a 4.43 a F (variance analysis) 8.76 2.62 10.39 1.02 8.43 Variation coefficient (%) 27.70 20.31 6.67 23.13 19.30 * Averages with same letters do not differ among themselves for the test of Tukey (P>0.05).
Significant increases in Brix and consequently sucrose content (SC), respectively, 14.6% and 42.9%, were observed in stalks of infected plants.
It is well known that sugar is transported via phloem from leaves (blade and sheath) to stalk and then downward to roots. Thus, sucrose transport downward to roots could be reduced if the root system is damaged, leading to sucrose over accumulation in the stalks.
SCYLV infected plants had an average root dry weight decrease of 43% compared to uninfected plants, which was probably related to reductions in the metabolic transport via phloem from leaves to roots.
However, the proportion of roots at each depth was not affected by SCYLV infection, and its vertical architecture distribution was preserved (Figure 1).
Fig. 1—Root system quantity (mg/litre) and distribution in the soil profile (0 to 60 cm).
In uninfected SCYLV plants, root dry weight was positively correlated with fresh weight, stalk number, Brix and SC (Figures 2 and 3).
These results suggest that in SCYLV uninfected plants, a well formed root system is crucial for plant development as it provides aboveground plant parts with sufficient water and nutrients for proper growth.
In contrast, for SCYLV infected plants, root dry weight was negatively correlated with fresh weight and stalk number (Figure 2).
Therefore, if we just evaluate the infected plants (squares and black line), the ones that suffered the largest reductions of root system have the smallest reductions of the above plant parts fresh weight.
Probably, this occurs due to the competition between root system and above plant parts for metabolites and the reduction of phloem transport.
Root dry weight in SCYLV infected plants was not significantly correlated with brix and sucrose content (Figure 3).
Probably, this lack of correlation may be viewed as indicative of a rupture in transport of both photo-assimilates and nutrients between above plant parts and the root system.
DAS-ELISA did not detect the virus in any of the tested plants, probably due to the low virus titre in the leaf tissue.
On the other hand, RT-PCR analysis revealed the presence of the virus in all tested plants grown from stalks showing symptoms. Plants grown from stalks without symptoms tested negative in RT-PCR. Depth 40-60 cm 20-40 cm 0-20 cm 104 mg/litre (10,4%) 177 mg/litre (17,7%) 717 mg/litre (71,8%) Uninfected plants 0-20 cm 20-40 cm 40-60 cm Depth 405 mg/litre (71,6%) 104 mg/litre (18,3%) 57 mg/litre (10,0%) Infected plants
a b
Fig. 2—Relationship between root dry weight (0–60 cm) and: a) leaves fresh weight; b) number of stalks.
a b
Fig. 3—Relationship between root dry weight (0–60 cm) and: a) Brix; b) sucrose content (SC).
REFERENCES
Gonçalves, M.C., Klerks, M.M., Verbeek, M., Vega, J. and Van den Heuvel, J.F.J.M. (2002).
The use of molecular beacons combined with NASBA for the sensitive detection of Sugarcane yellow leaf virus. European Journal of Plant Pathology, 108: 401–407.
Maia, I.G., Gonçalves, M.C. Arruda, P. and Vega, J. (2000). Molecular evidence that sugarcane
yellow leaf virus (SCYLV) is a member of the Luteoviridae family. Archives of Virology, 145(5): 1009–1019, 2000.
Scagliusi, S.M. and Lockhart, B.E. (2000). Transmission, characterisation and serology of
sugarcane yellow leaf luteovirus. Phytopathology, 90: 120–124.
Vega, J., Scagliusi, S.M.M. and Ulian, E.C. (1997). Sugarcane Yellow Leaf Disease in Brazil:
Evidence of association with a luteovirus. Plant Disease, 81: 21–26. y = 0.1303x + 0.3313 R2 = 0.8205* y = -0.1569x + 9.9347 R2 = 0.7832* 0 2 4 6 8 10 12 14 0 100 200 300 400 500 Roots dry weight (mg/litre)
C ane f res h w ei ght ( kg m -2 ) y = 0.0136x + 9.2637 R2 = 0.8530* y = -0.0854x + 27.29 R2 = 0.7632* 0 2 4 6 8 10 12 14 16 18 0 100 200 300 400 500 Roots dry weight (mg/litre)
N um b er o f st al ks pe r m et e r Infected Uninfected y = 0.0423x + 6.684 R2 = 0.9365** y = 0.0302x + 9.5136 R2 = 0.0842 ns 0 2 4 6 8 10 12 14 0 100 200 300 400 500 Roots dry weight (mg/litre)
o Br ix y = 0.0512x + 0.0809 R2 = 0.9798** y = 0.0511x + 2.7236 R2 = 0.2394 ns 0 1 2 3 4 5 6 0 100 200 300 400 500 Roots dry weight (mg/litre)
SC
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%
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EFFETS DU VIRUS DU SYNDROME DE LA FEUILLE JAUNE DE LA CANNE À SUCRE SUR LE RENDEMENT ET LE DÉVELOPPEMENT
DU SYSTÈME RADICULAIRE DE LA CANNE
Par
A.C.M. VASCONCELOS1, M.C. GONÇALVES2, L.R. PINTO1, M.G.A. LANDELL1 et D. PERECIN3
1Centro de Cana/Instituto Agronômico (IAC). Rodovia Anel Viário, km 321. CEP 14032-800,
Ribeirão Preto, SP, Brazil
2Centro de Sanidade Vegetal, Instituto Biológico
3Departamento de Ciência Exatas/Faculdade de Ciências Agrárias e Veterinárias/UNESP
E-mail: [email protected]
MOTS CLÉS: Amélioration Variétale, Canne à Sucre, Syndrome de la Feuille Jaune, Yellow Leaf.
Résumé
LE SUGARCANE yellow leaf virus (SCYLV) occasionne des pertes de rendements importantes dans
les variétés sensibles. Au Brésil, au début des années 1990 que le YLS fut considéré comme une maladie économiquement importante suite à des épidémies sévères dans la variété SP71-6163. Dès lors, les sélectionneurs prirent en compte la présence de la maladie pendant les stades de sélection et ses effets sur le développement végétal. Le but de ce présent travail était de mesurer les effets du SCYLV, l’agent causal du syndrome de la feuille jaune de la canne à sucre, sur le rendement et le développement du système radiculaire de la canne. L’essai fut mené sur la variété IAC89-2135, en plantation vierge, sur un sol ‘Hapludox typique’ au Ribeirão, Preto, SP au Brésil. Les techniques de DAS-ELISA et RT-PCR furent utilisées pour différencier les plantes saines de celles infectées. Le poids sec des racines et la masse fraîche des parties aériennes végétales étaient considérablement réduit dans les plantes infectées tandis que la teneur en Brix et en saccharose des tiges fut élevée. Malgré que les plantes infectées par le virus avaient conservé une architecture verticale du système radiculaire, une diminution en poids sec des racines fut notée, entraînant une corrélation négative avec la masse fraîche et le nombre des tiges. On peut donc conclure qu’une infection par le SCYLV peut considérablement altérer les systèmes radiculaire et vasculaire de la canne.
EFECTOS DE LA INFECCION DE LA HOJA AMARILLA DE LA CAÑA DE AZUCAR EN LA PRODUCCIÓN DE CAÑA Y DESARROLLO DEL SISTEMA DE RAICES
Por
A.C.M. VASCONCELOS1, M.C. GONÇALVES2, L.R. PINTO1, M.G.A. LANDELL1 y D. PERECIN
1Centro de Cana/Instituto Agronômico (IAC). Rodovia Anel Viário, km 321. CEP 14032-800,
Ribeirão Preto, SP, Brazil
2Centro de Sanidade Vegetal, Instituto Biológico
3Departamento de Ciência Exatas/Faculdade de Ciências Agrárias e Veterinárias/UNESP. E-mail:
PALABRAS CLAVES: Breeding, Sugarcane, Yellow Leaf Syndrome, Yellow Leaf. Resumen
LA ENFERMEDAD de la hoja amarilla de la caña de azúcar de la caña de azúcar produce pérdidas significativas en las variedades susceptibles de caña. En el Brasil, la hoja amarilla no se reconoció como una enfermedad importante hasta principios de los 1990s cuando una epidemia drástica ocurrió en la variedad SP71-6163. Desde entonces, los mejoradores comenzaron a tener en cuenta su presencia durante los estados de selección y sus efectos en el desarrollo vegetativo. El objetivo
del presente trabajo consistió en evaluar los efectos del Sugarcane yellow leaf virus (SCYLV), agente causal de la hoja amarilla en la producción de caña y desarrollo del sistema de raíces. El experimento se realizó en Ribeirão Preto, SP, Brasil, en un suelo Typic Hapludox, en la variedad IAC89-2135, durante el ciclo de plantilla. El diagnóstico del SCYLV se realizó empleando DAS-ELISA y RT-PCR para separar entre plantas sanas e infectadas. Las plantas infectadas mostraron una disminución significativa del peso seco de raíces y peso fresco de la parte aérea y un aumento en el Brix y contenido de sacarosa de los tallos. Aunque las plantas infectadas mantuvieron la arquitectura vertical del sistema radicular, el peso seco se redujo y correlacionó negativamente con el peso fresco y número de tallos, mostrando que las alteraciones en el sistema de raíces y vascular se puede constituir como los mas importantes efectos causados por la infección del SCYLV.
