Research Article - (2014) Volume 4, Issue 1
1Department of Agronomy, Ferdowsi University, Iran
2Department of Agronomy, Varamin Branch, Islamic Azad University, Varamin, Iran
3Young Researchers Club, Varamin-Pishva Branch, Islamic Azad University, Varamin-Pishva, Iran
Rhizomania or root madness is one of the main diseases of sugar beet (Beta vulgaris L.) and it is common all around the world. The disease usually causes more than 50% of product yield loss and even 100% in more acute cases. An experiment on more than 11 Rhizomania resistant cultivars, randomly placed on blocks with three replications (in two locations: Fariman Sugar Mill Research Farms (contaminated and free of contamination, Khorasan Razavi) was conducted in 2012 to measure resistance of the specimens. The results showed, for station 1, Merak and 006 cultivars were the most resistant cultivars concerning development of root per hectare. In addition, Merak, 006, Azar, Rozir, Delta, and Native Color cultivars had the maximum yield/ha. Moril cultivar had the lowest root yield and genotypes 004, Iranian Razifort, 005, and Zarghan had the lowest yield. However, in case of the station 2, 005 and 004 cultivars had the maximum and minimum root and sugar yields respectively.
Rhizomania, sugar beet, cultivar, resistant, stimulate, station
Rhizomania or Root madness is one of the most threatening diseases of sugar beet (Beta vulgaris L). The cause of the disease is beet necrotic yellow vein virus (BNYVV), which is communicated by Polymyxa betae Keslein. [18,19]
The first ever report of the disease with similar symptoms of Rhizomania was reported in North Italy (1952). Kanowa (1966) named the disease Rhizomania or root madness due to abnormal behavior of the root of the infected plant [12]. At the same time other reports of the disease came from Japan [11]. Afterward, in 1985 in France the relatively resistant variety of Rizor was developed and product yield was considerably increased in the farm planted with the new variety [15]. Stone et al. (2006) studied 21 genotypes resistant to Rhizomania in two farms (contaminated and free of contamination) in Siberia and Montenegro. They reported that comparing with the control group (12 MT/ha), Concento cultivar (85.78MT/ha) had the highest product yield in the farm infected with the disease. In addition, in comparison with control cultivar (10.92%), Ivona (15.365%) had the highest rate of sugar; and Remos cultivar (9.205MT) had the highest sugar yield comparing with the control group (0.842MT).
furthermore, no significant qualitative and quantitative difference was observed in the free of contamination farm [17]. Efficient control needs significant increase in disease inoculums in the soil as a way to increase resistance of the plant. Resistant against the disease is mono genic and this makes it vulnerable. Resistance mechanism includes limiting virus multiplication or transfer. Currently, there are several highly resistant to Rhizomania mono gene cultivars available in the market; including Dorethea, Avantage, Laetitia, etc. It is noticeable that the resistance is not 100% and it might fail depending the patho-type of the virus or severity of the disease. There are reports of Rhizomania from different parts of the world which indicate that the disease still is one of the main threats against sugar beet [13]. Sustained loss usually is more than 50% and reaches 100% in some cases. [15, 16]
Iezadpanah et al. (1996) made the first report of Rhizomania in Fars, Iran [1] and afterward, the case was witnessed in other sugar beet farms in the country including in Khorasan, Fars, Isfahan, Kermanshah, Ghazvin, Zanjan, Hamedan, Kohkuloyeh va Boirahmad, Char Mahal Bakhtiari, Semnan, and Lorestan [2-4]. Currently, the extent of economic loss of the disease have forced many sugar beet farms stop farming the plant. In addition, the disease considerably shrinks the mass of the root and sugar content. Consequently, product yield is reduced up to about half of the normal yield. Several measures have been prescribed to fight the disease thus far including farming operation, chemical solutions, and genetic solutions. [15, 16]
Farming methods include early planting, avoiding excessive moisture, shorter irrigation process and closer irrigation turns, avoiding contamination of the healthy farms, and other alternatives. However, in spite of all these measure, damages caused by the disease still can be considerable and make the measure obsolete [9, 14]. For chemical measures, there are several fungicides to fight the disease and among them, except for soil sterilizer (e.g. methyl bromide) other fungicides are ineffective [10, 16]. Currently, extensive surveys are in hands in different fields of diseases, among them studies to develop resistive cultivars is notable. The present research is aimed to assess performance of commercial cultivars of sugar beet (domestic or imported) after being affected by the disease and to recommend the most compatible and resistive case to be used in the contaminated regions.
The cultivars were prepared from the supplier institutes (11 cultivars, Table 3) and were randomly planted in randomly block design with three replications (5 May 2011) in two stations of the research farms of Fariman Sugar Co. (Tables 1 & 2). The site of experiment was adopted taking into account the climate of the region [6-8]. Each cultivar was planted on six lines (8m) and 50 rows. Irrigation method was sub-irrigation and during growth season, thinning, weeding, and noting were carried out. In 6th of November 2011 at 10.7°C, 4m2 of each block (two mid lines) was harvested and number/weight of roots were measured separately. Qualitative and quantitative traits including yield of root, rate of sugar, rate of molasses, sugar and white sugar, health threatening level of nitrogen, sodium, and potassium, alkalinity, and dry mass of root were determining and the data was analyzed in SPSS 15, SAS, and Excel. (Table 2, 5, 6).
Table 1: Plasma Na concentration (mmol/L).
Table 2: Plasma Na concentration (mmol/L).
Table 3: Plasma Na concentration (mmol/L).
Table 4: Plasma Na concentration (mmol/L).
Table 5: Plasma Na concentration (mmol/L).
Table 6: Plasma Na concentration (mmol/L).
Variation of the elements has been found in the root of sugar beet in Iran and Germany climate by researchers. Given that the study was carried out in Razavi Korasan, Iran, the related data were used for comparing the results. [11] (Table 5-7)
Table 7: Plasma Na concentration (mmol/L).
Results from station 1
1. Sugar and white sugar percentage The results revealed that the rate of sugar (impure sugar) and white sugar (pure sugar) were affected by the genotypes under study at 1% level (Table 8). As indicated in the table, comparison of average figures shows that cultivar 4 yielded highest level of sugar (21.50) and white sugar (18.67); and cultivars 8 and 9 had the lowest yield of sugar (18.88 and 18.70 respectively) and white sugar (15.87 and 15.41 respectively). Table 9)
Table 8: Plasma Na concentration (mmol/L).
Table 9: Plasma Na concentration (mmol/L).
2.Root yield
Root yield per area unit is mainly important concerning the sugar yield. Variance analyses showed that root yield was influenced by the genotype with variance of 161/166 and the effect was significant at 1%. That is, significant difference was observed regarding root yield among the genotypes udder study. (Table No. 8)
As listed in Table 9, maximum root yield was obtained by cultivars 7 and 8 (Iranian) with 72.71 and 69.08MT/ha respectively. Moreover, minimum root yield was obtained for cultivar 2 (46.83MT/ha) and the difference between the maximum and minimum yields is 25.55MT/ha.
3. Sugar extraction and molasses sugar rate
As indicated in the variance table below, variance of sugar extraction (15.619) and molasses sugar (0.471) of the cultivars are significant at 1% and 5% levels respectively (Table 8). Genotype 3 (88.15) had the maximum rate of sugar extraction and genotypes 2 (82.08), 9 (81.89), and 10(79.95) had the minimum rates of sugar extraction. Regarding molasses sugar extraction, cultivar 10 and 2 had the maximum molasses sugar extract (3.16 and 3.19 respectively) and minimum extractable sugar (82.08 and 79.95 respectively). It is notable that a wide gap exists cultivar 3 (8.20, 6.26, 6.07) and cultivars 2, 9, and 10; which is a crucial factor for sugar mill. That is, the higher the rate of extractable sugar, the higher the rate of white sugar; to put it another way, less rate of molasses sugar means less waste of product. (Table 9)
4.White sugar yield
There was a significant difference in white sugar yield (root yield * white sugar rate) between the cultivars under the effect of the genotypes and control group at 1% and variance level of 5.677 (Table 8). As listed in variance table, maximum white sugar yield was obtained in cultivars 7, 8, 3, 5, 6, and 7 at 12.73, 10.98, 10.77, 10.74, 10.24, and 9.73 MT/ha respectively; while minimum white sugar yield was obtained for the cultivars 1, 9, 10, 11, and 2 equal with 9.50, 8.71, 8.70, 8.56, and 8.07MT/ha respectively. (Table 9)
5.Dry mass rate
Difference between the experiment and control groups regarding dry mass rate was significant at 5% and variance of 2.301. That is, there is a significant difference regarding root performance among the genotypes under study (Table 8). As listed in Table 9, dry mass rate is maximum for cultivars 8 (27.62%) and 4 (27.52%); and minimum dray mass rate is for cultivar 6 (24.90%).
Results from station 2
1. Sugar and white sugar percentage
The results revealed that the rate of sugar (impure sugar) and white sugar (pure sugar) were affected by the genotypes under study at 1% level (Table 10). As indicated in the table, comparison of average figures shows that cultivar 4 yielded highest level of sugar (21.62) and white sugar (18.39); and cultivar 9 had the lowest yield of sugar (17.93) and white sugar (15.46). (Table 11)
Table 10: Plasma Na concentration (mmol/L).
Table 11: Plasma Na concentration (mmol/L).
2.Root yield
Root yield per area unit is mainly important concerning the sugar yield. Variance analyses showed that root yield was influenced by the genotype with variance of 55/055 and the effect was significant at 1%. That is, significant difference was observed regarding root yield among the genotypes udder study. (Table 10)
As listed in Table 11, maximum root yield was obtained by cultivar 11 (Iranian) with 63.00MT/ha.. However, no significant was observed regarding root yield between the cultivars.
3. Sugar extraction and molasses sugar rate
As indicated in the variance table below, variance of sugar extraction (15.619) is significant at 1%, while regarding molasses sugar (0.471) it is not significant (Table 10). Genotypes 4 and 7 (89.21 and 89.28 respectively) had the maximum rate of sugar extraction and genotype 9 (86.23) had the minimum rate of sugar extraction. Regarding molasses sugar extraction, cultivar 9 and 11 had the maximum molasses sugar extract (1.93 and 1.90 respectively) and minimum extractable sugar (86.23 and 86.65 respectively). It is notable that a wide gap exists cultivar 3 (8.20, 6.26, 6.07) and cultivars 2, 9, and 10; which is a crucial factor for sugar mill. That is, the higher the rate of extractable sugar, the higher the rate of white sugar; to put it another way, less rate of molasses sugar means less waste of product. (Table 11)
4.White sugar yield
There was a significant difference in white sugar yield (root yield * white sugar rate) between the cultivars under the effect of the genotypes and control group at 1% and variance level of 3.046 (Table 8). As listed in variance table, maximum white sugar yield was obtained in cultivars 1, 6, and 11 at 9.69, 10.18, and 11.85MT/ha respectively; while minimum white sugar yield was obtained for the cultivars 9 equal with 6.57MT/ha. (Table 11)
5.Dry mass rate
Difference between the experiment and control groups regarding dry mass rate was significant at 5% and variance (2.301). That is, there is a significant difference regarding root performance among the genotypes under study (Table 10). As listed in Table 11, dry mass rate is maximum for cultivars 1 (30.29%), 4 (30.21%), and 7 (30.12%); and minimum dray mass rate is for cultivars 11 (27.45%) and 5 (27.09%).
In the case of station 1 (contamination with Rhizomania), cultivar 4 (DELTA) had the maximum rate sugar (21.50%) and white sugar (18.67%), while the minimum rate of sugar was by cultivar 8 (006) and 9 (004) (18.88% and 18.78% respectively); and cultivar 19 (Rizofort (Iran)) yielded minimum rate of white sugar (15.31%). On the other hand, cultivar 7 had the maximum yield of sugar (15.06 MT/ha) and white sugar (12.73MT/ha) comparing with other treatment. This makes it one of the best options for the regions contaminated with virus (Table 9). In addition, cultivar 7 (MERAK) and 8 (006) had the maximum root yield (72.71 and 69.08MT/ha respectively); while maximum amount of white sugar was obtained from cultivars MERAK (12.73MT/ha), 006 (10.97MT/ha), AZAR (10.77MT/ha), ROZIR (10.74MT/ha), BOMIRNG (10.74MT/ha), and DELTA (9.73MT/ha). In general, cultivar 7 (MERAK) had higher root (71.71MT/ha) and white sugar (12.73MT/ha) yields in comparison with other genotypes under study. (Table 9)
Two qualitative factors of sugar beet are rate of molasses sugar and sugar extraction rate so that the lower the rate of molasses sugar, the higher the sugar extraction rate (Table 9). The results highlighted that cultivars with lower molasses sugar rate had higher sugar extraction rate and better white sugar yield. As indicated cultivar 2 (MORIL) and RIZOFORT (IRAN) had the highest rate of sugar molasses and consequently the minimum sugar extraction rate. It is noticeable that cultivars 9 (004), 11 (005), and 1 (ZARGHAN) had high molasses sugar rate and lower sugar extraction rate. On the other hand, more resistive cultivars 7 (MERAK), 8 (006), 3 (AZAR), 5 (BOMIRANG), 6 (DELTA), and 4 with higher root yield produced less rate of molasses sugar and higher sugar extraction rate. (Table 9)
Statistical analyses on the data obtained from station 2 (no contamination with Rhizomania) showed that cultivar 4 (DELTA) had the highest rate of sugar (21.62%) and white sugar (18.39%) (similar with the station 1). In fact, cultivar 4 (DELTA) produced highest rate of sugar and white sugar both in contaminated and free of contamination stations. Among other cultivars, 9 (004) produced the minimum rate of sugar (17.93%) and white sugar (15.46%). On the other hand, maximum yield of root, sugar and white sugar (MT/ha) was produced by cultivar 11 (005) (43.35, 7.62, and 6.57 respectively), 6 (BOMIRNG) 57.21, 11.63, 10.18 respectively), and 1 (ZARGHAN) (55.71, 10.95, and 9.69 respectively) (Table 11). Moreover, genotype 4 (004) had the minimum yield of root (43.35MT/ha), sugar (7.62MT/ha), and white sugar (6.57MT/ha) in comparison with other cultivars. It is notable that, except for cultivar 9 (004) no considerable difference was found between the genotypes under study. (Table 11)
The results regarding the station 2 also showed that cultivars with less molasses sugar rate had lower rate of sugar extraction and white sugar yield. Cultivar 9 (004) and 11 (005), comparing with other cultivars had the maximum level of molasses sugar and minimum sugar yield. Cultivar 9 (004), 11 (005, and 1 (RAZGHAN) with high rate of molasses sugar and more resistive cultivars 7 (MERAK) and 4 (DELTA) with low rate molasses sugar produced low and high rate of sugar extraction respectively. (Table 11)
Taking into account impossibility of diagnosing soil contamination with Rhizomania virus (in contrast with what is done to diagnose nemathod eggs and larva though testing the soil before plantation), attenuation of probable damages to sugar beet farm by Rhizomania virus is achievable by using the genotypes with good performance in the both conditions (contamination and free of contamination) including 006, BOMIRGN, MERAK, and DELTA. (Table 9, 11)
In general, the healthy end product counts for the farmer and the sugar mill. White sugar yield – the end product – is calculated by multiplying the root yield and white sugar rate. As listed in (Table 9, 11), different cultivars were significantly different regarding the two parameters of root yield and white sugar rate. Given the current market price of sugar, each MT increase in white sugar production per hectare means Rls.11750000000 increase in the profit; which with 170000 hectare of farm (2011), this figure comes to RLS.1990 billion or in other words 170.000MT sugar. This figures herald the importance of choosing suitable cultivar for cultivation.
Generally, negative effect of Rhizomania on lessening qualitative and quantitative yield of sugar beet is undeniable and adopting cultivars resistive to the disease is the best approach available. Apparently, different cultivars have different reactions to the disease, which is due to genetic and hereditary features. To have better result, conducting similar experiments in different climates is recommended.
Acknowledgement
Conducting the present study was not possible without financial supports for doing the experiments by Messrs Elahi (Eng.), Nazeran (Eng.), Araghi (Eng.) and other dear colleagues who made great contributions during the study.
