Journal of Sugar Beet
Year:2003 | Volume:19 | Issue:1|Papers Count:12

A comparative study was conducted to find a reliable and simple method for evaluation of resistance of sugar beet genotypes to Rhizoctonia root and crown rot. For this, 12 sugar beet genotypes were used in greenhouse, field and in vitro experiments. The field experiment was performed in micro plots (1×1×2 meter) using randomized complete block design with 4 replications. Prior to planting, the micro plots were disinfested with methyl bromide. Twelve weeks sugar beet plants were inoculated with a highly pathogenic isolate of R. solani AG2-2. Disease severity was measured 12 weeks after inoculation based on a 0-7 scale. Under the greenhouse conditions, evaluation of genotypes resistance at seedling and adult plant stages were conducted in two separate experiments. In the seedling stage, germinated seeds of the genotypes were inoculated using inoculums layer technique and mortality percent of seedlings was recorded till 5 weeks after planting. In the adult plant stage, inoculation was carried out 8 weeks after transplanting sugar beet seedlings into large plots. The experiment was conducted in a completely randomized design with 3 replicates and disease severity was measured three weeks after inoculation. In the detached root method, the genotypes were sown under field conditions. Seven months after planting, 30 roots of each genotype were randomly selected and detached root slices of one cm in diameter from each root were prepared in laboratory conditions. The detached roots were put in sterilized 10 cm Petri plates and then inoculated by 8 mm pieces of the actively growing colony of Rhizoctonia isolate. Seven days after inoculation, the diameter of rotting tissue on each detached root was measured. The in vitro test was performed in a completely randomized design with 5 replicates using 10 cm petri plates. For this, germinated seeds of the genotypes were placed on the periphery of an actively growing colony of R. solani on Water Agar (WA) medium and five days later the disease severity of seedlings was measured on the basis of a 0-4 scale. In order to assess the correlation among the five evaluation methods, Pearson Correlation Coefficient (PCC) was calculated. Results of the seedling-stage method in greenhouse as well as detached root method showed poor correlation with the other evaluating methods. The results of field, greenhouse and in vitro experiments exhibited positive and significant correlations. Significant correlations were also found between in vitro test with greenhouse (0.862) and field evaluation (0.685;(p≤0.05)), respectively using PCC test. Similar results were obtained from greenhouse and field evaluation (0.912) methods. Based on the results, the in vitro test is recommended as a simple and reliable method for screening sugar beet germplasms against R. solani root rot.

In order to determine possibility of using detached leaf disks for evaluating resistance to Cercospora beticola, the causal agent of leaf spot in sugar beet, twelve sugar beet cultivars exhibiting different levels of resistance to Cercospora leaf spot were evaluated under field and laboratory conditions. The field experiment was conducted in a complete randomized block design with six replicates in Ghaemshahr region, where conductive and favorable climatic conditions for disease development existed. In the laboratory experiment, levels of resistance of the cultivars were determined by assessing of disease severity of detached leaf disks laid in rows on top of 1.5% water agar in 20×30 cm Pyrex plates. The results of this study indicated that there was a high correlation between both evaluation methods. Therefore, the evaluation of resistance would be reliable through each of these methods. The leaf disk assay is a very rapid and useful evaluation method enabling the evaluation of a lot of plant materials within a short period in the laboratory independent of climatic conditions.

Effects of culture medium containing hormonal compositions on phenotypic and chromosomal variations of sugar beet cultured tissues were examined. Experiments were carried out in different NaCl levels. Cytological studies were conducted on calli originated from suspension culture. Hypocotyl of seven day old seedlings of the two diploid lines were cultured in MS medium containing hormonal compositions to produce callus. In the next step, cell aggregates and callus fragments were incubated onto PGoB media supplemented with different salt concentrations (0-300 milimolar NaCl) and their growth was investigated. The results showed that multigerm line derived-callus had obviously more tolerance to the different NaCl concentrations than monogerm line derived-callus; so that 15 and 75 percent of monogerm and multigerm line calli grew, respectively, after being transferred from control medium to the medium containing 200 mM NaCl. Callus fragments of multigerm line had desirable growth after being transferred to the medium containing 100 mM NaCl. Also, variation was seen among callus fragments in each treatment. In another experiment, somaclonal variation was studied at chromosomal level in callus cells obtained from suspension culture in which polyploidy and aneuploidy were observed in some cells. Therefore, it is noteworthy to characterize and control somaclonal variation in cell culture of sugar beet in the desired direction for selection of salt tolerant lines.

In order to evaluate the best drought resistance indices in sugar beet genotypes, an experiment was conducted in 2002 using a split- plot design within randomized complete block design with three replications at the Research Farm, Shiraz-Zarghan. The main plots consisted of three Irrigated regimes: non stress, 75% (mid stress) and 50% (intense stress) non stress and the ten genotypes as the sub factor. Water stress was initiated at about six-leaved stage, and the stress was continued throughout the growing season. Drought resistance indices consisting of stress susceptibility index (SSI), stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), stress tolerance (TOL) and harmonic mean (Harm), were evaluated for white sugar yield in stress and non-stress conditions. The results showed that drought stress reduced white sugar yield. Results from calculating drought tolerance indices, correlation among indices and white sugar yield in stress and non-stress conditions showed that STI, Harm, GMP and MP indices, effectively distinguished genotypes with high yield in both conditions and were determined as the best drought tolerance indices. Because of high correlation between STI and the other indices, its significance is more than the other ones. Finally, 7221-I-79, BP-Mashhad and control-Rasool genotypes were determined as the genotypes that have a high potential white sugar yield in both environments.

This study was carried out in Lorestan Silakhoor plain during 2001-2002. Twenty soil properties from 25 profiles were evaluated. Profiles studied were Entisols and Inceptisols. Moreover, soil classification resulted in 5 subgroups, 8 families and 17 soil series. In the study, parametric land evaluation method was used. The strong correlation between the land index and observed yield (r=0.55) suggested the potential usefulness and applicability of the parametric land evaluation method. The area is located in semiarid region, based on Broujerd station data. The objective of this research was to determine the growing period and Radiation Thermal Production Potential (RTPP) for sugar beet. The results indicated that growing period of sugar beet in the area starts on 6 November and ends on 3 May, which is about 179 days, and RTPP is 68628 kg/ha. Average sugar beet yield in the research area was 28448 kg/ha (1991-2001) with an average of 14.72% sugar content (Min. 13.78%, Max. 16.28%) based on Lorestan Sugar beet factory data. The net biomass production was calculated using climatic and crop data and predicted yield was obtained from the effects of soil, water and management limitations on RTPP. Therefore, observed yield can be increased by removing remediable soil limitations and promoting management level.

In some regions of Isfahan, although there is no soil and water salinity limitations, quality of sugar beet root is very low because of using high amount of irrigation water. A study was conducted to determine the relation between low irrigation and quality and quantity of sugar beet. In this study, a line source irrigation system for six water use treatments (from 10770 to 8554 m3/hec) was used. The results showed that root yield, sugar yield, sodium of root and white sugar yield decreased significantly when water use was decreased but sugar content and α- amino- N increased significantly. Maximum root yield (55 ton per hectar) was obtained at 10770 m3/hec water use treatment, where as root yield decreased to 20.10 ton per hectar at 8554 m3 irrigation water. Sodium of root responded to water contents, in that higher amount of water increased the sodium of root and as a result sugar content of sugar beet decreased. The results showed that water content less than 97.5% of the total water requirement did not increase water use efficiency for sugar yield. Also, white sugar yield responded to low irrigation and it was significantly decreased with water use deficit.

Monogerm and multigerm seed varieties are used in sugar beet cultivation. Singling is inevitable and mechanization almost impossible when multigerm seed varieties are used. For this and for some other reasons, economically sound and fully mechanized cultivation of sugar beet calls for the use of monogerm seed varieties. Throughout Europe, only monogerm varieties are used in sugar beet production. In sowing monogerm seeds, special types of machineries are implemented and land preparation techniques play a very important rule. In the past, lack of suitable machineries and well prepared lands discouraged farmers from sowing monogerm varieties and therefore, monogerm seed production showed no improvement in quality, quantity and diversity for many years. In recent years, with the growing interest of sugar beet producers, Sugar Beet Research Institute of Iran has focused on monogerm seed production. With the development of varieties suitable for different climatic areas, this institute has reached a high level of commercial success in monogerm seed production. In a multigerm seed production field, some fraction of the crop is monogerm. One way of monogerm seed production, called technical monogerm, is the separation of this fraction of monogerm seed from the multigerm seeds using a combination of round and slotted screens. Another type of monogerm seed is hybrid monogerm and its production is rather complex and requires special tools and material with a growing demand for monogerm seed, Sugar Beet Seed Research Institute has been focusing on the production and development of high quality basic seeds of monogerm type in recent years and the increasing level of commercial production of hybrid monogerm is a clear indication of its success. Table 1 shows the trend of commercial hybrid monogerm seed production in an interval of 5 years. Each year, field performances of domestic varieties are compared with top quality foreign varieties by researchers and technical staffs of SBSI, agricultural organizations and agricultural sectors of sugar refineries. Data gathered from 70 sugar beet production farms with a total of 203 hectares in Western Azerbaijan province for the production year of 2002 is shown in Table 2. At a large scale, average root yield is 5 tons per hectare with 9.01 tons of gross sugar. Domestic varieties show unique superiorities over foreign varieties and in some cases 40% yield increase is observed. Sugar Beet Seed Research Institute has developed Rhizomania and Nematode resistant lines and farmers will have access to the new varieties in the coming years.