Resistant Sugar Beet Cultivars Research Articles

<i>In Vitro </i>and<i> in Vivo </i>Management of <i>Sclerotium rolfsii</i> the Cause of Sugar Beet Root Rot Disease

Management of sugar beet damping off and root rot diseases caused by <i>Sclerotium rolfsii</i> is urgently needed. Therefore, antifungal activities of 13 materials including 2 bio agents, 2 seaweeds, 3 chemical inducers and 6 fungicides were evaluated. Required inoculum potential of either fungal mass or sclerotia to reach more than 50% of disease incidence was firstly investigated. Fungal mass inoculation (40-500g/10kg of soil) provided 70-100% damping off and 100% root rot. Meanwhile, 6.7-36.7% of damping off and no or negligible root rot were obtained using 300-500 sclerotia /10kg of soil. On the other hand, <i>S. rolfsii</i> mycelial growth was completely suppressed <i>in vitro</i> by all tested materials. However, various antifungal activities of these materials were shown <i>in vivo</i> after seed soaking in the 1^st (2020/2021) trail or seed soaking followed by soil drenching in the 2^nd (2021/2022) trail. Tipo top (Tebuoconazole 25.9%: 1cm/L) fungicide was the most effective material in the 1^st trail since the seedling survival was up to 80%, followed by potassium silicate (1cm/L) and Score (Difenoconazole 25%: 1cm/L) fungicide. Seed soaking followed by soil drenching with Tipo top in the 2^nd trail were protected sugar beet from sowing to harvest and enhanced the root weight. Additionally, this study illustrated that both of sugar beet root weight and sucrose content were decreased as root rot severity increased. In conclusion, chemical fungicides are unfortunately still the fast and potent way for <i>S. rolfsii</i> management, especially with the limitation of resistant sugar beet cultivars.

Screening of sugar beet pre-breeding populations and breeding lines for resistance to Ditylenchus dipsaci penetration and reproduction

Ditylenchus dipsaci is an economically important plant-parasitic nematode affecting European sugar beets. To date, no sugar beet cultivars carrying resistance against D. dipsaci are available to farmers. To find potentially resistant sugar beet lines restricting reproduction and penetration of D. dipsaci, three consecutive in vivo bioassays were carried out. The first experiment determined the penetration rate of D. dipsaci in 79 breeding lines and 14 pre-breeding populations. Based on these results, D. dipsaci penetration and reproduction resistance of eight genotypes was intensively investigated. It could be demonstrated that none of the genotypes showed resistance towards D. dipsaci. However, a high variation of the penetration rate by D. dipsaci was observed among the genotypes. The breeding line ‘DIT_119’ effectively reduced D. dipsaci penetration (34.4 ± 8.8 nematodes/plant at 22 days post-planting) compared to the susceptible control (109.0 ± 16.9) while ensuring a yield comparable to non-inoculated plants. However, the breeding line ‘DIT_119’ did not reduce D. dipsaci reproduction. The paternal line of the cultivar BERETTA KWS, demonstrating a high tolerance to D. dipsaci crown rot symptoms, did not reduce penetration and reproduction. Thus, no correlation can be established between reduced penetration rates, reproduction, and tolerance to D. dipsaci. This study provides an essential basis for the development of resistant sugar beet cultivars to D. dipsaci. The variations observed among genotypes now need to be confirmed with larger-scale screenings.

Genetic and biochemical variations among sugar beet cultivars resistant to Cercospora leaf spot

The goal of the study was to construct a reliable molecular and biochemical tool for the selection of resistant sugar beet cultivars to minimize the loss in productivity caused by Cercospora leaf spot disease. Three PCR marker systems: inter simple sequence repeats (ISSR), and sequence-related amplified polymorphisms (SRAP), and random amplified polymorphic DNA (RAPD) were used to assess the genetic diversity among eight cultivars of sugar beet and to detect the molecular markers linked to resistance to Cercospora beticola. Molecular tools successfully differentiated resistant from susceptible cultivars and detected 10 specific DNA markers in the resistant cultivars. Euclidean distance analysis based on physiological traits grouped the eight cultivars into two main clusters. Protein and isozyme patterns of peroxidase, polyphenol oxidase, chitinase, super oxide dismutase, glutamate oxalo-acetate transaminase and esterase were validated as quick means to select resistant cultivars of sugar beet. Specific protein and isozyme bands were lacking or were induced in cultivars based on their resistance phenotype. Our Results show that molecular markers and isozyme patterns are powerful tools for distinguishing resistant sugar beet cultivars resistant against Cercospora leaf spot.

Breeding and usage of sugar beet cultivars and hybrids resistant to sugar beet nematode Heterodera schachtii

Heterodera schachtii Schmidt, 1871 is one of the most economically important pests of sugar beet (Beta vulgaris L.) worldwide. It is also widespread in most sugar beet growing regions in Ukraine causing serious yield reduction and decreasing sugar content of sugar beet in infested fi elds. An advanced parasitic strategy of H. schachtii is employed to support nematode growth, reproduction and harmfulness. In intensive agriculture systems the nematode control measures heavily rely on nematicides and good agricultural practice (crop rota- tion in the fi rst place). But alternative strategies based on nematode resistant sugar beet cultivars and hybrids are required as none of nematicides approved for the open fi eld application are registered in Ukraine. Here we review the achievements and problems of breeding process for H. schachtii resistance and provide the results of national traditional breeding program. Since the beginning of 1980s fi ve sugar beet cultivars (Verchnyatskyi 103, Yaltuschkivska 30, Bilotcerkivska 45, BTs-40 and Yuvileynyi) and seventeen lines partly resistant or toler- ant to H. schachtii have been obtained throughout targeted crossing and progenies assessment in the infested fi elds. The further directions for better utilization of genetic sources for nematode resistance presented in na- tional gene bank collection are emphasized. There is a need for more accurate identifi cation of resistance genes, broader application of reliable molecular markers (suitable for marker-assisted selection of nematode resistant plants in the breeding process) and methods for genetic transformation of plants. Crop cash value and national production capacity should drive the cooperation in this fi eld. Knowledge as well as germplasm exchange are thereby welcomed that can benefi t breeding progress at national and international level.

Non-Invasive Spectral Phenotyping Methods can Improve and Accelerate Cercospora Disease Scoring in Sugar Beet Breeding

Breeding for Cercospora resistant sugar beet cultivars requires field experiments for testing resistance levels of candidate genotypes in conditions that are close to agricultural cultivation. Non-invasive spectral phenotyping methods can support and accelerate resistance rating and thereby speed up breeding process. In a case study, experimental field plots with strongly infected beet genotypes of different resistance levels were measured with two different spectrometers. Vegetation indices were calculated from measured wavelength signature to determine leaf physiological status, e.g., greenness with the Normalized Differenced Vegetation Index (NDVI), leaf water content with the Leaf Water Index (LWI) and Cercospora disease severity with the Cercospora Leaf Spot Index (CLSI). Indices values correlated significantly with visually scored disease severity, thus connecting the classical breeders’ scoring approach with advanced non-invasive technology.

EFFECT OF INOCULUM LEVEL, TYPE, PLANT AGE AND ASSESSMENT DATE ON EVALUATING SUGAR BEET RESISTANCE METHODS FOR ROOT-KNOT NEMATODE, Meloidogyne incognita

The objectives of this study were to determine the effect of inoculum level, inoculation date, assessment date and inoculum type, on evaluating M. incognita resistance in sugar beet, and to optimize the resistance screening technique used to categorize root-knot nematode resistant sugar beet cultivars under the greenhouse conditions (25±2.5°C). A series of greenhouse tests were done using seven sugar beet varieties with three levels of resistance to M. incognita. The three resistance levels could be separated based on gall indices as early as two weeks after inoculation (WAI) using 6000 eggs of M. incognita per plant. Results indicated that based on gall index, low inoculum level (500 and 1000 eggs/ plant) could separate four sugar beet varieties from each other only on the fourth assessment date (8 WAI) for inoculum level 500 eggs/ plant and on the third assessment date (6 WAI) for 1000 eggs/ plant inoculum level. Harvest date affected galling in sugar beet roots (P ≤ 0.001); there was a significant interaction of harvest date × variety (P ≤ 0.001), the increase of gall index was greater for variety Elan than for the other tested verities. Based on galled area index, the resistant and susceptible varieties could be separated successfully as early as 2 WAI. At the highest tested inoculation level (12000 eggs/ plant), but it couldn't be separate between the moderately resistant and the susceptible or between resistant and moderately resistant ones at P ≤ 0.001. Based on eggs per gram root, the four sugar beet varieties with three levels of resistance to M. incognita were separated at the inoculation rate of 8000 eggs/ plant by 6 WAI and at 500, 1000, 2000, 4000 and 12000 eggs/plant by 8 WAI. In addition to gall number, gall index, galled area index, eggs per gram root, egg mass number and egg mass index were also used to assess the resistance levels in the sugar beet varieties. Gall index was found to be the most sensitive method of all measures used for assessing resistance. Inoculum type i.e. eight thousand eggs and 2000 J2 did not result in significant differences in galled area index at the two investigated harvest dates. Plant age at time of inoculation affected gall development on the tested sugar beet varieties however; the effects on Av poly, Lados and M 9680 were not as great as on Del 939 and Elan. But, the same tested verities could not be separated into their appropriate resistance categories with inoculation at 0 and 40 day after planting. The importance of such study is the identification of a rapid method for assessing resistance in sugar beet varieties to root-knot nematodes, takes less than 100 days.

Integrated Control of Root and Crown Rot in Sugar Beet: Combined Effects of Cultivar, Crop Rotation, and Soil Tillage.

Rhizoctonia solani (AG 2-2IIIB), causing root and crown rot in sugar beet, poses an increasing problem in Europe. Agronomic measures have to be optimized to control disease and minimize yield and quality loss, because no fungicides can be applied. Resistant sugar beet cultivars have been introduced to reduce disease occurrence. Furthermore, crop rotation can influence R. solani occurrence. In contrast to other cereals, maize serves as a host of the fungus. In order to study the combined effect of these factors, a series of four field trials was established with crop rotations varying in the proportion of maize and comparing a resistant with a susceptible sugar beet cultivar in 2001-02 in southern Germany. Within crop rotations, cultivation methods were varied in the form of soil tillage, intercrops, or both. Sugar beet cultivar and crop rotation had the main impact on disease severity and sugar yield. With increasing proportion of maize, sugar yield decreased, whereas cultivation method had only a minor impact. Plowing directly before sugar beet increased sugar yield only within the unfavorable maize-maize-sugar beet rotation compared with mulching. These results give strong evidence that crop rotation of sugar beet with nonhost plants and cultivation of resistant sugar beet cultivars are adequate means for integrated R. solani control.

Distribution of Rhizomania Disease in Sugar Beet Growing Areas of Turkey

Rhizomania is one of the most destructive diseases affecting sugar beet. It leads to a severe loss in terms of root yield and sugar content up to 90 % and up to 70 % respectively, depending on the disease severity. It was reported in some regions of Marmara, Central Black Sea, and Central Anatolia and tends to spread in other regions in Turkey. The disease is caused by Beet Necrotic Yellow Vein Benyvirus (BNYVV) and transmitted by a fungus, Polymyxa betae. The primary source of its spread is through the movement of infested soils or beets. Only cultural control methods are employed to control this disease. At present, the most effective control measure is to use of partially resistant sugar beet cultivars. The other additional measures like planting early into cool soils, minimizing watering, avoiding soil compaction, and employing crop rotations can reduce levels of the virus in the soil. Therefore, it is essential to determine the infested areas and take cultural measures before the disease causes economically important yield losses. Based on a three-year crop rotation, surveys were conducted and sugar beet root samples were collected from the growing areas in 102 regions of 17 sugar factory boundaries and in three periods including 1996-1998, 1999-2001 and 2002-2004. These root samples were tested by means of DAS-ELISA and distribution of BNYVV was determined. Rhizomania was detected in the sugar beet production areas of 4, 9 and 15 sugar factories in 1996-1998 1999-2001, and 2002- 2004 at the rates of 19.30% (46200 ha), 31.42% (94140 ha), and 48.66% (203640 ha), respectively.

Distribution and Molecular Characterization of Resistance-Breaking Isolates of Beet necrotic yellow vein virus in the United States.

Beet necrotic yellow vein virus (BNYVV) is the causal agent of rhizomania in sugar beet (Beta vulgaris). The virus is transmitted by the plasmodiophorid Polymyxa betae. The disease is controlled primarily by the use of partially resistant cultivars. During 2003 and 2004 in the Imperial Valley of California, partially resistant sugar beet cultivars with Rz1 allele seemed to be compromised. Field trials at Salinas, CA have confirmed that Rz1 has been defeated by resistance-breaking isolates. Distinct BNYVV isolates have been identified from these plants. Rhizomania-infested sugar beet fields throughout the United States were surveyed in 2004-05. Soil surveys indicated that the resistance-breaking isolates not only existed in the Imperial Valley and San Joaquin Valley of California but also in Colorado, Idaho, Minnesota, Nebraska, and Oregon. Of the soil samples tested by baited plant technique, 92.5% produced infection with BNYVV in 'Beta 6600' (rz1rz1rz1), 77.5% in 'Beta 4430R' (Rz1rz1), 45.0% in 'Beta G017R' (Rz2rz2), and 15.0% in 'KWS Angelina' (Rz1rz1+Rz2rz2). Analyses of the deduced amino acid sequence of coat protein and P-25 protein of resistance-breaking BNYVV isolates revealed the high percentage of identity with non-resistance-breaking BNYVV isolates (99.9 and >98.0%, respectively). The variable amino acids in P-25 proteins were located at the residues of 67 and 68. In the United States, the two amino acids found in the non-resistance-breaking isolates were conserved (AC). The resistance-breaking isolates were variable including, AF, AL, SY, VC, VL, and AC. The change of these two amino acids cannot be depended upon to differentiate resistance-breaking and non-resistance-breaking isolates of BNYVV.

First Report of Rhizomania Disease of Sugar Beet Caused by Beet necrotic yellow vein virus in the Great Lakes Production Region.

Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV) and vectored by the soilborne fungus Polymyxa betae Keskin, is one of the most economically damaging diseases affecting sugar beet (Beta vulgaris L.). The virus likely originated in Europe and was first identified in California in 1983 (1). It has since spread among American sugar beet production regions in spite of vigorous sanitation efforts, quarantine, and disease monitoring (3). In the fall of 2002, mature sugar beet plants exhibiting typical rhizomania root symptoms, including proliferation of hairy roots, vascular discoloration, and some root constriction (2) were found in several fields scattered throughout central and eastern Michigan. Symptomatic beets were from numerous cultivars, all susceptible to rhizomania. Two to five sugar beet root samples were collected from each field and sent to the USDA-ARS in Salinas, CA for analysis. Hairy root tissue from symptomatic plants was used for mechanical inoculation of indicator plants. Mechanical inoculation produced necrotic lesions on Chenopodium quinoa and systemic infection of Beta vulgaris ssp. macrocarpa, both typical of BNYVV and identical to control inoculations with BNYVV. Symptomatic sugar beet roots were washed and tested using double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) for the presence of BNYVV using standard procedures and antiserum specific for BNYVV (3). Sugar beet roots were tested individually, and samples were considered positive when absorbance values were at least three times those of greenhouse-grown healthy sugar beet controls. Samples were tested from 16 fields, with 10 confirmed positive for BNYVV. Positive samples had mean absorbance values ranging from 0.341 to 1.631 (A405nm) after 30 min. The mean healthy control value was 0.097. Fields were considered positive if one beet tested positive for BNYVV, but in most cases, all beets tested from a field were uniformly positive or uniformly negative. In addition, soil-baiting experiments were conducted on seven of the fields. Sugar beet seedlings were grown in soil mixed with equal parts of sand for 6 weeks and were subsequently tested using DAS-ELISA for BNYVV. Results matched those of the root sampling. Fields testing positive for BNYVV were widely dispersed within a 100 square mile (160 km2) area including portions of Gratiot, Saginaw, Tuscola, and Sanilac counties in the central and eastern portions of the Lower Peninsula of Michigan. The confirmation of rhizomania in sugar beet from the Great Lakes Region marks the last major American sugar beet production region to be diagnosed with rhizomania disease, nearly 20 years after its discovery in California (1). In 2002, there were approximately 185,000 acres (approximately 75,00 ha) of sugar beet grown in the Great Lakes Region, (Michigan, Ohio, and southern Ontario, Canada). The wide geographic distribution of infested fields within the Michigan growing area suggests the entire region should monitor for symptoms, increase rotation to nonhost crops, and consider planting rhizomania resistant sugar beet cultivars to infested fields.

Comparisons of Soil and Seed Applied Systemic Insecticides to Control Beet Curlv Top Virus in the San Joaquin Valley

Beet curly top virus (BCTV), a gemini virus, remains a problem for farmers in the San Joaquin Valley (SJV) of California. It is spread by the beet leaf hopper (Circulifer tene/lus Baker), which has become naturalized in the state. Recent dependence on sugarbeet cultivars without BCTV resistance has led to increased concern about the potential for a BCTV epidemic. Two trials were carried out in successive years in the western SJV to test the effects of alternative protective insecticides for control of BCTV on susceptible and resistant sugarbeet cultivars. Two rates ofimidicloprid applied as a seed treatment (45 g and 90 g a.i. per 100,000 seeds) were compared to the current standard treatment of phorate applied to soil at 83.8 g a. i. per 1000 m of row, and an untreated control. Natural BCTV infection occurred in both years, but the second trial took place during a major beet leafhopper population increase and infection occurred much earlier in crop development. Sugarbeet root and sugar yields declined linearly with increasing rates of infection (r2 = 0.856). Yields declined because roots were significantly smaller with the non-tolerant cultivar. Sugar percentage was unaffected by insecticide treatments, but differed by cultivar. Imidicloprid and phorate provided similar levels ofprotection to plants, but were not able to prevent large yield losses among susceptible cultivars. Plant resistance provided more protection than systemic

Identification of a Beta maritima Source of Resistance to Root‐Knot Nematode for Sugarbeet

Root‐knot nematodes (Meloidogyne spp.) are economically important plant pests that cause root gall symptoms and limit sugarbeet (Beta vulgaris L.) production. With the increasingly restrictive use of nematicides, the development of resistant sugarbeet cultivars becomes urgent. This study was conducted to identify the source of root‐knot nematode resistance and to evaluate transmission of resistance in sugarbeet hybrid progeny. One hundred‐ninety B. vulgaris and 113 sea beet (B. maritima L.) germplasm lines and accessions were evaluated for nematode resistance, via 1000 second‐stage juveniles (J2) per‐plant inoculations, under greenhouse and growth chamber conditions from 1993 to 1994. Beet seedlings developed better root systems in conetainers and pulp pots than in growth pouches for host reaction to the nematode infection assay. From non‐cultivated sea beet, an accession (PI 546387) was identified that segregated for plants free from root gall formation and from reproduction of M. incognita Race 1. Resistance was transmitted to approximately 23% of the F1 progeny when resistant B. martima phenotypes were crossed to sugarbeet. Development of sugarbeet root‐knot nematode resistant cultivars should be facilitated by this identification of a resistance source and the close phylogenetic relationship of the two Beta taxa.