نوع مقاله : کامل علمی - پژوهشی
نویسندگان
1 مؤسسه تحقیقات اصلاح و تهیه بذر چغندرقند، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرج، ایران
2 بخش تحقیقات چغندرقند، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان آذربایجان غربی، سازمان تحقیقات، آموزش و ترویج کشاورزی،
3 مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان همدان، سازمان تحقیقات، آموزش و ترویج کشاورزی، همدان، ایران
4 بخش تحقیقات چغندرقند مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان فارس، سازمان تحقیقات، آموزش و ترویج کشاورزی، شیراز، ایران.
5 مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان خراسان رضوی، سازمان تحقیقات، آموزش و ترویج کشاورزی، مشهد، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Extended Abstract
Introduction
Sugar beet (Beta vulgaris L.) stands as a pivotal cornerstone in the global agro-industrial sector, serving as one of the primary sources of sucrose and bioethanol production. Despite significant agronomic advancements, the sustainability of sugar beet cultivation is incessantly compromised by biotic stressors, particularly soil-borne pathogens which can cause precipitous declines in root yield and sugar content. Among these, Rhizomania, caused by the Beet necrotic yellow vein virus (BNYVV) and transmitted by the vector Polymyxa betae, and Rhizoctonia root rot, caused by the fungal pathogen Rhizoctonia solani, represent two of the most devastating diseases worldwide. The simultaneous occurrence of these pathogens in major production regions necessitates the development of dual-purpose cultivars that exhibit not only high yield potential but also robust genetic resistance. Furthermore, given the diverse pedoclimatic conditions of sugar beet growing regions, the genotype-environment interaction (GEI) plays a critical role in phenotypic expression. Consequently, relying solely on yield potential is insufficient; identifying stable genotypes that maintain performance across varying environmental gradients is imperative. This study was conceptualized to evaluate the yield stability and pathological response of newly developed sugar beet hybrids—derived from the introgression of foreign germplasm with locally adapted domestic pollinators—against the dual threats of Rhizomania and Rhizoctonia root rot.
Materials and Methods
The genetic material for this investigation comprised 32 novel hybrids generated through a mating design. These hybrids were synthesized by crossing two single crosses (as female parents with established resistance backgrounds) with 16 diverse pollinator lines (as male parents). To provide a benchmark for performance, four commercial cultivars were included as checks. The agronomic evaluation was conducted through multi-environment trials across four distinct agro-ecological zones in Iran, Mashhad, Shiraz, Miandoab, and Hamedan. These locations were selected to represent a wide range of environmental conditions and natural disease pressures. The field experiments utilized a randomized complete block design with four replications at each site. Agronomic traits, specifically root yield (RY), sugar content (SC), and white sugar yield (WSY), were q uantified. Parallel to the field trials, a rigorous pathological assessment for resistance to Rhizoctonia root rot was conducted under controlled microplot conditions to minimize environmental error and ensure uniform infection pressure. This experiment involved artificial inoculation of the soil with the highly virulent Rhizoctonia solani isolate Rh133, grown on corn grain medium. The resistance to Rhizomania was evaluated under natural infection conditions in infested fields, capitalizing on the presence of BNYVV. Statistical analyses included a combined analysis of variance to assess the main effects of genotype, environment, and their interaction. Stability analysis was performed to identify genotypes with minimal variance across environments, ensuring that selected hybrids possess both high performance and dynamic stability.
Results and Discussion
The quantitative genetic analysis revealed that the main effects of genotype and environment, as well as the GEI, were highly significant (P≤0.01) for both RY and WSY. The significance of the GEI indicates that the relative ranking of the hybrids varied across the four tested locations, underscoring the necessity of stability indices for genotype selection. In the first set of experiments, stability and mean performance analysis highlighted hybrids 15, 7, 14, and 13 as the superior genotypes. These hybrids demonstrated a synergistic combination of high WSY and low interaction variance, suggesting their suitability for a broad range of environmental conditions. In the second experimental set, hybrids 14, 6, 12, and 11 emerged as the top-performing candidates, exhibiting exceptional agronomic traits superior to the trial means and competitive with the commercial checks. Regarding pathological traits, the screening for Rhizomania resistance indicated a high efficacy of the resistance genes present in the parental lines. Almost all experimental hybrids displayed high levels of resistance, scoring between 1 and 3 on the standard disease severity scale (where 1 indicates no symptoms and 9 indicates plant death). This suggests that the genetic background of the single crosses successfully conferred BNYVV resistance to the progeny. The evaluation of resistance to Rhizoctonia solani revealed significant genetic variability among the hybrids. In the first experiment, hybrids 12 and 9 recorded disease severity indices of 3.95 and 4.59, respectively. In the second experiment, hybrids 5, 3, and 1 demonstrated promising tolerance levels with indices of 4.56, 4.69, and 4.75, respectively. These scores are particularly significant given the virulence of the Rh133 isolate used in the artificial inoculation.
Conclusion
The significance of the GEI reaffirms that breeding for specific adaptation or wide stability is crucial for maximizing genetic gain in sugar beet. The identification of hybrids such as 14 and 12, which appeared in top rankings for either yield stability or disease resistance, offers promising genetic resources for future breeding programs. Crucially, the study successfully identified genotypes that possess dual resistance (or high tolerance) to both Rhizomania and Rhizoctonia, addressing a major gap in current disease management strategies. The hybrids identified with moderate resistance to Rhizoctonia, combined with their high Rhizomania resistance and competitive yield, represent viable alternatives to current commercial cultivars, potentially reducing the reliance on chemical fungicides and enhancing the economic stability of farmers in infested regions. In conclusion, this research has led to the isolation of superior sugar beet hybrids that harmonize yield potential, phenotypic stability, and biotic stress resistance. These genotypes are recommended for release or further pre-commercial trials in regions prone to Rhizomania and Rhizoctonia root rot complexes.
Keywords: Genotype-environment interaction, Microplot, Soil-borne diseases, Susceptibility.
References
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کلیدواژهها [English]
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