|ZOBIOLE, LUIZ - Dow Agrosciences|
|KASSEM, ABDELMAJID - Fayetteville State University|
Submitted to: Food and Nutrition Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2014
Publication Date: 10/1/2014
Citation: Bellaloui, N., Mengistu, A., Zobiole, L.H., Abbas, H.K., Kassem, A. 2014. Resistance mechanisms to toxin-mediated charcoal rot infection in maturity group III soybean: role of seed phenol lignin soflavones sugars and seed minerals in charcoal rot resistance. Food and Nutrition Sciences. 5:1843-1859.
Interpretive Summary: Charcoal rot is a soybean disease in the midsouth of USA that causes yield loss and poor seed quality, especially under drought conditions. Since there are no commercial varieties that are resistant to charcoal in the market, understanding the defense mechanism of soybean to this disease is crucial to minimize its negative impact on soybean yield and quality. The objective of this research was to investigate the effect of charcoal rot infestation on seed phenolics (compounds that are thought to be involved in disease resistance and defense mechanisms of plants), sugars, and minerals. A two-year field experiment was conducted at Stoneville, MS using susceptible and moderately resistant varieties. The results showed that the moderately resistant variety had higher concentrations of seed phenolics, total isoflavones, and seed coat lignin under infested and non-infested conditions and under irrigated or non-irrigated conditions compared with the susceptible variety. The same general trend was found for seed potassium, calcium, phosphorus, manganese, zinc, and copper concentrations in the moderately resistant variety compared with the susceptible genotype. The higher levels of stachyose and raffinose (sugars) under infestation and under nonirrigation reflect the role of these sugars under drought and disease stresses to protect the seeds against damage during seed maturation. The research demonstrated that differences between susceptible and moderately resistant genotypes for seed phenolic compounds such as lignin and isoflavones may indicate their association with resistance to charcoal rot. The results obtained from this research may justify soybean breeders using phenolic compounds as biomarkers to select for soybean resistance to charcoal rot.
Technical Abstract: Charcoal rot is a disease caused by the fungus Macrophomina phaseolina (Tassi) Goid, and thought to infect the plants through roots by a toxin-mediated mechanism, resulting in yield loss and poor seed quality, especially under drought conditions. The mechanism by which this infection occurs is not yet understood. Although moderately resistant soybean germplasm is available, there are no commercial soybean cultivars that are completely resistant to charcoal rot disease. The objective of this research was to further investigate the role of phytochemical compounds that may be associated with the defense mechanism in soybean using susceptible (S) (DK 3964) and moderately resistant (MR) (AG 3905) soybean genotypes to charcoal rot. A two-year field experiment was conducted to evaluate the effects of charcoal rot on seed phenol, isoflavones, seed coat lignin and mineral concentration by infesting the soil with charcoal rot (infested soil conditions, INF) or control (non-infested soil conditions, NINF). Assessment of inoculation, disease, and rating for root and stem severity were also assessed. The results showed that the moderately resistant genotype had higher concentrations of seed phenolics, total isoflavones, and seed coat lignin under infested and non-infested conditions and under irrigated or non-irrigated conditions compared with the susceptible genotype. The same general trend was found for seed K, Ca, P, Mn, Zn, B, and Cu concentrations in the moderately resistant genotype compared with the susceptible genotype. Our research demonstrated that differences between susceptible and moderately resistant genotypes for seed phytochemical components may be associated with resistance to charcoal rot infestation.