Stalk Rot Fungi Affect Leaf Greenness (SPAD) of Grain Sorghum in a Genotype- and Growth-Stage-Specific Manner

Abstract

Stalk rots are among the most prevalent and destructive sorghum diseases worldwide. Although experimental evidence is limited, delayed postflowering senescence due to the staygreen trait is accepted as a physiological means of stalk rot resistance. Staygreen has been shown to be correlated with chlorophyll content (as measured by a soil and plant analytical development [SPAD] meter). Field experiments were conducted to test the effects of Fusarium stalk rot and charcoal rot on SPAD readings at three developmental stages, to test whether staygreen genotypes are more resilient to stalk-rot-mediated chlorophyll degradation, and to examine the relationships between SPAD and stalk rot resistance and tolerance when plants were inoculated with causal organisms. Staygreen and nonstaygreen lines (two) and hybrids (two) established in the field were inoculated with Fusarium thapsinum, F. proliferatum, F. andiyazi, and Macrophomina phaseolina at 14 days after flowering. SPAD readings were obtained at soft-dough, hard-dough, and physiological maturity. Most pathogens significantly reduced the SPAD of the genotypes over the mock-inoculated control at three developmental stages. The stalk-rot-resistant and staygreen check line, SC599, showed a remarkable feature of negative senescence from soft dough to physiological maturity under disease pressure. Disease severity was significantly and negatively correlated with SPAD at all developmental stages, revealing the potential impact of the staygreen trait on stalk rot resistance. The difference between control and pathogen-treated total seed weight per panicle (i.e., tolerance) was significantly and positively correlated with the difference between control and pathogen-treated SPAD at physiological maturity, demonstrating the ability of staygreen trait to enhance stalk rot tolerance under disease pressure.

Dynamics of host glutathione and glutathione related enzymes in Macrophomina phaseolina-sorghum bicolor interaction

“…Charcoal rot is a high priority fungal disease in sorghum [ Sorghum bicolor (L.) Moench], causing tremendous crop losses where ever sorghum is grown (Tarr, 1962, Tesso et al ., 2012). Recent reports revealed the M. phaseolina ’s ability to negatively affect the physicochemical properties of sorghum grain (Bandara et al, 2017 a), sorghum yield components (Bandara et al, 2017 b), leaf greenness (Bandara et al, 2016) and sweet sorghum biofuel traits such and juice yield and biomass (Bandara et al, 2017 c). Our recent genes expression and functional investigations provided exciting insights into induced charcoal rot disease susceptibility in grain sorghum through up-regulated host oxidative stress after M. phaseolina infection (findings have been submitted for publication).…”

Response of Sorghum Enhanced in Monolignol Biosynthesis to Stalk Rot Pathogens

“…The transgenic lines overexpressing SbMyb60 were significantly shorter than the wild-type line, whereas the lines overexpressing SbCCoAOMT were not significantly different in height than the wild-type (Table 4). Because plant maturity can affect responses to stalk pathogens (Bandara et al 2016), plant stage was noted for individual plants, based on a 1 to 8 scale. The wildtype lines were in the milk to soft dough stages (Table 4).…”

“…1947, also triggers deterioration of the stalk, and the remaining vascular bundles become covered in dark mycelia with small black sclerotia as it progresses, which gives the disease its name (Kumari et al 2015;Mughogho and Rosenberg 1984;Rao et al 1980). Because of the numerous pathogens causing sorghum stalk rots and their multiple hosts, classical gene-for-gene resistance is not possible (Bandara et al 2016;Rao et al 1980;Tesso et al 2010). Development of sorghum with antimicrobial cell wall components or enhanced defense signaling may be an alternative breeding approach.…”

Host lipid alterations afterMacrophomina phaseolinainfection contribute to charcoal rot disease susceptibility in grain sorghum: Evidence from transcriptomic and lipidomic data

“…Charcoal rot is a high priority fungal disease in sorghum [ Sorghum bicolor (L.) Moench], causing tremendous crop losses wherever sorghum is grown (Tarr, 1962, Tesso et al ., 2012). Recent studies have shown that charcoal rot can negatively affect the grain sorghum physical and chemical properties (Bandara et al, 2017a), yield parameters (Bandara et al, 2017b), and leaf greenness (Bandara et al, 2016), as well as the key biofuel traits of sweet sorghum (Bandara et al, 2017c). There are limited options available to control charcoal rot disease.…”