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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Publications at this Location » Publication #200397

Title: Using Fungal Isolation Rates from Pearl Millet Caryopses to Estimate Grain Mold Resistance

item Wilson, Jeffrey - Jeff

Submitted to: International Sorghum and Millets Newsletter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2006
Publication Date: 12/20/2006
Citation: Chintapalli, R., Wilson, J.P., Little, C.R. 2006. Using Fungal Isolation Rates from Pearl Millet Caryopses to Estimate Grain Mold Resistance. International Sorghum and Millets Newsletter 146-148.

Interpretive Summary: Fungi that infect seeds can affect the stand establishment if seed are replanted, or can affect food quality and food safety if used as feed. Pearl millet is inherently resistant to fungi that produce aflatoxins and fumonisins, but seed and food quality are important criteria that have not been selected for in varieties grown in the U.S. In these experiments a fungal isolation technique confirmed that levels of susceptibility to grain molds affected rate of growth of fungi from the seed. Inherent levels of resistance to fungal colonization and persistence within the kernel may be due to structural or physiochemical differences, such as pre-formed or stress-responsive generation of phenolics, flavonoids, and anthocyanins. Differences in relative susceptibility will allow studies of the mechanisms of resistance, as well as the development new varieties with higher levels of resistance to infection of seeds.

Technical Abstract: Head mold of pearl millet is a disease that occurs in wet or humid conditions especially when varieties exhibit late maturity or when harvest is delayed. Fungi may colonize the caryopsis during grain development and maturation, and may affect germination and vigor if embryos are infected. Kernel bisection and surface sterilization was used to assess total fungi present in pearl millet caryopses to test the hypothesis that the rate at which fungi are recovered from the caryopsis may reflect an innate level of resistance. Four cultivars of pearl millet (2304, OP106, OP303, and Tifgrain (TG) 102) were evaluated on PDA or NS media. Best-fit linear and logarithmic curves were calculated for the recovery of total fungi and Fusarium spp. R2 values for linear and logarithmic curves were high for isolation of total fungi (> 0.933) and total Fusarium spp. (> 0.931). Slopes of best-fit isolation curves were compared to determine if seed from susceptible cultivars yield fungi at a greater rate than those from resistant cultivars. In these experiments, OP303 had greater isolation rates (slopes) for total fungi (P < 0.10) and total Fusarium spp. (P < 0.05) than the other cultivars. The rate of isolation from OP303 is consistent with previous observations concerning the relative susceptibility of this line. This technique may contribute to more general and robust isolation models that represent inherent differences in how well caryopses of different cultivars may be colonized and used as a resource by head mold fungi.