Relationship among seed germination and other characters associated with fusarium grain mould disease in sorghum (Sorghum bicolor L. Moench) using path coefficient analysis

Fusarium grain mould disease (FGMD) is a part of the grain mould disease complex and is caused by Fusarium species which are capable of infecting spikelet tissues at anthesis or immature grain up to physiological maturity. The disease causes severe losses in quality, viability and germination of sorghum seed. To determine the effect of FGMD associated characters (panicle grain mould score (PGS), seed rot, amount of Fusarium, and non-Fusarium infected seed and seed weight) on seed germination and to find the inter-relationship among these characters, replicated field trials were conducted with 36 sorghum recombinant inbred lines (RILs) during 2009 and 2010 at Hyderabad, India. PGS showed a strong positive relationship with seed rot and seedborne Fusarium (P < 0.01). Seed rot showed a significant positive relationship with seedborne Fusarium and a negative relationship with seed weight and germination (P < 0.01). Frequency of seedborne Fusarium on mould-infected sorghum seed had a strong negative correlation with that of non-Fusarium infection (P < 0.01), suggesting interactions between them in causation of grain mould in sorghum. Path coefficient analysis for seed germination revealed that seed rot (-0.43) and PGS (-0.28) had a maximum direct effect, accompanied with less interference by other factors, on seed germination. Seed rot has emerged as the most important parameter for determining seed germination in moulded sorghum grains. Few promising RILs that produced minimum premature seed rot were identified. The RIL numbers 144, 156 and 159 were superior to controls for many FGMD associated characters and could be useful sources for improvement of FGMD resistance.