RECOVERY OF Cephalosporium maydis THE CAUSAL AGENT OF MAIZE LATE WILT DISEASE FROM VARIOUS PLANT PARTS WITH SYMPTOMATIC OR ASYMPTOMATIC INFECTION AND ANATOMICAL CHARACTERS OF TOLERANT AND SUSCEPTIBLE HYBRIDS.

Recovery percentage of C. maydis, the causal agent of maize late wilt disease, was determined under greenhouse conditions in 2010 in three plant parts; i.e. second internode of stalk above the ground level (SIS), ear shank internode (EI) and tassel internode (TI), of ten maize hybrids with and without symptoms. The two maize hybrids, SC155 (susceptible) and SC124 (tolerant) were selected from the previous experiment to assess recovery percentage and seven anatomical parameters in 2011. These parameters were; vascular bundles number (VBN) / 0.49 mm² of area of stalk section, metaxylum cells number (MCN), protoxylum cells number (PCN), metaxylum cells diameter (MCD), protoxylum cells diameter (PCD), maximum of scleronchyma cell layers number (MASCLN) and minimum of scleronchyma cell layers number (MISCLN). These parameters were measured at the same time in cross sections of symptomatic (SI), asymptomatic (AI) and non infected (NI) plants by the agent. Recovery percentage in plants with symptomatic infection differed among hybrids depending on the degree of tolerance. The recovery percentage ranged from 10 to 85 % in SIS, from 10 to 85 % in EI, and from 10 to 69 % in TI.  In apparently healthy plants, recovery percentage ranged from 10 to 70 % in SIS, from 0 to 50 % in EI and from 0 to 20 % in TI. However, in 2011 experiment, the recovery percentage of the susceptible hybrid was significantly higher than those of the tolerant ones in all three plant parts with or without symptoms. Concerning the measurements of anatomical parameters, the susceptible maize hybrid had number of vascular bundles / 0.49 mm² of section area significantly higher than those of the tolerant ones only in plant sections with symptomatic and asymptomatic infection. Also tolerant plants with SI, AI, and NI showed significantly higher levels in maximum number of scleronchyma cell layers than the susceptible ones indicating that disease tolerance was associated with specific structure.  In summary, C. maydis not only had the ability to invade both the tolerant and susceptible maize plants but also moves from above ground internode to ear shank internode and tassel internode and may reach to the kernels through the cob and completing its disease cycle.