Biochemical modifications and corn stunt progression is dependent on maize susceptibility to Spiroplasma kunkelii infection

Once inoculated into maize plants, Spiroplasma kunkelii colonizes the sieve tubes of the phloem and moves systemically within the plant which, in turn, can set off defensive response to prevent infection and the development of corn stunt disease (CSD). The objective of this work was to verify the progress of CSD development along time, both considering disease incidence and PCR detection of S. kunkelii , in two maize hybrids in a greenhouse experiment, after vector-inoculation. Also, we evaluated the biochemical alterations in planta along time in those hybrids inoculated with S. kunkelii , for the total protein, peroxidase and β -1,3-glucanase activities, and carbohydrates. Plants were inoculated with S. kunkelii -infective Dalbulus maidis (Hemiptera: Cicadellidae), whereas control plants were subjected to sham-inoculation. Evaluations were taken in different timepoints, at 10, 20, 40, 60 and 80 days after the end of the 2-day inoculation access period. S. kunkelii was PCR-detected in maize inoculated plants with a difference of 20 days between the hybrids. Also, CSD symptoms were evident earlier in the same hybrid which S. kunkelii was first detected by PCR. There was no alteration on total protein content, but peroxidase and β -1,3-glucanase varied at the last three timepoints for the inoculated hybrids. There was a substantial increase of carbohydrates at 60 days after inoculation in one of the inoculated hybrid. The biochemical modifications together with the successful molecular detection of CSD pathogen and CSD symptoms onset in the hybrids inoculated with S. kunkelii evidence the synchronic dynamics of compounds imbalance potentially involved in defensive mechanisms and plant nutrition against infection with the advancement of the infection process in planta , and this occurs differentially within hybrids, suggesting that they respond with distinctive susceptibility to S. kunkelii infection.