STUDIES ON SWEET-POTATO WITH CHLOROTIC LEAF DISTORTION, CAUSED BY FUSARIUM-LATERITIUM

The response of sweetpotato to inoculation with the chlorotic leaf dis tortion (CLD) pathogen, Fusarium lateritium, was investigated. Analyse s included vine growth, canopy biomass, chlorophyll concentration, net photosynthetic rate and yield on CLD affected (CLD+) and CLD free (CL D-) mericlones (clones derived from meristiem-tip culture) of sweetpot ato genotypes. Gentotype L82-527, showed delayed Vine growth but overc ame the delay in one of two sequential plantings while NC-845, L85-237 , L86-33, 'Porto Rico', 'Jewel' and 'Beauregard' were unaffected. Chlo rotic, newly opened leaves on CLD+ plants had lower chlorophyll a and b concentrations and lower net photosynthetic rates. However, no reduc tions in net photosynthesis were observed when mature CLD+ leaves were measured; a few genotypes had lower chlorophyll content. Chlorotic le af distortion did not lower marketable yields in any genotype. Our res ults suggest that only young foliage is adversely affected by CLD and that the photosynthetic potential is essentially regained in older lea ves with no consequential effect on yield.