SEASON OF HARVEST OF Amaranthus cruentus L. IN RELATION TO SEED-BORNE MYCOFLORA AND MAJOR SHOOT DISEASES

ABSTRACT

The quality of Amaranthus cruentus L. seeds were influenced both by seasons of harvest and varietal type. The wetness that accompanied harvests of the first (April June) and second (August-October) seasons greatly-reduced the quality of seeds of cultivars. Quality reduction were in the form of seed malformation, discolouratlon and mycelial growth on them. Fifteen fungal species were found to be associated with seeds of the cultivars used. There was a seasonal variability in the occurrence, distribution and the quantity of the seed-borne fungi. Least number a nd mean percentage seed infection were recorded for NHAC1 0-0 while NHAC30 and NHAc33 carried the highest percentage inoculum on the seed testa.  Three of the seed-borne fungi were highly pathogenic on seedlings of two of the cultivars wh Ile two of the fungi were seed transmitted. Six of these seed-borne mycoflora are new records on Amaranthus seeds in Nigeria. For the two year trials, significantly (p=0.05) least incidence (0%) of dieback, stem blight (8%) were recorded during the first season for NHAc33 and NHAc30 while 4% mean leaf blight was obtained from NHAc 100 in the third (December-. February) season. Least mean percentage leaf blight was recorded for all the cultivars also by the third season. Conversely, the second season recorded the highest incidence of all these aerial symptoms of the disease caused by Choanephora cucurbitarum (Berk & Rav.) Thaxt. in all the cultivars. Hot water treatment of infected seeds of all cultivars at 600 C for 6 to 8 minutes completely disinfested them of the seed-borne funyi with consequent increase (7 95%) in seedling emergence. Also soaking in or dusting of infected see ds with a mixture of Benlate-Captafol or single Captafol at lag a~i./kg seed controlled the seed-borne fungi. Pre harvest sprays of Benlate CaptafoI mixture or Captafol at 3.3 kg/ha controlled inflorescence infection and seed-borne fungi with resultant yield increases and seedling emergence 'over the non-treated control.