Screening and selection of some tomato germplasm collections for high yielding varieties with desirable post-harvest qualities

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Twenty tomato varieties selected from forty-two varieties after a preliminary trial were screened at the Department of Horticulture UST, Kumasi from April 1997 to August 1997 (wet season trial) and then from October 1997 to February 1998 (dry season trial) for their suitability for processing and fresh market. Data collected on vegetative characteristics were growth habit and plant height at flowering. Reproductive and yield characters which were evaluated were number of days to 50% flowering, number of days from flowering to first harvest, number of days from sowing to first harvest, number of flowers at first truss, number of fruits set at first truss, mean fruit weight, yield per plant, and yield/ha. Fruit quality was also determined by assessing fruit shape, shelf-life, total soluble solids, pH, titratable acidity, percent cracked fruits, fruit firmness, colour of firm ripe fruits, fruit diameter, pericarp thickness, and number of locules per fruit. Other characters studied were seed yield, that is, in the number of seeds per fruit, the 1000 seed weight for the size of the seeds, and percent disease incidence. Results showed significant differences (P<0.05) between the varieties in all the parameters evaluated in both the dry and wet seasons with the exception of pH of the fruits, % disease incidence of plants and 1000 seed weight. Varieties NR 46, NR 45 and NR 44 out-yielded the other varieties in both seasons. The quality results showed that the other varieties NR 1, NR 2, NR 3 etc. had lower pH, lower titratable acidity, fewer seeds, fewer locules, thicker pericarp and were firmer and stored longer than NR 46, NR 45 and NR 44. However, these varieties (NR 46, NR 45 and NR 44) had many seeds, more locules and higher titratable acidity and were therefore not suitable for processing. They also had some adaptive qualities in terms of disease resistance, which the others lacked. NR 1 and NR 2 were very promising during the dry season and were recommended for processing. The rest of the varieties lacked the qualities which would make them suitable for processing. They were therefore recommended for the Ghanaian fresh market. An improvement package in the form of further breeding to improve disease tolerance was recommended.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of Master of Science degree in Post-Harvest Physiology, 1999