Evaluation of some introduced fresh market tomato (Solanum lycopersicum L) for genetic variability and adaptability in Ghana using morphological and molecular markers.

The tomato sector in Ghana has failed to realize its full potential, in terms of attaining yields comparable to other countries, sustaining its processing plants and improving livelihoods of those households involved in tomato production. The need therefore, to evaluate some introduced tomato varieties in order to identify varieties with good attributes and make recommendation to tomato farmers cannot be overemphasized. This study thus looked at some introduced tomato varieties from the USA for adaptability to environmental conditions in Ghana with focus in the Ashanti region. Field experiments were conducted at the Department of Horticulture, KNUST and Horticulture Division of CSIR – Crops Research Institute (CRI), Kwadaso. Four tomato varieties from the USA and a local check from CSIR- CRI, Kumasi, Ghana were planted to plots of 264 m2 (12 m x 22 m). Data were taken as soon as plants were established on the fields. These included number of days to flowering (1st, 50%, 100%), plant height, stem length, stem diameter, number of leaves under 1st inflorescence, number of flowers per inflorescence, growth habit, number of plants harvested, number of marketable and non- marketable fruits, average weight of marketable fruits, total marketable fruit weight and yield (tonnes per hectare), fruit shape, disease and insect pest incidence, post-harvest characters such as brix and shelf life. A sensory evaluation was carried out at CRI, Kwadaso. A total of twenty volunteers participated in a sensory test. Selected tomato fruits from each variety were used in preparing soup, stew and salad. Accessions were labeled as 100, 200, 300, 400, and 500 without displaying the actual variety names to the participants. They were scored for taste, flavour, sweetness, appearance, colour and mouth-feel. Additionally, PCR analysis was done using fifteen (15) SSR primer pairs obtained from Metabion International Laboratory, Germany to determine the diversity existing among the tomato varieties. Agronomic characters of the tomato varieties showed significant differences in almost all the genotypes across locations. The highest average plant height at both locations was recorded on Shasta (KNUST-98.2 cm and Kwadaso-84.1 cm). Likewise varied differences were also found on the number of inflorescence per plant and flowers per inflorescence. The tomato varieties showed one to two growth patterns; determinate or semi determinate. Low disease infections and pest pressure were observed during the growing season and this may be due to good agronomic practices carried out on the field. On the sensory evaluation test, significant differences were only found in the soup and stew preparations on their appearance and flavour respectively. This was evident on OP-B149, Shasta for the soup appearance and Heinz, OP-B155 for stew flavour. The 15 SSR markers used for genetic characterization revealed substantial genetic variation among the tomato varieties studied. Based on yield (t/ha), number of plants per plot (establishment), marketable fruits, average fruit weight, plant height and shelf life, Shasta and CRI-POO were rated high in terms of adaptability.

Source: KNUST