GENETIC GAIN AND VARIABILITY IN FRUIT YIELD AND ASSOCIATED TRAITS OF TOMATO [Lycopersicon esculuntum (L.) Mill] VARIETIES IN ETHIOPIA

Abstract

Tomato is one of the most important dietary vegetable food crops in Ethiopia. It serves as a cash-generating crop to small and large scale farmers and employment for the production and processing in local industries. Notwithstanding this, information on genetic progress achieved over time from a breeding program is useful to develop effective and efficient breeding strategies for tomato improvement is very limited in Ethiopia. The objective of this study was to estimate the magnitude of genetic gain and variability of fruit yield and associated trait. In the present study, 16 (released from 1997 to 2015) tomatoes were evaluated in Sodo district using a randomized complete block design with three replications during 2021 cropping season. The analysis of variance indicated highly significant differences among the varieties for all traits except for number of primary branches per plant and number of seeds per fruit. The average annual rate of increase per year of release for the period 1997-2015 as estimated from the slope of the graph of linear regression of mean fruit yield on a year of variety release was 0.127 t ha-1 with a relative genetic gain of 0.40% yr-1 . Recently released varieties demonstrate a yield improvement of 0.40 kg ha-1 (1.47%) over the oldest varieties in the last 18 years. Marketable yield, fruit diameter, fruit length, fruit width, fruit growth rate per plant and fruit yield per day showed a significant trend of increment. All other traits showed a significant decreasing trend over the year of release. High (509.61%) and low genetic advance (0.74%) was exhibited by fruit growth rate per plant and total soluble solid, respectively. Fruit yield was significantly and positively correlated with fruit diameter, fruit width, fruit length, fruit growth rate per plant, fruit yield per day and marketable yield both at the genotypic and phenotypic levels. Path coefficient analysis showed that the maximum positive direct contribution towards fruit yield was through fruit width, fruit yield per day and marketable yield. The study concluded that inconsistent yield improvement have been achieved in fruit yield through the last 18 years of tomato improvement. Therefore, further effort should be strengthened and continued to achieve more progresses in these and other relevant traits to design appropriate tomato fruit yield improvement strategy in the country