MSc

The present study entitled “Identification of cherry tomato genotypes from F3 segregants of intraspecific cross” was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 2018 - 2019 with an objective to evaluate F3 segregants of the cross between cultivated tomato variety Anagha (Solanum lycopersicum L.) and Solanum lycopersicum var. cerasiforme for morphometric traits and fruit quality specific to cherry tomato and genotyping the superior segregants with SSR markers.
The materials chosen for the experiment was obtained from five F2 plants selected from the cross between Anagha (Solanum lycopersicum L.) and Solanum lycopersicum L. var. cerasiforme (LA2805) done in a completed Ph.D. project of the department. A total of 150 F3 segregants from thirty plants from each F2 family was used for the study.
Observations on nine morphometric traits were recorded in the F3 segregants and based on that twenty superior segregants were selected. These twenty segregants were subjected to fruit quality analysis and molecular marker analysis.
Since the F3 segregants were originated from five F2 families the interfamily and intrafamily variation for each character was assessed.
Among the morphometric traits, plant height did not show much variation between families and within family. Plant height of selected genotypes showing determinate to semi-determinate growth habit with a maximum of 261 cm and a minimum of 72 cm indicating selection in these segregants can lead to the development of a determinate cherry tomato variety. Weight of fruit did not show much variation between the families but within the family there was much variation, all the segregants except (P-3-17)- 11 had fruit weight higher than LA2805 and (P-1-21)- 4 is having almost double the fruit weight of LA2805 parent. Number of fruits cluster-1 of all the segregants were less than LA2805. So, more emphasis should be given on this trait in the selection in further generations.
Dendrogram based on morphometric and fruit quality data revealed that the selected superior F3 segregants grouped into two major clusters. Anagha formed an individual cluster and remaining F3 segregants along with LA2805 constituting major cluster indicating all the small fruited cherry tomato genotypes grouped into one cluster.
Analysis for qualitative traits (Lycopene, vitamin C, pH and TSS) showed that lycopene showed variation between the families and within the family. Lycopene content of all the segregants except (P-3-17)- 11 was higher than LA2805. This is a good indication as higher lycopene content is a valuable character with respect to quality of cherry tomato. Vitamin C content of two of the segregants (P-2-11)- 6 and (P-3-17)- 11 were higher than LA2805 parent indicating this character will have scope for selection in further generations. Intrafamily variation was seen for all the characters except for pH which showed a constant around 4 with maximum pH recorded in (P-5-27)- 20. TSS (%) of fruits did not show much variation between the families but within the family there was much variation with maximum TSS (%) of 6.8 was recorded in (P-3-17)- 11.
Molecular marker analysis was done using ten SSR markers reported as specific to cherry tomato. Out of the twenty segregants, the segregants (P-1-21)- 4 and (P-2-11)- 6 showed the presence of all the SSR markers linked to cherry tomato. The segregants (P-2-26)- 8, (P-3-17)- 11, (P-4-8)- 14 showed eight specific markers of cherry tomato.
A proximity dissimilarity matrix was constructed between the selected segregants and the parents based on the recorded morphometric and fruit quality data. The results of the data revealed that distance from the cherry tomato parent was less than 9.00 indicating that these selected superior segregants were showing more to cherry tomato morphometric and fruit quality traits. The segregants (P-2-26)- 8, (P-3-17)- 11 and (P-4-8)- 14 which had Euclidean coefficient of dissimilarity assessed based on morphometric and fruit quality traits 4.22, 4.60 and 6.19 respectively showed eight specific markers linked to cherry tomato. The segregants (P-1-21)- 4 and (P-2-11)- 6 which showed the presence of all the ten specific markers to cherry tomato had Euclidean coefficient of dissimilarity of 5.54 and 6.53 respectively.
Based on the morphological, biochemical and molecular data five F3 segregants (P-1-21)- 4, (P-2-11)- 6, (P-2-26)- 8, (P-3-17)- 11 and (P-4-8)- 14 were selected to carry forward to further generations for getting a cherry tomato variety with determinate growth habit, higher fruit weight, high number of fruits cluster-1, high lycopene and vitamin C content.