CHARACTERIZATION AND INHERITANCE STUDIES OF DESIRABLE ATTRIBUTES IN TOMATO

Abstract

Fifty nine tomato accessions were characterized for 13 quantitative and 23 qualitative attributes at Agricultural Research Institute, Mingora, Swat, during 2006 under lath-house conditions. Seven selected tomato accessions along with one commercial variety were crossed in half diallel fashion, during 2007 and evaluated for inheritance pattern of important traits during 2008. The germplasm exhibited a wide range for various parameters accompanied with substantial variation for number of NFPC, DFFR, FrW, FL and FW. Based on descriptive statistics, the germplasm was categorized into different groups. Significant correlations of both positive and negative nature were recorded among various attributes both for quantitative and qualitative traits. First four principal components with eigen values >1 contributed 70.0 and 65.3% of the variability for quantitative and qualitative traits, respectively. Quantitative traits viz. DF, DFFR, FrW, pH of juice, LL, LW, FL and FW contributed more positively towards PC1, while DF, PLH, ST, IL and LW contributed toward PC2. Qualitative traits viz. MFIFC, ECMF, MFIFCI and UFS contributed more positively with relatively greater magnitude of variance to PC1, while, FS, FF, and LP contributed towards PC2, ECMF, MFIFC, UFS, FF and SC contributed maximally to PC3, MFIFC, MFIFCI, UFS, SP, and LP contributed positively to PC4, respectively. Tomato accessions were grouped into two main groups comprising two and three clusters for quantitative traits, while, three main groups of five, two and seven sub clusters for qualitative traits, respectively, based on Ward’s method of Euclidean dissimilarity coefficient matrices. Results regarding inheritance of quantitative attributes indicated that parents P28, P30, P45 and P51 performed relatively better per se as well as in hybrid combinations for most of the traits. Hybrids P28×P51, P45×P51 were selected on the basis of early maturity and superiority of yield related fruit attributes. Maximum mid parent heterosis of 53.1 % was observed for NFPC, 20.0% for NFrPC, 32.7% for FL, 10.6% for FW, 48.7 % for FrW, 34.9% for YPP, 59.0% for VL, -53.8% for IL, -2.7% for DFFR, 73.3% for SG, -8.2% for pH of juice, 86.4% for TSS and 34.1% for RS, respectively. Estimates of variances due to GCA and SCA (Griffing’s approach) exhibited preponderance of non-additive gene action for all the traits except for yield plant-1and vine length. All the parents exhibited high GCA effects for multiple traits and hence could be utilized for the development of superior combinations in tomato hybridization programs. The cross combinations with high SCA common for different characters P5(45)×P6(51), P1(E-02)×P7(54) and P2(28)×P3(30)) could be used both for hybrid as well as pure line breeding. Estimates of genetic parameters (Hayman’s approach) revealed preponderance of non-additive gene action for all traits except YPP and DFFR. Unequal positive and negative allelic frequencies among the parents were found for YPP, NFPC, FL, FrW, VL and IL. Directional positive allelic dominance was observed for NFPC, FrW and IL, negative directional dominance was recorded for YPP, NFrPC, DFFR and PLH, while bidirectional dominance of genes was evinced by FL, FW, SG, pH of juice, TSS and RS, respectively. Prevalence of recessive over dominant genes was obvious for YPP, NFrPC, DFFR and PLH, while for all other traits, dominant and recessive genes were exhibiting equal proportion in the parents. Symmetrical gene distribution with positive and negative effects was recorded for NFrPC, DFFR, PLH, SG, TSS and RS, respectively. Heritability estimates in broad sense were high for all traits, whereas, heritability in narrow sense was high for YPP, DFFR and PLH. The graphic analysis revealed over-dominance for all traits except YPP and DFFR, suggesting ineffectiveness of selection in early segregating generations for traits improvement, while the two traits with partial dominance could provide the basis for effective selection in early segregating generations for the improvement of these parameters.