Estimates of genetic parameters of pigments and agronomic traits in green and purple lettuce

Abstract

Understanding genetics and the gene interactions involved in the expression of certain characteristics becomes a determining factor for better exploration of its use. The development of breeding programs that combine one or more desirable trait into a single cultivar is directly impacted by this lack of knowledge of the genetic bases involved. The objective of the present study was to estimate the genetic parameters involved in pigment expression and agronomic characteristics in lettuce. Parental evaluations of lettuce, P1 (green) and P2 (purple) parental generations, the segregating generations F1 and F2, and the backcrosses Bc1 and Bc2 originating from the UFU-Crespa199#1#1 x UFU-Albina#2 crossing were evaluated. The chlorophyll and anthocyanin contents, number of leaves and plant diameter were evaluated. The study was conducted by testing all generations and the estimates obtained by averages and variances. Indications of polygenic or oligogenic inheritance were verified by the characteristic number of leaves, plant diameter, and anthocyanin content. The complete and additive-dominant models satisfactorily explained the performance of the variables, except the anthocyanin content.

Genetic parameters and selection of biofortified lettuce genotypes based on selection indices

“…Characters with a high h 2 indicate a high component of the inheritable fraction of the variation (genetic component) in their phenotypic expressions, demonstrating that gains can be achieved through visual selection (Silva et al, 2019), as performed in the present study Peixoto et al (2020) estimated the genetic parameters of eight variables analyzed in 25 lettuce genotypes from the same breeding program (generation F7) and also found high h 2 values for the number of leaves (91.42%), SPAD index (95.96%), and plant diameter (72.77%), confirming the high magnitude of h 2 for these traits. In contrast to this study, Oliveira et al (2019) found low heritability estimates of 6.94% for the chlorophyll index, which may be related to the fact that although it was carried out in the same experimental area with the same cultural practices, different parents were used. Thakur et al (2016) found a heritability value of 58.10% for β-carotene in lettuce, which may have been influenced by the fact that the experiment was conducted under protected conditions.…”

“…Thirteen genotypes were selected by all indices, thus presenting suitable agronomic traits that are promising for advancing generations within the breeding program aimed at obtaining biofortified lettuce strains. SH -Smith (1936) and Hazel (1943); MM -Sum of ranks- Mulamba & Mock (1978); WI -Base-index- Williams (1962) Table 5. Indication of the top 17 lettuce genotypes, selected by the classic indexes proposed by Smith (1936) and Hazel (1943) (SH), Mulamba & Mock (1978) sum of ranks index (MM), and Williams base index (1962) (WI)…”

“…For the Williams index, the following index was used as the selection criterion (Eq. 13): The selection criterion used was increased for all traits for direct and indirect selection (Mulamba & Mock, 1978;Smith, 1936;Hazel, 1943;Williams, 1962) indices. The economic weight adopted was the coefficient of genetic variation for each variable, as recommended by Cruz (2012).…”

“…Currently, there are no commercial lettuce cultivars available that have desirable agronomic traits along with a high carotenoid concentration. This may be due to the limited knowledge of the variables that govern the genetic inheritance of chlorophyll production and the main agronomic traits of interest in lettuce (Oliveira et al, 2019).…”

Fenotipagem por imagem, estimativas de parâmetros genéticos e índices de seleção em alface biofortificada

“…A razão CVg/CVe apresentou valores superiores à unidade para as variáveis NF (1,04), ANT (1,21), PEND (1,63) (AZEVEDO et al, 2014;OLIVEIRA et al, 2019;SILVA et al, 2019) e ANT (OLIVEIRA et al, 2019), corroborando os resultados do presente trabalho.…”