Combining ability, heritability and genotypic relations of different physiological traits in cacao hybrids

Abstract

Selecting parents and evaluating progenies is a very important step in breeding programs and involves approaches such as understanding the initial stages of growth and characterizing the variability among genotypes for different parameters, such as physiological, growth, biomass partitioning and nutrient translocation to the aerial part. In these cases, facilitating tools can be used to understand the involved gene dynamics, such as diallel crosses and genetic and phenotypic correlations. Our main hypothesis is that the contrasting phenotypes of these parental genotypes of cocoa used are due to genetic factors, and progenies derived from crosses of these parental genotypes are useful for breeding programs related to plant architecture, physiological parameters and translocation of mineral nutrients. We aimed to evaluate the combining abilities in progenies of cacao (Theobroma cacao L) originating from contrasting parents for canopy vigor. Emphasis was given to the evaluation of morphological and physiological parameters and the phenotypic and genotypic correlations to understand the dynamics of the action of the genes involved, as well as in expression profile from genes of gibberellins biosynthesis pathway in the parents. Fifteen F1 progenies were obtained from crosses of six clones (IMC 67, P4B, PUCALA, SCA 6, SCA 24 and SJ 02) that were evaluated in a randomized complete block design with four replicates of 12 plants per progeny, in a balanced half table diallel scheme. It is possible to identify and select plants and progenies of low, medium and high height, as there is expressive genetic variability for the evaluated parameters, some of these on higher additive effects, others on larger nonadditive effects and others under a balance of these effects. Most physiological parameters evaluated show that for selection of plants with the desired performance, no complex breeding methods would be necessary due to the high and medium heritability observed. Strong genetic components were observed from many of the correlations, which indicate the possibility to formulate selection indices for multi-traits, such as dwarfism or semidwarfism, tolerance to increase of leaf sodium concentrations and maintenance of the photosynthetic apparatus integrity under these conditions. Additionally, plants with higher carbon fixation, better water use, higher carboxylation efficiency and greater magnesium accumulation in leaves can be selected.

Genetic combining ability of coriander genotypes for agronomic and phytochemical traits in response to contrasting irrigation regimes

“…The diallel mating design has been used to quantify the nature of gene action which control traits and also to estimate general combining ability (GCA) and specific combining ability (SCA) of parents and crosses, respectively. Examples of its use in a wide array of crops include those of Gao et al [ 28 ] in Agaricus bisporus , Townsend et al [ 29 ] in Artemisia annua , Zhang et al [ 30 ] in barley, Khodadadi et al [ 18 ] in coriander, dos Santos et al [ 31 ] in Theobroma cacao , Pereira et al [ 32 ] in cacao and Hirut et al [ 33 ] in potato. GCA is defined as the average yield of a parental genotype over relevant hybrids and corresponds to additive genetic effects, while the SCA is defined as the yield of a hybrid that deviates from what would be expected if traits were controlled by additive effects alone, i.e.…”

Analisis Daya Gabung dan Korelasi Karakter Jumlah Buah Kakao pada Persilangan Setengah Dialel

“…Pada tanaman kakao, pendugaan daya gabung berbagai karakter penting pada sejumlah genotipe tetua juga telah dilaporkan. Menurut Tan (1990); Nyadanu et al (2012); dos Santos et al (2016); Pereira et al (2017); dan Nyadanu et al (2019) pendugaan daya gabung berbagai karakter pada sejumlah tetua tanaman kakao dengan berbagai metode pendekatan telah dilakukan untuk mengetahui tetua dan atau kombinasi tetua persilangan yang berpeluang untuk menjadi penghasil hibrida baru yang unggul. Di Indonesia, pendugaan daya gabung dan heterosis untuk karakter ketahanan terhadap serangan jamur P. palmivora pada tanaman kakao menggunakan lima genotipe tetua, yaitu klon ICCRI 03, TSH 858, DR 1, ICS 13, dan SCA 6 juga telah dilaporkan oleh Rubiyo, Trikoesoemaningtyas, & Sudarsono (2011) melalui pendekatan metode Griffing 2, dan oleh Tresniawati, Dani, Wicaksono, & Rubiyo (2014) menggunakan metode Griffing 4 untuk karakter tinggi jorket, lingkar batang, serta persentase tanaman berbunga dan berbuah.…”

Gene Action of Cassava Resistance Metabolites to Whitefly (Bemisia tabaci)

“…Since traits controlled by additive gene action are fixable, the pedigree method would be useful in selecting for these metabolites as desirable traits that are controlled by additive gene action since they are fixable [59]. Results of GCA and additive variance being highly significant for traits such as dry matter content [60], dry matter and reaction to thrips [61] mealybug [58] and cassava green mite (CGM) resistance have been reported in cassava [62] as well as various mineral components which are vital for secondary metabolism in cacao [63].…”