Botanical Identification and Genetic Diversity in Melons From Family Farming in the State of Maranhão

Abstract

-The aim of this work was to perform botanical identification and to estimate genetic diversity in two sequential inbred generations (progenies S 1 and S 2 ) of melon accessions from traditional agriculture in the state of Maranhão, in order to generate useful information for commercial melon breeding. Two field experiments were carried out in a completely randomized block, using four replicates of 15 accessions from a first selfing cycle in 2013, and three replicates of 25 subaccessions (generation S 2 ) in 2014. Flower and fruit descriptors were measured to obtain quantitative and qualitative data, in addition to a systematized photographic documentation of fruit for visually comparing the progenies S 1 and S 2 . Distance matrices for quantitative and qualitative data were obtained and used to perform a joint analysis and UPGMA method. Large genetic diversity was found in the accessions analysed, since the presence of melon progenies was observed in the Cucumis melo ssp. agrestis, with its botanical varieties momordica and conomom, and of the Cucumis melo ssp. melo, with the botanical varieties cantalupensis and chandalak. Divergence analysis showed the formation of three groups in generation S 1 and four groups in S 2 . However, the groups were not separated either by subspecies or by botanical variety. Thus, in addition to the large genetic diversity among and within melon accessions from family farming in the state of Maranhão, the progenies presented a large introgression of traits of the different subspecies and their botanical varieties due to the reproductive system and seed management of these species.Keywords: Botanical variety. Cucumis melo L.. Endogamic progenies.CLASSIFICAÇÃO BOTÂNICA E DIVERGÊNCIA GENÉTICA EM MELÕES DA AGRICULTURA FAMILIAR MARANHESE RESUMO -O trabalho teve como objetivos realizar a classificação botânica e estimar a diversidade genética em duas gerações endogâmicas sequenciais (progênies S 1 e S 2 ) de acessos de melão da agricultura familiar do Maranhão, visando gerar informações úteis para o melhoramento do melão comercial. Foram conduzidos dois experimentos de campo em blocos casualizados completos, com quatro repetições e 15 acessos em 2013 e, três repetições e 25 subacessos em 2014. Para avaliação dos acessos foram aplicados descritores quantitativos e qualitativos de flor e fruto, além de uma documentação fotográfica sistematizada dos frutos com análise visual, comparando os frutos das gerações S 1 e S 2 . Foram obtidas as matrizes de distância nos dois tipos de descritores e se fez a análise conjunta e em seguida realizou-se o agrupamento pelo método UPGMA. Verificou-se que nos acessos analisados, existe uma grande diversidade genética, pois foram encontradas progênies de melão da subespécie agrestis e suas variedades botânicas momordica e conomom e da subespécie melo com as variedades botânicas cantalupensis e chandalak. A análise de divergência na geração S 1 mostrou a formação de três grupos e na geração S 2 foram formados quatro agrupamentos, entretanto os grup...

Genetic parameters in melon sub-accessions from traditional agriculture

“…The data of analysis of variance showed significant differences among melon sub-accessions for all characteristics evaluated (Table 2), denoting the existence of genetic variability among sub-accessions. Similar results were found in previous studies on melon accessions from traditional agriculture (AMORIM et al, 2016;MACÊDO et al, 2017;ANDRADE et al, 2019), supporting those found in the present study and, therefore, denoting the possibility of selecting agronomically superior accessions for the characteristics analyzed (CRUZ; REGAZI; CARNEIRO, 2012). Means followed by same lowercase letter in the columns, or uppercase letter in the rows, are not statistically different from each other by the Scott Knott test at 5% significance.…”

“…Prolificacy and fruit cavity diameter presented only 18.5% variation, highlighting the variety makuwa and botanical varieties not defined (ND), respectively. Regarding the other characteristics, the highest variations were found for sub-accessions of ND varieties (Table 2); these variations are probably because of the high variability among plants within the sub-accessions, which is due to the introgression of alleles among different botanical varieties (MACÊDO et al, 2017;AMORIM et al, 2016).…”

“…The high variability found among sub-accessions is partially due to existing differences among plants within each sub-accession. Studies on melon germplasm showed a high variation among accessions (DANTAS et al, 2012;ARAGÃO et al, 2013;TRIMECH et al, 2013;YILDIZ ;AKGUL;SENSOY, 2014;ANDRADE et al, 2019) and among plants within accessions (AMORIM et al, 2016;MACÊDO et al, 2017). 1 SV = source of variation; DF = degrees of freedom; EARL = earliness; FW = fruit weight; FD = fruit diameter; FL = fruit length; FCD = fruit cavity diameter; FCL = fruit cavity length;; PT = pulp thickness; SS = soluble solid contents (°Brix); PROL = prolificacy; G = genotype; E = environment; G×E = genotype-environment interaction; RES = residue; CV = coefficient of variation; Fmax = ratio between the highest and lowest residual mean square; **, * = significant at 1% and 5% significance, respectively; ns = not significant.…”

“…Previous studies using melon germplasm from family farming showed the existence of high variability among melon accessions (DANTAS et al, 2012;ARAGÃO et al, 2013;AMORIM et al, 2016;MACÊDO et al, 2017;ANDRADE et al, 2019). However, some important characters for the improvement of melon were not emphasized in these studies, mainly regarding characteristics of some botanical varieties (PITRAT; HANELT; HAMMER, 2000), which are believed to be important factors and, therefore, should be considered.…”

“…Melons from traditional agriculture are an important source of alleles for breeding programs. Although several studies have shown variability among melon accessions (AMORIM et al, 2016;MACÊDO et al, 2017), there is no study on this germplasm, focused on generating information for selection of genotypes. It denotes the need for studies using melon germplasm from family farmers for morphological characterization of different botanical varieties based on genetic parameters, focused on selecting superior genotypes.…”