Breeding and Biotechnology of Plant and Flower
Farhad Shokouhifar; Mojtaba Mamarabadi; Sahba Toosi
Abstract
Introduction
Melon (Cucumis melo L.) is a diploid plant with (2n = 2x = 24) chromosomes, dicotyledonous and annual, which has been receiving lots of attention for its biological characteristics and economic value for a long time. Iran with production of about 1.6 million tons per year ranks third in ...
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Introduction
Melon (Cucumis melo L.) is a diploid plant with (2n = 2x = 24) chromosomes, dicotyledonous and annual, which has been receiving lots of attention for its biological characteristics and economic value for a long time. Iran with production of about 1.6 million tons per year ranks third in melon production in the world after China and Turkey. Vascular wilt caused by the soil borne fungus Fusarium oxysporum f. sp. melonis is one of the most important diseases causing damage to the melon plant. Due to the survival of this fungus in the form of chlamydospores in the soil and plant debris its control has been a difficult challenge so that, the only way to deal with this disease is to use resistant cultivars. The present study was conducted to characterize morphologically different melon cultivars with varying levels of resistance against Fusarium vascular wilt. Furthermore, the presence pattern of two MRGH genes belonging to the MRGH21 linkage group was tracked in the genome of the melon line, and their variations were defined. Moreover, the potential for using these genes in gene-assisted selection was investigated.
Materials and Methods
Five different varieties of melon named Charentais T, Charentais Fom1, Charentais Fom2, BG-5384 and the local cultivar Khatouni were grown under greenhouse conditions. Different characteristics of the plant, including leaf shape, male flowers, female flowers and normal flowers, and after harvesting the fruits, fruit weight, fruit diameter and length, diameter of flesh and middle cavity. The differentiation of resistant and sensitive cultivars was investigated based on the evaluated morphological traits. Additionally, the presence patterns of resistance genes were examined in the genomic data of the aforementioned melon cultivars. The genomic analysis of melons aimed to locate the MRGH21 linkage group, which carries several resistance genes. The sequence of this linkage group was tracked from two gene bank databases in NCBI and MELONOMICS database.
Results
Based on the obtained results, although it was possible to differentiate melon cultivars based on morphological traits, but since the study of these traits in the evaluation of a large number of samples in selective studies is a very time-consuming and costly task. Therefore, the presence pattern of resistance genes were analyzed in the genomic data of different melon cultivars. The sequence between two genes MRGH12 and MRGH13 including MRGH21 linkage group as one of the linkage groups carrying a number of resistance genes on Ch09 chromosome was retrieved form two gene bank databases in NCBI and MELONOMICS. Due to the presence of multiple point mutations in the genomic data, the MRGH13 gene sequence was selected for investigation in melon cultivars. Specific primers, PSh21-F/R, were designed to track part of this gene's sequence. The tracking results showed that a single specific band, corresponding to the expected size, could be detected in the cultivars Charentais Fom1 and BG-5384. Sequence analysis using the InterPro network tool confirmed the possible role of the protein coded by the MRGH13 gene. It was identified as a member of the protein family carrying leucine-rich repeat sequences, including the TIR, NB-ARC, and LRR domains.
Discussion
Attaining suitable markers to distinguish melon cultivars resistant to Fusarium wilt disease can support the development of breeding programs with higher accuracy and speed. The results of the present study showed that based on the morphological traits such as leaf shape, the presence of full flowers, and the number of petals, some differences can be observed between different melon cultivars, but the noteworthy point is that in selection programs searching for these morphological traits will be a very time-consuming and expensive task due to the large number of investigated samples. Therefore, if molecular markers related to the resistance trait are available, the efficiency of breeding programs is expected to increase significantly. In the present study MRGH13 gene was selected to be investigated for tracking in melon cultivars and specific primers were designed to track part of the sequence of this gene. The tracking results showed that a single specific band could be detected in the cultivars Charentais Fom1 and BG-5384. Biological processes related to MRGH13 protein in the QuickGO network tool showed its relevance in the signaling pathway that regulates immune responses. In future studies, it is suggested to evaluate the ability to distinguish resistant cultivars based on resistance genes, including the MRGH13 gene, in a larger number of samples. Moreover, considering to the predicted functions of MRGH13 protein, more investigation on its interaction with other resistance proteins as well as proteins of pathogenic agents can be useful for identification of its functional role in resistance.
