Applied mutagenesis could improve economically important traits in bitter gourd (Momordica charantia L.).

Mutants with unique characters have played a key role in discovery of gene, mapping, functional genomics and breeding in many vegetable crops, but information on bitter gourd is lacking. Induction of mutation by gamma rays (Co60 source) at five different doses (50 Gy, 100 Gy, 150 Gy, 200 Gy and 250 Gy) was studied in four widely divergent bitter gourd genotypes BG-1346501, Meghna-2, Special Boulder and Selection-1 in M1 generation. Reduction in seed germination percentage, vine length and pollen fertility occurred in M1 generation with the increasing doses of mutagens. LD50 dose for BG-1346501, Meghna-2, Special Boulder and Selection-1 corresponded to 290.76 Gy, 206.12 Gy, 212.81 Gy and 213.49 Gy ᵞ radiation, respectively suggested low to medium doses (200-250 Gy) of gamma rays would be helpful in producing useful and exploitable mutants for further breeding. No remarkable effect of ᵞ radiation on fruit physicochemical characters in M1 generation were observed. M2 generation, raised from two widely divergent genotypes, BG-1346501 and Meghna-2, were screened critically and observed no significant reduction in seed germination and pollen viability, however little damage occurred particularly in vine length. There is possibility of isolating segregates in M2 generation with enhanced nutrient contents at low radiation dose. Highest mutation frequency resulted by treating Meghna-2 at 200 Gy and BG-1346501 at 100 Gy. Both genotype and mutagenic doses influenced mutagenic effectiveness. Spectrum of mutation was very low; number of putative mutants isolated from M2 generation was five in Meghna-2 and three in BG-1346501. Among six putative macro mutants isolated from M3 generation, we could identify two putative mutants, namely Meghna-2 with gynoecious sex form and BG-1346501 with high charantin, appreciable ß-carotene and high ascorbic acid contents having ample promise for further utilization in bitter gourd breeding after critical testing in subsequent generations for estimation of genetic gain and trait heritability to confirm the mutant stability.

Identification and Characterization of Phenylpropanoid Biosynthetic Genes and Their Accumulation in Bitter Melon (Momordica charantia).

Phenylpropanoids and flavonoids belong to a large group of secondary metabolites, and are considered to have antioxidant activity, which protects the cells against biotic and abiotic stresses. However, the accumulation of phenylpropanoids and flavonoids in bitter melon has rarely been studied. Here, we identify ten putative phenylpropanoid and flavonoid biosynthetic genes in bitter melon. Most genes were highly expressed in leaves and/or flowers. HPLC analysis showed that rutin and epicatechin were the most abundant compounds in bitter melon. Rutin content was the highest in leaves, whereas epicatechin was highly accumulated in flowers and fruits. The accumulation patterns of trans-cinnamic acid, p-coumaric acid, ferulic acid, kaempferol, and rutin coincide with the expression patterns of McPAL, McC4H, McCOMT, McFLS, and Mc3GT, respectively, suggesting that these genes play important roles in phenylpropanoid and flavonoid biosynthesis in bitter melon. In addition, we also investigated the optimum light conditions for enhancing phenylpropanoid and flavonoid biosynthesis and found that blue light was the most effective wavelength for enhanced accumulation of phenylpropanoids and flavonoids in bitter melon.