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.

Skin colour, carotenogenesis and chlorophyll degradation mutant alleles: genetic orchestration behind the fruit colour variation in tomato.

The genetics underlying the fruit colour variation in tomato is an interesting area of both basic and applied research in plant biology. There are several factors, like phytohormones, environmental signals and epistatic interactions between genes, which modulate the ripe fruit colour in tomato. However, three aspects: genetic regulation of skin pigmentation, carotenoid biosynthesis and ripening-associated chlorophyll degradation in tomato fruits are of pivotal importance. Different genes along with their mutant alleles governing the aforementioned characters have been characterized in detail. Moreover, the interaction of these mutant alleles has been explored, which has paved the way for developing novel tomato genotypes with unique fruit colour and beneficial phytonutrient composition. In this article, we review the genes and the corresponding mutant alleles underlying the variation in tomato skin pigmentation, carotenoid biosynthesis and ripening-associated chlorophyll degradation. The possibility of generating novel fruit colour-variants using different combinations of these mutant alleles is documented. Furthermore, the involvement of some other mutant alleles (like those governing purple fruit colour and high fruit pigmentation), not belonging to the aforementioned three categories, are discussed in brief. The simplified representation of the assembled information in this article should not only help a broad range of readers in their basic understanding of this complex phenomenon but also trigger them for further exploration of the same. The article would be useful for genetic characterization of fruit colour-variants and molecular breeding for fruit colour improvement in tomato using the well-characterized mutant alleles.

Inheritance pattern of okra enation leaf curl disease among cultivated species and its relationship with biochemical parameters.

Okra production in eastern India at present is severely threatened by whitefly-mediated okra enation leaf curl disease (OELCuD). Identification of resistant genotype and understanding the genetic control and biochemical relationship of OELCuD resistance are prerequisite for developing an effective breeding strategy. This study was conducted employing six populations (P1, P2, F1, F2, BC1 and BC2) of two selected (resistant x susceptible (RxS)) crosses. Associationship between severity of OELCuD and biochemical parameters of parents and hybrids at preflowering and flowering stages was studied. Segregation pattern of the genotypes in F2 generation showing OELCuD reaction of two crosses suggested that two duplicate recessive genes was operative for resistance to OELCuD. Generation mean analysis revealed involvement of both additive and nonadditive effects in the inheritance of disease resistance. Hence, postponement of selection in later generations or intermating among the selected segregates followed by one or two generations of selfing to break the undesirable linkage and allow the accumulation of favourable alleles could be suggested for the development of stable resistant genotype against this disease. Higher peroxidase activity and total phenol content in leaf emerged as reliable biochemical markers for early selection of genotype resistant to OELCuD.

Genetic control of reproductive and fruit quality traits in crosses involving cultivars and induced mutants of tomato (Solanum lycopersicum L.).

Development of mutants and their effective utilization to incorporate desirable traits in tomato would be a sound improvement strategy to develop so called 'smart' tomato variety of the coming century. Initially we developed three induced mutants from two varieties, 'Patharkuchi', a local adapted cultivar and an introduced variety 'Berika', and then three crosses (Berika 9 P Mut-5, Berika 9 P Mut-11, Patharkuchi 9 B Mut-1) were made to involve in these two varieties and their respective mutants. Six generations (P1, P2, F1, F2, BC1 and BC2) of three crosses were utilized to study the genetic control of yield and quality traits, and to study the genetic basis of formation of dark green fruit. The nature and magnitude of gene action controlling the inheritance of 27 quantitative traits differed from one cross to another and from one trait to another, mostly conditioned by nonadditive gene action and duplicate epistasis. The prevalence of duplicate epistasisin three crosses for most of the traits revealed that the pace of progress through conventional selection process would be hindered as this kind of epistasis might result in decreased variation in F2 and subsequent generations. Recurrent selection in biparental progenies would be helpful for exploiting this type of nonallelic interaction through generation of high frequency of desirable recombination and concentration of genes having cumulative effects in the population. We also observed complex genetic behaviour of some of the traits revealing significant epistatic components. Inheritance study of 'dark green fruit' (dg1) of Berika 9 P Mut-5 cross revealed a single recessive gene governing the trait and expressed when the mutant gene was in homozygous recessive condition (designated as dg-1/dg-1).

Bioactive attributes of tomatoes possessing dg, ogc, and rin genes.

We present the results of the first study characterizing new tomato hybrids, possessing dark green (dg), old gold crimson (og(c)), and ripening inhibitor (rin) genes, that determines the bioactive molecules and in vitro antioxidant potential of the peel and pulp of the fruits. The hybrids developed from Berika and BCT-115 (having the dg gene) were superior to those developed from BCT-119 and BCT-111 (carrying og(c) and rin genes, respectively), in relation to their nutritional potential. A wide range (mg/100 g FW) of ascorbic acid (∼21-40), lycopene (∼2-4), ß-carotene (∼0.5-1.7), total flavonoids (∼4.6-20.0), and total phenols (∼16-30) was recorded in the pulp. The peel fraction of the tomatoes was identified as an important reservoir of antioxidant bioactive compounds viz. lycopene (∼8-25), ß-carotene (∼1.6-3.1), total flavonoids (∼42-82), and total phenols (∼59-83). The radical scavenging activity ranged from ∼45-78 and 21-50% in the peel and pulp, respectively, whereas the metal chelating activity was found to range from ∼23-42 and ∼15-26% in peel and pulp, respectively, among all the hybrids. This finding offers a new direction towards the development of new tomato hybrids that possess not only a good shelf life, but also a nutritional status as well. Moreover, utilizing tomato peel as a source of phytochemicals could offer diverse opportunities for nutraceutical and functional food applications.