Assessment of Genetic Diversity in Guava (Psidium guajava) Germplasm Using Microsatellites

Although the varietal diversity is fairly rich in guava, most varieties lack one or more desirable characters. Hence, attempts were made for improving specific traits, viz., attractive pink pulp colour, soft seeds, medium fruit size, high TSS and high ascorbic acid. Genetic diversity analysis is a prerequisite for identifying potential parents in breeding programs and germplasm conservation. Molecular characterization helps discriminate closely-related genotypes, as, this technique is unaffected by environment, rendering it more reliable. In this study, 48 polymorphic SSRs screened from a total of 115 SSR markers were used for analyzing marker segregation in 72 guava accessions. Statistical analysis was done using IDENTITY1.0 and CERVUS 3.0 software. Cluster analysis was done with DARwin 5.0 software, using Wards Minimum Variance method, and weighted group neighbour joining method, to check reliability of grouping among clusters. The trend in grouping was found to be similar in both methods. Dendrograms generated showed that the hybrids clustered with their parents; exotic collections fell into two different sub-groups based on productivity; the wild species formed one group; and Navalar cultivars from Dharwad clustered together, reflecting similar origin

Seeding the meiotic DNA break machinery and initiating recombination on chromosome axes

Programmed DNA double-strand break (DSB) formation is a crucial feature of meiosis in most organisms. DSBs initiate recombination-mediated linking of homologous chromosomes, which enables correct chromosome segregation in meiosis. DSBs are generated on chromosome axes by heterooligomeric focal clusters of DSB-factors. Whereas DNA-driven protein condensation is thought to assemble the DSB-machinery, its targeting to chromosome axes is poorly understood. We uncover in mice that efficient biogenesis of DSB-machinery clusters requires seeding by axial IHO1 platforms. Both IHO1 phosphorylation and formation of axial IHO1 platforms are diminished by chemical inhibition of DBF4-dependent kinase (DDK), suggesting that DDK contributes to the control of the axial DSB-machinery. Furthermore, we show that axial IHO1 platforms are based on an interaction between IHO1 and the chromosomal axis component HORMAD1. IHO1-HORMAD1-mediated seeding of the DSB-machinery on axes ensures sufficiency of DSBs for efficient pairing of homologous chromosomes. Without IHO1-HORMAD1 interaction, residual DSBs depend on ANKRD31, which enhances both the seeding and the growth of DSB-machinery clusters. Thus, recombination initiation is ensured by complementary pathways that differentially support seeding and growth of DSB-machinery clusters, thereby synergistically enabling DSB-machinery condensation on chromosomal axes.Meiotic cells deliberately break their DNA to allow chromosomes to swap genetic material. Here, authors reveal genetically separable pathways controlling the seeding and growth of chromosome-bound protein condensates responsible for DNA breaks

Pyogenic granuloma: Reappraisal of etiopathogenesis and case report of large sized pyogenic granuloma

The Connective tissue disorder category encompasses variety of lesion & in that list pyogenic granuloma is most common. Though the term is a misnomer as there is no pyogenic organism involved in its pathogenesis but it’s just a reactive inflammatory lesion due to local trauma, hormonal influence & few drugs. Usually the pg are small in size not exceeding 2-3 cms but sometime it can grow to large extent as it is observe in our case. In such scenario proper diagnosis & differential diagnosis become mandatory as clinician may misdiagnose the lesions with some malignant lesion due its mammoth size. Our case report highlights the thorough evaluation of large pyogenic granuloma

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Developing Mapping Populations for Identifying Genomic Regions Controlling Resistance to Bark-Eating Caterpillar (<i>Indarbela tetraonis</i>) in Guava

<p>The bark-eating caterpillar (<i>Indarbela tetraonis</i> Moore) is one of the two species of insect pests known to infest guava (<i>Psidium guajava</i>). Severe infestation with this pest causes drying up of shoots, which ultimately results in substantial losses in fruit yield and quality. Genetic options are considered most eco-friendly and cost effective to mitigate such losses. DNA marker-assisted breeding of guava for improved resistance to bark-eating caterpillar is expected to increase the efficiency of developing resistant cultivars. As a prelude to this, an investigation was carried out to identify pairs of genotypes contrasting for responses to infestation by bark-eating caterpillar and for a large number of simple sequence repeat (SSR) markers, for use as putative parents to develop mapping populations for chromosomal localization of genomic regions controlling resistance to bark-eating caterpillar in guava. Dendrogram generated by 135 polymorphic SSR markers could separate five morphologically resistant and three morphologically highly susceptible genotypes into two different clusters, barring two exceptions (Bangalore Local and 7–12EC 147036). Four pairs of accessions, viz., Superior Sour Lucidum and Seedless, Portugal and Seedless, Lalit and Seedless, Spear Acid and Seedless, had contrasting response to bark-eating caterpillar and were polymorphic at 111, 103, 101, and 101, SSR loci, respectively. These contrasting pairs of accessions are suggested for use as parents to develop mapping populations to identify DNA markers linked to genomic regions controlling resistance to bark-eating caterpillar, which could help in implementing SSR marker-assisted breeding of guava for resistance to bark-eating caterpillar.</p