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Guava (Psidium guajava L.), a rich source of nutrients, is an important tropical and subtropical fruit of the Myrtaceae family and exhibits magnificent diversity. Genetic diversity analysis is the first step toward the identification of parents for hybridization, genetic mapping, and molecular breeding in any crop species. A diversity analysis based on whole-genome functional markers increases the chances of identifying genetic associations with agronomically important traits. Therefore, here, we sequenced the genome of guava cv. Allahabad Safeda on an Illumina platform and generated a draft assembly of ~304 MB. The assembly of the Allahabad Safeda genome constituted >37.95% repeat sequences, gene prediction with RNA-seq data as evidence identified 14,115 genes, and BLAST n/r, Interproscan, PfamScan, BLAST2GO, and KEGG annotated 13,957 genes. A comparative protein transcript analysis of tree species revealed the close relatedness of guava with Eucalyptus. Comparative transcriptomics-based SSR/InDel/SNP-PCR ready genome-wide markers in greenish-yellow skinned and white fleshed-Allahabad Safeda to four contrasting cultivars viz apple-color-skinned and white-fleshed-Lalima, greenish-yellow-skinned and pink-fleshed-Punjab Pink, purple-black-skinned and purple-fleshed-Purple Local and widely used rootstock-Lucknow-49 were developed. The molecular markers developed here revealed a high level of individual heterozygosity within genotypes in 22 phenotypically diverse guava cultivars. Principal coordinate, STRUCTURE clustering, and neighbor-joining-based genetic diversity analysis identified distinct clusters associated with fruit skin and flesh color. The genome sequencing of guava, functional annotation, comparative transcriptomics-based genome-wide markers, and genetic diversity analysis will expand the knowledge of genomes of climacteric fruits, facilitating trait-based molecular breeding and diversifying the nutritional basket.

Background: Guava (Psidium guajava L.) is an important fruit crop of tropical and subtropical areas of the world. Genomics resources in guava are scanty. RNA-Seq based tissue specific expressed genomic information, de novo transcriptome assembly, functional annotation and differential expression among contrasting genotypes has a potential to set the stage for the functional genomics for traits of commerce like colored flesh and apple color peel. Results: Development of fruit from flower involves orchestration of myriad molecular switches. We did comparative transcriptome sequencing on leaf, flower and fruit tissues of cv. Allahabad Safeda to understand important genes and pathways controlling fruit development. Tissue specific RNA sequencing and de novo transcriptome assembly using Trinity pipeline provided us the first reference transcriptome for guava consisting of 84,206 genes comprising 279,792 total transcripts with a N50 of 3603 bp. Blast2GO assigned annotation to 116,629 transcripts and PFam based HMM profile annotated 140,061 transcripts with protein domains. Differential expression with EdgeR identified 3033 genes in Allahabad Safeda tissues. Mapping the differentially expressed transcripts over molecular pathways indicate significant Ethylene and Abscisic acid hormonal changes and secondary metabolites, carbohydrate metabolism and fruit softening related gene transcripts during fruit development, maturation and ripening. Differential expression analysis among colored tissue comparisons in 3 cultivars Allahabad Safeda, Punjab Pink and Apple Color identified 68 candidate genes that might be controlling color development in guava fruit. Comparisons of red vs green peel in Apple Color, white pulp vs red pulp in Punjab Pink and fruit maturation vs ripening in non-colored Allahabad Safeda indicates up-regulation of ethylene biosynthesis accompanied to secondary metabolism like phenylpropanoid and monolignol pathways.

The basic principle of crop regulation is to manipulates the natural flowering and fruiting of guava plant in desired season of the year that contribute to increased fruit yield, quality, profitability and sustainability of the environment by reducing the use of the frequency of the pesticides. This concept is based on the fact that guava flowers are borne only on new, succulent, vigorously emerging vegetative growths. These new growth flushes can be either new emergences of lateral bud on older stems or extensions of already established terminals of various size and vigor. The crop regulation can be achieved by the adoption of the various practices like withholding irrigation after harvesting during the months of April-May in Northern Indian plains. This results in the shedding of flowers and the tree goes to rest. The basin of the tree is dug up, manured and irrigated in June. After about 30-35 days the tree put forth profuse flowering and fruit mature in winter. Terminal portion of the shoots up to 20 or 30 cm length should be pruned between 20 th to 30 th April. Always avoid severe pruning in guava. Apply the recommended dose of fertilizers during the month of June to encourage vegetative growth in July-August for getting maximum flowering during August-September for winter season crop. To regulate the guava crop, it is essential to reduce the fruit set during the rainy season and subsequently increase the fruit set during winter season by the use of different chemicals like NAA ethereal and urea etc. Key words:Crop regulation, Deblossoming, Guava, NAA, Water stress.Guava is most important commercial fruit crop grown in sub-tropical region of the Indian subcontinent. It gives an assured crop with very little care. Its cost of production is also low as compared to most of other commercial fruit crops. It has gained considerable prominence on account of its high nutritive value, cheap and easily availability at moderate prices. It is a good source of Vitamin C (150-200 mg/100 g of pulp). Guava fruit contains antioxidant factors and is known to control the systolic blood pressure. In guava, two distinct seasons of flowering, spring (March-April) and rains (June-July) occur from which fruits ripen during rainy and winter season respectively. In North Indian climate the rainy season crop of guava is poor in quality and nutritive value and is affected by many insect pests and diseases. The winter season fruits are superior in quality free from diseases and pests and give higher income. But it is advisable to take only one crop every year. This requires management of flowering to obtain the most desireable crop, by the methods like withholding irrigation, pruning, thinning of flowers by chemically or manually. The work carried out by various scientists on crop manipulation is reviewed under different sub heads. Why crop regulation:The rainy season crop of guava is poor in quality and crop is affected by many biotic and abiotic stresses as compared to winter season crop. The winter season crops which ripen f...

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