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SummaryNext generation sequencing (NGS) technologies have revolutionized the pace and scale of genomics-and transcriptomics-based SNP discovery across different plant and animal species. Herein, 72-base paired-end Illumina sequencing was employed for high-throughput, parallel and large-scale SNP discovery in 41 growth-related candidate genes in Eucalyptus camaldulensis. Approximately 100 kb of genome from 96 individuals was amplified and sequenced using a hierarchical DNA ⁄ PCR pooling strategy and assembled over corresponding E. grandis reference. A total of 1191 SNPs (minimum 5% other allele frequency) were identified with an average frequency of 1 SNP ⁄ 83.9 bp, whereas in exons and introns, it was 1 SNP ⁄ 108.4 bp and 1 SNP ⁄ 65.6 bp, respectively. A total of 75 insertions and 89 deletions were detected of which approximately 15% were exonic. Transitions (Tr) were in excess than transversions (Tv) (Tr ⁄ Tv: 1.89), but exceeded in exons (Tr ⁄ Tv: 2.73). In exons, synonymous SNPs (Ka) prevailed over the non-synonymous SNPs (Ks; average Ka ⁄ Ks ratio: 0.72, range: 0-3.00 across genes). Many of the exonic SNPs ⁄ indels had potential to change amino acid sequence of respective genes. Transcription factors appeared more conserved, whereas enzyme coding genes appeared under relaxed control. Further, 541 SNPs were classified into 196 'equal frequency' (EF) blocks with almost similar minor allele frequencies to facilitate selection of one tag-SNP ⁄ EF-block. There were 241 (approximately 20%) 'zero-SNP' blocks with absence of SNPs in surrounding ±60 bp windows. The data thus indicated enormous extant and unexplored diversity in E. camaldulensis in the studied genes with potential applications for marker-trait associations.

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Bulk seedlots of two unpedigreed multiprovenance seed production areas (SPAs) each of Eucalyptus camaldulensis and Eucalyptus tereticornis and one pedigreed seedling seed orchard (SSO) of E. tereticornis were planted in genetic gain trials at three southern Indian trial sites. At the time of seed collection, fewer than 30% trees flowered in these orchards, except in one E. camaldulensis SPA where 73% of the trees flowered, which had an estimated outcrossing rate of 86%. The E. tereticornis SSO was dominated by pollen from five highly fecund families of the Indian Mysore gum land race, which contributed 59% of the fruits produced. The SPA and SSO seedlots were compared with a bulked natural-provenance seedlot of E. camaldulensis (Morehead, Laura, and Kennedy Rivers, Queensland), another natural-provenance seedlot (Petford, Queensland), commercial eucalypt clones at two sites, and a Mysore gum seedlot at one site. At 3 years, progeny from all the four SPAs displayed good survival (79-93%) and performance similar to that of the natural provenances and the commercial clones. Progeny from the E. tereticornis SSO had significantly lower growth (at two sites) and lower survival at all three test sites. The Mysore gum seedlot displayed high fecundity and lower growth but better survival than the SSO progeny. Seed orchard genetic composition and flowering contributions thus affected progeny performance and the extent to which orchard genetic diversity was captured in the progeny. SPA progeny displayed greater fecundity than the natural provenances, indicating a response to selection for fertility.

Lignin composition [syringyl/guaiacyl (S/G) ratio] and cellulose content in wood have an important bearing on pulp yield. This paper deals with the development of a calibration model for S/G ratio using five Eucalyptus species from different sites by diffuse reflectance near infrared spectroscopy. The model was constructed with 120 samples covering an S/G ratio range from 1.8 to 3.6, determined by pyrolysis-gas chromatography-mass spectrometry. The calibration plot has an R 2 value of 0.825 which was validated in E. camaldulensis, E. urophylla and E. pellita. Variation in S/G ratio was studied in more than 3000 E. camaldulensis trees across three diverse sites in southern India. The S/G ratio was lower in a low rainfall site (Mahabubnagar) compared to a higher rainfall site (Ongole). A positive correlation (R 2 = 0.72) was observed between S/G ratio and Kraft pulp yield in E. camaldulensis. Alkali consumption in Kraft pulping experiments was inversely proportional to the S/G ratio (R 2 = 0.914).