Analysis of stability for nut yield and ancillary traits in cashew (Anacardium occidentale L.).

Cashew is cultivated in varied agro-ecological regions of India and yield levels vary with regions. Therefore, to identify stable genotype for yield, 18 genotypes were tested in four environments for nut yield and ancillary traits during 2008 to 2018 in randomized block design with two replications. The data of 6th annual harvest and cumulative nut yield of six years was analyzed employing additive main effect and multiplicative interaction (AMMI) and genotype and genotype by environment (GGE) methods. Analysis of variance for 6th annual harvest indicated significant differences (p < 0.01) for eight traits. Environments varied significantly (p < 0.01) for seven traits. Genotype by environment (G × E) interactions were significant (p < 0.01) for all traits. Analysis of variance for cumulative yield revealed significant variations between genotypes, environments, G x E interactions. Interaction principal component analysis (IPCA) 1 (84.39%) and IPCA 2 (10.27%) together captured 95% of variability. Genotypes, environments and G × E interaction were accounted for 16.18%, 4.50% and 77.22% respectively of total variation. The environment Pilicode discriminated better while Vridhachalam was representative. BPP-8 and Vengulra-7 were the winning genotypes in Bhubaneswar while Kanaka and Priyanka in Pilicode, Vengurla-4 in Jhargram and UN-50 in Vridhachalam. Therefore, promoting cultivation of these winning genotypes in the corresponding environments is highly recommended to enhance cashew nut production. As per ASV (AMMI stability value,) K-22-1 was stable genotype followed by Bhubaneswar-1. As per YSI (yield stability index), Bhubaneswar-1 was stable and high yielding followed by K-22-1 and BPP-8. Thus stable genotypes identified in this study viz., K-22-1 and Bhuvaneswar-1 are recommended for cultivation in west and east regions of India which have most cashew growing areas for increasing the cashew nut production.

De novo assembly and characterization of the draft genome of the cashew (Anacardium occidentale L.).

Cashew is the second most important tree nut crop in the global market. Cashew is a diploid and heterozygous species closely related to the mango and pistachio. Its improvement by conventional breeding is slow due to the long juvenile phase. Despite the economic importance, very little genomics/transcriptomics information is available for cashew. In this study, the Oxford nanopore reads and Illumina reads were used for de novo assembly of the cashew genome. The hybrid assembly yielded a 356.6 Mb genome corresponding to 85% of the estimated genome size (419 Mb). The BUSCO analysis showed 91.8% of genome completeness. Transcriptome mapping showed 92.75% transcripts aligned with the assembled genome. Gene predictions resulted in the identification of 31,263 genes coding for a total of 35,000 gene isoforms. About 46% (165 Mb) of the cashew genome comprised of repetitive sequences. Phylogenetic analyses of the cashew with nine species showed that it was closely related to Mangifera indica. Analysis of cashew genome revealed 3104 putative R-genes. The first draft assembly of the genome, transcriptome and R gene information generated in this study would be the foundation for understanding the molecular basis of economic traits and genomics-assisted breeding in cashew.