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.

First report of Neopestalotiopsis clavispora causing cashew leaf blight disease in India.

Cashew (Anacardium occidentale) is an important commercial crop and highly prone to many biotic and abiotic stress. During March 2021, severe leaf blight symptoms were observed in Priyanka variety with 25-30% incidence grown under greenhouse nursery at ICAR-Directorate of Cashew Research (ICAR-DCR), Puttur (12º74'08.92"N; 75º22'97.22"E), Karnataka. Initial symptoms include small, irregular necrotic spots and later, the spots enlarged and covered major portion of the leaf lamina. In severe infection, leaves exhibited coalescing of spots leading to blight appearance. The infected leaves were randomly collected (n=5) and surface sterilized with 1% sodium hypochlorite for 1 min followed by three washes in sterile distilled water (SDW). Samples were plated on PDA plates amended with Rifampicin (40 mg/L) and kept for incubation at 25±2 oC for 5 days (12/12 h dark light period). A white-greyish, aerial, cottony mycelium on upper side with light yellow colour on the reverse side was consistently isolated. The black viscous acervuli were observed after 10-12 days of incubation. The conidia were fusiform, five-celled, versicoloured with three olivaceous brown median cells, two terminal hyaline cells, measured 23.3±2.12 - 28.33±2.7 x 3.6±0.8 - 4.28±0.78 µm (n=30). The apical cells had two to three flexuous, unbranched appendages, and basal appendage was solitary, tubular and unbranched. Morphological and cultural characteristics confirmed the pathogen as Neopestalotiopsis sp. (Maharachchikumbura et al. 2012). Further, two representative isolates (CLB_SCN1 & CLB_SCN2) were subjected for molecular characterization selected for molecular identification based on ITS-rDNA, tef-1α and tub2 gene sequences and phylogenetic analysis. Genomic DNA was isolated from 15 days old cultures and internal transcribed spacer (ITS) of ribosomal DNA (rDNA) (White et al. 1990), translation elongation factor 1α (tef-1α) gene (O'Donnell et al. 1998) and beta tubulin (tub2) using ITS1/ITS4, TEF1/TEF2 and Bt2a/Bt2b (Carbone and Kohn 1999; Glass and Donaldson 1995) were amplified using primer pairs respectively. PCR amplicons were sequenced, and the sequences were deposited in GenBank (accession numbers: ITS: OP880881.1, OP880882.1; tef-1α: OP882579.1, OP882580.1; and tub2: OP882581., OP882582.1). The phylogeny was constructed based on combined ITS, tef-1a, and tub2 regions. Neighbour-Joining (NJ) analysis was conducted and the tree was constructed with the substitution models (branch support was evaluated by 1,000 bootstrap replications). Combined phylogeny confirmed that the sequences shared a common clade with N. clavispora. Hence, morphological, microscopic and molecular characterization confirmed the pathogen as N. clavispora. The pathogenicity test was done on six months old healthy grafts of Priyanka variety (n=9) and repeated thrice. Conidial suspension (2×106 spores/ml) of N. clavispora CLB_SCN1 (15 days old culture) was sprayed on the healthy cashew seedlings, and kept in greenhouse by covering with polythene bags for 24 h (>80 % RH) and maintained under greenhouse condition. The control grafts were inoculated with SDW. The inoculated plants showed blight symptoms after 7-10-day post inoculation and control remained heathy. Re-isolation was done from the symptomatic leaves and identity was confirmed using cultural and molecular studies. Earlier reports showed that, N. clavispora has been reported to cause cardamom leaf blight (Biju et al 2018) and leaf spot disease of plum (Banerjee and Rana 2020). To best of our knowledge, this is the first report of cashew leaf blight disease caused by N. clavispora from India (Farr and Rossman, 2022). Early detection will help farmer in better management and avoiding economic loss caused by N. clavispora.