Allelic diversity of S‑RNase alleles in diploid potato species

S-ribonucleases (S-RNases) control the pistil specificity of the self-incompatibility (SI) response in the genus Solanum and several other members of the Solanaceae. The nucleotide sequences of S-RNases corresponding to a large number of S-alleles or S-haplotypes have been characterised. However, surprisingly few S-RNase sequences are available for potato species. The identification of new S-alleles in diploid potato species is desirable as these stocks are important sources of traits such as biotic and abiotic resistance. S-RNase sequences are reported here from three distinct diploid types of potato: cultivated Solanum tuberosum Group Phureja, S. tuberosum Group Stenotomum, and the wild species Solanum okadae. Partial S-RNase sequences were obtained from pistil RNA by RT-PCR or 3’RACE (Rapid Amplification of cDNA Ends) using a degenerate primer. Full length sequences were obtained for two alleles by 5’RACE. Database searches with these sequences, identified sixteen S-RNases in total, all of which are novel. The sequence analysis revealed all the expected features of functional S-RNases. Phylogenetic analysis with selected published S-RNase and S-like-RNase sequences from the Solanaceae revealed extensive trans-generic evolution of the S-RNases and a clear distinction from S-like-RNases. Pollination tests were used to confirm the self-incompatibility status and cross-compatibility relationships of the S. okadae accessions. All the S. okadae accessions were found to be self-incompatible as expected with crosses amongst them exhibiting both cross-compatibility and semi-compatibility consistent with the S-genotypes determined from the S-RNase sequence data. The progeny analysis of four semi-compatible crosses examined by allele-specific PCR provided further confirmation that these are functional S-RNases

DNA methylation in diploid inbred lines of potatoes and its possible role in the regulation of heterosis

Self-incompatible diploid potatoes were altered to self-compatible ones by a function of S-locus inhibitor gene and continued selfing generated highly homozygous inbreds. In this study, this process was investigated for the status of DNA methylation by a simple method using genomic DNA digested by methylation-sensitive restriction enzymes prior to RAPD analysis. We detected 31 methylation-sensitive RAPD bands, of which 11 were newly appeared in the selfed progenies, and 6 of them stably inherited to subsequent generations. Aberrant segregations and paternal- or atavism-like transmission were also found. Segregating methylation-sensitive bands in initial populations became fixed in the advanced selfed progenies by 75.0–93.8%, of which 41.7% were fixed to all present and 58.3% to all absent. Because DNA methylation is generally recognized to suppress gene expression as regulatory factors, homozygosity/heterozygosity of methylated DNA may be involved in inbreeding depression/heterosis

Direct and Indirect Effects of Yield Contributing Characters on Grain Yield in Rice (Oryza sativa L.)

The present study consists of 23 rice genotypes including one check variety were evaluated at Field Experimentation Centre of the Department of Genetics and Plant Breeding, Direct and indirect effects of yield contributing characters on grain yield in Rice (Oryza sativa L.) for 13 quantitative characters. The experiment was conducted by using Randomized Block Design with three replications during Kharif, 2021. MTU-1224 (54.85gm) to be high yielding followed by, RNR-1446 (41.4gm), SHIVA 555 (39.267gm), MTU-1121 (39.2gm), MTU-1272 (38gm) showed higher yield over the NDR359 (check). High to moderate estimates of GCV and PCV were recorded for Number of tillers/hill followed by Grain yield per hill, Test weight, Number of spikelet’s/hill, Biological yield, Harvest index, Number of panicles/hill, Flag leaf width, Flag leaf length and Plant height. Grain yield indicated significant positive correlation with Harvest index followed by Number of panicles/hill, Number of tillers/hill, Number of spikelet’s/Panicles and Biological yield at both phenotypic level and genotypic level. Positive significant direct effects on grain yield per hill were exhibited by harvest index, biological yield and days to 50% flowering at genotypic level and phenotypic level. Thus, these traits are identified as the efficient and potential for indirect selection for the improvement of rice productivity in the present experimental materials