Assessment on performance and variability in different sweet orange (Citrus sinensis Obseck) cultivars under Punjab conditions

Based on morphological characterization, the performance of eighteen sweet orange, (Citrus sinensis Obseck) cultivars were evaluated. On the basis of two year data, the maximum mean fruit weight (316.25 gm) was recorded in Moro, while the maximum mean fruit diameter and mean fruit length was recorded in Mosambi and Olinda Valencia (87.32 mm and 81.33 mm, respectively). Albedo thickness was recorded maximum in Ruby Nucellar (3.42 mm). Highest total soluble solids was recorded in cultivar Moro (11.450 brix), while the titratable acidity was recorded maximum in Valencia Calizonida (1.21 %). Fruit axis diameter and Fruit rind thickness were recorded maximum in Rhode Red Valencia and Vernia (15.12 mm and 8.11 mm, respectively). In the variability studies, the maximum genotypic coefficient of variance (GCV) and phenotypic coefficient of variance (PCV) was recorded maximum for titratable acidity (27.88 and 27.94, respectively) followed by albedo thickness (23.77 and 23.78, respectively) and fruit weight (21.52 and 21.67, respectively). Genetic advance per cent of mean was recorded for titratable acidity (57.31%) followed by albedo thickness (48.96 %) and fruit weight (44.03 %) suggesting that further selection will be effective for improvement in these traits

Optimization of explants, media, plant growth regulators and carbohydrates on callus induction and plant regeneration in Citrus jambhiri Lush.

Callus induction was attempted from the four explants viz. root, cotyledon, epicotyl, and leaf segments excised from in vitro raised seedlings of C. jambhiri. Among various MS media supplementations with growth regulators and carbohydrates, the maximum (95.50%) and the earliest (8.30 days) callogenesis was obtained in epicotyl segments, when cultured on MS medium supplemented with NAA (10.0 mgl-1) + BAP (1.0 mgl-1) + sucrose (8%). The modified MS (macro and micro-nutrients reduced to half) fortified with BAP (5.0 mgl-1) + GA3 (3.0 mgl-1) recorded maximum shoot regeneration (43.10%) from callus, with an average of 5.30 shoots per callus after 35.50 days of culturing. However, prolonged exposure to GA3 resulted in thin elongated shoots and leaves. The age of the callus substantially influenced the plant regeneration frequency. The potency of the callus to regenerate decreased significantly with an increase in the age of the callus. Shoot regeneration was recorded maximum (43.43%) in 60 days old calli, followed by 90 days old (30.48%) calli, whereas it was minimum (10.46%) in 150 days old calli. The maximum (79.50%) shoot proliferation was recorded in MS medium supplemented with BAP (1.0 mgl-1) + Kin (0.5 mgl-1) with an average of 5.06 shoots per culture. The MS medium fortified with NAA (1.0 mgl-1) + IBA (1.0 mgl-1) induced maximum (77.33%) rooting, with an average of 3.19 roots per shoot after 13.4 days of culturing. Rooted plants were hardened and survived the best (83.6%) on the potting mixture consisting of cocopeat + vermiculite + perlite (2:1:1)

Comprehensive genome-wide identification and transferability of chromosome-specific highly variable microsatellite markers from citrus species

Abstract Citrus species among the most important and widely consumed fruit in the world due to Vitamin C, essential oil glands, and flavonoids. Highly variable simple sequence repeats (SSR) markers are one of the most informative and versatile molecular markers used in perennial tree genetic research. SSR survey of Citrus sinensis and Citrus maxima were identified perfect SSRs spanning nine chromosomes. Furthermore, we categorized all SSR motifs into three major classes based on their tract lengths. We designed and validated a class I SSRs in the C. sinensis and C. maxima genome through electronic polymerase chain reaction (ePCR) and found 83.89% in C. sinensis and 78.52% in C. maxima SSRs producing a single amplicon. Then, we selected extremely variable SSRs (> 40 nt) from the ePCR-verified class I SSRs and in silico validated across seven draft genomes of citrus, which provided us a subset of 84.74% in C. sinensis and 77.53% in C. maxima highly polymorphic SSRs. Out of these, 129 primers were validated on 24 citrus genotypes through wet-lab experiment. We found 127 (98.45%) polymorphic HvSSRs on 24 genotypes. The utility of the developed HvSSRs was demonstrated by analysing genetic diversity of 181 citrus genotypes using 17 HvSSRs spanning nine citrus chromosomes and were divided into 11 main groups through 17 HvSSRs. These chromosome-specific SSRs will serve as a powerful genomic tool used for future QTL mapping, molecular breeding, investigation of population genetic diversity, comparative mapping, and evolutionary studies among citrus and other relative genera/species