The present work analyzed the stainability and in vitro germinability of the gamma-ray-irradiated fresh and cryopreserved pollens of 3 Citrus species: C. limon, C. limetta, and C. sinensis. Fruit set after pollinating 75 flowers of C. grandis with irradiated and nonirradiated (control) fresh and cryopreserved pollen was also assessed. Results showed that in solid and liquid culture media the highest in vitro germination values were detected in fresh (61.45% and 62.53%, respectively) as well as cryopreserved (53.17% and 55.36%, respectively) C. sinensis nonirradiated pollens. However, at a higher irradiation dose of 500 Gy in both culture media, the minimum reduction of germinability of fresh (30.85% and 28.01%) and cryopreserved pollens (33.37% and 31.06%) was found in C. limon. Contrary to in vitro germination, the minimum reduction in stainability of fresh and cryopreserved pollens, as assessed by acetocarmine (9.51% and 11.85%, respectively) and FDA tests (10.78% and 12.73%, respectively), was recorded in C. limetta. Regardless of irradiation dose, the highest fruit setting in C. grandis at 40 days after pollination was detected when it was pollinated with both fresh (38.02%) and cryopreserved (34.92%) C. limetta pollen grains.

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Perennial trees especially fruit trees are considered to be the most competent biological system where atmospheric carbon dioxide is transformed into long-lived soil carbon despite their nutritional and export value. Higher carbon stock helps to sustain production and soil ecosystem services. Better crop nutrition promotes carbon stock. Feasibility of integrated nutrient management in carbon sequestration needs to be evaluated under a subtropical humid condition. An experiment was carried out in randomized block design to study the feasibility of integrated nutrient management for improving soil properties, nutrient availability, fruit yield, and carbon stock in a mango (Mangifera indica L.) (cv. Langra) orchard under a subtropical condition. Various combinations of integrated (farmyard manure, vermicompost, straw mulch, biofertilizers) nutrient management practices were evaluated in two consecutive years in a 30year-old mango orchard. The results revealed that the organic mulching with straw and conjoint application of farmyard manure and vermicompost improve nutrient availability, microbial activeness (29-44%), and carbon stock (~40%) in soil at 0-60 cm soil depth which ultimately improves fruit yield (26-34%). Hence, adoption of integrated nutrient management practices through the application of farmyard manure, vermicompost, and organic mulching with straw would uphold the fruit yield and carbon stock in soil and also promote CO 2 sequestration in soil and less greenhouse gas emission, which paved viable economic options to mitigate climate change.

The present investigation was carried out for the induction of haploid plants in Citrus grandis through in situ parthenogenesis by pollination with gamma-irradiated pollen of C. limetta and C. sinensis, treated with 50, 100, 200, 300, and 400 Gy gamma ray doses followed by in vitro ovule culture. Ovule culture at 50 days after pollination (DAP) was found optimum for the maximum recovery of in vitro-raised plantlets as compared to 35 and 20 DAP. At 50 DAP, irrespective of the pollen parent, plantlet regeneration capacity decreased at 300 and 400 Gy irradiation treatment (0.62% and 0.60%, respectively) with maximum recovery in the nonirradiated control (3.07%). Chromosome counting in actively growing root tips of all the in vitro-raised ovule cultured plantlets revealed that two haploid plants with chromosome number of nine were induced in C. grandis from the ovule culture that was cultured at 50 DAP following pollination with irradiated pollen of C. sinensis at 400 Gy and C. limetta pollen at 300 Gy. However, irradiation doses below 300 Gy were incapable of inducing any haploids in either cross combination. Similarly, all the plantlets regenerated from in vitro embryo culture of mature seeds were found to be diploid in nature, irrespective of the pollen parent and irradiation dose. Molecular analysis of the in vitroraised haploid and diploid plants using SSR markers confirmed the maternal origins of the haploid plants; however, the diploid plants were found zygotic in nature with one allele from the seed parent and the other one from the pollen parent.

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The rate of pineapple propagation through conventional technique is quite low and time taken and that by seed is apparently hard to germinate. Non-availability of quality planting material is one of the major constraints for expansion of its cultivation area in Bihar. Keeping this in view an experiment was conducted for in vitro establishment for large scale disease free planting materials production. The most commonly encountered problem during in vitro pineapple germplasm establishment is the rate of contamination, which is very high in case of pineapple. Suckers of pineapple cultivar Kew were used as explants for the study. In this experiment the efficiency of three sterilizing agents (Clorox, HgCl2 and NaOCl) at different concentrations and duration was evaluated in terms of number of aseptic cultures. Results revealed that when no sterilant was used all the cultures were contaminated. The contamination of explants significantly decreased with increase in concentration of different sterilants and their time of exposure. The highest survival of explants (58.31±1.71%) were observed when explants were treated with Clorox 40% for 20 minutes which also resulted in 17.89±0.25% and 25.03±2.63%  mortality and per cent contamination respectively. As the duration of Clorox 40% was increased, percent contamination decreased but simultaneously increased the mortality rate at 25 mins of duration. The percent survival also increased when explants were treated with different concentrations of HgCl2 and NaOCl at different time durations. However, NaOCl treatments were less effective as compared to other two sterilants.

Polyploid breeding is an effective tool to induce variability in the existing population, specifically in the crops having very narrow genetic base such as acid lime. Hence, an experiment was conducted to induce polyploidy in acid lime through colchicine treatment. Higher frequency of triploids were obtained in 250 μM colchicine treatment (27.27%), whereas combination of 3× (21.42%), 4× (13.33%) and aneuploid (6.67%) were induced at 500 μM colchicine treatment. Measurement of stomatal density and guard cell size of colchiploids revealed that the former one has negative relation with ploidy level and a positive relation was observed between guard cell size and ploidy level. Further, area and size of nuclei also had a positive relation with ploidy level. Hence, stomatal density, guard cell and nuclei size can be used effectively as morphological marker for preliminary polyploid screening. From the experiment, it can be concluded that 500 μM colchicine treatment of in vitro derived shoot tip explants of acid lime is optimum for creating maximum possible variability through polyploidization in the existing acid lime population.