Summary
6. SUMMARY Casuarina is an important tree species grown extensively in many parts of the India. The studies on genetic improvement in a major fuel wood species depend on the assessment of existing variability for quantitative and qualitative characters and identification of diverse species of Casuarina. The acclimatization of Casuarina species are highly influenced by environmental factors such as optimal climate; drought and black cotton salinity soil in Northern dry zone of Karnataka have not been endeavored so far. Casuarinas have a wide range of environmental adaptability and occupy from high rainfall coastal sites to Northern dry zone of Karnataka. Several farmers favor planting Casuarina in dry zone areas because of its commercial viability. The biometrical techniques and data analysis in the present investigation revealed important finding whose merits are summarize under the following heads. 6.1. Growth performance of five Casuarina species The results of the study reveals that Casuarina equisetifolia has the best growth performance followed by C. glauca among five species studied and appears to be promising for rehabitation of degraded lands in Northern dry zone of Karnataka. Growth performance of Casuarina equisetifolia was better than C. glauca and C. cunninghamiana in black cotton soil. Among eleven quantitative morphological traits studied, total tree height and diameter at breast height had significantly higher effect upon tree biomass in C. equisetifolia and lower in C. obesa. However, qualitative parameters viz., survival, stem straightness, Crown area and number of branches exhibited superior performance in C. equisetifolia and C. cunninghamiana. Physical properties of wood viz., specific gravity, green wood and dry wood density were significantly higher in Casuarina obesa and C. equisetifolia among species. Calorific value of wood was significantly higher in C. equisetifolia among five species. However, effect of Casuarina species on physico-chemical parameters of soil viz., bulk density, soil ph and electrical conductivity resulted in the highest soil enrichment in C. obesa followed by C. equisetifolia and C. cunninghamiana. Soil nitrogen, phosphorous and potash content were significantly higher underneath C. equisetifolia followed by C. glauca and C. obesa.
High magnitude of phenotypic coefficient of variation and genotypic coefficient of variation were recorded for number of root nodules seedling -1, free proline content, number of branches tree -1, Crown area, length of needle, bark thickness and wood volume among the species. Estimation of high heritability with high genetic advance as per cent mean was observed for number of needles seedling -1, number of root nodules seedling -1, total chlorophyll, free prolin content, fresh seedling weight, dry seedling weight, clear bole height, number of branches tree -1, Crown area, length of needle, bark thickness, wood volume and tree biomass revealed that there is a preponderance of additive gene action in these traits. Tree biomass was positively and significantly correlated with seedling height, collar diameter, number of needles seedling -1, number of roots seedling -1, total chlorophyll, fresh seedling weight, dry seedling weight, total tree height; clear bole height, diameter at breast height, Crown area and wood volume at both genotypic and phenotypic levels. Path analysis revealed that contribution of the volume of wood had highest direct positive effect upon tree biomass among thirteen characters studied at both genotypic and phenotypic levels, partially due to its direct effect through total tree height, seedling height, Crown area, collar diameter, dry seedling weight and clear bole height. However, number of needles seedling -1, fresh seedling weight, total chlorophyll, number of roots seedling -1 and diameter at breast height had direct negative effect upon tree biomass. Various Casuarina species were resolved into 4 clusters based on D² analysis. Cluster IV (Casuarina equisetifolia) would be prolific to maintain future seed material which was grouped in genetically divergent species. Hybridization concerning species of clusters IV and II were advocated in order to achieve high yielding tree biomass in Casuarina. It was inferred from this study that tree biomass contributed maximum percentage towards genetic divergence, followed by wood volume and diameter at breast height among 13 parameters studied in five Casuarina species.
6.2. Phenology of five Casuarina species Casuarina equisetifolia have both monoecious as well as dioecious trees while, rest of species viz., C. obesa, C. gluaca C. cunninghamiana and C. cristata were strictly dioecious with bearing female flowers and male flowers on other tree. Casuarina species has two major flowering seasons. The first season is between late January to early May and the second season is from third week of July to early October. Male and female flowering period was found from late January to early May and peak flowering in second week of March to first week of April during first season. However, second season was between third week of July to late October and peak flowering in second week of September to early October was observed. Synchronization of male and female flowering were observed between C. equisetifolia and C. cunninghamiana hence these two species may be utilized for hybridization programme. Phenotypic variability for floral morphological parameters viz., inflorescence length, flower width, stigma length, stigma width and number of floral buds per inflorescence were significantly higher in dioecious trees than monoecious in Casuarina equisetifolia. The female reproductive success was significantly higher in open pollinated trees than cross pollinated and hand self pollinated in all species. Dioecious trees of C. equisetifolia have significantly higher female reproductive success than monoecious trees. The morphological traits viz., length and width of male inflorescence and number of floral whorls cm -1 inflorescence -1 were significantly higher in dioecious trees of C. equisetifolia than monoecious ones. The seed filling cone -1, number of fruit set inflorescence -1, fruit set percentage inflorescence -1 and short duration of fruit maturity (18 week) were superior in C. equisetifolia and C. cunninghamiana. 6.3. Variability of cone / seed parameters in five Casuarina species Variability studies among eight morphological traits of cone viz., fresh cone weight, dry cone weight, cone length, cone width, number of ridges cone -1 and number of seeds cone -1 were significantly higher in dioecious C. equisetifolia and lower in C. obesa followed by C. glauca and C. cristata. Significantly higher number of seeds ridge -1 was exhibited in C. cunninghamiana and dry matter cone -1 in C. glauca among the species.
Significantly higher number of seeds g -1 was registered in C. glauca among species. Casuarina equisetifolia (dioecy) was significantly superior over C. equisetifolia (monoecy) and other four species in seed width, seed thickness and 1000 seed test weight. Seeds of C. equisetifolia (monoecy) followed by C. equisetifolia (dioecy) and C. cristata were showed gelatinous layer when compared with other three species. Similarly seed coat and colour of all the species had same texture. Casuarina species indicated a wide variation in its seed size and accordingly the seed were grouped into four sieve size classes. The effect of seed sizes with 2.78 mm and 2.25 mm sieves were promoted higher germination among the species. C. glauca and C. cunninghamiana were on par with each other in (2.78 mm and 2.25 mm) sieves for seed germination. The seeds of C. equisetifolia graded by using sieve size 2.78 mm recorded significantly highest germination per cent and lowest was in C. obesa (Fig.5). It shows that, seed germination percentage differed significantly with respect to seed sizes and germination decrease with decrease in size of seed and vice versa. 6.4. To find out the suitable substrata and pretreatments to improve seed germination Influence of various substratas, growth regulators and pre-treatment for breaking dormancy increased germination percentage. Freshly collected seeds of C. equisetifolia registered significantly highest seed germination and lowest in C. obesa under sand seed tray over other two methods. All five Casuarina species had high percentage of seed germination when stored upto 3 month as compared to 6 month and above for seed storage in sand seed tray method. Casuarina equisetifolia followed by C. glauca recorded higher seed germination while it was lower in C. obesa for seed stored up to 12 month and 15 month. However, seed germination was recorded zero between paper method and soil raised bed substrata for seed stored upto 18 month and 21 month of storage among the species. The higher speed of average seed germination was registered in 18 th day after sowing on sand seed tray method for Casuarina equisetifolia and lowest in C. obesa and C. cristata. The seeds started germinating after 6 days of sowing and germination gradually increased its speed up to 18 th day and was constant for all the species later. C. glauca and C. cunninghamiana were on par with each other for speed of seed
germination. The maximum seed vigour index was registered in C. glauca and least in C. obesa. Casuarina glauca and C. equisetifolia were on par with each other for seed vigour. Casuarina equisetifolia seed has stained a deeper red color than the C. obesa at 1 per cent of tetrazolium. Casuarina glauca and C. cunninghamiana were on par with each other for seed viability. Although TZ test for seed viability has been observed upto 21 month storage after harvest in normal room condition, Casuarina seeds had shown the maximum viability upto 3-month storage. The response of pretreatment for seed germination varies with species to species and it was improved with freshly collected seeds upto 3 month storage but its response was declined for longer duration of seed storage. In Casuarina seed germination was significantly higher in combination with GA 3 and KNO 3 for seed stored upto 3 month and unable to germinate afterward among all the treatments. However, C. equisetifolia and C. glauca recorded higher seed germination in combination with GA 3 and KNO 3 upto 18 th and 21 st month of storage period. Among the species, seed germination was recorded zero in combination with hot water, prechilling and cold water pretreatments for stored seeds upto 18 month and above seed storage. 6.5. Variability of half sib progenies in five Casuarina species Growth performance was significantly higher in Casuarina equisetifolia and lower in C. obesa over period of 12 month after sowing of seeds for twelve quantitative morphological traits viz., seedling survival, seedling height, collar diameter, number of branches seedling -1, number of needles seedling -1, needle length, number of inter nodes seedling -1, number of roots seedling -1, root length, number of root nodules seedling -1, suitability index and volume index. However, Casuarina cunninghamiana and C. glauca were on par with each other for growth performance. Growth performance of half sib progenies for seven quantitative traits were significantly higher at 6 month when compared to the 3 month after seed sown, this became less linear and the progenies started showing tremendous growth especially after 12 months of sowing.
Present results revealed that the performance of progenies were significantly higher in C. equisetifolia and lower in C. obesa for nine parameters contributing to total seedling biomass. Total nitrogen content in half sib progenies recorded higher in Casuarina equisetifolia and lower in C. obesa. Significant increase in total chlorophyll and chlorophyll b content was observed in C. equisetifolia and lower in both of C. obesa and C. cristata. Casuarina cunninghamiana and C. equisetifolia have maintained significantly higher free proline content and could be inferred as tolerant to drought condition.