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Philippine Journal of Crop Science (PJCS) April 2012, 37 (1):27-35
Copyright 2012, Crop Science Society of the Philippines...
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Root Growth Potential, Variability and Heritability of Yemane (Gmelina arborea Roxb) in the Philippines

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Root Growth Potential, Variability and Heritability of Yemane (Gmelina arborea Roxb) in the Philippines

  1. 1. Philippine Journal of Crop Science (PJCS) April 2012, 37 (1):27-35 Copyright 2012, Crop Science Society of the Philippines Full Paper Root Growth Potential, Variability and Heritability of Yemane (Gmelina arborea Roxb) in the Philippines Onofre S. Corpuz Cotabato Foundation of Science and Technology, Doroluman Arakan, 9417 Cotabato, Philippines; nfr_uplb@yahoo.com The experiment was undertaken to characterize root growth potential (RGP) and determine growth variability and heritability of eight hundred Yemane (Gmelina arborea Roxb) based on provenance in 3 provinces in the Philippines. Significant variations of morphological characteristics of seedlings of Yemane by seed sources were found in the study. Seed sources from Quezon and Cotabato Provinces differed in all morphological traits compared with the seed sources from Davao del Sur. The root growth potential in terms of the number of first order lateral roots (FOLR) was positively correlated with all seedlings morphological characters, such as root collar diameter, primary root length, stem height, and root:shoot ratio. The frequency distribution of FOLR revealed to be normal. The seedlings FOLR was fro m 3 to 35 with an average of 18. Three natural FOLR groupings were established such as: R1 (0–10); R2 (11– 20); and R3 (21–30+). The entire traits measured were genetically influenced by the seed sources based on observed high heritability estimates. Keywords: FOLR, heritability, RGP, variability INTRODUCTION Strategies in assessing quality of planting stocks need to veer away from using the traditional approach of looking only into the sound morphological characteristics of seedlings to be planted (Grossnickle et al. 1991). These morphological indices however, often fail to account for difference in seedling physiology. Hence, holistic assessment of stock quality requires the integration of both morphological and physiological attributes of seedlings (Carandang 1994). Consideration of both attributes provides an effective appraisal of the fitness of seedlings for field planting purposes. In the Philippines, many studies on seedling attributes dealt with morphological traits, while only few were done in root growth in relation to field planting performance. Lateral root development of large leaf mahogany (Swietenia macrophylla King) (Carandang 1994), and root growth potential of narra (Pterocarpus indicus Willd.) transplants (Gazal 1998) were among the studies conducted in the country. Root growth potential (RGP) is the ability of a tree seedling to initiate and elongate roots when placed into an environment favorable for root growth. The magnitude of RGP is often correlated with survival and seedling growth following outplanting (Ritchie 1984). The RGP develops in seedlings at the nursery or greenhouse. Following planting, the expression of RGP or actual root growth, is affected by soil temperature, soil moisture, and other factors (Ritchie 1984). The RGP is measured by growing seedlings for certain period under environment favorable to enhance root growth, before assessment for the amount of roots developed is done. RGP is the most reliable predictor of field performance in trees (Ritchie 1984). Root growth potential is seldom used as a measure of seedling quality. Studies elsewhere were done mainly to temperate tree species, such as: Pinus radiata (Rook 1971); Sitka spruce (Deans et al. 1990), Douglas-fir (Sharpe and Mason 1992; Rose et al. 1991, Haase and Rose 1994), Loblolly pines (Larsen 1986; Williams et al.1988; Feret and Krebs 1985), Slash pine (McGrath and Duryea 1994), and Ponderosa pine (Stone and Jenkinson 1959). Methods of measuring RGP have been standardized in many temperate countries, but have not been done in the tropics including Philippines. Thus the potential of using RGP as an indicator of seedling quality and performance of one important tree species in the Philippines need to be explored. This study attempts to provide a basis for interpreting RGP and heritability of Yemane, one of the most common exotic tree species used for reforestation and plantation in the country at present. In this study, four seed sources of Yemane seeds in three provincial locations in the Philippines were tested for RGP, variability and heritability. The objectives of this study were: i) to characterize the RGP of Yemane based on provenance, ii) to test
  2. 2. whether RGP is closely related to stem and other root morphological characteristics, and iii) to determine the frequency distribution and family mean heritability of first order lateral root of the species. N W E S Quezon North Cotabato Davao D el Sur Them e1.s hp MATERIALS AND METHODS The experiment was conducted at the Agroforestry Nursery of Matalam Cotabato, Philippines for 2 months (6 September– 6 November, 2006). One seedbed lined with plastic sheet at the bottom was constructed. The bed was walled with bamboo slats and filled with a top soil up to a height of 30.48 cm. Eight hundred seeds (200 per provenance) from three provincial sources (Figure 1) were sown in a seed bed with shallow drills 3 cm apart following a Completely Randomized Design with four replications. Seeds from Candelaria, Quezon were purchased from Ecosystems Research and Development Bureau, College Laguna while seeds from Cotabato and Davao were personally collected by the researcher 1 month before sowing. Seedlings were grown for 60 days. Watering and weeding operations were done to attain optimum germination. The soils in the seedbeds with a ratio of 1:2 sand and garden soil were sterilized before sowing the seeds. Growing plants were not applied with fertilizer and chemicals within the 60 days growing period. After 60 days, the seedlings were carefully lifted from the seedbed and washed with running water throughout to remove excess soil particles. Number of first order lateral roots (FOLR) (Figure 2) that developed were counted to establish root groupings for Yemane by seed source. Root collar diameter, stem height and length of the primary root were also measured. Root collar diameter, the portion of the seedling where white pigment portion of the shoot to root system starts, was measured using a vernier caliper. Stem height was measured from the root collar to the tip of the seedling, while the length of the primary root was measured from the root collar to the tip of the root. Data Analysis The initial individual family and the subsequent consolidated datasets that were collected were subjected to ANOVA using statistical analysis system (SAS) version 5. The relationship of number of lateral roots counted with the other roots and stem morphological characters of the species as influenced by seed sources were determined by correlation analysis. Root classes were set based on recognized natural groupings by provenance. The distributions of the 28 100 0 100 200 Mile s Figure 1. Map showing the study site Matalam and provincial seed sources of Yemane used in the study. Figure 2. First order lateral roots (FOLR) of Yemane seedlings. number of lateral roots were examined using Kolmogorov’s goodness of fit test. The hypothesis of approximate normality was tested using untransformed data. Seedling morphological characters are then subjected to ANOVA based on the groupings established, such as: 0–10 (low) 11–20 (medium); 21–30 + (high). Root Growth Variability and Heritability of Yemane
  3. 3. 2 h= MS F - MSFxR MS F 25 20 No. of FOLR Family mean heritability of all seedlings morphological characters were estimated based on the ANOVA of plot means. The narrow sense heritability was computed using the following equation derived from ANOVA: 15 10 Where: h2 = Narrow sense heritability MSF = Mean square value for family MSFxR = Mean square value for family by replication interaction 5 b a 0 Bansalan Dvo. Sur Candelaria, Quezon Root Collar Diameter Highly significant variation in root collar diameter was observed among seedlings coming from various sources. Seedlings from Kabacan, Cotabato and Candelaria, Quezon differed in diameter with the seedlings from Bansalan, Davao del Sur and Arakan, Cotabato. The highest mean collar diameter was (0.36 cm) from Kabacan, Cotabato, followed by Quezon (0.35 cm), while the lowest was found with the seedlings from Arakan, Cotabato (0.24 cm) (Figure 5). Length of the Primary Roots Primary root length of seedlings from the four seed sources varied significantly. The seedlings with the longest primary roots were recorded from seeds obtained in Candelaria, Quezon (20.60 cm) and Kabacan, Cotabato (19.10 cm). Shortest primary roots were obtained from seedlings coming from Davao del Sur (11.52 cm) (Figure 6). OS Corpuz Arakan, Cotabato 3. Number of first order lateral roots of Yemane from different seed sources in the Philippines. 25 Stem Height (cm) Stem Height The four seed sources varied significantly in terms of stem height. Longest shoot was observed in the seedlings obtained from Candelaria, Quezon with an average stem height of 23.55 cm. Seedlings from Bansalan, Davao del Sur had the shortest mean stem (16.17 cm) (Figure 4) but did not vary with the seeds coming from Cotabato and Quezon Provinces. Figure 20 15 10 5 a b b b 0 Bansalan Candelaria, Kabacan, Dvo. Sur Quezon Cotabato Arakan, Cotabato SEED SOURCES Figure 4. Stem height (cm) of Yemane from different seed sources in the Philippines. 0.35 Root Collar Diameter (cm) Number of first order lateral roots (FOLR) The different seed sources of Yemane significantly differed in terms of number of FOLR. Seeds from Kabacan, Cotabato and Candelaria, Quezon were significantly different from the seeds sourced from Arakan, Cotabato and Bansalan, Davao del Sur. Highest average number of FOLR was found in Kabacan, Cotabato (21.36) followed by Quezon (19.83) but were not significantly different. The lowest mean (12.49) was obtained from Davao del Sur materials (Figure 3). Kabacan, Cotabato SEED SOURCES RESULTS Variation in Morphological Characteristics of Yemane Seedlings a b 0.3 0.25 0.2 0.15 0.1 0.05 a b b a 0 Bansalan Candelaria, Kabacan, Dvo. Sur Quezon Cotabato Arakan, Cotabato SEED SOURCES Figure 5. Root collar diameter of Yemane from different seed sources in the Philippines. 29
  4. 4. 1.0 20 15 10 5 a b b a Root/shoot Ratio Primary Root Lenght (cm) 25 0 Bansalan Candelaria, Kabacan, Dvo. Sur Quezon Cotabato Arakan, Cotabato 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Bansalan Dvo. Sur SEED SOURCES Root:Shoot Ratio The root:shoot ratio of seedlings from Candelaria, Quezon differed significantly with those from Bansalan, Davao del Sur and Arakan, Cotabato but did not differ with those from Kabacan, Cotabato. Highest mean root:shoot ratio (0.900) was observed in seeds coming from Candelaria, Quezon, followed by Kabacan, Cotabato (0.823) while the lowest was from Arakan, Cotabato (0.712) (Figure 7). Frequency Distribution of First Order Lateral Roots in Seedlings of Yemane Considering all the experimental seedlings regardless of seed sources, the number of first order lateral roots in 2 month-old seedlings of Yemane was found to be normally distributed (Figure 8). Despite being a discrete variable, a large population of 1,100 experimental seedlings caused approximation of normal distribution. Test for approximate normality using the untransformed values of number of FOLR observed by Kolmogorov’s goodness of fit procedure further affirmed the appearance of the curve. The lowest number counted was 4, while the highest was 35. Both extreme values accounted for only a seedling each. Seedlings with 18 FOLR were counted the most. This findings emphasized that FOLR growth in Yemane is not affected by population and provenance. Table 1 shows that greater number of seedlings fall under Classes 2 and 3. It can be inferred that 2 month -old seedlings of Yemane have 11- 30 first order lateral roots. Seedlings with more than 31 FOLR are exceptions and their occurrence under normal conditions may not be that significant. The initial FOLR groupings were empirically determined as low (0 to 6), medium (7 to 12), and high (12) in northern red oak (Quercusrubra) seedlings (Kormanik et al. 2002). 30 Candelaria, Quezon ab Kabacan, Cotabato b Arakan, Cotabato SEED SOURCES Figure 7. Root:shoot ratio of Yemane seedlings from different seed sources in the Philippines. 120 Cumulative Frequency (%) 100 No. of Seedlings Figure 6. Primary root length (cm) of Yemane from different seed sources in the Philippines. a b 80 60 40 Frequency 20 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 Frequency/Cumulative Percent Figure 8. Frequency distribution and cumulative percent of FOLRs of seedlings of Yemane from different seed sources in the Philippines. Table 1. Categories of Yemane seedlings based on number of FOLRs. Class 1 2 3 Number of FOLR 0 – 10 11 – 20 21 – 30 & Up Percent of Total Seedlings 16.55 47.00 36.45 Variation in Seedling Morphological Characteristics Based on FOLR Categories It has been observed that all the morphological characters exhibited highly significant variations among classes of FOLR. Remarkable increase in the length of seedling primary roots as the number of FOLR increases was observed. The longest average Root growth variability and heritability of Yemane
  5. 5. length of primary roots was obtained in Class 3 seedlings, having more than 30 FOLRs, while the shortest in Class 1, having a maximum of 10 FOLRs. Although remarkable and significant increase in stem height and root collar diameter of seedlings were observed among classes of FOLR, ranking of the three root classes in terms of root:shoot ratio did not differ (Table 2). Nonetheless, the mean shoot height did not differ between Class 2 and Class 3, but were significantly higher than seedlings in Class 1 (Table 2). Table 2. Variations in the different morphological features of Yemane seedlings based on first order lateral roots categories. The average collar diameter differed across the 3 root classes. Collar diameter progressive by increased with necessary FOLR. The highest collar diameter seedlings belonging to the Class 3 with a mean root collar diameter of 0.30 cm. The lowest average stem diameter on the other hand, (0.25cm) was noted in Class 1. Table 3. Pearson correlation coefficient between number of FOLR and seedling morphological characters of Yemane. The primary root length of Classes 1 and 3 differed significantly, but both are statistically similar to Class 2. The longest roots (18.2 cm) in Class 3 was significantly varied with Class 1 (15.7 cm) but insignificantly different with Class 2 (17.0 cm) (Table 2). **highly significant * significant at 0.05 level Shoot Height Collar Diameter 1 2 3 19.271 a 21.943 b 22.633 b 0.2515 a 0.2836 b 0.3045 c 15.730 a 16.963 ab 18.151 b Means with the same letters are not significantly different at p 0.05 using LSD test. Seedling Trait Stem height Root collar diameter Root length Root:shoot ratio All correlations were determined to be high (0.590.89) and were statistically significant. Highest correlation with the number of FOLR was observed on collar diameter of seedlings (r=0.88) while the lowest was on root:shoot ratio (R = 0.59). This implies that with increasing FOLR, stem height, root collar diameter, root length and root:shoot ratio increases, thus developing a healthy and vigorous seedlings. Family Mean Heritability Estimates for Seedling Morphological Traits Narrow sense heritability estimates for the various seedling morphological characteristics of Yemane seedlings were generally high. Highest genetic control appears to be in FOLR (h2=0.89) followed by root length (h2=0.87), root collar diameter (h2=0.85), root:shoot ratio (h2=0.88) and the lowest was stem height (h20.21) (Figure 9). R 0.7082** 0.8838** 0.8217** 0.58599* Prob>lRl 0.0022 0.0001 0.0001 0.0179 1 0.8 0.6 0.4 0.2 0 HERITABILITY Correlation Between FOLR and other Seedling Morphological Traits The number of FOLR in the seedlings of Yemane were positively correlated with other roots and stem morphological characteristics (Table 3). Root: Shoot Ratio 0.78002 a 0.82624 a 0.84494 a Root Length Heritability Estimates Average root:shoot ratio followed increasing trend similar to that of the classes of lateral roots. This finding is consistent with the findings of Carandang (1994). Seedlings with the most desirable form ratio belong to the highest class while seedlings with the poorest form ratio belonged to those with less than 10 FOLRs but this observation is not significant in the study conducted. Root Class FOLR Height Dia. Root L. RSR 0.8929 0.2081 0.8458 0.8714 0.5386 SEEDLING TRAITS Figure 9. Family mean heritability of Yemane seedlings from four locations in the Philippines. DISCUSSION The ranking of the seed sources are relatively consistent in all seedling morphological traits. It was apparent that the seedlings from Candelaria, Quezon and USM Kabacan, Cotabato consistently showed superior morphological values in all parameters measured. Either of the two location source rank first in the five seedling morphological traits considered in the study. The reverse is true with the seedlings sourced from Bansalan, Davao del Sur and Arakan, Cotabato. Either of the 2 location source ranked less in all seedling morphological traits. Thus, among the four seed sources studied, Quezon or Kabacan, Cotabato would be the best choice as source of seeds for quality seedlings. The significant variations in seedling morphological characters among the different seed sources of Yemane in the Philippines is not surprising, since only OS Corpuz 31
  6. 6. three provinces were considered in the study. Tree species in most cases are reservoir of extensive variations in almost all traits with the exceptions of those in the clonal plantations as reported by Carandang (1994). Tree species are products of long evolutionary forces and most tree populations are still in the wild state. Perry (1978) stated that forest geneticists, tree breeders or tree improvement workers are quite fortunate to be working with an undisturbed pool of natural variability that has developed over a long period of time. Stands of trees within a given site may differ, much more within different locations. This is a clear category of variability that the present study dealt with. Usually, the genetic differences in such stands are relatively small, but there are times when unexplained pockets of variation are found (Ledig and Fryer 1971). This is especially true for form characteristics which usually slightly differ genetically for trees on any common site (Carandang 1994). Individual trees of a species may also greatly vary from one another even if grown under similar condition. This is another type of variation encountered in the present study using Yemane. This is also the major type of variation that is valuable in tree improvement works particularly in the choice of the most appropriate selection procedure and the development of a breeding program for a particular tree species. The presence of significant variations among the sources of seeds of Yemane considered in the study is an indication that selection for the qualify seedling characteristics will work among the various stands of species in the Quezon, Cotabato and Davao del Sur provinces. Previously, Carandang (1994) found significant differences among different seedling morphological traits such as root length, shoot length, stem diameter, shoot weight, total weight, and root:shoot ratio of large leaf mahogany in Mt. Makiling Forest Reserve. Tumaliuan (1983), also found significant variations among parent trees of agoho (Casuarina equisetifolia Forst) in different provenances, in terms of seedling height, root collar diameter and total dry weight. The manner in which the seedlings are categorized based on the number of first order lateral roots could be very subjective. In the present study, more number of categories involving narrower ranges of FOLR number is still possible but, one has to bear in mind that the practical usefulness of making lateral root growth as a criterion for seedling stock assessment should take into consideration the simplicity of operation (Carandang 1994). Duryea and McClain (1984) stated that the developments in forest nursery operations must integrate a number of seedling physiological and morphological attributes in seedling stock assessment. Implicit therefore in the target 32 seedling concept is the development of simple grading schemes using minimum, maximum and standard values for as many seedling parameters as possible (Rose et al. 1990). The three classes established in the study are deemed appropriate for field testing. As shown in Table 4, a comparison of unclassified and classified seedling morphological traits revealed the same result. Unclassified seedlings are ungrouped seedlings in terms of root classes, while classified seedlings are those that are grouped based on number of FOLRs. Variability in seedling morphological characters exists among the three root classes defined. As indicated in the result of the study, the three root categories significantly varied among seedlings morphological traits tested in the study. Table 4. Comparison of significant variation in seedling traits between unclassified and classified seedlings according to the number of lateral roots Seedling Trait Stem height Root collar diameter Length of primary root Root:shoot ratio Unclassified Seedlings s s s s Classified Seedlings s s s s s – significant at 5% level It should be emphasized that the root classes of seedlings of Yemane in this study is an initial attempt at establishing seedling quality of the species based on RGP. The groupings made in this study based on the number of FOLR may further be refined and or modified when more studies are conducted to determine the reproducibility of the scheme for Yemane. This has been the experience of Kormanik, Muse and Sung (1992) with loblolly pine as cited by Carandang (1994). Kormanik (1986) showed that, within reasonable limits of seedling bed density, the number of first order lateral roots was not markedly affected by common nursery cultural management techniques. Furthermore, nursery field experiments have shown that regardless of the phenotypic characteristics of a sweetgum and other tree, associated progeny have a predictable frequency distribution when seedlings are stratified by first order lateral roots. Kormanik and Ruehle (1986) have also made lateral root counts on walnut (Juglans nigra L.), northern red oak, green ash (Fraxinus pennsylvanica Marsh), and long-leaf pine (Pinus palustris Mill.) and found relationship between roots and other seedling traits. By combining minimum seedling size and counts of lateral roots, they estimated that more than 60% of the walnut and red oak should be culled. This finding is in agreement with the results reported by Johnson (1984) from a 7-year field study with northern red oak. With further trials on the consistency of variability of stem and root characters, there is reason to believe that the initial result of the study is reproducible. Root growth variability and heritability of Yemane
  7. 7. The results of this study indicate that the FOLR categories developed for seedlings of Yemane are positively associated with the other seedling morphological traits. Shoot length, collar diameter, root length, and root:shoot ratio generally increased according to increasing categories of FOLR number. The use of the number of FOLR as an expression of seedling quality finds merit in its positive correlations with the other seedling morphological traits considered in the study. All morphological features specifically height and stem diameter, currently provide the best estimate of seedling performance after outplanting (Mexal and Landis 1990). Diameter is considered to be one of the best predictor of field survival while height seems to predict height growth in plantation (Ritchie 1984). Root morphology is highly correlated with both height and collar diameter which support the earlier findings of Mexal and Landis (1990). Root morphology, specifically the number of FOLR is more useful as an indicator of growth considering the trend towards the use of root growth potential as an indicator of early field performance and subsequent growth (Larsen et al. 1986; Ritchie and Dunlap 1980). As a measure of root growth potential (Stone and Schubert 1959; Burdett 1979), the number of lateral roots is widely adopted in physiological grading of forest nursery seedling stocks. The positive correlation of FOLR with stem and other root morphological characters as observed is highly significant. Operational experiences tend to indicate that, other factors being equal, seedlings with large stem diameter outperform those with smaller ones (Chavasse 1990; Cleary et al. 1979; Sutton 1979). When seedlings are carefully lifted as what has been done in the study, stem diameter is closely related with root morphological characters particularly number of FOLR. The findings confirmed with Rowan (1986) which stated that at harvest, large diameter seedlings have more primary root laterals. While it is possible that large diameter seedlings inherently have a more fibrous root system, it is more likely that smaller seedlings have thinner primary lateral roots that are more easily stripped during lifting operations (Carandang 1994). The improved field performance ascribed to larger diameter may partially, be the result of decreased root stripping. Blake et al. (1989) found that the relationship between field survival and seedling diameter was also affected by root mass especially for smaller diameter seedlings. Seedlings with good root mass consistently survived better than those with poor root mass. The positive correlation of FOLR growth with stem diameter and seedling height has some physiological basis. Evidences from the works of Richardson (1957; 1958) point to the fact that lateral root initiation and growth are influenced by both nutritional and hormonal factors derived from the shoot. OS Corpuz Significance of the Family Mean Heritability Estimates Heritability was originally defined by Lush as the proportion of phenotypic variance among individuals in a population that is due to heritable genetic effects (Nyquist 1991). It also indicates the degree to which parents pass their characteristics along to their offspring (Zobel and Talbert 1984). In the context of the present study, the heritability estimates of the different seedling morphological traits provide information on the extent in which the said traits are genetically controlled. High heritability values then means that a variation among families in the particular seedling morphological trait is largely due to the differences in the genetic constitution of the individual families. Estimates of family heritability in the study are of the narrow sense (h2) which defines the ratio of the additive genetic variance to the total variance. At the start, it is important to know that the different traits of seedlings of Yemane will only apply to the particular population of the species in the three seed sources (e.g. Quezon, Cotabato and Davao Sur). Only Cotabato Province was replicated in terms of seed source, such as Kabacan and Arakan, Cotabato, so that these values are not fixed and are simply determined to provide a general idea of the extent of genetic control and strength of inheritance of the said characters. With the exception of stem height, all other seedling morphological traits of Yemane in the four seed sources were found to be highly controlled genetically as shown by the high heritability estimates of all morphological traits (Figure 6). This finding confirms that genetically determined variation exists in root system of plants (Street 1957). Brisette (1990) recognized that genetics plays a critical role in determining root system development of forest trees, both in the nursery and in outplanting. Kormanik (1986) contended that while stem diameter maybe considered a better indicator of seedling vigor, it cannot fully explain the differences in seedling performance after outplanting. Webb (1969) earlier cautioned against using stem diameter when comparing early plantation performance of sweetgum seedlings from the same family when grown at varying seedling bed densities. This is because stem diameter represents a seedling’s response to edaphic conditions. Nursery cultural conditions such as seedling bed density, fertility, moisture and mycorrhizal conditions have been shown to affect stem diameter. Unfortunately, the edaphic conditions that stimulate stem diameter increases are not found in the field. Kormanik’s study on sweetgum revealed that the distributions of seedlings among root grades remained relatively constant within an open pollinated mother tree seedlot. This finding led to his recommendation that seedling grading based on lateral root morphology maybe a practical way to identify the seedlings with the best potential. 33
  8. 8. CONCLUSION Variability and strong genetic control of FOLR of Yemane seedlings from the three provincial seed sources were found in the study. The seedlings in the different root classes vary in terms of morphological traits such as stem height, collar diameter, root length, and root:shoot ratio. Seedling stem diameter was highly related with FOLR such that, stem diameter can be good indicator of field performance, Candelaria, Quezon and USM Kabacan, Cotabato are better seed sources when establishing Yemane plantations in Matalam, Cotabato because of their superior seedling morphological traits. RECOMMENDATIONS It says that the ultimate test of the quality of seedling is its early performance after outplanting and its subsequent growth during the early years in plantation. The lateral root classes established in this study will be further tested in terms of early field performance in the succeeding experiment. The RGP interactions with cropping pattern, sources of seeds and distance of planting will also be considered. This study revealed that variations in root and stem characteristics exist among the four locations (three provinces in the Philippines) of seed sources of Yemane. A study should be conducted to determine if such variations will be evident also among the other locations in the Philippines with consideration on seeds coming from other municipalities within a province. Only Cotabato province has two locations considered in this study. REFERENCES Campo del AD, Carrillo RMN, Hermoso J, Ibanez AJ. 2006. Relationship between root growth potential and field performance. Ann. Forestry Science 64 (2007) 541-548. Burdett AN. 1979. New methods of measuring root growth capacity: their value in assessing Lodgepole stock quality, Canadian Journal of Forest Research. 9: 63: 67. Carandang WM. 1994. Lateral root development and seedling performance of large leaf mahogany (Swietenia macrophylla King). [Ph.D Thesis] College, Laguna, Philippines: University of the Philippines Los Baños. 223 p (Available at UPLB Library). Chavasse CGR. 1990. Planting stock quality. A review of factors affecting performance. New Zealand Journal of Forestry 25: 144-171. 34 Cleary BD, Greaves RD, Hermann RK. 1978. Regenerating Oregon’s Forests. Oregon State University Extension Center, Corvallis, Oregon. OR. 287 p. Corpuz OS. 2011. Root growth of four hardwood tree species in the Philippines. The Center for Sustainable Development. CSDi Community http://www.csd-i.org/read-forest-trees-docs/. Nov. 5, 2011. Corpuz OS 2011. Growth, survival and heritability of Yemane as affected by provenance, root classes and spatial arrangement. In: Sales EK, Editor. Proc. Commission on Higher Education Zonal Center for Region IX, XII, CARAGA. Proc. National Research and Development Conference, Davao City, Philippines. 48 p. Corpuz OS, Abas EL, Sambayon JA. 2011. Growth and heritability of three year old Gmelina plantation. In: Sales EK, Editor. Proc. Commission on Higher Education Zonal Center for Region IX, XII, CARAGA. Proc. National Research and Development Conference, Davao City, Philippines. 48 p. Corpuz OS, Carandang WM, Visco RG, Lapitan RL, Castillo ASA. 2009. Root growth potential as affected by planting distance and provenance on the growth and survival of Gmelina arborea. World Agroforestry Centre. 2009. Book of Abstracts, 2nd World Congress of Agroforestry, Agroforestry - The Future of Global Land Use. Nairobi: World Agroforestry Centre. Corpuz OS, Carandang WM. 2011. RGP of selected tropical hardwood tree species in the Philippines as affected by root pruning. In: Sales EK, Editor. Proc. Commission on Higher Education Zonal Center for Region IX, XII, CARAGA. Proc. National Research and Development Conference, Davao City, Philippines. 48 p. Corpuz OS, Carandang WM. 2011. Effect of root growth potential, planting distance and provenance on the growth and survival of Gmelina arborea Roxb. The Asian International Journal of Life Sciences. ASIA Life Sciences 21 (1): 1-18, 2012. Corpuz OS, Carandang WM. 2012. Root Growth Potentials and Heritability of Gmelina arborea. 1st ed. LAP LAMBERT Academic Publishing. Germany. 256 p. Duryea ML, McClain KM. 1984. Altering seedling physiology to improve reforestation success. In: Huryea and Brown (eds). Seedling Physiology and Reforestation Success. MartinusNijhoff/Dr. W. Junk Publishers. The Hague. p 77-114. Root growth potential, variability and heritability of Yemane
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