M. George1, Ombir Singh, and D. Saikia
Rain Forest Research Institute
Jorhat — 785001, Assam
1 E.Mail: rainfor@sancharnet.in
Abstract:
Dipterocarpus retusus is an important species of raw material for plywood production in northeast India. The irregular management practices and regeneration problems resulted in the degradation of natural forest population of this species. In order to conserve the natural forest of D. retusus and to ensure the sustainable supply of raw material to the local plywood industries, there is a need to raise plantations of the improved quality seeds. To achieve the objective, Rain Forest Research Institute (RFRI), has started an improvement program for this species in 1998 and accordingly, a progeny trial of the species was established to screen out superior genotypes for further multiplication. An evaluation of this progeny trial of 17 half-sib families of D. retusus was conducted at the age of fifth year for plant height (H), diameter at breast height (DBH), clear bole height (CBH) and crown diameter (Cr. dia.). Significant variation in all progenies was observed for the traits studied. The performance of progenies viz., JKG —3, DMP-9 and JKG- 2 was found highly significant for all the traits over the check progeny. In inheritance study, heritability for height, diameter at breast height, clear bole height and crown diameter was recorded as 0.92, 0.56, 0.90 and 0.83, respectively. These results indicates that the out standing progenies can be used in recombination breeding and mass multiplication in different afforestation and reforestation programs till final results obtained. The genetic information from early testing can also be used to enhance selection efficiency at mature stage by culling inferior families.
Key words: Dipterocarpus retusus, progenies, variability, heritability, genetic advance
Dipterocarpus retusus Syn. Dipterocarpus macrocarpus, commonly known as Hollong belongs to family Dipterocarpaceae, is indigenous to Southeast Asia and a majestic hardwood species. Its natural distribution ranges from 10º S to 28º N latitude and 92 – 115º longitude and found up to elevations of 800 m. In this region, the species is distributed in “Z” shape, from upper Assam (India) to China, Myanmar, Thailand, Vietnam, Malaysia and Indonesia. In Northeast India, it is distributed in the alluvial deposits of Brahmaputra valley in the states of Assam, Arunachal Pradesh and Nagaland (Joshi, 1980, Rawat, 1998). Its unique morphological character of producing up to 40 meters of clean commercial bole and preferable anatomical characters makes it most suitable species in plywood industry and is a highly demanded commercial timber species in the region (Anonymous, 1997; Rajput et. al., 1996). The irregular management practices coupled with its heavy demand in plywood industries resulted in the degradation of the natural forest population of this species. In order to conserve the natural forest of Dipterocarpus retusus and to ensure the sustainable supply of raw material to the local plywood industries, there is a need to raise quality plantations of the species. To achieve this, Rain Forest Research Institute, has started an improvement program and as part of this; a progeny trial of the species was established in the year 1999 (Thakur et.al., 2002).
Progeny selection refers to selection of plants from a diverse population on the basis of their progeny test. The success of plantation establishment and productivity is determined largely by the grower’s choice of species and seed source (Larsen, 1954; Callaham, 1964; Lacaze, 1978). Therefore, progeny trials are the essential components of a genetic improvement program to evaluate growth performance, stem form, and susceptibility to pests and diseases on the basis of genetic potency of parents and expression pattern of the governing genes in particular environment. The primary aim of such trials is to identify best performing progenies early for abundant quality seed production by promoting inter-mating of the selects. Since, time is one of the most important considerations in selective breeding of long- lived tree species (Zobel, 1978), the selection for economic traits of growth, form, pest resistance and wood quality is commonly made at or before 1/3 or 1/2 of the rotation age (Lambeth, 1980; Zobel and Talbert, 1984). Both early — mature genetic correlation and heritability of the early trait affect the magnitude of genetic gain increase for the mature trait from early selection (Wu, 1998). The expected response in a trait at rotation age due to early selection constitutes an indirect genetic gain (Wu et al; 2000). Information obtained about heritability and genetic gain can also be used in increasing the selection intensity or reduced field- testing size and shortened generation interval by rouging of inferior progenies.
Accordingly, the present study was taken up to identify the best genotypes for the production of improved, seeds and quality planting stocks for future breeding programs.
Materials and Methods:
Seventeen half-sib progenies of Dipterocarpus retusus viz., DMP-2, JKG-3, LK-1, DR-1, DMP-4, JKG-2, LK-4, DB-9, DMP-9, DB-2, JKG-4, DMP-5, DK-4, DR-2, DK-1, LK-3 and DMP-7 raised from seeds of plus trees selected in upper Assam and Arunachal Pradesh were investigated in this progeny trial along with control. The progeny trial was established at Jorhat (Assam) located at 26º46´ N latitude, 94º13´ E longitude and 95 m altitude. The climate of the region is moist and deciduous with an annual mean rainfall of approximately 2500 mm and temperature of 23.9ºC and soil is red laterite, well drained, acidic in nature. The progenies were planted in 1999 in randomized complete block design (RCBD) with three replications under tree geometry of 10 x 3 m spacing.
The progeny trial was assessed at the age of 5th year in the month of April 2004 and data was recorded for plant height (H), diameter at breast height (DBH), height at first branch /clear bole height (CBH) and crown diameter (Cr. dia.). Analysis of variance (ANOVA) was carried out using GENSTAT 2000 software to detect significant differences among progenies. The following is the format of analysis of variance table:
Analysis of Variance Table (ANOVA) …
Sources: 8th Round-Table Conference on Dipterocarps
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