Abstract: Pusa RH10, a popular high yielding superfine grain aromatic rice hybrid and its parents Pusa6A and PRR78 are highly susceptibility to blast disease. Marker assisted backcross breeding (MABB) approach was employed to incorporate blast resistance genes viz., Piz-5 and Pi54, from the donor lines C101A51 and Tetep into the genetic background of PRR78 to develop Pusa1602 (PRR78 + Piz5) and Pusa1603 (PRR78 + Pi54), respectively. Foreground selection for the genes Piz-5 and Pi54 was effected using tightly linked molecular markers, AP5930 and RM206, respectively in two independent backcross series. Further, foreground selection was coupled with stringent phenotypic selection for agronomic, grain and cooking quality traits, to accelerate recurrent parent phenome recovery. Five superior BC2F2 plants homozygous from each of the backcross series were selected and advanced to BC2F5 generation through pedigree selection to develop improved versions of PRR78 with blast resistance. Background analysis revealed the recurrent parent genome recovery up to 89.01% and 87.88% in Pusa1602 and Pusa1603 lines, respectively. The hybrids produced by crossing Pusa6A with improved lines of PRR78, were on par with original Pusa RH10 in terms of yield, grain and cooking quality traits with an added advantage of blast resistance.
Abstract: In the present study, we tested rice genotypes that included un(der)exploited landraces of Tamil Nadu along with indica and japonica test cultivars to ascertain their genetic diversity structure. Highly polymorphic microsatellite markers were used for generating marker segregation data. A novel measure, allele discrimination index, was used to determine subpopulation differentiation power of each marker. Phenotypic data were collected for yield and component traits. Pattern of molecular differentiation separated indica and japonica genotypes; indica genotypes had two subpopulations within. Landraces were found to have indica genome, but formed a separate subgroup with low linkage disequilibrium. The landraces further separated into distinct group in both hierarchical clustering analysis using neighbour-joining method as well as in the model based population structure analysis. Japonica and the remaining indica cultivars formed two other distinct groups. Linkage disequilibrium observed in the whole population was considerably reduced in subpopulations. Low linkage disequilibrium of landforms suggests their narrow adaptation in local geographical niche. Many population speciï¬c alleles could be identiï¬ed particularly for japonica cultivars and landraces. Association analysis revealed nine markerâtrait associations with three agronomic traits, of which 67% were previously reported. Although the testing landraces together with known cultivars had permitted genomewide association mapping, the experiment offers scope to study more landraces collected from the entire geographical region for drawing more reliable information.
Abstract: Rice as the major staple food of the world although is high in calories but deficient in essential micronutrients. This deficiency can be tackled by biofortification of rice grains with enhanced micronutrient content. Field experiments were carried out across three locations involving 17 genotypes, with the objective of assessing the genotype à environment interaction for native soil micronutrient assimilation in rice kernels and the influence of intrinsic soil variables on micronutrient content in rice grains. Contents of Fe, Zn, Cu and Mn in the milled kernels were found to vary significantly among genotypes and locations. There was significant genotype-by- environment interaction (GEI) for all the nutrients. Further, it was found that soil pH and soil available P had significant influence towards grain Fe content. Soil Zn availability and the electrical conductivity of the soil solution were found closely associated with grain Zn content. The two factors that regulated Cu and Mn content of rice grains were soil organic carbon content and soil Cu availability. The factorial regression (FR) approach to assess the role of significant intrinsic soil factor (s) on enrichment of specific micronutrient in the milled rice kernels showed differential genotype responses that ultimately determined grain micronutrient accumulation in each genotype. These determinants enabled prediction of genotypes suited to different environments. In certain cases, further examination of environmental co-factors is advocated to bring out a comprehensive picture of the micronutrient assimilation in milled rice grains.
Abstract: Marker assisted backcross breeding (MABB) provides a great opportunity for precise transfer of desirable donor segment by minimizing the linkage drag into a recurrent parent. In our lab, MABB was used for incorporating bacterial blight (BB) resistance genes (xa13 and Xa21) into the genetic background of Pusa Basmati1, which led to development of Improved Pusa Basmati 1 (Pusa 1460) as one of the first products of molecular breeding. Further, the parental lines of superfine grain aromatic rice hybrid Pusa RH 10 namely, Pusa 6A, Pusa 6B and PRR78 were improved for resistance to BB and blast by transferring genes xa13+Xa21 and Pi54 +Piz5, respectively. Presently, the pyramiding of genes for resistance to BB (xa13 and Xa21), blast (Piz5 and Pi54) and brown plant hopper (BPH; Bph 3, Bph 17, Bph 18, Bph20 and Bph 21) into Basmati rice varieties viz., Pusa Basmati 1121 and Pusa Basmati 6 is under way. In addition, a major QTL for salt tolerance (Saltol) is being transferred to Pusa Basmati 1121, which is widely grown in Haryana, the state having problem of salinity owing to underground brackish water. In order to develop genetically enhanced donor sources for resistance to biotic (BB, blast and BPH) and abiotic (salt tolerance, and phosphorus uptake) stresses in Basmati background, isogenic lines are being developed for major resistance genes/QTLs for respective stresses in the background of Pusa Basmati 1. Molecular mapping of fertility restorer gene(s) in Basmati restorer line PRR78 led to identification of two Rf gene linked molecular markers, RM258 and RM6100. Of these, RM6100 on validation in a set of rice germplasm showed 97.4% efficacy in identifying restorer lines from germplasm.QTL mapping using RIL population has unveiled several novel QTLs for grain and cooking quality traits. Molecular markers are also being routinely used for establishing variety/hybrids identity and authentication of genetic purity of hybrid seed lots.
Abstract: One of the activities that geneticists pursue is the generation of genetic maps of organisms that chart the locations of the different genes on the chromosomes. Damodar Dharmanada Kosambi was not a geneticist by training and profession, but amathematician. Yet, in 1944, Kosambi wrote
a classic paper about mapping function in genetics in the journal Annals of Eugenics. His lone paper in genetics was tilted âThe estimation of map distance from recombination valuesâ. The mapping function that Kosambi derived is still widely used by geneticists the world over for the mapping of
genomes..
Abstract: Para rubber (Hevea brasiliensis) trees are naturally adapted to the Amazonian tropical climate. In India rubber trees are traditionally cultivated in the warm humid tropics of the south. Northeast India is a non-traditional area for rubber cultivation. A major limiting factor on tree growth in the northeast region is stress due to low temperature. Being a deciduous tree, rubber trees exhibit annual natural defoliation prior to the winter season, and ensuing new leaf growth usually coincides with the low temperature period. Flushing behaviour of trees during this period provides an opportunity to assess their winter hardiness. A study was carried out on five clones, RRIM 600, SCATC 93/114, GT 1, PB 5/51 and Haiken 1, to evaluate phenological behaviour of leaf growth during the period of low temperature stress. Trees were monitored for expansion of leaf area, internode length, petiole length and development of chlorophyll. Wide variation was observed among these clones for all the traits. SCATC 93/114 was better adapted for low temperature stress as this clone was found to have faster expansion of leaf area and better chlorophyll development, followed by Haiken 1. PB 5/51 was found to show poor performance during low temperature. Haiken 1 and PB 5/51 also exhibited better relative growth rate during winter months confirming their low temperature tolerance. Ontogenetic variations in leaf development are good indicators of assessing inherent cold tolerance in Hevea clones.
Abstract: Corynespora leaf fall (CLF) disease caused by Corynespora cassiicola (Berk & Curt.) Wei. has emerged as major leaf disease of Hevea rubber infecting cultivated clones and causes economic losses. Sixty two cultivated Hevea clones were tested for CLF disease resistance under natural infection in the field and in the nursery. It was found that 10 clones in the main field and 4 clones in nursery showed no infection during initial screening, but subsequently they also showed differential reaction. Based on the average disease intensity across years, popular high yielding clone RRII 105 was found highly susceptible and commercially cultivated clones, RRIM 600 and GT 1 were classified under resistant group (PDI <5), while popular clones like RRII 208, PB 252, PB 5/51 and PB 213 were grouped as tolerant clones (PDI 5-10). Analyses of variance revealed significant variations among clones, year and clone x yearâs interaction components. Though average performance of clones vacillated across years, their susceptibility rankings remained relatively constant. Cluster analyses reveled natural grouping of five distinct clusters. The most susceptible clones, including RRII 105 remained very susceptible throughout the study period. None of the clones tested showed true genetic resistance bordering immunity. About 63% of clones in nursery and 68% in field tests were classed in the first cluster which showed some tolerance or lesser susceptibility to the disease (PDI 5-25). Clones in the remaining clusters were susceptible (PDI >25). As availability of suitable sources of resistance is a basic tool for the breeder, information generated is useful in successful resistance breeding programmes for CLF disease.
Abstract: Extensive cultivation of Hevea brasiliensis in India now focus on non-traditional regions for rubber cultivation. As a prelude for selection of genotypes for commercial cultivation, many introduced genotypes are being tested in genotype adaptation experiments in these regions. Present study, reports for the first time, growth and yield adaptation of 28 genotypes in a non-traditional rubber growing region of peninsular India viz., the coastal Karnataka region. Agroclimate of this region was found favoring growth and establishment of all the genotypes evaluated. However, not all the genotypes grew and yielded well. Only four genotypes, RRII 203, KRS 25, PB 260 and PB 235 showed good growth and yield. On grouping, the genotypes fell into categories of moderate high yielders, moderate low yielders and low yielders. The most popular variety of the traditional region, RRII 105 did not perform well in this region. Biological stability in growth and yield of RRII 203 and PB 260 was identified as stable and these genotypes were the best adapted. KRS 25 and PB 235 had unstable yielding pattern. The best identified genotypes can be considered for extensive culture as single clone plantations or as major constituent of clone blends as well as parents in future breeding programmes. Other moderate stable yielders may be used for clone blending in smaller proportions and may be subjected to yield improvement.
Abstract: Drought resistance is becoming an indispensable character for rice improvement due to the dwindling global water resources. Genetic improvement for drought resistance is achieved through physiological dissection and genetic analysis of independent component traits associated with crop productivity under stress. A subset mapping population of 93 near flowering recombinant inbred lines with uniform phenology was constituted for genetic analysis of reproductive stage drought resistance. The population was phenotyped for 22 physio-morphological traits under two contrasting water regimes imposed at reproductive stage. Broad sense heritabilities of morphological traits were lower under stress than irrigated. Predominant association of plant height, panicle exsertion and harvest index with grain yield were observed under stress. The sustenance of panicle exsertion through maintaining growth during moisture stress was found as a significant trait associated with the grain yield through minimizing spikelet sterility. Selective genotyping was carried out with 23 polymorphic microsatellite markers of the established target genomic regions for drought resistance. The study validated the association of a QTL region on the long arm of chromosome 1 with plant height, panicle length, panicle exsertion, biological yield and stomatal conductance under stress. This region, flanked by markers RM246 and RM315, was known to possess the semi-dwarf gene, sd-1. Role of another major interval lying between RM256 and RM149 on chromosome 8 in defining the drought resistance could be established through identification of QTLs associated with leaf rolling, panicle exsertion, plant height, panicle length, senescence and biological yield under moisture stress condition. Few other QTLs were also identified.
Abstract: Cooking quality in rice grains is a complex trait which requires improvement. Earlier reports show varying genetic influence on these traits, except for a common agreement on waxy (Wx) and alkali degeneration (Alk) loci on chromosome 6. The present study involved 86 doubled haploid lines derived from an indica à japonica cross involving IR64 and Azucena. Grain parameters viz., raw grain length (RGL), raw grain breadth (RGB), cooked grain length (CGL), cooked grain breadth (CGB), gelatinization temperature (GT), grain shape (RGS), length elongation ratio (LER) and breadth expansion ratio (BER) were subjected to mixed model mapping of quantitative trait loci (QTL). Segregation data of 175 markers covering a distance of 2395.5 cM spanning the entire genome were used. Fifteen main effect QTLs were detected spread over the genome, except on chromosomes 4, 8 and 11. Thirty epistatic interactions significantly influencing the traits were detected. Twelve of the main effect QTLs were involved in epistatic interactions. One main effect QTL associated with LER was detected near Alk locus. QTLs located for grain length on chromosomes 9 and 10 are reported for the first time. Detection of many epistatic loci and involvement of main effect QTLs in interactions demand for judicious selection of QTLs in marker-assisted selection programmes
Abstract: Genetic diversity of the cultivated wheat is narrowing down and is increasingly becoming non-complacent in tackling new pathogenic races and adverse environmental situations. Wild relatives of wheat are rich repositories of beneficial genes that are capable of defying adverse situations. However, these wild species are not readily crossable with cultivated ones. The present study attempted crossing three wild wheat species as females with three cultivated species of varying ploidy to understand the intricate behaviour of hybrids in relation to cytology, morphology and molecular recombination. Post-fertilisation barriers caused hybrid recovery in wild species in contrast to cultivated species. Triticum monococcum did not produce hybrids in any of the crosses. Various degrees of chromosome anomalies and hybrid sterility were seen with hybrids of T. timopheevi and T. sphaerococcum. Cytoplasmic factors were suspected to add more to the abnormality. G genome from T. timopheevi could enhance more pairing between B and D of cultivated species. Precocity of certain chromosomes in laggard formation was evident, pointing towards evolutionary self balance of the genomes which prevented homeologous pairing. They are eliminated in hybrids. Molecular diversity clearly corroborated with genetic proximity of the species, which distinguished themselves by the maintaining the genome homeology.
Abstract: Agricultural environments deteriorate due to excess nitrogen application. Breeding for low nitrogen responsive genotypes can reduce soil nitrogen input. Rice genotypes respond variably to soil available nitrogen. The present study attempted quantification of genotype x nitrogen level interaction and mapping of quantitative trait loci (QTLs) associated with nitrogen use efficiency (NUE) and other associated agronomic traits. Twelve parameters were observed across a set of 82 double haploid (DH) lines derived from IR64/Azucena. Three nitrogen regimes namely, native (0 kg/ha; no nitrogen applied), optimum (100 kg/ha) and high (200 kg/ha) replicated thrice were the environments. The parents and DH lines were significantly varying for all traits under different nitrogen regimes. All traits except plant height recorded significant genotype x environment interaction. Individual plant yield was positively correlated with nitrogen use efficiency and nitrogen uptake. Sixteen QTLs were detected by composite interval mapping. Eleven QTLs showed significant QTL x environment interactions. On chromosome 3, seven QTLs were detected associated with nitrogen use, plant yield and associated traits. A QTL region between markers RZ678, RZ574 and RZ284 was associated with nitrogen use and yield. This chromosomal region was enriched with expressed gene sequences of known key nitrogen assimilation genes.
Abstract: Genetic diversity among 35 rice accessions, which included 19 landraces, 9 cultivars and 7 wild relatives, was investigated by using microsatellite (SSR) markers distributed across the rice genome. The mean number of alleles per locus was 4.86, showing 95.2% polymorphism and an average polymorphism information content of 0.707. Cluster analysis based on microsatellite allelic diversity clearly demarcated the landraces, cultivars and wild relatives into different groups. The allelic richness computed for the clusters indicated that genetic diversity was the highest among wild relatives (0.436), followed by landraces (0.356), and the lowest for cultivars. Allelic variability among the SSR markers was high enough to categorize cultivars, landraces and wild relatives of the rice germplasm, and to catalogue the genetic variability observed for future use. The results also suggested the necessity to introgress genes from landraces and wild relatives into cultivars, for cultivar improvement.
Abstract: Hailstorms are a regular phenomenon in the Northeast India during the pre-monsoon period. Though their intensity used to be mild, occurrence of strong hailstorms causing severe damage is not unusual in this region. Hevea brasiliensis Muell Arg., the Para rubber tree is reported to suffer extensively under hailstorm damage. An incidence of such a devastating hailstorm was reported from rubber plantations at Agartala, Tripur a in 1986.
Abstract: The wild species of Sesamum have long been recognized as an important source of many valuable pest and disease resistance genes and other novel traits such as male sterility and plant type for the cultivated taxon. Utilization of these species in crop improvement is marginal because of their inherent low crossability with the cultigen. An understanding of the biological nature of incompatibility systems that impede hybridization offers tools for successful introgressions into cultivated sesame. The objective of this investigation was to observe pollen germination and pollen tube growth in cross pollinated S. indicum pistils as an indicator of pre-zygotic barriers operating in wide crosses involving S. indicum. Three wild species: S. alatum, S. radiatum and S. laciniatum were used as pollen donors in hybridization with S. indicum. In the cross S. indicum à S. alatum 85.23% of pollen grains germinated and pollen tubes reached ovaries within 8 h after pollination. In other two crosses, S. indicum à S. laciniatum and S. indicum à S. radiatum the level of incompatibility was high as evidenced by a reduced pollen germination and slow rate of pollen tube growth. Measures to circumvent incompatibility in these crosses to produce interspecific hybrids are discussed.
Abstract: Two clone evaluation trials with five clones each were planted during 1987 and 1988 to study the adaptability of H. brasiliensis clones in the Coastal Karnataka region. Growth of the clones was monitored by measuring girth initially at annual intervals and later at quarterly intervals. The growth was compared by means of absolute girth and girth increment values. Clones PB 235 and RRII 118 were found to be the more vigorous. A quadratic trend was fitted for annual average girth as a function of age. Clones showed non-significant variation for girth increment. The growth in terms of girth increment (GI) was fitted as a power function of age (X). Since all the clones irrespective of the trials showed similar growth trend, a general equation, GI=616.012 X-1.8982 was fitted. Comparison of quarterly and half-yearly girth increment has shown that, growth was maximum during the rainy season (April-October). There was no definite pattern of contribution so far as individual quarters were concerned.
Abstract: Corynespora leaf fall (CLF) disease caused by Corynespora cassiicola (Berk & Curt) Wei. is currently considered as one of the major leaf diseases of Hevea brasiliensis in South and South East Asian countries. Chemical control of this disease by high volume spraying in mature plantations is expensive. Field experiments were conducted from 1998 to 2000 to assess the efficacy of oil-dispersible and dust fungicide formulations in controlling the disease. Four oil-dispersible fungicides viz. mancozeb 75 % powder, mancozeb 50 % liquid, copper oxychloride (COC) 56 % powder and mancozeb 50 % + COC 15 % (mixed powder) and three dust fungicides viz. hexaconazole 2 % carbendazim 1.5 % and tridemorph 1.5 % were tested. Mancozeb 75 % powder and mancozeb liquid formulations were found to be more effective treatments among the oil-dispersible fungicides. COC 56 % ODP and mancozeb + COC mixed formulations also gave significant control of the disease. Hexaconazole 2 % and carbendazim 1.5 % were found to be superior among the dust formulations. Dusting during refoliation period is more advantageous for controlling CLF disease as compared to spraying of oil-dispersible fungicides.
Abstract: A study was carried out in ten oriental clones of Hevea brasiliensis, planted in a clone evaluation trial in Tripura (North East India) to understand the clonal variation and environmental influence on phenotypic expression of yield and related traits during two peak yielding seasons. Pheno-typic coefficient of variation for plugging index (PI), inorganic phosphorus (Pi), sucrose content (SC), total volume (TV) and dry rubber yield (RY) was high when compared to that for initial flow (IF), dry rubber content (DRC) and total solids content (TSC). Mean performance of clones RRII 105, RRIM 600 and PB 235 was better for yield and related traits. These clones had less outflow of sucrose indicating better efficiency of metabolism. Stability of clones decreased with better yielding nature, except for RRIM 600, which showed better stability. GT1 and RRII 118 showed higher stability for most of the traits. The 10 clones were grouped into three clusters using non-hierarchical Euclidean cluster analysis. Cluster I included high yielding clones RRII 105, RRM 600 and PB 235, cluster II consisted of RRII 118, RRII 203, PB 86 and GT 1 which were medium yielding clones and cluster III comprised the low yielding clones RRIC 105, Gl 1 and Harbel 1. Average inter cluster distance showed that cluster III was more divergent from clusters I and II. Phenotypic variation in the character expression for yield of clones was considerably influenced by factors, which were associated with senescence and low temperature reaction. The clones, which were stable and high yielding like RRM 600 would be more desirable for this region.
Abstract: Widespread incidence of Corynespora leaf fall (CLF) disease in mature rubber plantations was reported in 1996 from Nettana in South Karnataka, India. Surveys carried out in coastal Karnataka and North Malabar region of Kerala during 1998-2000 disease seasons indicated that the disease incidence and severity of infection varied between light to severe in all the locations. The intensity of infection was found to increase gradually and the incidence to widen year after year. Subramanya region in Karnataka exhibited maximum intensity of the disease. Fresh incidence was noticed in Hosdurg and Nileshwar in Kerala during 2000. Variation in intensity of disease among different clones was observed with the clone RRII105 showing high and RRIM 600 and GT 1 showing low infection in all the locations surveyed.
Abstract: A study was undertaken to assess the variation and covariation of yield and related traits of ten clones of Hevea brasiliensis, during the peak yielding season for two years in Tripura, North East India. Initial flow rate (IF), plugging index (PI), dry rubber content (DRC), total solids content (TSC), inorganic phosphorus (Pi), sucrose content (SC), total volume of latex (TV) and dry rubber yield (RY) exhibited considerable seasonal and clonal variation. The response patterns of different traits varied from linear (IF, DRC, TSC and SC) to non-linear (PI, Pi, TV and RY). The patterns were similar during both the years under study. TV was found to be the major factor contributing to seasonal fluctuations in the dry rubber yield, DRC and TSC were found negatively associated with Pi and SC as observed in stimulated trees. SC was found to be the major determining factor of TV. Pi influenced TV positively through SC, while IF and DRC influenced TV negatively through SC. It appeared that the trees experience some kind of stimulation during the peak yielding season, causing increased laticifer activity and higher sucrose loading resulting in drainage of excess unutilized sucrose through latex serum. The phenomenon also causes prolongation of latex flow. Influence of wintering process and low temperature in determining the yield was evident.
Abstract: The distribution pattern of soil microflora was studied in a five year old rubber plantation in Tripura by placing fertilizers at varying soil depths. The fungal, bacterial and mycorrhizal population were found to decrease significantly in deeper soil layers. Horizontal distribution of bacteria showed maximum activity in the region of higher root concentration. The mycorrhizal infection was found higher towards the base of the trees and also away from the site of fertilizer placement.
Abstract: North-East India is an ideal non-traditional tract for growing the rubber tree (Hevea brasiliensis). The first trial for evaluating clones in this tract was laid out during 1979 at Agartala involving fifteen oriental clones. Apart from the growth and yield, secondary attributes of clones were also studied. 80.80% of growth was contributed during May to October. The highest percentage of initial survival and growth was exhibited by RRIM600. Precocity in tapability was seen in RRII118, RRIC105 and PB235. Initial yield pattern showed PB235, RRIM600, RRIM703 and RRII105 as high yielding clones, and RRII105 followed by PB235 having higher dry rubber content. PB5/51 showed moderate tolerance to wind damage.
Abstract: Spatial distribution of roots and nutrients in the horizontal and vertical planes was assessed in a five year old rubber plantation in Tripura, India. Root concentration was seen in the top 18 cm layer. Horizontally the roots were found upto 200 cm away from the plant base. Nutrient concentrations were also higher in the top layer than in the lower layers. There was a positive correlation between available phosphorus and fine root concentration suggesting influence of phosphorus in root development.
Abstract: Determination of biomass in tree crops like Hevea is cumbersome and a most viable alternative method is to estimate the biomass as a function of a common measure of growth, like girth. In the present study relationships were worked out with girth at 150 cm from bud union and above ground biomass for trees of clone RRIM 600. Both power as well as exponential regression equations fitted were found to be reliable in all classes of girth from 45 to 93 cm. The relationships are W = 0.0202 G2.244 (power) and W = 24.8486 e0â¢0343G (exponential).
Abstract: A study was undertaken to group rubber (Hevea brasiliensis) clones based on their wintering behaviour in Tripura, one of the rubber growing areas of North East India. Fifteen clones from a clone evaluation trial were scored for the wintering pattern at .weekly intervals for six weeks from December to February during 1988-89, 1989-90 and 1991-92 period. Wintering pattern of clones was uniform for all the years under study. Mean weekly scores were used for clustering process. Three distinct clusters of early, intermediate and late wintering clones were obtained viz., (i) RRII105 and RRIC105, (ii) RRIM600, PB86, GT1, RRIC52 and PB235 and (iii) RRII118, RRIM605, Gl1, Harbel1, RRII5, PB5/51 and RRIM703. The remaining clone, RRII203, was found to fall in between the second and the third dusters. The results can be used in characterizing clones as well as selecting clones for establishing polyclonal breeding gardens.
Abstract: Selecting genotypes combining high yield and stability using appropriate statistical methods can bring out better cultivars. An attempt has been made in the above lines to isolate better Hevea clones based on their initial yielding performance at Rubber Research Institute of India, Agartala in North-East India which is a non-traditional rubber growing tract. Selection was made among fifteen oriental clones based on the parameters viz., mean dry rubber yield, stability variance, Rank-sum index (Index I), S3i and S6i. The data are based on average monthly dry rubber yield for three tapping seasons viz., 1990-91, 91-92 and 92-93. Index I is found to be a better indicator tor selecting clones combining both yield and stability. S3i and S6i are found to tend more towards stability than yield. All .the better yielders selected based on high yield alone viz., PB 235, RRIM 600, RRII 105, RRIM 703, RRII 203, RRII 118 and RRIC 105 are also found to be better performers based on Index I. However, the stability in yield over months is found decreasing when the yielding potential goes up. These clones can be utilized for setting up of composite clone gardens in the non-traditional regions.
Abstract: Wounding of plants can be defined a incisions, abrasions or other injuries due to external violence like cutting, slotting, tearing and attacking in any part of a tree or plant. Wounding can be fatal, in which case the plant succumbs to the injuries, sub-fatal when the damage goes deep inside the system causing internal as well as external damages but plant survives, and superficial where the plant recovers almost to the normal state.
Abstract: The relationship between girth and the above ground biomass was studied in two clones, with varied growth habits, of Hevea brasiliensis. The clones chosen were RRIM 600 and RRII 118. A set of relationships were developed using the biomass as a power function of girth for different age groups from first year after planting upto fifth year. The regression equations were found non-significant for individual clones as well as for years from second year onwards. A general equation was thus developed and is given as biomass in g(W) = 2.278479 X2â¢263 (where, X is the girth at 15 cm height from bud union). The relation is found to be good fit from 16 em or more girth, and is location specific.
Notes: Hevea brasiliensis, Girth, Biomass, Regression model
Abstract: The agroclimatic suitability of north eastern (NE) region of India for cultivation of rubber (Hevea brasiliensis) has been well established and studies conducted have pointed out that the growth of Hevea tree in this region is comparable to that in traditional regions. Nevertheless, there are some climatic constraints for growth and yield. Of the constraints, low temperature during winter followed by a period of water stress is the major limiting factor. Isolated stress factors such as hailstorm, cyclone etc. also pose problems in the establishment of rubber plantations in the region.
Abstract: To know the combining ability of seed weight in chickpea, five lines namely Co1, CO2, CoG4, CoG6 and lCCV2 as females and three testers namely Annigeri, CO3, and L550 as males were crossed in a line x tester model. The effects of the parents and the sca effects of the hybrids were estimated. The estimates of gca revealed that significant and positive effects were observed with, CoG4 (5.241), CoG6 (1.627) and ICCV2 (1.775) among lines and with Annigeri (1.468) among testers. The hybrids CoG4 x Annigeri showed high sca effects (2.982), while CoG6 x Co3 (4.028) and ICCV2 x Co3 showed high sca (1.524) with high per se performance. The gca and sca variance ratio showed the preponderance of non-additive gene action for the seed weight in chickpea (0.1734 : 1).
Abstract: F2 progenies of the indica hybrids Zhen Shan 97A X IR50, Erjiu-nan 1A X IR50 and MS37A X IR50 were evaluated in the 1988 wet season. All fertile progeny had well-exserted panicles while plants with poorly exserted panicles were sterile. ShR [Sarocladium oryzae] infection was severe in plants with poorly exserted panicles and this was attributed to the presence of half-opened leaf sheaths favouring infection.
Abstract: A study was carried out to determine the clone X environment interaction during the early growth phase of 15 Hevea clones at Taranagar Farm of the Regional Research Station of the Rubber Research Institute oflndia. The results showed that the rate of increment in girth- significantly d-ecreased with increasing age irrespective of seasons (winter/summer). However, there was wide differences between the girth increment during summer and winter months. GE interaction parameters like ecovalence and stability .variance showed that clones studied have differential adaptability. The data suggest that clones RRIM 600, PB 86 and GT 1 are widely adapted showing more flexibility and those like RRII 105 are specifically adapted with less flexibility. The results indicate that selection for phenotypic stability can lead to isolation of stress resistant genotypes.
Abstract: Hevea brasiliensis (Wild. ex. A. de Juss) Muell - Arg., the natural rubber tree, is one of the domesticated wild forest trees, and is one among the least genetically manipulated crops of the world. The basic reason for the lesser genetic manipulation was the extensive out-crossing nature of the tree, long breeding cycle and narrow genetic base when compared to other cultivated species. Apart from these, the major economic output from the tree - the natural rubber- is of physiological and complex biochemical origin
Abstract: Plantation crops include perennials grown over large areas in monoculture, excepting fruit trees grown in orchards. These crops face both abiotic and biotic stresses, incited by factors those coexist in plantations. Plantation crops are well adapted and are grown mostly in the tropics, where innumerable stress factors operate. Historical significance of few stress havocs in plantation species is remarkable. A wide range of anatomical, physiological and biochemical features contribute to various stress adaptation in plantation crops. Notwithstanding, improvement of stress resistance in plantation species has been mandated to combat unfriendly factors that jeopardize intensive and extensive cultivation. Conventional breeding is cumbersome in plantation crops, where in the process got have to involve many generations running for decades, and expensive in terms of time, space and large volume of individuals handled. Recent developments in molecular genetics and biotechnology are aiding acceleration of breeding process plantation species. Integration of proper crop management strategies with improved cultivars is essential to meet the goals of stress management. This review presents a comprehensive coverage of various adaptive mechanisms and mitigation strategies for several biotic and abiotic stresses affecting major plantation crops like cardamom, cashew, cocoa, coconut, coffee, date, eucalyptus, oil palm, rubber and tea.
Abstract: Epidemics of Corynespora leaf fall (CLF) disease has been reported from most of the Asian rubber growing countries. Normally, the CLF disease appears during refoliation period causing repeated leaf fall. To develop a tool to the integrated disease management, field experiments were conducted to evaluate the efficacy of water based fungicides for the control of the disease. Water dispersible formulations of four fungicides, viz., mancozeb 75% WP, carbendazim 50% WP, copperoxychloride (COC) 50% WP and bordeaux mixture (BM) 1% were sprayed with an interval of 10-12 days. Among the fungicides tested, mancozeb (2.5g/l) and carbendazim (1g/l) were found to be more effective. COC (2.5g/l) was also found to be comparable to BM. Mancozeb and carbendazim had showed greater disease suppression than other fungicides. The cost analysis revealed mancozeb to be the best fungicide, being both cheap and effective. Since, the spraying of systemic fungicide is more advantageous for protecting the plant parts not covered by spraying, use of carbendazim can be advocated in older rubber plantations.
Abstract: Tripura offers a potential non-traditional environment for Hevea with an extreme minimum temperature of 3.8°C, and with a near zero precipitation during winter. Hevea thus encounters an exceptional stress situation In Tripura almost similar to the rubber areas of South China. A breeding experiment was conducted with six clones (RRII208, RRIM600 and PRl07, SCATC88-13, SCATC93-114 and Haiken1) of which three are Chinese. The analysis of stability variance involving data on girth increment indicated Haiken1 to be the most stable clone followed by the other clones in the descending order: PR107, SCATC 93-114, SCATC88-13, RRIM600 and RRII208. Haiken1 and RRll208 were prominent through their increased contribution towards girth increment during winter. The attainment of optimum tappability was achieved in almost all clones consistently except in PR107. However, PR107 showed a great deal of resistance towards wind stress. A survey of Oidium incidence showed all clones to be susceptible. However, the severity of incidence varied among clones. The initial yielding pattern (g/tree/tap) showed Haiken1 and RRII208 to be superior followed by RRIM600.
Abstract: The wintering and flowering patterns of Hevea clones in coastal Karnataka, one of the major non-traditional areas growing rubber, were studied. Forty clones were studied for wintering and twenty-three clones for flowering. The study was carried out at weekly intervals during the wintering and flowering seasons of 1998-99, 1999-2000 and 2000-01. In general, wintering pattern of the clones was not uniform over seasons. While three distinct clusters were obtained for 1998-99 and 2000-01 seasons, four clusters were obtained for 1999-2000. However, certain clones exhibited uniformity of wintering pattern in all the seasons. Further, results indicated that some of the clones were more influenced by the environment than others for wintering pattern. Individual clusters had close relatives grouped together irrespective of seasons, thus, indicating the genetic control on wintering behaviour. The observations on flowering indicated that commencement of flowering depends on wintering pattern. Wide variations were observed for the male to female flower ratios, pollen stainability and also initial fruit set. Owing to the adverse influence of environment, natural fruit recovery was seldom achieved. The results generated can be used for characterisation of clones and also to select them for appropriate breeding programmes apart from designing suitable breeding orchards.
