Tea is the world's most popular non-alcoholic beverage. China and India are known to be the largest tea producing countries and recognized as the centers for the domestication of the tea plant ...(Camellia sinensis (L.) O. Kuntze). However, molecular studies on the origin, domestication and relationships of the main teas, China type, Assam type and Cambod type are lacking.
Twenty-three nuclear microsatellite markers were used to investigate the genetic diversity, relatedness, and domestication history of cultivated tea in both China and India. Based on a total of 392 samples, high levels of genetic diversity were observed for all tea types in both countries. The cultivars clustered into three distinct genetic groups (i.e. China tea, Chinese Assam tea and Indian Assam tea) based on STRUCTURE, PCoA and UPGMA analyses with significant pairwise genetic differentiation, corresponding well with their geographical distribution. A high proportion (30%) of the studied tea samples were shown to possess genetic admixtures of different tea types suggesting a hybrid origin for these samples, including the Cambod type.
We demonstrate that Chinese Assam tea is a distinct genetic lineage from Indian Assam tea, and that China tea sampled from India was likely introduced from China directly. Our results further indicate that China type tea, Chinese Assam type tea and Indian Assam type tea are likely the result of three independent domestication events from three separate regions across China and India. Our findings have important implications for the conservation of genetic stocks, as well as future breeding programs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
With the adverse effects of climate change, selecting the best tolerant varieties to drought stress is highly necessary to sustain the yield and productivity of agricultural crops including tree ...crops. However, classical drought tolerance selection studies of tree crops have several limitations due to their relatively long lifespan. In this study, we propose a method to identify stable high-yielding trees under changing soil moisture conditions using yield data of existing elite tree populations. We develop this method using the data from a tropical tree palm, Coconut (Cocos nucifera L.) as a model crop. Our selection method considers individual palms as different genotypes. The method considered both mean trait values and their stability across different environments therefore, it can be effectively used to identify elite genotypes of tree crops for drought tolerance.•We propose an analysis framework to identify stable, high-yielding individuals of tree crops under limited soil moisture conditions using the data of existing tree populations.•Individual trees that produce stable and higher yields under soil moisture stress were identified based on mean yield and regression-based coefficient over different environments characterized by inter-annual rainfall variability.•Individual trees selected by this method can be used as parental populations in breeding programs that focus on developing drought-tolerant varieties.
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•Within population selection strategy was applied on a heterogeneous and heterozygous population to develop drought tolerant coconuts.•Progeny of selected coconuts Ambakelle Special (AS) was compared ...with unselected CRIC60 coconuts based on yield data.•Despite of the climatic variation prevailed, the AS maintained a superior and stable yield throughout the study period.•The stability parameters (regression coefficient (bi) and deviations from the regression (S2di) and kernel weight were used to select parents for future breeding programmes for drought tolerance.
Coconut (Cocos nucifera L.) is a major plantation crop in humid tropics that affects the socio-economic life of several developing countries. Being a rainfed crop, coconut is highly prone to drought and breeding for drought tolerance has become a high priority research. We have identified that selection within populations as the way forward to improve drought tolerance. The current study evaluates the comparative performance of Ambakelle special (AS), a progeny of a within population selection with unselected CRIC60 to identify stable higher yielding palms for future breeding programs. Six-year yield data (2014-2019) from 110 palms in each group were evaluated. Results revealed variety, year and interaction have significant impact on annual yield (P<0.05) however, variety x year showed a non-cross-over interaction. AS recorded significant higher mean annual yield (101 nuts/palm/year) compared to CRIC60 (90 nuts/palm/year). Due to low rainfall condition prevailed from July 2016; lower nut yields were recorded for both varieties in 2017 and 2018. However, AS maintained its superiority indicating a better adaptation than CRIC60 under low rainfall conditions. Regression coefficient (bi) and mean annual yield were used in stability analysis and selected 45 palms as stable and higher yielding genotypes. Out of these 45 palms, thirty-three palms (73.3%) were from AS progeny further indicating the adaptability of AS to varying environmental conditions. Twenty palms (16 AS and 4 CRIC60) were further selected using variance of deviations from the regression (S2di) and mean kernel weight to be used in the future breeding programs for drought tolerance in coconut.
Tea is the most popular non-alcoholic beverage worldwide and is one of the most important tree cash crops in East Africa. However, no comprehensive study has been carried out on the genetic structure ...and diversity of tea germplasm for this region to date. In the present study, 193 tea accessions held at the ex situ Germplasm Bank of the Tea Research Institute (TRI), Kenya, were analysed using genetic data from 23 polymorphic simple sequence repeat (SSR) loci. A total of 266 alleles were detected with the number of alleles per locus ranging from 4 to 19 with an average of 7.88. Genetic clustering by STRUCTURE was used to correct misidentified accessions based on morphological characters. After reassignment of the tea accessions, Camellia assamica exhibited the lowest genetic diversity (Hs = 0.648) despite being the most widely cultivated tea type in the East African region. C. assamica subsp. lasiocalyx showed the highest genetic diversity (Hs = 0.76), which supported its origin by hybridization among tea types. Tea cultivars cultivated across the region exhibited lower genetic diversity (Hs = 0.661) compared to material held at the ex situ Germplasm Bank of TRI. Tea accessions clustered in the neighbour-joining tree on the basis of geographical origin, pedigree and leaf pigmentation, indicating their common origin. Our results indicated further that East African tea germplasm has a complex breeding history with a majority of the hybrids being F2 generation and backcross plants. C. assamica contributed significantly more genetic materials in the tea breeding programmes in East Africa. This study highlights the importance of ex situ germplasm banks to conserve the highest genetic diversity, which is an important resource for future tea crop improvements in East Africa.
•Main yield components of coconut sensitive to temperature and moisture stress were no. of female flowers/inflorescence and nut set/inflorescence.•Moisture stress at floral primordia initiation and ...the temperature stress at nut setting are the most critical factors affecting the coconut yield.•Planting of dwarf x tall hybrids even under the moisture and temperature stress conditions gives a comparatively higher nut yield than planting tall cultivars.
The yield (no. of nuts/palm/year) of coconut (Cocos nucifera L.) is highly influenced by the amount and distribution of rainfall and year-round temperature. This study was conducted to evaluate the variation in yield and yield components of two groups of coconuts; talls (two cultivars) and dwarf x tall hybrids (four hybrids) in response to within year variation of rainfall and temperature under average management conditions in Wanathawilluwa, dry zone (DL3) of Sri Lanka. No. of inflorescence, no. of female flowers, no. of button nuts, and no. of mature nuts were recorded at monthly intervals from July 2013 to May 2015 at Wanathawilluwa. For comparison, no. of mature nuts was recorded at Raddegoda in the wet intermediate zone (IL1a) of Sri Lanka. Daily rainfall and temperature were collected from the nearest weather stations. The results revealed that the no. of inflorescences produced by a palm within a year is not different among cultivars. However, tall cultivars produced a significantly lower no. of female flowers/palm/year than hybrids but, no difference was observed within groups. The no. of female flowers/inflorescence showed a significantly positive correlation with the mean monthly rainfall received during 7, 8 and 9 months prior to opening of the respective inflorescence. This observation was recorded for the first time and can be used to mitigate the effect of drought. Number of nuts set/inflorescence varied significantly with the month in which the inflorescence opened. Both at Wanathawilluwa and Raddegoda, hybrids showed a significantly higher yield compared to that of tall cultivars, Raddegoda however, showed a higher yield in all cultivars attributing to the favourable soil and weather conditions. When the inflorescences were not exposed to temperature stress during the first three months, dwarf x tall hybrids showed a significantly higher nut set/inflorescence and mature nuts/bunch than tall cultivars. In conclusion, the main yield components affected by moisture and temperature stresses were the no. of female flowers/inflorescence and the no. of nut set/inflorescence. The moisture stress at the time of floral primordia initiation and the temperature stress at the time of nut setting are the most critical factors affecting the coconut yield.
A Tea is the most popular non-alcoholic beverage in the world. Asia accounts for 85% of the global tea production. Comprehensive studies on the genetic diversity and origin of domestication of tea ...plant are scarce, while the studies carried out to date also used fewer number of markers narrowing down its scope. Genotyping by Sequensing (GBS) is a novel next generation sequensing technique which generates large amounts of Single Nucleotide Polymorphysms (SNPs) that are vital for modern genetic analysis. Therefore, 114 wild, landraces and cultivated tea samples collected across 14 countries in Asia were subjected to GBS analysis to study the genetic relationships and origin of domestication of tea plant in Asia. A set of 247,760 high quality SNPs were generated and used for the genetic analysis of 112 samples. Multiple analysis with SNPs revealed three independent domestication events for cultivated tea confirming the results of simple sequence repeat analysis. Most of the wild species clustered together while few species/samples clustered differently showing their gene flow with the cultivated tea or possible hybrid origins. Structure and neighbour joining tree analysis clearly showed a differential clustering of Assam tea collected from India, Sri Lanka and other South Asian countries with the Assam tea collected from China and neighbouring countries in East Asia. Future studies with the recently published tea genome possibly identify differentially selected genes/biochemical pathways during tea domestication. Based on the findings of this most comprehensive study done on tea plant to date, incorporation of Chinese Assam tea germplasm into the breeding programmes in India, Sri Lanka and other South Asian countries is recommended.
Tea is the world's most popular non-alcoholic beverage. China and India are known to be the largest tea producing countries and recognized as the centers for the domestication of the tea plant ...(Camellia sinensis (L.) O. Kuntze). However, molecular studies on the origin, domestication and relationships of the main teas, China type, Assam type and Cambod type are lacking. Twenty-three nuclear microsatellite markers were used to investigate the genetic diversity, relatedness, and domestication history of cultivated tea in both China and India. Based on a total of 392 samples, high levels of genetic diversity were observed for all tea types in both countries. The cultivars clustered into three distinct genetic groups (i.e. China tea, Chinese Assam tea and Indian Assam tea) based on STRUCTURE, PCoA and UPGMA analyses with significant pairwise genetic differentiation, corresponding well with their geographical distribution. A high proportion (30%) of the studied tea samples were shown to possess genetic admixtures of different tea types suggesting a hybrid origin for these samples, including the Cambod type. We demonstrate that Chinese Assam tea is a distinct genetic lineage from Indian Assam tea, and that China tea sampled from India was likely introduced from China directly. Our results further indicate that China type tea, Chinese Assam type tea and Indian Assam type tea are likely the result of three independent domestication events from three separate regions across China and India. Our findings have important implications for the conservation of genetic stocks, as well as future breeding programs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Coconut palm (Cocos nuciferd), is a major and economically important plantation crop widely cultivated in Sri Lanka. A sudden outbreak of a rapidly spreading non-lethal syndrome was first reported in ...coconut palms from southern Sri Lanka in 2006. This syndrome was named Weligama coconut leaf wilt disease (WCLWD) as it occurred in the Weligama area. WCLWD symptoms are flaccidity and marginal necrosis of leaflets and intense yellowing of the fronds, similar to the Kerala wilt disease of coconut in India. As the disease progresses the crown becomes smaller, the trunk begins to taper and the palm becomes unproductive. Abiotic factors and extra-cellular pathogens were discarded as the cause of WCLWD. Considering that a phytoplasma was previously associated with Kerala wilt disease, the possible phytoplasma aetiology of WCLWD was investigated. DNA extracted from midribs of spear leaves was subjected to nested PCR with phytoplasma universal primers R16F2n/R16R2 and R16mF2/R16R2 nested with fU5/rU3; P1/P7 nested with Chrfor/rU3; and direct PCR with Pc399/P1694. PCR products of expected sizes were obtained from diseased but not from healthy palms from a disease-free area. The sequences generated from the PCR products were submitted to similarity search (BlastN) in the NCBI database which confirmed that a phytoplasma belonging to the 16SrXI 'Candidatus Phytoplasma oryzae' group is associated with WCLWD. The phytoplasma was found to be highly similar but not identical to Sugarcane white leaf phytoplasma (99%), Sugarcane grassy shoot phytoplasma (99%) and Kerala wilt phytoplasma (99%).
Coconut (Cocos nucifera L.) is a tropical palm offering multiple uses. Conservation of coconut germplasm has been undertaken globally in view of its economic importance. This research was designed to ...evaluate nine Sri Lankan indigenous coconut germplasm representing the three varieties Typica, Nana, and Aurantiaca. Total annual nut yield and the weights of fresh nut, husked nut, split nut, and fresh and dry kernel were scored and analyzed with analysis of variance. The annual average number of bunches varied from 14.9 to 16.8 which is significantly higher than the generally accepted 12–14 bunches in tall coconuts. The high potential of phenotypes Ran thembili and Gon thembili for kernel production was revealed. The high potential of Gon thembili, Sri Lanka Tall, and Ran thembili to produce fibre was also identified. Phenotypes Ran thembili and Gon thembili displayed their potential as pure cultivars and as parents in hybridization. King coconut, Red dwarf, and Bodiri were shown to be suitable as beverage coconuts due to the high production of nuts, bunches, and the quantity of nut water. This study reiterated the importance of conservation and characterization of indigenous coconut varieties globally for their effective use in the genetic improvement of the coconut palm.
King Coconut (KC) is an indigenous and highly valuable germplasm resource in Sri Lanka. Yet, KC populations' genetic diversity, relationships, and conservation strategies are not fully understood. ...Indigenous old KC populations have been dispersed across a few ancient villages in Sri Lanka. Five geographically dispersed locations were selected in Sri Lanka, and 20 KC individuals from each location were collected for the current study. Six randomly selected samples from every geographical location, together with the standard two Sri Lanka Red Dwarf and two Sri Lanka Tall varieties were initially genotyped using 21 SSR markers for polymorphism. Based on the results, ten polymorphic SSR markers were selected and used for genotyping. Power Marker, STRUCTURE, and GenAlex software were used for the SSR genetic analysis. Results revealed 0.62 mean Gene Diversity (Hs), 4.2 mean allele number, and 0.55 polymorphic information content (PIC). Clear differentiation of populations was observed with the STRUCTURE and UPGMA dendrogram. Single branching in the UPGMA dendrogram for Anuradhapura and Marandawila KC populations revealed high genetic uniformity over multi-branched Kadugannawa and Colambageara populations. According to AMOVA, 64% of the genetic variation has been partitioned among populations, indicating moderate population differentiation. Detail analysis, including a higher number of KC populations and systematic molecular analysis using more SSRs/SNPs needed in the future before implementing conservation and utilization strategies.
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