Most indigenous rice landraces are sensitive to photoperiod during short day seasons,and this sensitivity is more pronounced in indica than in japonica landraces.Attempts to identify photoperiod sensitive(PPS)cultivar...Most indigenous rice landraces are sensitive to photoperiod during short day seasons,and this sensitivity is more pronounced in indica than in japonica landraces.Attempts to identify photoperiod sensitive(PPS)cultivars based on the life history stages of the rice plant,and several models and indices based on phenology and day length have not been precise,and in some cases yield counterfactual inferences.Following the empirical method of traditional Asian rice farmers,the author has developed a robust index,based on the sowing and flowering dates of a large number of landraces grown in different seasons from 2020 to 2023,to contradistinguish PPS from photoperiod insensitive cultivars.Unlike other indices and models of photoperiod sensitivity,the index does not require the presumed duration of different life history stages of the rice plant but relies only on the flowering dates and the number of days till flowering of a rice cultivar sown on different dates to consistently identify photoperiod sensitive cultivars.展开更多
Different cultivars of rice(Oryza sativa)open at different times of the day,and the overlap of anthesis time in rice between the neighbouring cultivars is of crucial importance to the degree of cross pollination in ri...Different cultivars of rice(Oryza sativa)open at different times of the day,and the overlap of anthesis time in rice between the neighbouring cultivars is of crucial importance to the degree of cross pollination in rice.Nevertheless,none of the past experiments with cross pollination between different rice cultivars ever reported the respective flower opening time(FOT)and flower exposure duration(FED)of the parent cultivars,until recently.The authors present here the first record of FOT and FED of 1114 indica rice landraces of South and Southeast Asia,growing during sum-mer and winter seasons in three consecutive years.The authors also present an analysis of the influences of the grow-ing season on the anthesis behaviour,and present the first records of the FOT and FED variability on sunny and cloudy days of a large number of landraces.The data show that rice florets tend to open later in the morning(that is,take longer time to anthesis after sunrise)on sunny days than on cloudy days,and also significantly later during long day seasons(spring and summer)than during short day season(winter);and that FED is inversely related to both FOT and the length of duration from sunrise to first flower opening.The wide ranges of FOT(8:50 a.m.to 12:40 p.m.)and FED(15 to 194 minutes)also suggest the ample time window for receiving pollen from neighbouring cultivars with differ-ent FOT,enhancing the chances of cross pollination between hundreds of rice landraces with FOT and FED overlaps.展开更多
Allelic diversity for five genetic loci (DL, FON4, OsMADS24, OsMADS45 and Spw1) associated with floral organ development were investigated among a small heterogeneous rice population which included one wild species (O...Allelic diversity for five genetic loci (DL, FON4, OsMADS24, OsMADS45 and Spw1) associated with floral organ development were investigated among a small heterogeneous rice population which included one wild species (O. rufipogon Griffiths), one indigenous less popular natural floral organ mutant (O. sativa var. indica cv. Jugal), one indigenous normal line (O. sativa var. indica cv. Bhutmoori) and one improved high yielding line (O. sativa var. indica cv. IR 36). Detailed spikelet morphology showed that var. Jugal had variable number (1 - 3) of carpels within a single spikelet which was unique and resulted in variable (1 - 3) number of kernels within a single matured spikelet (grain). The genomic DNA of each investigated line was amplified with primer sequences designed from the selected genetic loci and the derived polymorphism profiles were used for study of allelic diversity for the studied loci. The derived genetic distances among the rice lines were used for dendrogram construction. In constructed dendrogram, the mutant genotype (Jugal) showed highest similarity with the wild rice (O. rufipogon) instead of the rice lines. To verify this finding, the genomic DNA of each studied line was also amplified with four SSR loci, tightly linked to saltol QTL, mapped to rice chromosome 1. The amplified products were screened for polymorphism and another dendrogram was constructed to reveal the genetic distance among the lines for selected salt tolerance linked SSR loci. In SSR derived dendrogram, the wild rice (O. rufipogon) got totally separated from the all three rice genotypes though all the studied four lines showed equal sensitivity for salt sensitivity in a physiological screening experiment. From the combined experiment, it can be concluded that genetic architecture of floral organ development loci in var. Jugal may have some uniqueness which is not present in normal rice but common to O. rufipogon, a species which is regarded as immediate progenitor of present day modern rice (O. sativa). Though this uniqueness was not confirmed by second set genetic loci associated with salt tolerance in rice, the information resulted from this experiment was preliminary and based only on allelic size (molecular weight of amplicon), which should be confirmed through sequence analysis for further analysis.展开更多
文摘Most indigenous rice landraces are sensitive to photoperiod during short day seasons,and this sensitivity is more pronounced in indica than in japonica landraces.Attempts to identify photoperiod sensitive(PPS)cultivars based on the life history stages of the rice plant,and several models and indices based on phenology and day length have not been precise,and in some cases yield counterfactual inferences.Following the empirical method of traditional Asian rice farmers,the author has developed a robust index,based on the sowing and flowering dates of a large number of landraces grown in different seasons from 2020 to 2023,to contradistinguish PPS from photoperiod insensitive cultivars.Unlike other indices and models of photoperiod sensitivity,the index does not require the presumed duration of different life history stages of the rice plant but relies only on the flowering dates and the number of days till flowering of a rice cultivar sown on different dates to consistently identify photoperiod sensitive cultivars.
文摘Different cultivars of rice(Oryza sativa)open at different times of the day,and the overlap of anthesis time in rice between the neighbouring cultivars is of crucial importance to the degree of cross pollination in rice.Nevertheless,none of the past experiments with cross pollination between different rice cultivars ever reported the respective flower opening time(FOT)and flower exposure duration(FED)of the parent cultivars,until recently.The authors present here the first record of FOT and FED of 1114 indica rice landraces of South and Southeast Asia,growing during sum-mer and winter seasons in three consecutive years.The authors also present an analysis of the influences of the grow-ing season on the anthesis behaviour,and present the first records of the FOT and FED variability on sunny and cloudy days of a large number of landraces.The data show that rice florets tend to open later in the morning(that is,take longer time to anthesis after sunrise)on sunny days than on cloudy days,and also significantly later during long day seasons(spring and summer)than during short day season(winter);and that FED is inversely related to both FOT and the length of duration from sunrise to first flower opening.The wide ranges of FOT(8:50 a.m.to 12:40 p.m.)and FED(15 to 194 minutes)also suggest the ample time window for receiving pollen from neighbouring cultivars with differ-ent FOT,enhancing the chances of cross pollination between hundreds of rice landraces with FOT and FED overlaps.
文摘Allelic diversity for five genetic loci (DL, FON4, OsMADS24, OsMADS45 and Spw1) associated with floral organ development were investigated among a small heterogeneous rice population which included one wild species (O. rufipogon Griffiths), one indigenous less popular natural floral organ mutant (O. sativa var. indica cv. Jugal), one indigenous normal line (O. sativa var. indica cv. Bhutmoori) and one improved high yielding line (O. sativa var. indica cv. IR 36). Detailed spikelet morphology showed that var. Jugal had variable number (1 - 3) of carpels within a single spikelet which was unique and resulted in variable (1 - 3) number of kernels within a single matured spikelet (grain). The genomic DNA of each investigated line was amplified with primer sequences designed from the selected genetic loci and the derived polymorphism profiles were used for study of allelic diversity for the studied loci. The derived genetic distances among the rice lines were used for dendrogram construction. In constructed dendrogram, the mutant genotype (Jugal) showed highest similarity with the wild rice (O. rufipogon) instead of the rice lines. To verify this finding, the genomic DNA of each studied line was also amplified with four SSR loci, tightly linked to saltol QTL, mapped to rice chromosome 1. The amplified products were screened for polymorphism and another dendrogram was constructed to reveal the genetic distance among the lines for selected salt tolerance linked SSR loci. In SSR derived dendrogram, the wild rice (O. rufipogon) got totally separated from the all three rice genotypes though all the studied four lines showed equal sensitivity for salt sensitivity in a physiological screening experiment. From the combined experiment, it can be concluded that genetic architecture of floral organ development loci in var. Jugal may have some uniqueness which is not present in normal rice but common to O. rufipogon, a species which is regarded as immediate progenitor of present day modern rice (O. sativa). Though this uniqueness was not confirmed by second set genetic loci associated with salt tolerance in rice, the information resulted from this experiment was preliminary and based only on allelic size (molecular weight of amplicon), which should be confirmed through sequence analysis for further analysis.
