Morpho-physiological trait variation of pre-harvest sprouting tolerance to simulated rain in mungbean (Vigna radiata)

Preharvest sprouting (PHS) is one of the most important factors for lower productivity in mungbean [Vigna radiata (L.) R. Wilczek]. The morpho-physiological characters, ultra-structural variations in pods and seeds, changes and regulatory water absorption pathway of 30 mungbean genotypes in relation to pre-harvest sprouting behaviour was studied during kharif 2017–19 at Seed Research Technology Center, Indian Institute of Rice Research, Rajendranagar, Hyderabad, Telangana. Mungbean genotypes subjected to PHS imposed by simulated rainfall were evaluated. Rainfall simulator generates a rainfall spectrum that was similar to natural rainfall. Genotypes LGG 450 and K 851 with low score (%), while ML 267 and MGG 295 with high score (%) were screened as tolerant and susceptible to PHS. Accordingly, higher seed yield was recorded in LGG 450 (4.94 g/plant) followed by K 851 (4.20 g/plant) while lower seed yield was recorded in ML 267 (0.26 g/plant) followed by MGG 295 (0.79 g/plant). The findings were further corroborated with SEM studies by presence of sparse, wiry, short, twist or shriveled trichomes; thick cuticular pod wall, wide locular gap between seed coat (seed) and pod wall helping for the slow diffusion of moisture from endosperm to embryo. Further, the presence of lea-protein-insulated starch grains of endosperm merits lipophilic nature which might hindered dissipation of water to embryo via endosperm. The SEM studies have established ultrastructural features that determine the resistance to pre-harvest sprouting of mungbean and development of future resistant lines identification

Expression Analysis of Novel microRNAs in Rice During High Temperature Stress

MicroRNAs (miRNAs) are small non-coding RNAs which play an important role in regulating the genes involved in plant growth and development. Several studies showed that miRNAs are involved in plants response to different kinds of abiotic stresses also. In our previous study, temperature responsive miRNAs were predicted in O.sativa. 27 miRNAs were predicted to be novel in rice using homology search. In continuation to our previous study, expression of 14 novel miRNAs was done in shoot and root of 13 days old seedlings of five different rice cultivars using real time PCR. Expression these miRNAs was analyzed in control and high temperature stress environment. Out of 14 predicted novel miRNAs, two novel miRNAs- miR157a and miR165a showed expression in all five rice cultivars. Interestingly, miR165a showed a differential expression pattern among heat tolerant (N22, IR64 and Rasi) and susceptible (Vandana and Sampada) cultivars suggesting that it might have specific role in high temperature tolerance

A multi-dimensional approach from seed-to-seed to understand and improve heat stress tolerance in rice

In changing climatic conditions, stress caused by high temperature poses a serious threat to rice cultivation. Physiological, biochemical, and molecular analysis of rice cultivars revealed that Nagina22 (N22) shows lesser reduction in chlorophyll content, net photosynthetic rate, spikelet fertility and grain yield, but increased membrane thermal stability, antioxidant enzymes activity and transpiration rate (E) at high temperature. DREB, RAB, LEA, and genes associated with hormones signalling were induced during germination, while OsFd (an iron sulphur cluster binding protein) and CWIP (cell wall integrity protein) emerged as high priority candidate genes in seedling and reproductive stages. Their function is being analysed by transgene expression and CRISPR/Cas genome editing approaches. Field screening in polyhouse, late sowing and temperature gradient chamber for 20 morpho-physiological traits indicated the importance of both yield and spikelet fertility, and photosynthesis traits. N22 showed the least Heat Susceptibility Index (HSI) for yield/plant, spikelet fertility, flag leaf SPAD and stomatal conductance, while Vandana showed the highest HSI for spikelet fertility and flag leaf temperature. QTLs for HSI of spikelet fertility were identified on chromosome 1 and HSI of yield per plant on chromosomes 1, 2, 3, 4, 7 and 8; and PV of 6% to 57% using 174 F2-3 Vandana x N22 mapping population. Simultaneously, RNAseq was performed to identify the genome wide miRNAs and transcriptome of N22 and Vandana from shoot and root after short and long duration of heat stress treatments; and recovery phase for an eQTL-guided function-related co-expression analysis to identify the putative regulators and gene regulatory networks

Expression Dynamics of Genes and microRNAs at Different Growth Stages and Heat Treatments in Contrasting High Temperature Responsive Rice Genotypes

The global warming-driven climate change is becoming a major challenge for rice cultivation in Asia and Africa. High-temperature stress impairs the physiology and growth of rice plant, and ultimately results in reduced grain yield. This study was aimed to decipher the physiological and molecular changes occurring during different growth stages of heat-tolerant (N22) and -susceptible (Vandana) rice cultivars under three different heat treatments. Chlorophyll content, membrane integrity, gas exchange parameters and expression of genes and miRNAs were analyzed in N22 and Vandana at seedling, vegetative, and reproductive growth stages after exposing to short and long duration of high temperature stress, and recovery. A number of genes and miRNAs showed dynamic changes in their expression patterns at different growth stages and heat treatments, highlighting the necessity to understand gene regulation before employing the genes for modification through transgenic or gene editing approaches. Predominantly N22 showed distinct and unique capability to reprogram its physiological and molecular machinery during prolonged heat stress at reproductive stage, suggesting that the dynamics in gene regulation is crucial to determine its heat tolerant ability. The study has larger implications in deploying genes for the development of heat tolerant rice cultivars through breeding, transgenic, and genome editing approaches

Deep sequencing of small RNAs reveals ribosomal origin of microRNAs in Oryza sativa and their regulatory role in high temperature

MicroRNAs are small noncoding regulatory RNAs which control gene expression by mRNA degradation or translational repression. They are significant molecular players regulating important biological processes such as developmental timing and stress response. We report here the discovery of miRNAs derived from ribosomal DNA using the small RNA datasets of 16 deep sequencing libraries of rice. Twelve putative miRNAs were identified based on highly stringent criteria of novel miRNA prediction. Surprisingly, 10 putative miRNAs (mi_7403, mi_8435, mi_12675, mi_4266, mi_4758, mi_4218, mi_8200, mi_4644, mi_14291, mi_16235) originated from rDNA of rice chromosome 9. Expression analysis of putative miRNAs and their target genes in heat tolerant and susceptible rice cultivars in control and high temperature treated seedlings revealed differential regulation of rDNA derived miRNAs. This is the first report of rDNA derived miRNAs in rice which indicates their role in gene regulation during high temperature stress in plants. Further studies in this area will open new research challenges and opportunities to broaden our knowledge on gene regulation mechanisms

Identification of promising lines for yield from IR64/Akihikari Recombinant Inbred Lines under low nitrogen

Not AvailableFor identification of lines with promising yield under low nitrogen (N), a total of 117 Recombinant Inbred Lines (RILs) derived from IR64, an improved and released variety in Akihikari as recurrent parent, were evaluated for two seasons dry (Rabi) 2014 and wet (Kharif) 2015 under field with low and recommended N. The difference between the mean yields of the low and recommended N in both seasons was not significant indicating the differential genotypic response under low and recommended N and the difference between the means of season was about 30%, indicating the role of the season in determining the yield under differential N. Out of 50 promising lines identified for low and recommended N, six promising lines were identified with yields ranging from 11.2 ± 0.65 to 18.3 ± 1.06 (Dry 2014) and 7.1 ± 0.41 to 15.4 ± 0.89 (Wet 2015) under low N suggesting the possibility of evaluation of the mapping populations as a promising strategy for the identification of breeding lines with promising yield under low N.Not Availabl