Effect of elevated CO2 and high temperature on seed-set and grain quality of rice

Hybrid vigour may help overcome the negative effects of climate change in rice. A popular rice hybrid (IR75217H), a heat-tolerant check (N22), and a mega-variety (IR64) were tested for tolerance of seed-set and grain quality to high-temperature stress at anthesis at ambient and elevated [CO2]. Under an ambient air temperature of 29 °C (tissue temperature 28.3 °C), elevated [CO2] increased vegetative and reproductive growth, including seed yield in all three genotypes. Seed-set was reduced by high temperature in all three genotypes, with the hybrid and IR64 equally affected and twice as sensitive as the tolerant cultivar N22. No interaction occurred between temperature and [CO2] for seed-set. The hybrid had significantly more anthesed spikelets at all temperatures than IR64 and at 29 °C this resulted in a large yield advantage. At 35 °C (tissue temperature 32.9 °C) the hybrid had a higher seed yield than IR64 due to the higher spikelet number, but at 38 °C (tissue temperature 34–35 °C) there was no yield advantage. Grain gel consistency in the hybrid and IR64 was reduced by high temperatures only at elevated [CO2], while the percentage of broken grains increased from 10% at 29 °C to 35% at 38 °C in the hybrid. It is concluded that seed-set of hybrids is susceptible to short episodes of high temperature during anthesis, but that at intermediate tissue temperatures of 32.9 °C higher spikelet number (yield potential) of the hybrid can compensate to some extent. If the heat tolerance from N22 or other tolerant donors could be transferred into hybrids, yield could be maintained under the higher temperatures predicted with climate change

Effect of Heat and Drought Stress on Sorghum (Sorghum Bicolor). II. Grain Yield

Three early and four later flowering lines of sorghum were subjected to three drought stress treatments (early, late and early plus late stress) in the field during the dry season at Hyderabad in India. Mean diurnal temperature and evaporation rate were uniformly high throughout the experiment. The late and early plus late stress conditions were severe, while the early stress was mild. Grain yield was affected by both the timing and the severity of the stress. The largest reduction (87%) in grain yield resulted from stress imposed during booting and flowering (late stress) in the early flowering lines; the same stress treatment on vegetative plants had no effect on grain yield. Increasing the duration of severe stress on vegetative plants (early plus late stress) reduced grain yield by 50–60%. Grain yield was strongly and positively correlated with the number of grains m-2. Variation in grain yield was associated with variation in total dry matter rather than with harvest index, which was only reduced when stress occurred at flowering. Treatment effects on thermal growth rates (g m-2 °Cd-1) during the phase from booting to flowering confirmed that growth during this phase is the major determinant of yield potential (number of grains). The importance of phonology in research into drought resistance is discusse

Effect of the duration of the vegetative phase on crop growth, development and yield in two contrasting pearl millet hybrids

The phenotype of medium duration pearl millet varieties grown in West Africa differs from that of the shorter duration millets grown in India. African varieties are usually much taller, have longer panicles, fewer productive tillers, and a lower ratio of grain to above-ground dry-matter (harvest index). The effect of crop duration on plant phenotype was investigated in two hybrids using extended daylengths to increase the duration of the vegetative phase (GSl: sowing to panicle initiation). The two hybrids, 841A × J104 and 81A × Souna B, were considered to represent the Indian and African phenotype, respectively. Tiller production and survival, leaf area, and dry-matter accumulation and partition, were monitored over the season. Grain yield and its components were determined at maturity. The two hybrids responded similarly to the short and long daylength treatments. The duration of GSl was increased from 20 to 30 days, resulting in increased number of leaves, leaf area, and stem and total dry-matter accumulation; there was no effect on tiller production and survival, or on panicle growth rate. Grain yield was, therefore, the same in both GSl treatments, and harvest index (HI) was much reduced in the long GSl treatment owing to the increased stem growth. One evident effect of a longer GSl was on dry-matter partitioning between shoots; partitioning to the main stem (MS) was increased, whereas partitioning to the tillers was reduced. There was no difference in crop development, growth or yield between the two hybrids in either GSl treatment. The only significant differences were in the efficiency with which intercepted radiation was converted to dry matter, which was greater in 841A × J104 than in 81A × Souna B, and in the balance between MS and tillers; the grain yield of the MS was significantly greater in 81A x Souna B than in 841A × J104, but at the expense of number of productive tillers. The results demonstrate that both African and Indian phenotypes are equally productive under good agronomic conditions. The lower HI in longer duration African millets is a consequence of a much extended stem growth phase and therefore increased competition between stem and panicle during grain filling. Possible ways to increase grain yield in the medium duration African millets are considered

Potential and realized yield in pearl millet (Pennisetum americanum) as influenced by plant population density and life-cycle duration

A single hybrid of pearl millet, 841A×J104, was grown at four plant populations covering the range 2–20 plants m−2 under 13.5 or 15.5-h photoperiods during the vegetative phase (emergence to floral initiation) to effect a short (75-day) or long (90-day) crop duration, respectively. The effect of these treatments on tiller production, leaf-area production, dry-matter accumulation and grain-yield is described, and the relationship between radiation interception (Qi) during the phase from floral initiation to flowerng (GS2), and number of grains (yield potential) and grain-yield is examined. The treatments caused significant variation in tiller and leaf-area production, radiation interception and numbers of grains per unit area at maturity. Number of grains, which ranged from 37 to 71×103 m−2, was correlated (r2=0.83) with intercepted radiation during GS2. Thus at high plant population in the long ncrop-duration treatment, where leaf area was highest during GS2, number of grains was greatest. Grain-yield less strongly correlated (r2=0.63) with intercepted radiation during GS2 because, in crops with many grains, grain-size was reduced. Possible reasons for reduced grain-size in crops with high yield-potential are discussed

Resilient Dryland Systems for Reducing Vulnerability to Drought and Climate Change While Increasing Crop Diversity and Value: The ICRISAT Experience

The impact of escalating human activity on the greenhouse gas emission, global warming and changes in global climate patterns and its consequent impacts on life and global phenomena is among the most debated issues of the first decade of the 21st century. It is being discussed worldwide at various levels in the society - from global, regional and national institutions through to the development agencies and down to private citizens and to farmers in the developing world

Effect of Heat and Drought Stress on Sorghum (Sorghum Bicolor).I.Panicle Development and Leaf Appearance

Seven sorghum lines, flowering from 50 to 87 days after sowing, were subjected to early drought stress, late stress, and both early and late stress in the field during the dry season in India. Panicle initiation was delayed by 2–25 days and flowering by 1–59 days by the drought stress treatments, the greatest effect being in the treatment subjected to both early and late stress. Stress increased the period between panicle initiation and flowering by retarding the rate of panicle development; when stress was severe panicle development stopped. Upon relief of stress following irrigation, panicle development resumed at rates comparable to those in a fully irrigated control. The rate of leaf appearance was affected in a similar manner to panicle development soon after water was withheld. Rate of leaf appearance and panicle development decreased as pre-dawn leaf water potential decreased and ceased at water potentials of −0.55 and −0.7 MPa, respectivel

Impacts of climate change on rainfed agriculture and adaptation strategies to improve livelihoods

Farmers living and working in the semi-arid tropics (SAT) of Africa and Asia are acutely vulnerable to climate variability and change due to their limited natural and financial resources coupled with poor infrastructure, institutional support, and gover- nance (World Bank 2008). Coping with variability is nonetheless a way of life for many of these farmers, and farmers in many different regions of the world have adopted or adapted strategies to manage variability. In this chapter we first describe the impacts of climate change on crop and livestock production, water resources, and prices, poverty, and malnutrition in South Asia and sub-Saharan Africa (SSA). Secondly, we examine adaptation strategies, focusing on the social/institutional aspects needed to support farmers’ adaptation strategies as well as describing briefly strategies used by farmers

Implications of high temperature and elevated CO2on flowering time in plants

Citation: Jagadish, S. V. K., Bahuguna, R. N., Djanaguiraman, M., Gamuyao, R., Prasad, P. V. V., & Craufurd, P. Q. (2016). Implications of high temperature and elevated CO2on flowering time in plants. Frontiers in Plant Science, 7. doi:10.3389/fpls.2016.00913Flowering is a crucial determinant for plant reproductive success and seed-set. Increasing temperature and elevated carbon-dioxide (e[CO2]) are key climate change factors that could affect plant fitness and flowering related events. Addressing the effect of these environmental factors on flowering events such as time of day of anthesis (TOA) and flowering time (duration from germination till flowering) is critical to understand the adaptation of plants/crops to changing climate and is the major aim of this review. Increasing ambient temperature is the major climatic factor that advances flowering time in crops and other plants, with a modest effect of e[CO2]. Integrated environmental stimuli such as photoperiod, temperature and e[CO2] regulating flowering time is discussed. The critical role of plant tissue temperature influencing TOA is highlighted and crop models need to substitute ambient air temperature with canopy or floral tissue temperature to improve predictions. A complex signaling network of flowering regulation with change in ambient temperature involving different transcription factors (PIF4, PIF5), flowering suppressors (HvODDSOC2, SVP, FLC) and autonomous pathway (FCA, FVE) genes, mainly from Arabidopsis, provides a promising avenue to improve our understanding of the dynamics of flowering time under changing climate. Elevated CO2mediated changes in tissue sugar status and a direct [CO2]-driven regulatory pathway involving a key flowering gene, MOTHER OF FT AND TFL1 (MFT), are emerging evidence for the role of e[CO2] in flowering time regulation. © 2016 Jagadish, Bahuguna, Djanaguiraman, Gamuyao, Prasad and Craufurd

Climate change and resilient dryland systems: experiences of ICRISAT in Asia and Africa

The article reviews and summarizes the climate change mitigation and adaptation work undertaken by ICRISAT. The effects of climate change are already being experienced in several parts of the world. Even though the effects of climate change will be felt over all kinds of agricultural production systems, they will be more pronounced in dryland areas where agriculture is totally dependent on rainfall. Simulation output analyses reveal that crop yield will decrease due to climate change and variability in drylands, but this can be mitigated in large parts by the application of existing knowledge on crop, soil and water management, and by re-targeting and redeployment of the existing germplasms of the crops in the medium term (2010–2050). Integrated watershed management is an important tool to mitigate the climate change effects through soil conservation, improved water availability and other secondary benefits. Similarly, conservation agriculture practices under the integrated genetic and natural resources management strategy can help minimize the adverse effects of climate change on dryland agricultural productivity

A phenotypic marker for quantifying heat stress impact during microsporogenesis in rice (Oryza sativa L.)

Gametogenesis in rice (Oryza sativa L.), and particularly male gametogenesis, is a critical developmental stage affected by different abiotic stresses. Research on this stage is limited, as flowering stage has been the major focus for research to date. Our main objective was to identify a phenotypic marker for male gametogenesis and the duration of exposure needed to quantify the impact of heat stress at this stage. Spikelet size coinciding with microsporogenesis was identified using parafilm sectioning, and the panicle (spikelet) growth rate was established. The environmental stability of the marker was ascertained with different nitrogen (75 and 125 kg ha–1) and night temperature (22°C and 28°C) combinations under field conditions. A distance of –8 to –9 cm between the collar of the last fully opened leaf and the flag leaf collar, which was yet to emerge was identified as the environmentally stable phenotypic marker. Heat stress (38°C) imposed using the identified marker induced 8–63% spikelet sterility across seven genetically diverse rice genotypes. Identifying the right stage based on the marker information and imposing 6 consecutive days of heat stress ensures that >95% of the spikelets in a panicle are stressed spanning across the entire microsporogenesis stage