Journal of Agronomy and Crop Science最新文献

The cover image is based on the Original Article Biomass production of 14 accessions of cactus pear (Opuntia spp.) under semi-arid land conditions by Dhurba Neupane et al., https://doi.org/10.1111/jac.12705.

Cotton is well adapted to dry areas, but progressive water deficits can lead to declines in net photosynthesis (A), ultimately reducing yield. However, the exact mechanism responsible for this decline in net photosynthesis (stomatal or non-stomatal) is not fully understood under field conditions, partially due to limitations in the ability to collect critical data. To our knowledge, no other study has compared the drought responses of Pima and upland cotton using both CO₂ response and chlorophyll fluorescence under field conditions. To this end, a field study was conducted to quantify the impact of progressive mild drought, as measured by midday stomatal conductance to water vapour (g_s), on cotton leaf metabolism in Pima and upland cotton. Survey gas exchange and rapid photosynthetic CO₂ response (RACiR) were conducted during flowering on the same leaf. The study observed decline in A as g_s declined for both species. Correlation analysis indicated typical relationships with A and parameters associated with stomatal limitations such as decreased CO₂ inside the leaf and at the site of carboxylation; however, it was found that while Pima exhibited a strong relationship between maximum electron transport rate (J_max) and electron transport rate (ETR), upland cotton did not. Furthermore, when ETR is broken down into proportions contributing to net photosynthesis and photorespiration (ETR_A, ETR_P, respectively), we found that a greater proportion of ETR is being shuttled to the photorespiratory pathway in upland, relative to Pima as g_s decreases. Our results fill critical knowledge gaps that can be useful for modellers and breeders when preparing for future climate change scenarios.

Based on our primary database of the flower opening time (FOT) and flower exposure duration (FED) of 1114 rice (Oryza sativa ssp. indica) landraces, we examined the influences of growing season, sunrise time as well as day maximum and minimum temperatures on the anthesis behaviour of indica rice landraces of South and Southeast Asia, flowering in summer and winter in 3 consecutive years (2020–2022). We also compared the FOT and FED on sunny and cloudy days of a small set of landraces, and also during summer and winter. Our data show that rice florets tend to open later in the morning and lengthen the sunrise-to-anthesis duration (SAD) on hotter sunny days during tropical summer than during winter and on cloudy days. These findings contradict the widely held conjecture, based on studies conducted at colder latitudes, that rice flowers open earlier in the morning to avoid heat stress. We propose that indica rice landraces are sufficiently adapted to tropical summer because they were selected and bred over millennia to withstand heat stress during tropical summer, so their FOT and SAD are weakly influenced by high day temperatures. However, the significant reduction in FED of these landraces, whose flowers open later in mid-day, seems to be an adaptive mechanism to avoid longer exposure to rising air temperature approaching day maximum temperature.

In recent years, the frequency and intensity of exposure to heat stress have increased gradually, seriously hampering the production of maize. This paper presents a study designed to analyze how the development, physiology and dispersal of pollen from the heat-resistant maize variety Zhengdan958 and the heat-sensitive maize variety Xianyu335 are affected by exposure to heat stress during the tasselling stage. Our results showed That exposure to heat stress significantly increased the antioxidant enzyme activity in pollen. Upon visual inspection of the pollen, we found that the lower water content had given rise to wrinkles in the pollen surface, sunken germination pores, and morphological deformations. In addition, the anther dehiscence process was hindered, resulting in a reduced amount of pollen being dispersed. We also found elevated levels of abscisic acid (ABA), jasmonic acid (JA) and its derivatives, indole acetic acid (IAA) and gibberellin-3 (GA₃) in heat-pollens, as well as elevated ratios of IAA to ABA and ABA to GA₃. Ultimately impaired pollen fertility. Summarizing, our experiment revealed that reduced pollen quantity and quality are significant contributors to fertility losses in summer maize exposed to heat stress at anthesis, and we hope that our analysis of the physiological mechanisms involved can contribute to the development of crop management measures aimed at countering the increasingly detrimental effects of heat stress on the production of summer maize.

Wheat crops underpin contemporary global food security. Predominant wheat production zones in China include the Huang-Huai-Hai-Plain and the Mid-Lower Reaches of the Yangtze River, although climatic effects on productive potential across these regions vary markedly in space and time. Here, we conducted field experiments during the wheat season of 2015–2018 to examine environmental effects on growth, with fertilization and irrigation provided at levels ensuring that nutrient and water stress exposure was minimal. Yields in Huang-Huai-Hai-Plain and the Mid-Lower Reaches of the Yangtze River averaged 8950 and 4818 kg ha⁻¹, respectively. Yield variation across regions was primarily related to spike number per unit area and grain number per spike. Maturity biomass was higher in Huang-Huai-Hai-Plain; this translated into higher grain yields. Lower temperature and longer growing duration between emergence and jointing in Huang-Huai-Hai-Plain afforded higher tillering and spike numbers, whereas higher growth rates from jointing to maturity resulted in higher biomass production in Huang-Huai-Hai-Plain compare with the Mid-Lower Reaches of Yangtze River. Growth rate, grain numbers and yield were positively correlated with the ratio of daily intercepted solar radiation to mean temperature during jointing to anthesis, termed photothermal quotient. Collectively, our results suggest that growth rate accounted for more variation in biomass production compared with growth duration, and the photothermal conditions in the Mid-Lower Reaches of the Yangtze River were restrictive for spike development and yield formation. Our results help disentangle drivers of crop growth through the development of agro-environmental conceptual frameworks, enabling a better understanding of yield variability in space and time.

Halo-hydromorphism limits productivity in approximately 100 million hectares worldwide. Tall wheatgrass (Thinopyrum ponticum) is a species widely used in these environments for its seeding potential, being the addition of nitrogen a considered technological tool to increase forage quality and production. The objective of the study was to determine the impact of nitrogen fertilization on the capture and use of resources (radiation, water and nitrogen) in a cool season perennial sward growing in contrasting halo-hydromorphic conditions. Cultivated pastures from three independent sites were used. Sites were described according to the degree of halo-hydromorphism using soil salinity and water table attributes (salinity and depth) as environmental indicators: low HHM site [electrical conductivity (EC_1:2.5) 0.97 dS/m; water table salinity 2.03 dS/m; depth 85 cm], intermediate HHM site (EC_1:2.5 3.86 dS/m; water table salinity 7.40 dS/m; depth 134 cm) and high HHM site (EC_1:2.5 4.49 dS/m; water table salinity 7.85 dS/m; depth 31 cm). At each site, a late spring regrowth (~750°Cd) was studied by applying two treatments (n = 5): without (N0) and nitrogen fertilization (N150; 150 kg/ha of nitrogen in the form of urea). The response of tall wheatgrass to nitrogen fertilization in halo-hydromorphic conditions depends on soil salinity and water table attributes. N150 treatments production was twice as high as in N0 in low HHM and intermediate HHM environments (from 1750 to 3500 kgDM/ha and from 1080 to 1985 kgDM/ha, respectively). Meanwhile, in high HHM conditions, forage production was only 40% higher when nitrogen was added (from 625 to 870 kgDM/ha). In low HHM the higher N150 production was related to tiller density and size, whereas in intermediate HHM and high HHM was linked only to tiller size. In N150 treatments, the nitrogen nutrition index was negatively affected with the increase in HHM conditions (0.77, 0.62 and 0.55 for low HHM, intermediate HHM and high HHM, respectively). Instead, nitrogen nutrition index of N0 was similar in all the environments (~0.42). In N150, forage production capacity analysed in terms of radiation and water use efficiency (RUE and WUE, respectively) was similar in low HHM and intermediate HHM environments (RUE ~0.81 gDM/Mj and WUE ~13 kgDM/mm). These findings emphasize the importance of conducting analyses based on resource use and capture to understand productive responses to the increase in growth-limiting factors. Furthermore, they contribute to the identification of environments suitable for nitrogen fertilization.

In this study, we investigated the genetic mapping of root biomass and root/shoot ratio. We utilized a large (n = 345) bi-parental recombinant inbred line (RIL) population from the ‘Penny’ × ‘Yecora-Rojo’ cross to investigate the partitioning of biomass above- and belowground and to identify the quantitative trait loci (QTL) that influence root biomass and root/shoot ratio. Genotyping of 345 RILs by using genotyping by sequencing produced 2918 single-nucleotide polymorphism markers by which a genome-wide map of 3507 cM was constructed. Phenotyping was conducted in an augmented design with large pots in controlled environment. We identified two significant QTL regions, QRt.peye-5A and QRt.peye-5B, which control root biomass and the root/shoot ratio. QRt.peye-5A, marking a 3.15 Mbp region on chromosome 5A, explained 11% of variations in root biomass and 9.5% of variations in root/shoot ratio, with the narrow region harbouring 28 genes. QRt.peye-5B, marking a 12.2 Mbp region on chromosome 5B, explained 7% of variations in root/shoot ratio and harbours 104 genes. The root/shoot ratio enhancing alleles at QRt.peye-5A and QRt.peye-5B come from ‘Penny’ and ‘Yecora-Rojo’ respectively. These QTL regions contains genes such as the two MADS box transcription factors on the 5A QTL that are candidate genes for Vrn1 locus, and other genes previously postulated for root traits such as a COBRA-like COBL2 and landmark hormonal responses genes such as IAA16, IAA4 and BRI1, DREB2A-INTERACTING PROTEIN2 (DRIP2) and bHLH92 which has a role in amelioration of stress conditions.

A positive relationship between protein concentration and yield has been documented in different combinations of genotype and environment, often under potential conditions. However, the ecophysiological bases underlying this positive relationship under heat stress (HS) and drought stress (DS) during seed filling are still lacking. Our objective was to evaluate the relationship between seed protein content and concentration with yield in field experiments exposed to HS, DS and HS × DS interaction during the seed filling. Two field experiments were conducted and assimilates accumulation, remobilization and redistribution patterns were analysed in high and low seed protein soybean genotypes. The crop was exposed to four treatments: control (ambient temperature and soil water content near field capacity), HS (episodes above 32°C, 6 h d⁻¹) during 15 days, DS (soil water content ≤25% of field capacity) during the whole seed filling and HS × DS. Significant and positive relationships between seed protein content and concentration with yield were observed across treatments and genotypes. Under DS and HS × DS, assimilates available during the seed filling decreased, and assimilates remobilization and partition to seeds were limited, responses significantly associated with seed protein content and concentration, and yield reductions. Furthermore, we demonstrated here that the high leaf N content at the beginning of seed filling, the short early reproductive phase duration, the high source to sink ratio and the high dry matter stem remobilization capacity, as well as the low seed number and high seed weight are intrinsic characteristics of the high protein genotype that could be associated with its high seed protein content and concentration and yield under stressful conditions. This knowledge is key to develop soybean management strategies to improve seed protein level and yield under contrasting productive scenarios.

Timely sowing of wheat (Triticum aestivum L.) is a crucial agronomic measure to realize its genetic yield potential, particularly under ever-changing climatic conditions. The present study appraised the genotypic variations of wheat genotypes for dry matter and nutrients' accumulation, partitioning, remobilization and stress indices under timely and late sown conditions of irrigated semi-arid ecology. Five potential wheat genotypes viz. HD-2967, HD-3086, HD-3249, DBW-187 and HD-3226 were evaluated under field conditions, however, the studies for root-system traits were made in PVC tubes. Timely sown wheat had grain yield advantage of 18%, and genotypes DBW-187 (5.77 t ha⁻¹) and HD-2967 (4.78 t ha⁻¹) produced the highest grain yield under the timely and late sown conditions respectively. The days (d) to anthesis and grain filling period under the late sown was hastened by 5.2 d, and shortened by 7.4 d. Timely sowing enhanced the post-anthesis dry matter accumulation and remobilization to the tune of 18.8% and 23% respectively. Nitrogen, phosphorus and potassium accumulated post-anthesis and their remobilization under the timely sown was significantly greater than the late sown, while the contribution of remobilization to grain content was higher under the late sown except for the nitrogen. The canopy temperature was cooler by 2°C under the timely sown, while the canopy temperature depression was greater by 0.8–1.04°C, at anthesis and dough stages of the crop. The leaf chlorophyll content (SPAD meter value) at anthesis and dough stages improved by 10% and 7.6% due to timely sowing. The genotypes HD-2967 and HD-3249 had relatively greater geometric mean productivity and stress tolerance index coupled with a comparatively higher yield stability index. Further, the root-system traits, that is, total root length (TRL), root biomass and root length density (RLD) were significantly superior both at 50 DAS (days after sowing) and at anthesis under the timely sown compared to the late sown. This study clearly outlined that timely sowing of wheat resulted in higher post-anthesis dry matter accumulation, nutrient acquisition and remobilization along with improved root-system traits and grain yield. Screening of the genotypes, based on stress indices would result in a better understanding of the genotypic performance and improve the genetic yield potential under varying environmental conditions.

Drought is one of the meteorological disasters to which maize is most vulnerable during its seedling stage in Northeast China. The absence of phenological data impedes the precise evaluation of the likelihood of drought during this phase. In response to these issues, this study develops a phenology model and reconstructing the data. Furthermore, it effectively assessed drought risk at the site scale by utilizing drought indicators. Using reconstructed phenological data from 217 sites from 1981 to 2015, we analysed the duration and trends of each phenological period and assessed the spatial and temporal distribution of drought frequency at each growth stage. The study demonstrated that the average date ranges for the sowing, emergence, three-leaf, and seven-leaf stages annually were 115–138 days, 130–151 days, 135–160 days, and 150–180 days, respectively. Additionally, there was a significant trend towards earlier dates in all phenological stages. Our research reveals notable fluctuations in drought frequency during various growth stages of early maize in Northeast China. Particularly, the period from the three-leaf to the seven-leaf stages emerges as the most drought-prone, while the initial emergence to three-leaf stage also shows considerable vulnerability. On average, the frequency of drought events during the critical three- to seven-leaf stage stands at 35%. This average is surpassed in regions like Heilongjiang, northwest Jilin, northern Inner Mongolia, and southwest Liaoning, indicating a heightened risk in these areas. The early maize growth stage drought types are mainly light and moderate drought, with the three-leaf to seven-leaf stage, and Heilongjiang and Inner Mongolia, as the key stages and regions of concern, respectively. Identifying the principal types of drought and their occurrence in distinct regions and growth stages is pivotal for averting and reducing disasters.