Percentage Of Yield Reduction Research Articles

Development of Lentil (Lens culinaris) Genotypes Resistant to Pea Aphid, Acyrthosiphon pisum (Hemiptera: Aphididae) under Field Condition

Development of effective and sustainable pea aphid (Acyrthosiphon pisum) management methods are required because it causes yield loss of 26% in lentil (Lens culinaris) through direct feeding and indirectly by transmitting several viral diseases. The aim of this study was to verify field resistance of lentil genotypes to pea aphid in locations that had different altitudinal ranges but similar cropping system. A pea aphid susceptible check variety EL-142 and eight resistant lentil genotypes were tested at four locations for four seasons in randomized complete block design with three replications. Seeds were sown in rows at the rate of 65 to 80 kg ha-1 and recommended planting date for each location. Pea aphid was sampled by beating the plants on a board that had six 10 cm x 13 cm (20 cm x 39 cm) rectangles. The seasonal pattern of pea aphid density build up was similar on both resistant and susceptible lentil genotypes. However, in seasons and locations where the pea aphid infestation was severe, the susceptible check had two to four times greater pea aphid density than the pea aphid resistant genotypes. Moreover, the percentage yield reduction was positive for all resistant genotypes and it ranged from 5.5 to 93.9%. The resistant lentil genotypes reduced the pea aphid density and gave higher (up to 1456 kg ha-1) grain yield than the susceptible check (as low as 45 kg ha-1). Thus, the resistant genotypes can be used independently or in combination with other pea aphid management tactics as required.

Weed Management Practices in Cowpea (Vigna unguiculata L.): A Review

Cowpea is an important pulse crop. Weeds posses a severe problem in cowpea production and, if it is not managed with best management practices, can act as a hibernating agent and reduce yield and quality. An attempt was made to collect published data on weed management practices aimed at maximizing yield of cowpea. This work was done at Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore - 641 003, Tamil Nadu, India. The literature search was done during July 2023 to January 2024. About 120 review and research papers were screened from various databases, including the TNAU library, Google Scholar, Scopus, Research Gate, ARCC journals and 75 papers were used to write this paper. This review article documents information gathered on importance of cowpea, nutritional profile of cowpea, anti-nutritional factors, health benefits, critical period of weed control, yield reduction percentage, weed flora in cowpea, SSB, mulching, manual weeding, cultural practices, chemical methods and IWM in cowpea was comprehensively presented.

Quantifying the spatial water salinity threshold of saline water irrigation by applying distributed WAVES model

CONTEXTSaline water irrigation presents a viable solution to alleviate freshwater scarcity. However, it's crucial to consider the threshold of salinity, as excessive levels can adversely affect crop yield, crop productivity and soil sustainability. Additionally, due to varying surface conditions and management practices at the regional level, a distributed approach to saline water irrigation management is necessary. OBJECTIVEThe primary goal of this research was to develop a regional agro-hydrological crop model. The validated regional model was then employed to identify the spatial water salinity threshold for saline water irrigation. METHODSIn this research, we utilized the WAVES (WAter Vegetation Energy and Solute model), which was adapted for mulching environment and validated in severely arid and saline fields. To account for spatial variations, we applied a distributed method to upscale the WAVES to the regional level. Multisource and multiscale data were used for regional model validation. Different scenarios of salinity levels for saline water irrigation were simulated, and a comprehensive criterion to determine water salinity threshold was proposed considering cotton yield, water productivity and soil salt accumulation. RESULTS AND CONCLUSIONSModel evaluation indicated a high level of accuracy for the developed regional model. The comparison between simulated and measured values for soil salt content, soil water content, cotton leaf area index, measured lint yield, and statistical yield resulted in indices of agreement of 0.90, 0.71, 0.93, 0.58, and 0.70, respectively. The validated regional model was employed to simulate various saline water irrigation scenarios. The findings revealed that under identical irrigation water salinity, cotton cultivation on sandy loam soil is more productive but has a larger yield reduction percentage compared to silty loam soil. Moreover, the research indicates a groundwater depth of 1.5 m is associated with higher cotton production. Additionally, a spatial pattern of the irrigation water salinity threshold for saline water irrigation was determined, suggesting that the water salinity in most areas of the Tarim Irrigation District should not exceed 6 g L−1. Notably, in the current practice of pumping groundwater in situ for irrigation, approximately 46% of the areas are at risk, indicating that it's not suitable for saline water irrigation. SIGNIFICANCEThis study developed a distributed model under a typical irrigation district characterized by mulching, severe drought and salinization and defined the distributed spatial threshold for saline water irrigation. These research results hold significant implications for guiding regional-scale saline water irrigation and groundwater extraction.

Deciphering variability for heat tolerance index in maize hybrids and identification of stress resilient heterotic combinations

Aim: High temperature at any critical stage for a prolonged duration is documented to negatively affect the growth and yield related processes in maize. Therefore, the present study was planned to identify resilience of different heterotic combinations to heat stress under field conditions. Methodology: A set of 20 parental lines were used as parents and 21 single cross hybrids raised in kharif 2020 using 16 lines as female parent and four lines as male parent along with three commercial checks using randomized block design under two regimes: Normal Sownin mid of February, i.e., timely sown condition (spring season crop) and late sown in mid of March (heat stress crop). Data was recorded for yield and its contributing traits. Results: Heat stress led to early onset of flowering, thus resulting in shortening of vegetative phase. Consequently, days to grain filling period was found to be reduced (84-106 days) under late sown as compared to 100-123 days under normal sown condition. Amongst the top performing six hybrids in both normal sown and late sown conditions, three hybrids were common viz., JH 20003, JH 20015 and JH 20018, though with different ranking, inferring their wider adaptability and tolerance to heat stress. Under late sown conditions, days to grain filling (r2=0.55) and thousand seed weight (r2 =0.50) showed significantly positive correlation with grain yield while as highly significant and negative association was observed between anthesis silking interval and grain yield (r2 = -0.76). Among the 21 hybrids, three hybrids (JH 20001, JH 20004, and JH 20015) showed greater potential under heat stress conditions on the basis of yield performance under stress, percent yield reduction and heat tolerance index. Interpretation: Based on multiple selection criteria, three hybrids viz., JH 20001, JH 20004, and JH 20015 were suggested for commercial utilization after validation. This study also led to identification of donor inbreds which can contribute to breeding for heat stress tolerance. Key words: Grain yield, Heat tolerance index, Heat stress, Maize, Percent yield reduction

Salinity Stress Tolerance in Potato Cultivars: Evidence from Physiological and Biochemical Traits.

Salinity stress is a major constraint to sustainable crop production due to its adverse impact on crop growth, physiology, and productivity. As potato is the fourth most important staple food crop, enhancing its productivity is necessary to ensure food security for the ever-increasing population. Identification and cultivation of salt-tolerant potato genotypes are imperative mitigating strategies to cope with stress conditions. For this purpose, fifty-three varieties of potato were screened under control and salt stress conditions for growth and yield-related traits during 2020. Salt stress caused a mean reduction of 14.49%, 8.88%, and 38.75% in plant height, stem numbers, and tuber yield, respectively in comparison to control. Based on percent yield reduction, the genotypes were classified as salt-tolerant (seven genotypes), moderately tolerant (thirty-seven genotypes), and salt-sensitive genotypes (nine genotypes). Seven salt-tolerant and nine salt-sensitive genotypes were further evaluated to study their responses to salinity on targeted physiological, biochemical, and ionic traits during 2021. Salt stress significantly reduced the relative water content (RWC), membrane stability index (MSI), photosynthesis rate (Pn), transpiration rate (E), stomatal conductance, and K+/Na+ ratio in all the sixteen genotypes; however, this reduction was more pronounced in salt-sensitive genotypes compared to salt-tolerant ones. The better performance of salt-tolerant genotypes under salt stress was due to the strong antioxidant defense system as evidenced by greater activity of super oxide dismutase (SOD), peroxidase (POX), catalase (CAT), and ascorbate peroxidase (APX) and better osmotic adjustment (accumulation of proline). The stepwise regression approach identified plant height, stem numbers, relative water content, proline content, H2O2, POX, tuber K+/Na+, and membrane stability index as predominant traits for tuber yield, suggesting their significant role in alleviating salt stress. The identified salt-tolerant genotypes could be used in hybridization programs for the development of new high-yielding and salt-tolerant breeding lines. Further, these genotypes can be used to understand the genetic and molecular mechanism of salt tolerance in potato.

Identification of drought tolerant recombinant inbred lines (RILs) based on selection indices in bread wheat

Water scarcity throughout wheat-growing periods is a major issue in India, therefore breeding methods, as well as the efficient selection approaches for moisture stress conditions are required to retain the level of crop production. In the current study recombinant inbred lines were developed through a donor, WH 730 crossed with recepient MACS 2496. Further segregating generations were advanced through the single seed descent method at Karnal. The F7 and F8 generations of 231 recombinant inbred lines along with five checks were planted in Alpha Lattice design for screening under normal and restricted irrigated conditions. A significant yield reduction was observed under restricted irrigated conditions than the normal irrigated condition during cropping season 2019-20 & 2020-21. Under stress condition significant association was found among yield and selection indices viz., stress susceptibility index (SSI), tolerance index (TOL), mean productivity (MP), stress tolerance index (STI), yield index (YI), drought resistance index (DI), sensitivity drought index (SDI), relative drought index (RDI), yield stability index (YSI) and percentage of yield reduction (PR). Based on selection indices, 22 recombinant lines were identified superior. These selected recombinant inbred lines may be subjected to further evaluation, and also incorporated as donor parents in future hybridization programs. The panels of extreme phenotypic lines were also used to know the location of particular drought-engaged genes and quantitative trait loci.

EFFECT OF VIRUS AND MYCOPLASMA DISEASES ON PRODUCTIVITY OF ALFALFA HAY CULTIVARS

Purpose: To evaluate the productivity of different alfalfa hay cultivars under the effect of local virus and mycoplasma diseases. Methodology: The study was conducted under center pivot irrigation system similar to TADCO mechanized alfalfa hay crop production. Results: Imported alfalfa hay cultivars were found infected with three virus and mycoplasma diseases: alfalfa enation virus, alfalfa mosaic virus and alfalfa witches' broom. Infections with these diseases lead to a severe reduction on the productivity of alfalfa hay cultivars in the third cropping season. Alfalfa enation virus was found to cause the most economic damage to the alfalfa hay crop, and the percentage yield reduction from this disease reached 17.6, 36.8% in the second and third seasons of cultivation respectively. Unique Contribution to Theory, Practice and Policy: The authors recommended to grow alfalfa hay cultivars with less susceptibility to virus diseases infections as we found variability in the productivity of the tested cultivars. The study also recommends to grow alfalfa hay cultivars under mechanized system for two seasons as we observed significant yield reduction in the third season due to high infestation with weeds and grasses which affected the hay quality. In the first field trial (1999 - 2002), productivity of alfalfa hay cultivars CUF 101 and Siriver reached above 30 M.T. /Ha under aphid-controlled conditions. In the second field trial (2002 - 2004), alfalfa hay productivity of the cultivars Fast Grow, SW 9500, Magic (SW 9301) and Super Supreme reached above 30 M.T./Ha in the first season 2003; and in the second season 2004, productivity of Magic, Fast Grow and Super Supreme reached above 26 M.T./Ha. Productivity over the two seasons 2003 and 2004 shown Fast Grow and Magic were the highest with 60.38, 59.85 M.T./Ha. respectively.

Effect of projected climate scenarios on the yields of potato crop and agronomic adaptation options as evaluated by crop growth model

Potato is the most important non-cereal crop in the world and the most prominent winter season crop in India. Growth and yield of potato crop is very much sensitive to higher temperatures and the moisture stress. Hence, the anticipated increase of temperature due to global warming and climatic variability will have anadverse impact on potato production. Keeping this in view, a research work was carried out with the objectives to assess the impact of climate change on potato production and evaluating agronomic adaptation options through a crop growth simulation model (CGSM). Field experiments were carried out to prepare the minimum dataset for calibration and validation of one CGSM, namely InfoCrop. After validation, the model was used to predict the future tuber yield of ten selected stations situated under different agroclimatic regions of the State. In the future scenario 2050, the simulated yield for mid November planted crop likely to be about 11% less than the present level of mean yield. If the crop is planted in December, the percentage of yield reduction may be around 25%.The projected yield reduction, for the stations of higher latitude, is found to be negligible. Three possible agronomic adaptation options, viz., adjustment of date of planting, increase of seed rate and varying sprout length of seed tubers, have been tried as adaptation strategies to combat the adverse effects of climate change. It is concluded that the mid-November planting and longer sprout length will be the best adaptation option. However, the enhanced seed rate is not a viable adaptation option.

Yield Components and Efficiency Index of Maize Yield: Relationship to Yields in Tidal Fields

Identification of the advantages of hybrid maize lines is needed to support the increased production and development of maize in tidal fields. This study aimed to identify the agronomic characters and yield components of hybrid maize lines/varieties and their relationship with high yield and efficient fertilization in tidal fields. The design used was a Split Plot with three replications. The Main Plot was a hybrid maize line/variety (L39/MR4, MGOLD/G8, G28/MGOLD, P27). The subplots were Composite Fertilizer with 2 measures, namely 600 kg/ha and 720 kg/ha. The fertilizers of Urea (50%), SP 36 and NPK (100%) were given at 10 days after planting (DAP). The remaining Urea was given at 30 DAP, 50% and 58.33% respectively in the Composite Fertilizer treatment of 600 kg/ha and 720 kg/ha. The technical culture applied was optimum tillage with the 70 cm x 25 cm spacing, the irrigation being carried out at D/DAP and 15 DAP, the optimal control on the weed and Plant Pest Organisms. The result showed that the number of rows/cobs was an alternative variable in identifying maize lines/varieties with high yield and efficient fertilization. This character was closely correlated with seed/ear weight (r = 0.94) and Grain Yield Efficiency Index/GYEI (r = 0.84). All Genotypes were nutrient efficient (GYEI > 1) except G28/MGOLD (IGYEI < 1). Another approach used to identify efficient fertilization lines/varieties was the variable percentage of yield reduction through regression equations with GYEI (y = - 0.0104 x + 1.0426). The character of high number of rows/cob could be used as genetic material in plant breeding programs. The lines/varieties as a component of efficient technology and high productivity would contribute to increase production and development of maize in tidal fields.

Heavy soil drying during mid-to-late grain filling stage of the main crop to reduce yield loss of the ratoon crop in a mechanized rice ratooning system

Yield loss (YLoss) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology. Soil drying before the harvest of the main crop has been proposed to overcome this problem. The objective of this study was to determine the effect of soil drying during the mid-to-late grain filling stage of the main crop on grain yield of the ratoon crop in a mechanized rice ratooning system. Field experiments were conducted to compare YLoss between light (LD) and heavy (HD) soil drying treatments in Hubei province, central China in 2017 and 2018. YLoss was calculated as the percentage of yield reduction in the ratoon crop with the main crop harvested mechanically, relative to the grain yield of the ratoon crop with the main crop harvested manually. In comparison with LD, soil hardness was increased by 42.8%–84.7% in HD at the 5–20 cm soil depth at maturity of the main crop. Soil hardness at 5 and 10 cm depths reached respectively 4.05 and 7.07 kg cm−2 in HD. Soil drying treatment did not significantly affect the grain yield of the main crop. Under mechanical harvesting of the main crop, HD increased the grain yield of the ratoon crop by 9.4% relative to LD. Consequently, YLoss was only 3.4% in HD, in contrast to 16.3% in LD. The differences in grain yield and YLoss between the two soil drying treatments were explained mainly by panicles m−2, which was increased significantly by HD in the track zone of the ratoon crop compared with LD. These results suggest that heavy soil drying practice during the mid-to-late grain filling stage of the main crop is effective for reducing YLoss of the ratoon crop in a mechanized rice ratooning system.

Effects of Soybean Planting Date on Yield Loss From Defoliation

Soybean, Glycine max (L.) Merr., is planted during 3.5-4 mo across the Mid-South United States. Currently, no information exists regarding the effects of planting date on soybean yield loss from early season defoliation. In 2015 and 2016, to evaluate the effects of planting date on yield loss from defoliation, soybean were planted in field plots 2 wk apart from early April to mid-June, for a total of six planting dates. Each planting date included a nondefoliated control and a 100% defoliation treatment where leaves were manually excised at the V4 growth stage. Mean yield loss from defoliation varied across planting dates, with mid-April plantings having the least amount yield reduction, 573 kg/ha, and early-June plantings having the greatest yield reduction, 904 kg/ha. Percent yield reduction from defoliation increased as planting was delayed, suggesting that defoliation thresholds might need adjustment based on planting date and yield potential. However, more research is needed at lower levels of defoliation to accurately delineate such thresholds.

Quantifying crop pollinator dependence and its heterogeneity using multi‐level meta‐analysis

Abstract Biotic pollination can benefit crop production, but its effects are highly variable. To maximise benefits from this ecosystem service, we need a greater understanding of the factors that cause variation so that ecological intensification can be more effectively applied. We focus on understanding the benefits of pollination to faba bean Vicia faba. We use a literature review followed by multi‐level meta‐analysis to estimate overall benefits of pollination to faba bean yield and to quantify variation (heterogeneity) in these benefits associated with different contextual factors (e.g. plant genotype, growing environment). Our overall estimate of pollination benefit to faba bean yield, expressed as the percentage yield reduction without pollination, is 32.9% (confidence interval: 21%–43%). Based on the prediction intervals, which include the heterogeneity in pollination benefit, there is an 80% chance that pollination will increase yield of a faba bean crop. Half of all heterogeneity in pollination dependence was due to differences between plant genotypes. The number of beans per plant showed similar pollination dependence to yield mass per plant while pod number and number of beans per pod underestimated yield benefits. There was weak evidence to suggest pollination benefits vary between pollinator species, with honeybees showing a smaller yield increase. Differences in the experimental method used to assess pollination benefit did not significantly affect the estimate, including the growing environment, measurement scale, or whether the effects of experimental pollinator enclosures were controlled. This suggests that simplified experimental studies comparing yield of open‐pollinated and enclosed plants can provide reliable insights into pollination benefits across a large range of plant genotypes and landscapes. Synthesis and application. We found high variability in pollination benefits both between and within publications in our meta‐analysis. Plant genotype, how yield was measured, and pollinator species affected the level of pollination benefit. Despite variability in pollination benefits due to various contextual factors (both inside and outside of grower control), there is a high likelihood that biotic pollination will increase faba bean yield. Our findings support ecological intensification and specifically the management of pollinators to maximise pollination benefits to faba bean production.

Effect of Virus and Mycoplasma Diseases on The Productivity of Alfalfa Hay Cultivars

Purpose: To evaluate the productivity of different alfalfa hay cultivars under the effect of local virus and mycoplasma diseases.Methodology: The study was conducted under center pivot irrigation system similar to TADCO mechanized alfalfa hay crop production. Results: Imported alfalfa hay cultivars were found infected with three virus and mycoplasma diseases: alfalfa enation virus, alfalfa mosaic virus and alfalfa witches’ broom. Infections with these diseases lead to a severe reduction on the productivity of alfalfa hay cultivars in the third cropping seasons. Alfalfa enation virus was found to cause the most economic damage to the alfalfa hay crop, and the percentage yield reduction from these disease reached 17.6, 36.8% in the second and third seasons of cultivation respectively.Unique contribution to theory, practice and policy: The authors recommended to grow alfalfa hay cultivars with less susceptibility to virus diseases infections as we found variability in the productivity of the tested cultivars. The study also recommends to grow alfalfa hay cultivars under mechanized system for two seasons as we observed significant yield reduction in the third season due to high infestation with weeds and grasses which affected the hay quality. In the first field trial (1999 – 2002), productivity of alfalfa hay cultivars CUF 101 and Siriver reached above 30 M.T. /Ha under aphid-controlled conditions. In the second field trial (2002 – 2004), alfalfa hay productivity of the cultivars Fast Grow, SW 9500, Magic (SW 9301) and Super Supreme reached above 30 M.T./Ha in the first season 2003; and in the second season 2004, productivity of Magic, Fast Grow and Super Supreme reached above 26 M.T./Ha. Productivity over the two seasons 2003 and 2004 shown Fast Grow and Magic were the highest with 60.38, 59.85 M.T./Ha. respectively

Morphological and Ultra-Structural Characterization of Blackgram [Vigna mungo (L.) Hepper] Genotypes Grown under High Temperature Stress

Background: In this decade, increasing temperatures and adverse environmental factors are expected to influence the crop yield, seed quality and germination ability. Prolonged heat stress affects the pod setting, seed morphology and alters the starch granules.Methods: In this study, Scanning Electron Microscopy (SEM) and Light microscope was used to investigate the variations of morphological and ultra-structural characteristics in blackgram genotypes grown under high temperature (38+2°C) stress (HTS). Nineteen blackgram genotypes were evaluated under open top temperature controlled chamber (OTC) and the genotypes were classified into three categories such as heat tolerant, moderately heat tolerant and heat susceptible genotypes based on the Temperature Induction Response (TIR) and yield reduction percentage under HTS. Two genotypes were selected and examined the seed size, surface pattern, starch granule size and hilum from the each category.Result: Seed coat morphology was captured using SEM and light microscope showed that the tolerant genotype VBG-07-001 had a clear shiny surface, thin and reduced cotyledon fissures, compact surface devoid of surface deposits and pits whereas rest of the genotypes (VBG-06-001, VBN-6, CoBg-11-02, CoBg-11-03 and VBG-08-003) had a rough surface. A bold and well-structured starch granule was observed in heat tolerant lines whereas, unstructured and pleated granules were observed in moderately tolerant and heat stress lines. These morphological and ultra-structural studies revealed remarked diversity among different genotypes that can be regarded as useful to screen the genotypic tolerant characters for HTS.

Biochemical and yield evaluation of onion (Allium cepa L.) genotypes under waterlogging condition

The present investigation entitled “Biochemical and yield evaluation of onion (Allium cepa L.) genotypes under waterlogging condition” was carried out at ICAR-Directorate of Onion and Garlic Research, Rajgurunagar, Pune (Maharashtra). Onion crop is extremely sensitive to waterlogging or soil flooding stress due to its shallow root growth habit. The climate change and rainfall distribution pattern most of the onion growing belt might be subjected to heavy rainfall leading to soil flooding condition and cope up with such situation need to identify the improved onion genotypes with better adaptive traits and tolerance for waterlogging condition Therefore, the main objective of the present study was screening of elite genotypes for water logging tolerance under pot condition. The experiment was laid out in factorial CRD for pot condition during kharif, 2018. The pot experiment was conducted in rainout shelter using plastic pot and plants were treated with creating artificial waterlogging condition with the help of tank pit and another set were kept outside in rainout shelter as control. The experimental materials comprises of 17 onion entries including red and white onion entries. The seedlings of each entry were raised from seeds in nursery for 45 days with recommended cultural practices and transplanted in pot. The biochemical traits leaf antioxidant, leaf flavonoids and phenol content exhibited maximum in genotype RGP 5 under waterlogging condition. The waterlogging condition was increased quality traits which producing more secondary metabolites for defense strategy of the plant. Further, the yield attribute like bulb yield percent was minimum decreased in genotype RGP 5 with the percent reduction of 18.59% and the genotype W 344 recorded maximum percent reduction with decline by 83.49% under water logging treatment. It may due the water logging condition inhibits the translocation of assimilates from source organs to sink organ. Therefore, on the basis of overall yield reduction percentage and other important traits, genotype RGP 5 can be categorized as water logging tolerant genotypes, whereas genotype W 344 and W 448 recognized as water logging sensitive genotypes among all the tested onion genotypes.

Development of Mungbean yellow mosaic virus Resistant Genotypes in Mungbean through Interspecific Crosses of Wild Vigna Species

Mungbean Yellow mosaic disease is a main destructing viral disease in mungbean caused by Mungbean yellow mosaic virus (MYMV) which leads to severe sometime 100 percent yield reduction and it necessitates for developing MYMV resistant lines. The present investigation was carried out with an objective of evolution of MYMV resistant progenies through incorporating wide genes of same genera. An attempt was made between V. radiata x V. umbellata crosses. This agroinoculation technique was employed to examine the F2 individuals, which were derived from a cross between VMGG012-005 (Moderately susceptible) x VGGru1 (resistant homozygous advanced line from Vigna radiata x Vigna umbellata derivative used as MYMV donor) to screen for the MYMV resistant progenies. In the field condition, MYMV infection can be evaluated by MYMV disease rating scale (1-9).

The Dynamic Yield Response Factor of Alfalfa Improves the Accuracy of Dual Crop Coefficient Approach under Water and Salt Stress

The accurate quantification of crop water use or evapotranspiration (ET) under water and salt stress is needed for efficient water management and precision irrigation in water scarce regions. However, few studies were examined on alfalfa water use and its components under water and salt stress. We carried out two field experiments to quantify alfalfa water use through setting up different water and salt gradients, including two irrigation levels (full and deficit irrigation) and four soil salinity levels (0, 2‰, 4‰ and 6‰ salt of mass ratio) in an arid region of Northwest China. Electrical conductivity of soil saturation extract (ECe), soil water content (SWC), leaf area index (LAI) and soil evaporation (E) were measured. The SIMDualKc model, which uses the FAO56 dual Kc approach, was calibrated and validated using measured SWC and E. Model results show a good agreement between observed and simulated SWC and E without stress. The depletion fraction for no stress (p) and the percent yield reduction per unit increase in soil salinity (b) were 0.50 and 6.0%/(dS m−1), respectively, slightly lower than those of FAO-56 (0.55 and 7.3%/(dS m−1)). The difference indicates that alfalfa has a lower capacity of water use but a greater tolerance to salt stress after soil salinity reached its sensitivity threshold in the arid region. The model performed a reduced accuracy under water and salt stress and the differences tended to increase as stress increased, which was partly attributed to constant yield response factor (Ky) under different soil water and salt stress. The key parameter Ky dynamically increased with the increased degree of stress. Compared to constant Ky, the simulations of SWC and E showed improved accuracy with dynamic Ky. These results suggested that the response and acclimation of alfalfa to stress might be incorporated into the dual Kc model through the diversity of Ky.

Cadmium toxicity in African yam bean (Sphenostylis stenocarpa (HOCHST. EX A.RICH.) HARMS genotypes

The aim of the study was to investigate the growth responses of African yam bean (Sphenostylis sternocarpa (Hochst. ex A. Rich.) Harms (AYB) to cadmium pollution. Top garden soil (0 – 10 cm) was obtained as pooled and polluted with cadmium (as CdCl2) at the rate of 12 mg kg-1, which is equivalent to 3 times the ecotoxicological screening value of Cd. The polluted soils were made ready for use 3 days later. Nine selected AYB accessions (TSs-87, TSs-89, TSs-90, TSs-91, TSs-92, TSs-93, TSs-94, TSs-95, and TSs-96) were pre-soaked for 30 minutes and then sown in the polluted and unpolluted soils. Data collected were subjected to ANOVA, and means were separated at 95 % confidence interval. Results showed that incidence of cadmium pollution significantly delayed seedling emergence in all tested AYB accessions by at least one day (p < 0.05). Despite exposure to Cd, TSs-96 attained 50 % emergence faster than other accessions. Although there were general reductions in yield due to exposure to Cd, TSs-92 showed the least percentage yield reduction (50 %), compared to 74 % yield reduction in TSs-93, thereby suggesting a comparatively better yield capacity compared to the other test accessions. Overall, decrease in total chlorophyll content seems to be the major reason of injury in Cd-exposed plants.

AGRONOMIC CHARACTERS OF DROUGHT-TOLERANT SOYBEANS AT THE REPRODUCTIVE STAGE

In Indonesia, soybeans are typically cultivated during the dry season, thus making it prone to drought stress in the reproductive stage. The objective of the research was to characterize the agronomic characters of several soybean genotypes which were tolerant to drought at the reproductive stage. A total of 19 soybean genotypes were evaluated for its agronomic characters and tolerance to drought stress in Probolinggo (East Java, Indonesia) during the dry season (June – September). The research was arranged in a randomized block design with four replicates. Soybean cultivars were sown at two separate experiments, normal/optimal (plants were irrigated during the growth period) and stress (plants were irrigated up to 40 days after planting) conditions. Drought stress during the reproductive stage did not affect the characters of plant height, the number of branches per plant, the number of nodes per plant, and the number of pods per plant. Meanwhile, the number of empty pod, seed weight per plant, and seed yield were significantly affected. There were two genotypes which were identified as the tolerant genotypes to drought stress at the reproductive stage, i.e. MDT15-6-11 and MDT15-W-3034. The agronomic characters of MDT15-6-11 were showed as having a low percentage of yield reduction, hence it was able to mantain its high yield. The MDT15-W-3034 was identified as drought-tolerant due to the slow wilting, high plant character, a slow vegetative phase, and high yields. The genotypes obtained from this study could be recommended to be released as new soybean drought-tolerant varieties due to its high yield and tolerant to drought stress. Those genotypes could also be used as gene donors for soybean improvement to drought stress at the reproductive stage.

Influence of mild saline stress and growing season on yield and leaf quality of baby lettuce grown in floating system

Consumer demand has been increasing and many vegetable farmers have oriented their production plans towards baby leaf vegetables such as lettuce. The management of the nutrient solution as well as the growing conditions could significantly affect the yield and quality of leafy vegetable crops. The aim of the present work was to determine the effects of increasing the level of salinity in the nutrient solution (1, 10 or 20 mM NaCl) during two consecutive growing seasons (spring and autumn) on the yield and quality of Lactuca sativa L. var. acephala grown in floating raft culture. Increased salinity in the nutrient solution decreased marketable yield and dry biomass with more detrimental effect during the warm season. The percentage of yield reduction in comparison to the non-saline control was 7 and 20% in the spring season and 4 and 13% in the autumn growing season at 10 and 20 mM NaCl, respectively. Plants grown in the spring season exhibited higher yield and dry biomass but lower leaf quality than those grown in the autumn season. When averaged over salinity level the lipophylic antioxidant activity, total ascorbic acid, phenols and nitrate contents were significantly increased by 7.1, 20.1, 19.4 and 24.4%, respectively, in plants grown in spring as compared to autumn growing season. The floating system could be considered an efficient and low-cost tool to improve quality aspects through proper management of the salt concentration in the nutrient solution with an acceptable yield reduction.