Drought Tolerant Maize Varieties Research Articles

The Maize Gene ZmGLYI-8 Confers Salt and Drought Tolerance in Transgenic Arabidopsis Plants.

Methylglyoxal (MG), a highly reactive and cytotoxic α-oxoaldehyde compound, can over-accumulate under abiotic stress, consequently injuring plants or even causing death. Glyoxalase I (GLYI), the first enzyme of the glyoxalase pathway, plays multiple roles in the detoxification of MG and in abiotic stress responses. However, the GLY1 gene in maize has been little studied in response to abiotic stress. In this study, we screened a glyoxalase I gene (ZmGLYI-8) and overexpressed in Arabidopsis. This gene was localized in the cytoplasm and can be induced in maize seedlings under multiple stress treatments, including salt, drought, MG, ABA, H2O2 and high temperature stress. Phenotypic analysis revealed that after MG, salt and drought stress treatments, overexpression of ZmGLYI-8 increased the tolerance of transgenic Arabidopsis to MG, salt and drought stress. Furthermore, we demonstrated that the overexpression of ZmGLYI-8 scavenges accumulated reactive oxygen species, detoxifies MG and enhances the activity of antioxidant enzymes to improve the resistance of transgenic Arabidopsis plants to salt and drought stress. In summary, this study preliminarily elucidates the molecular mechanism of the maize ZmGLYI-8 gene in transgenic Arabidopsis and provides new insight into the breeding of salt- and drought-tolerant maize varieties.

Combating Soil Drought in Maize (Zea mays L.): Genetic-Engineering Strategies for Drought Tolerant Varieties

Drought is the global challenge of crop agriculture across the globe. The detrimental effect of drought hinders a significant growth and development impairment leading to devastating harvest losses. Maize, a vital staple for food faces future challenges with a rapidly expanding drought area. To address this challenge, scientists and breeders are urged to develop new varieties that are not only resistant or tolerant but also even potentially thrive under drought planting conditions. New breeding technologies involving molecular biology and biotechnology have been developed and implemented thus offering a promising solution. Genetic engineering has allowed humans to straightforwardly transfer beneficial genes across species and varieties, thus deliberating gene pool transfer of similar species and varieties. Furthermore, this technology has evolved to the level of creation, deletion, or modification of existing alleles with high precision through CRISPR/Cas9-mediated genome editing. This review article delves into the morpho-physiology, biochemical, and molecular responses of maize varieties against drought stress. It subsequently explores how genetic engineering has been utilized to optimize the selected genes underlying those responses. By exploring the current progress of genetic engineering, this article aims to prepare the ground for future advancement in combating drought through drought-tolerant maize varieties. Thus, this review article has the potential to contribute to improving food security in the increasing drought challenges.

A Review on Biotechnological Innovations in Developing Stress-Tolerant Crops for Adverse Environmental Conditions

The development of stress-tolerant crops through advanced biotechnological approaches is critical for enhancing global food security and sustainability in the face of climate change and increasing environmental stresses. Emerging tools such as CRISPR/Cas9 gene editing and synthetic biology are revolutionizing genetic engineering by enabling precise, targeted modifications of plant genomes to improve drought, salinity, heat, and cold tolerance. Integrative approaches that combine genomics, transcriptomics, proteomics, and metabolomics provide a comprehensive understanding of plant stress responses, facilitating the identification of key regulatory genes and metabolic pathways. High-throughput phenotyping and RNA interference (RNAi) technologies further enhance trait identification and manipulation, accelerating the development of robust stress-tolerant varieties. The deployment of these crops has demonstrated significant yield improvements and stability in adverse conditions, reducing the risk of crop failures and food shortages. Drought-tolerant maize and rice varieties have increased yields by 20-30% under water-scarce conditions, while salt-tolerant rice and wheat varieties have enabled cultivation in saline soils. Heat-tolerant crops maintain productivity in high-temperature regions, and cold-tolerant varieties extend growing seasons in temperate areas. These advancements not only enhance crop productivity but also promote sustainable agricultural practices by reducing the need for chemical inputs and supporting the resilience of food systems. Moreover, the socio-economic benefits include improved livelihoods for smallholder farmers through increased incomes and economic stability. Continued interdisciplinary research and collaboration are essential to fully realize the potential of these technologies in addressing global agricultural challenges and ensuring a stable food supply for future generations.

Factors Influencing Farmers’ Attitude to Adopt Drought Tolerant Maize Varieties in Ondo State, Nigeria

The study investigated factors influencing farmers’ attitude towards adoption of drought-tolerant maize varieties. One hundred maize farmers were selected using a multi-stage sampling procedure and data were collected through structured questionnaires. Information was collected on the socio-economic characteristics of the maize farmers, farmers’ level of awareness of drought-tolerant maize varieties, farmers’ attitudes towards agricultural innovation, constraints to adoption of drought-tolerant maize varieties and, factors influencing farmers’ attitude towards adoption of drought-tolerant maize varieties. Data were analyzed using frequencies, percentages, Pearson Product Moment Correlation and Logit regression. The findings revealed that 76% of the maize farmers had limited awareness regarding the benefits and characteristics of drought-tolerant maize varieties. Also, the majority (74%) of the farmers lacked knowledge about the quality and advantages of these varieties. Despite positive attitude (mean = 4.28) which was measured at ordinal level, several constraints to adoption were identified, mainly low output of drought tolerant maize varieties (mean = 2.30). The findings also showed the substantial impact of two key factors (that is, sex and income) as factors influencing farmers’ attitude to adopt drought-tolerant maize varieties. Farmers are yet to take advantage of drought-tolerant maize varieties as a mitigating strategy against climate change. The need for extension services and non-governmental organizations to step up awareness creation and training on best agronomic practices in growing the maize varieties is recommended.

Gender, agricultural risk perceptions, and maize seed systems: A case study of drought-tolerant maize varieties in Uganda

CONTEXTDrought-tolerant maize (DTM) varieties and other agricultural technologies can play an important role in maintaining crop production and livelihoods, yet their uptake remains low. Most research on risks in agriculture only considers climate risks as a barrier to adopting agricultural technologies. Farming communities face other agricultural risks related to health, finances, markets, and institutions. These risk perceptions may be different for male and female farmers. OBJECTIVEWe explore the agricultural risk perceptions of male and female smallholder farmers, assessing gender roles and norms and their influence on risk perceptions. Subsequently, we discuss the implications of these perceptions and gender roles and norms on the uptake of drought-tolerant maize varieties in Uganda. METHODSWe conducted a qualitative study with men's and women's focus groups in twelve villages in three districts in Uganda. We used participatory rural appraisal tools with each group to structure the discussions. RESULTS AND CONCLUSIONSProduction risks, health risks, social norms, and financial constraints may play an important role in smallholder agricultural decision-making. These risks are inseparable and different for men's and women's groups. Women tend to prioritize climate and crop management risks, while men place more weight on financial constraints. The perceived impact of health risks, risks related to social norms, and market risks vary across men and women in different districts. Dokolo reflects more traditional gender roles, while Iganga and Masindi note more contested gendered power over maize cultivation. The risk and concern ranking in Dokolo shows more similarity between men and women compared to Iganga and Masindi. Women tend to have less access to DTM varieties in the formal seed system, while they tend to have fewer resources to mitigate health and crop production risks. To reach and benefit more women with DTM varieties, we draw attention to access to information, bringing seed closer (potentially subsidized), gender transformative interventions, and investment in open-pollinated varieties disseminated through the informal seed system. SIGNIFICANCEOur research emphasizes the importance of considering multiple risks in agriculture when promoting resilient farming systems rather than focusing solely on climate risk. We also show the importance of applying a gender lens to these risks and the uptake of DTM varieties. Serving as an inclusive and pro-poor risk management technology, DTM would benefit from ensuring that the technology becomes available to male and female farmers in multiple seed systems, including formal seed systems (primarily hybrids) and informal seed systems (primarily open-pollinated varieties).

Approaches and progress in breeding drought-tolerant maize hybrids for tropical lowlands in west and central Africa.

Drought represents a significant production challenge to maize farmers in West and Central Africa, causing substantial economic losses. Breeders at the International Institute of Tropical Agriculture have therefore been developing drought-tolerant maize varieties to attain high grain yields in rainfed maize production zones. The present review provides a historical overview of the approaches used and progress made in developing drought-tolerant hybrids over the years. Breeders made a shift from a wide area testing approach, to the use of managed screening sites, to precisely control the intensity, and timing of drought stress for developing drought-tolerant maize varieties. These sites coupled with the use of molecular markers allowed choosing suitable donors with drought-adaptive alleles for integration into existing elite maize lines to generate new drought-tolerant inbred lines. These elite maize inbred lines have then been used to develop hybrids with enhanced tolerance to drought. Genetic gains estimates were made using performance data of drought-tolerant maize hybrids evaluated in regional trials for 11 years under managed drought stress, well-watered conditions, and across diverse rainfed environments. The results found significant linear annual yield gains of 32.72kg ha-1 under managed drought stress, 38.29kg ha-1 under well-watered conditions, and 66.57kg ha-1 across multiple rainfed field environments. Promising hybrids that deliver high grain yields were also identified for areas affected by drought and variable rainfed growing conditions. The significant genetic correlations found among the three growing conditions highlight the potential to exploit the available genetic resources and modern tools to further enhance tolerance to drought in hybrids.

Reproductive Characters and Yield of Selected Drought Tolerant Maize Varieties in a Rainforest Agroecology of Nigeria

Reproductive Characters and Yield of Selected Drought Tolerant Maize Varieties in a Rainforest Agroecology of Nigeria

On-farm demonstration of improved and drought tolerant maize varieties with associated management practices

Maize is an important cereal crop in the central Rift Valley of Ethiopia. It plays a greater role in ensuring food security. The study was designed to evaluate and promote Melkassa-6Q variety with standard check (Melkassa-2). The study sites were Adama and ATJK districts. The districts were selected based on their maize production potential and accessibility of the site for demonstration. Training and field days were implemented to facilitate the successful implementation of the activity and create awareness among farmers about the varieties. Grain yield was recorded and the varieties were compared to each other based on their yield performance. Farmers ‘feedback was also collected and farmers preference ranking of each demonstrated variety was done depending on the farmers’ set criteria for variety evaluation. The mean yield of Melkassa-2 (standard check) is about 39 qt/ha across locations whereas the mean yield of Melkassa-6Q is 36.4 qt/ha which is 2.6 qt below the standard check. In addition to yield, Melkassa-2 variety was preferred over Melkassa-6Q variety in overall farmers’ evaluation criteria for maize variety evaluation. Therefore, there should be an adequate quality seed supply of Melkassa-2 variety till the best-performing maize variety is released by the research system.

Performance Evaluation of Drought Tolerant Hybrid Maize (Zea mays) Varieties in East Hararghe Zone, Ethiopia

Performance Evaluation of Drought Tolerant Hybrid Maize (Zea mays) Varieties in East Hararghe Zone, Ethiopia

Adoption of drought-tolerant maize varieties and interrelated climate smart agricultural practices in Nigeria

BackgroundIn Sub-Saharan Africa, drought is one of the prevailing climatic conditions that has led to the modification of improved seeds to be resilient enough to improve yield and increase farm households' welfare. However, like most climate-smart agricultural practices, the adoption of drought-tolerant maize varieties is low. This study examines the simultaneous adoption decisions of drought tolerant maize varieties and other climate-smart agricultural practices such as intercropping, row-planting, inorganic fertiliser, manure, and residue incorporation using nationally representative survey data from 1370 rural households in Nigeria. Multivariate Tobit and ordered probit models are applied to assess the complementarity and or substitutability effect among CSAPs, the predictors of the joint adoption, and the adoption intensity of CSAPs.ResultsThe results show a significant positive correlation between DTMVs and inorganic fertilisers, DTMVs and intercropping, and DTMVs and manure. However, the strongest adoption complementarity is found between DTMVs and manure. The probability and the extent of adoption of CSAPs are commonly determined by household wealth, access to loans, access to training in improved production practices, and membership in input supply and farm cooperatives.ConclusionThe study suggests that the adoption of DTMVs has varying degrees of relations with other CSAPs informing the need for policies aimed at increasing its adoption to consider existing CSAPs among maize farm households.

Adoption of drought tolerant maize varieties and farmers’ access to credit in Nigeria: Implications on productivity

In this study, we examined the determinants of choice of variety including DTMV, local variety and combination of the two varieties using multivariate probit model. In addition, we examined factors influencing adoption of DTMV and access to credit among the maize farmers using endogenous switching probit model (ESPM). Consequently, we ascertained the probable effects of adoption of DTMV on maize productivity using endogenous switching regression model (ESRM). We used IPWRA to correct for biased estimates of ATT, ATE and POM of the endogenous treatment. Our results are in four folds: First, from the multivariate probit model, we found that age, gender, household size, farming experience, membership in farmers association, access to extension contacts, location and access to credit variables influenced the maize farmers’ decision to choose between DTMV, local varieties and combination of both. Second, the result of the ESPM shows that variables age, gender, farm size, years of formal education and membership in association affects maize farmers’ access to credit. Third, from ESRM results, we found that gender, household size, marital status, membership in association, access to extension contacts and location variables translates to increase maize productivity for the maize farmers who adopted DTMV. Lastly, the result of IPWRA indicates that adoption of DTMV increased the productivity of the maize farmers. To ensure access to DTMV seed varieties, stakeholders and government should take lead in dissemination of these varieties to reach the target farmers.

Effects of Climate Change and Drought Tolerance on Maize Growth.

Climate change is affecting all regions of the world with different climates, and the scale of damage is increasing due to the occurrence of various natural disasters. In particular, maize production is highly affected by abnormal climate events such as heat waves and droughts. Increasing temperatures can accelerate growth and shorten the growing season, potentially reducing productivity. Additionally, enhanced temperatures during the ripening period can accelerate the process, reducing crop yields. In addition, drought stress due to water deficit can greatly affect seedling formation, early plant growth, photosynthesis, reproductive growth, and yield, so proper water management is critical to maize growth. Maize, in particular, is tall and broad-leaved, so extreme drought stress at planting can cause leaves to curl and stunt growth. It is important to understand that severe drought can have a detrimental effect on the growth and reproduction of maize. In addition, high temperatures caused by drought stress can inhibit the induction of flowering in male flowers and cause factors that interfere with pollen development. It is therefore important to increase the productivity of all food crops, including maize, while maintaining them in the face of persistent drought caused by climate change. This requires a strategy to develop genetically modified crops and drought-tolerant maize that can effectively respond to climate change. The aim of this paper is to investigate the effects of climate change and drought tolerance on maize growth. We also reviewed molecular breeding techniques to develop drought-tolerant maize varieties in response to climate change.

Drought stress induced by polyethylene glycol (PEG) in local maize at the early seedling stage

Drought stress adversely impacts growth, crop production, reproductive organ development, and yield characteristics in maize. As a drought-sensitive crop, maize (Zea mays L.) shows considerable varietal differences. A study was conducted at the Tissue Culture Laboratory, Department of Biology, Faculty of Mathematics and Natural Sciences, University of North Sumatra, Medan, Indonesia in order to identify drought-tolerant maize varieties. During germination and early seedling growth, 16 local accessions were evaluated for drought tolerance. Based on local climate and soil conditions, these specific accessions were chosen. The varieties were tested against five levels of drought stress imposed by Polyethylene glycol 6000 (PEG-6000) at 10, 20, 30, 40, and 50%. An experiment with three replications was conducted using a completely randomized design. In the study, local maize accessions (BI3, SB5, DS2, and MN3) and the hybrid variety (H) showed the capability of tolerating drought stress. Generally, germination time, germination percent and vigor index, root and shoot length, shoot ratio, and fresh and dry weight were decreased by increasing PEG concentrations (up to 50%). According to ANOVA results, shoot water content was not significantly affected by the PEG, nor was the interaction between the PEG and the accessions. The root water content, however, was significantly affected by PEG, and the interaction between PEG and accessions. Although interactions between accessions with low PEG concentrations improved germination characteristics, the root histology of the accessions varied. According to drought tolerance indexes, five maize accessions are drought-tolerant, including H (0.683), SB5 (0.617), DS2 (0.565), MN3 (0.512), and BI3 (0.504). The drought-tolerant varieties are recommended in regions with low rainfall or low water sources since they are less water-intensive and produce higher yields.

The Effect of Drip Irrigation Quota on Biochemical Activities and Yield-Related Traits in Different Drought-Tolerant Maize Varieties

Drip irrigation has a close relationship with the growth and development of maize grains and yield formation in semiarid areas. To explore the response mechanism of grain yield formation to drip irrigation quotas, a 2-year pond planting experiment was conducted under controlled conditions, by using two maize varieties with differences in drought resistance as experimental materials. Six treatments were set up, including CK1 (drought-resistant variety, 500 mm), T1 (drought-resistant variety, 350 mm), T2 (drought-resistant variety, 200 mm), CK2 (drought-sensitive variety, 500 mm), T3 (drought-sensitive variety, 350 mm), and T4 (drought-sensitive variety, 200 mm). The changes in maize grain filling characteristics, related hormones, enzyme activity related to starch synthesis, sugars and amino acids contents, and yield were analysed. The results showed that 100-grain weight at different filling times, filling rate, average filling rate, auxin, cytokinin, acid sucrose invertase, sucrose synthase, starch synthase, and adenosine diphosphate glucose pyro phosphorylase activities in maize grains decreased and the abscisic acid content and content of various amino acids and sugars in grains increased with the decrease in drip irrigation quota. The percentage of changes in drought-sensitive maize varieties was relatively high. The maize yield decreased with the decrease in drip irrigation quota. In summary, there was no significant difference in grain filling characteristics, hormone content, starch synthesis enzyme activity, and yield between maize treated with T1 (drought-resistant variety, 350 mm) and the control treatment. This effectively maintained grain growth and yield formation, achieving the goal of water saving and stable yields.

Effects of Tied Ridges and Drought Tolerant Maize and Legume Varieties on Maize Yields in Semi Arid Areas of Northern Tanzania

This paper is based on research findings and field experience of maize and legume crops using integrated technologies in Mwanga and Same Districts, Kilimanjaro region, Tanzania. Field experiments were conducted over the period of two years (2013-2014) to investigate the effects of tied ridges, drought tolerant maize and legumes on maize grain yield. The experiment was arranged in randomised complete block design (RCBD) with three replications. The data collected included maize plant height, biomass yield and grain yields. The data were coded into different variables and subjected to analysis of variance (ANOVA) using the STATISTICA computer package and the treatments mean separation test were done using Fischer Least Significance Difference (LSD).
 Results obtained from both Same and Mwanga Districts showed that tied ridges and cropping systems had significant (P ≤ 0.001) effect on maize plant height, biomass and grain yield in both cropping seasons. Further, the results showed significant interactive (P ≤ 0.05) effect between tied ridges and cropping systems on maize plant height and biomass yield for Mwanga and Same Districts in both seasons although no significant interactive effects observed for maize grain yield. The results further showed that maize yields increased from 0.65 to 1.26 t ha-1 and 0.4 to 1.5 t ha-1 for Mwanga and Same Districts, respectively.
 On average, the highest yield increment of more than 60% due to tied ridges and drought tolerant maize and legume varieties were obtained from the two districts in both seasons over the control. Therefore, use of tie ridges, drought tolerant maize varieties and legumes as a package has significant effect on maize grain yield in semi arid areas of northern Tanzania and can be extrapolated to other areas with similar climatic conditions.

Potential impact of scaling adaptation strategies for drought stress: a case of drought-tolerant maize varieties in Tanzania

ABSTRACTDrought-tolerant maize varieties (DTMVs) offer hope as an adaptation strategy for farmers facing increasing frequency of droughts in sub-Saharan Africa. Adoption of these varieties also offers hope to enhance sustainability in the agricultural production system. However, these varieties are not yet widely cultivated, and the potential economic benefits not fully understood. This study examines the scalability of DTMVs in Tanzania under three scenarios: (1) scalability conditional on knowledge of DTMVs; (ii) scalability conditional on (physical) seed availability in addition to awareness; and (iii) scalability conditional on seed affordability in addition to awareness and (physical) seed availability. The study uses household production and consumption data from major regions in Tanzania. The results from the economic surplus model indicate that by 2032, the adoption of DTMVs could generate between US$ 373 million and US$ 499 million in cumulative benefits for both producers and consumers. Such benefits could potentially lift up to 1.6 million people out of poverty by 2032. It is estimated that consumers would get 40% of the benefits and producers 60%, with the largest benefits occurring in the major maize-producing regions of Mbeya, Rukwa, Ruvuma, Mwanza, Arusha, and Kagera. Consumers in Dar es Salaam would also benefit significantly from the price reductions resulting from increased production. The largest returns on investment would occur in Dodoma, Geita, Simiyu, Singida, and Kagera. These findings justify the investment of both public and private funds to support the scaling of DTMVs in Tanzania.

Beyond average: are the yield and income impacts of adopting drought-tolerant maize varieties heterogeneous?

ABSTRACT Assessing the benefits of adopting climate-resilient farming technologies without considering the heterogeneity among farmers, may not provide a sufficient evidence base for policy. Yet, most empirical studies do not go beyond documenting the average effects of climate-resilient technologies. Using farm household survey data from Nigeria, this paper examines whether and to what extent the yield and income impacts of adopting drought-tolerant maize varieties are heterogeneous. We used the stratification-multilevel, matching-smoothing and smoothing-differencing econometric methods to analyse the heterogeneous effects of the varieties on maize yield, crop income and household income. Our results show that the adoption of drought-tolerant maize varieties significantly increased maize yield, crop and household income. In addition, we find that the yield and income impacts of the adoption of drought-tolerant maize varieties are heterogeneous and depend on the farm households’ propensity to adopt the drought tolerant maize varieties. Specifically, we find that the estimated yield effects of the drought-tolerant maize varieties are larger for farmers with the highest propensity to adopt the varieties, which suggests a positive selection. Our results emphasize the need for proper targeting of interventions to incentivize the uptake of climate-resilient farming technologies in order to improve the outcomes of households in drought-prone areas.

Reducing susceptibility to drought under growing conditions as set by farmers: The impact of new generation drought tolerant maize varieties in Uganda

Given the challenges brought about by the increasing frequency of climatic stressors (droughts) and other biotic challenges (pests and diseases), breeding for tolerance to these traits is now seen as an indispensable adjunct to the enhancement of yield potential. Drought tolerant (DT) maize varieties that do well under moderate drought and outperform (or do not underperform) commercial checks under normal rainfall are becoming available. This study examines the role of these maize varieties in mitigating the effects of drought on maize yields in drought-prone areas of eastern Uganda. We estimate the causal impact of these new generations of maize varieties using a multinomial endogenous switching regression treatment effect framework. The average treatment effects of adopting DT maize show that farmers who actually cultivated DT maize achieve 30% more yield than what they would have obtained with non-DT hybrids. Similarly, average treatment effects on the untreated, revealed that farmers who grew non-DT modern and local maize would have 32 and 54% more yield, respectively, if they instead had adopted DT maize. While being superior to all other maize seeds, the magnitudes of the benefits of DT maize varieties were more pronounced in areas with comparatively less rainfall amount providing strong evidence that the yield potential of these varieties is stable across space and a wide range of rainfall conditions. If the genetic gains of these varieties can be secured over the long term, their impacts in improving the resilience of maize farming systems are likely to be considerably large and favorable.

Relationships between Grain Weight and Other Yield Component Traits of Maize Varieties Exposed to Heat-Stress and Combined Heat- and Water-Stress Conditions

It is necessary to identify the appropriate traits that influence yield in a given environment as part of a breeding programme. The objective of this study was to identify the morphological traits that contribute to maize grain weight (GWt) under abiotic stress conditions. Three drought-tolerant maize varieties were grown under no-stress (NHWS), heat-stress (HS), and combined heat- and water-stress (CHWS) conditions. Data from 19 morphological traits were analysed. The correlation results revealed that eight traits consistently produced a significant positive relationship with GWt under the three growth conditions. The path coefficient analysis revealed that in the NHWS, HS, and CHWS conditions, five traits consistently had a positive direct effect on the GWt. Given the magnitude of the positive direct effects, increasing dry biomass yield, harvest index, and grain number in the NHWS; grain number, harvest index, and ear width in the HS; and harvest index, days till silk appearance, leaf chlorophyll content, and grain number in the CHWS will increase GWt. Under various abiotic stress conditions, maize phenotypic expression varied. Therefore, the identified traits that contributed positively to GWt under various stress conditions should be considered when developing a maize improvement programme in a stress-prone environment.

English

Stay green is the plant’s ability to sustain photosynthetically functional green leaf area for longer periods, even with excessive water stress. This study was done to understand the gene action that controlled inheritance of the stay green trait with the general objective of contributing to breeding more drought tolerant maize varieties. 10 F1 hybrids from crosses between highly performing and the least performing drought tolerant inbred lines as regards selected stay green physiological determinants were planted under a rain out shelter with a well-watered control and excessive water-stress treatments applied from six weeks after planting and eight weeks after planting. With progress in days after flowering, data were collected on relative chlorophyll per unit leaf area (RC: LAUG), maximum quantum yield of photosystem II photochemistry (ΦII), non-photochemical quenching (NPQ) and linear electron flow (LEF). RC: LAUG and NPQ were mainly inherited by additive gene action. ΦII was controlled more by the environment than interallelic interactions while LEF inheritance was controlled mainly by interallelic interactions. Key words: Additive, inheritance, non-additive, photosynthesis, stay green.