Deciphering the Role of Stay-Green Trait to Mitigate Terminal Heat Stress in Bread Wheat

The present study aimed to reveal the impact of the stay-green trait in bread wheat under terminal heat stress. Field experiments (early and late sowing; for two consecutive years) were conducted to investigate the influence of terminal heat stress on the morpho-physiological traits in different stay-green types i.e., non-stay-green, moderately non-stay-green, moderately stay-green, and stay-green. In addition, the greenhouse experiment was performed to dissect the stay-green trait in functional stay-green, non-functional stay-green, and non-stay-green genotypes. The results of the field experiments confirmed that genotypes exhibiting the stay-green trait have a significantly high chlorophyll content, normalized difference vegetative index, grain yield, biological yield, kernel weight, and low canopy temperature under control and heat stress conditions. In the greenhouse experiment, functional stay-green and non-functional stay-green genotypes showed a high chlorophyll content and photochemical efficiency, whereas biological yield and grain yield showed a significant relation with the functional stay-green genotype under control and terminal heat stress treatments. The sequencing and expression analysis of chlorophyllide a oxygenase (CaO), light-harvesting complex (Cab), stay-green (SGR), and red chlorophyll catabolite reductase (RCCR) in functional stay-green, non-functional stay-green, and non-stay-green genotypes revealed variations in the exons of CaO and RCCR; and significant difference in the regulation of CaO and Cab at 7 days after anthesis under terminal heat stress. This study confirms that genotypes displaying the stay-green trait can aid wheat breeders to cope with increasing temperature in the impending decades.

Peanut genotypes with high chlorophyll content and low leaf temperature are preferred in breeding program for drought prone areas

An understanding of drought stress and water use in relation to plant growth is of importance for sustainable agriculture. Groundnut genotypes respond differently to different stages of drought stress. The aim of this research was to study the response of groundnut genotypes to different stages of moisture stress. Seven groundnut genotypes (Samnut 25, Kwankwaso, Maibargo, Samnut 23, Samnut 24, EX dakar, and Samnut 21) and three water supply (80% field capacity, 40% field capacity and without irrigation) with three replications were used for the study. The water stress was imposed after 14 days of initial growth of the plants and was maintained by using TDR to check the moisture level every three days. Significant differences was observed between the genotypes for leaf temperature and chlorophyll content at two weeks after imposition of moisture stress. Also, significant differences was observed between the moisture levels for all variable measured except for the chlorophyll content before imposing moisture stress. An interaction effect was observed between the genotypes and water stress for root length and Mai Bargo produced the highest root length when terminal drought was simulated. The research shows that the genotypes have varying responses to leaf temperature and chlorophyll content and will consistently vary under different moisture stresses. Therefore, genotypes identified with high chlorophyll content and low leaf temperature can be selected as parents for further breeding program or introduction into drought prone areas.

Genetic characterization and molecular mapping of novel chlorophyll deficiency gene in air-cured tobacco (Nicotiana tabacum L.)

This study was performed to genetical and morphological investigation of a novel chlorophyll deficiency gene in tobacco leaf. One low chlorophyll content (LCC) variety (Urumieh 2) and high chlorophyll content (HCC) variety (Burley Ree 103) from the Burley type was crossed and the F2 generation was grown on the field. One hundred plants were selected, contained low and high chlorophyll content. These plants were sampled and DNA was extracted. Sixty RAPD primers were tested on parents, LCC and HCC Bulks based on Bulk Segregant Analysis (BSA). Chi-square test confirmed the monogenic segregation. Regresion analysis showed that there was strong relationship between greenness degree and chlorophyll contents. Four primers (OPE17, OPC09, OPB08 and OPR02) showed polymorphism and after the test on 97 samples from the F2 generation two markers were selected (OPB08-1050 and OPC09-1900). That showed 15.9 and 10.8 CM distance from chlorophyll locus respectively.

SPAD-502 readings in response to photon fluence in leaves with different chlorophyll content

The chlorophyll meter (SPAD-502) is widely used to estimate chlorophyll content, but non-uniform chloroplast distribution can affect its accuracy. This study aimed to assess the effect of photon fluence (F, irradiance x time of illumination) in leaves with different chlorophyll content and determine the effect of chlorophyll a/b on SPAD values of four tropical tree species (Croton draconoides Müll. Arg., Hevea guianensis Aubl., Hymenaea courbaril L. and Matisia cordata H.B.K.). There were also determined calibration equations for the chlorophyll meter and assessed the effect of F on SPAD values between 07:00 h and 17:00 h. Calibration equations were obtained after determining leaf chlorophyll content in the laboratory. Increases in F with time caused a reduction in SPAD values in species with a high chlorophyll content, with reductions of 20% in M. cordata and 10% in H. guianensis. Leaves of C. draconoides and H. courbaril had lower chlorophyll content and showed no changes in SPAD values with increase in F. The chlorophyll a/b ratio increased with SPAD values and the SPAD/chlorophyll relationship was best described by an exponential equation. It seems that F may affect SPAD values in leaves with high chlorophyll content, probably due to non-uniform chloroplast distribution at high irradiance. This indicates that SPAD values tend to be more accurate if recorded early in morning when irradiance is low.

The influence of blanching pretreatments on the quality of dehydrated broccoli stems/ Influencia del tipo de escaldado en la calidad de tallos de bróculi deshidratados

Different blanching treatments were applied to sliced broccoli stems prior to dehydration in order to improve product quality. The pretreatments used were a conventional blanching in water at 100°C, and a stepwise blanching using different temperatures for the first step (50, 55, 60, 65 and 70°C). Five rehydration temperatures were used (25, 40, 55, 65 and 80 °C). Rehydration rate, chlorophyll content and texture of the rehydrated product were evaluated. Rehydration was modeled based on Fick's diffusion equation. A good agreement between the model and the experimental data was obtained when D eff and W e values were identified for each temperature (average percent variation 99.3). Samples stepwise blanched at 60 °C showed, on average, the lowest We and Ea values. Stepwise blanching at 60 and 65 °C and rehydration at 25, 40 and 55 °C were the combinations that gave the firmest product. Stepwise blanching at 50 °C and rehydration between 25 and 65 °C was the combination that preserved the highest chlorophyll content. From these results, it seems difficult to obtain firm samples with high chlorophyll content without any chemical additive.

Differences between genotypes of tomato (Lycopersicon esculentum Mill.) in net photosynthesis, light absorption by leaves, chlorophyll content and specific leaf fresh weight under low-energy conditions.

Differences in net photosynthesis between tomato genotypes, grown under low light intensity and, from day 30, at 3 night temperatures, were largely due to differences in the capacity of the leaves to absorb light. Variation in chlorophyll content and leaf thickness largely explained the differences in light absorption. Genotypes with large thin leaves and a high chlorophyll content were thought to be best adapted to low-energy conditions. (Abstract retrieved from CAB Abstracts by CABI’s permission)