The green area displayed by a crop is a good indicator

The green area displayed by a crop is a good indicator of its photosynthetic capacity, while chlorophyll retention or stay-green is regarded as a key indicator of stress adaptation. (NDVI) at physiological maturity was estimated using the regression of NDVI over time from the mid-stages of grain-filling to physiological maturityCand for the rate of senescence during the same period. Under heat and heat combined with drought environments, stay-green calculated as NDVI at physiological maturity and the rate of senescence, showed positive and negative correlations with yield, respectively. Moreover, stay-green calculated as an estimation of NDVI at physiological maturity and the rate of senescence regressed on degree days give an independent measurement of stay-green without the confounding effect of phenology. On average, in both populations under heat and heat combined with drought environments CTgf and stay-green variables accounted for around 30% of yield variability in multiple regression analysis. It is concluded that stay-green traits may provide cumulative effects, together with other traits, to improve adaptation under stress further. (2011) has shown that delaying leaf senescence was associated with increased grain yield or grain protein concentration, but this depended largely on the type of environment considered. Reports of stay-green heritability have been highly variable, for example, it was not particularly high in wheat (Tao (2007) identified stay-green sorghum using the onset of leaf senescence, the absolute and relative rate of leaf senescence, and green leaf area and SPAD chlorophyll content at maturity. The onset of senescence was generally delayed in the stay-green genotypes (Harris (2007) observations of highly significant correlations between predicted SPAD at maturity and SPAD taken at maturity as a measurement of stay-green. Moreover, NVP-BEZ235 higher NDVI values estimated at physiological maturity correspond to a stay-green phenotype, whereas low NDVI values NVP-BEZ235 correspond to a senescent phenotype. The RS was calculated as the slope of the linear NDVI decline over thermal time as shown in Fig. 1 (adapted from Bogard 2011). Regarding RS, stay-green phenotypes are defined here as those showing smaller rates of senescence. Both measurements of stay-green were not confounded by phenology: for rate of senescence, degree days were used instead of days to heading or anthesis; NDVI at physiological maturity is estimated for each genotype exactly at physiological maturity. For population 2, only two measurements of NVP-BEZ235 NDVI were taken under full irrigation during grain-filling and to calculate both RS and NDVI at physiological maturity only these two points were used for regression analysis. Fig. 1. Diagram illustrating calculations of rate of senescence (RS) and greenness of the plot at physiological maturity (Stg). The rate of senescence (RS) was determined as the slope of the NDVI decay against thermal time (TT). The greenness of the plot at maturity … Statistical analysis The adjusted means for each environment and genotype were obtained using the mixed models theory and conducted with the MIXED procedures from the SAS Institute (2004) considering the effects of replications and blocks within replications as random and genotypes as fixed. Principal component analysis was performed using a mean INF2 antibody of all sites for each genotype and trait using the PRINCOMP procedure (SAS Institute, 2004). Broad sense heritability (H2) was estimated for each trait individually in each environment and across all environments as: =genotypic variance, and =genotype by environment interaction variance. Phenotypic correlations were calculated using the CORR procedure and multiple regression analysis was obtained with the STEPWISE procedure using canopy temperature at grain-filling, SPAD, stay-green associated traits (NDVI at physiological maturity and rate of senescence), and days to heading and to maturity (SAS Institute, 2004). Results Environmental characterization and overall analysis of yield and physiological traits Both populations were grown under NVP-BEZ235 four different conditions in Mexico, including: a full irrigation control; a drought treatment where irrigation was withheld after germination; a late sowing treatment to increase temperatures during grain-filling with full irrigation; and a late sowing treatment with reduced irrigation such that mild NVP-BEZ235 drought during grain-filling also coincided with warm temperatures (Table 1). Measurements were taken in all environments but are only presented for the.

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