Heterosis and combining ability for floral and yield characters in rice using cytoplasmic male sterility system.

Developing high-yielding rice genotypes is decisive to ensure global food security with current population growth and the threat of environmental pressures. Cytoplasmic male sterility (CMS) system provides a valuable approach for commercial exploitation of heterosis and producing high-yielding and quality hybrid rice. Three CMS lines and ten diverse restorers were crossed using line × tester mating design. The obtained thirty F1 hybrids and their thirteen parents were evaluated. Yield traits as well as certain floral traits characters that influence the efficiency of crossing and hybrid seed production as the duration of floret opening (min), stigma exsertion (mm), stigma length (mm), opening floret angle, and anther length (mm) were assessed. Highly significant variations were detected among parents, crosses, and parents vs. crosses for all the studied traits. The CMS line L2 and the restorer T5 were determined as good combiners for stigma exsertion, stigma length, opining floret angle, and duration of floret opening. Besides, the hybrids L1 × T1, L1 × T3, L2 × T2, L2 × T5, L3 × T4, L3 × T5, and L3 × T9 exhibited positive SCA effects for most floral traits. Moreover, the CMS lines L1 and L3 as well as the restorers T1, T2, T3, T6, and T9 were identified as good general combiners for grain yield and certain related traits. The hybrids L1 × T1, L1 × T5, L1 × T7, L2 × T3, L2 × T4, L2 × T5, L2 × T10, L3 × T1, L3 × T2, and L3 × T6 displayed positive SCA effects for grain yield and one or more of its attributes. Both additive and non-additive gene effects were involved in the governing inheritance of all evaluated traits. The biochemical variations among the certain evaluated genotypes were further studied. The esterase and peroxidase isozymes were applied for verifying the genetic diversity at the protein level among the used CMS lines, restorers, and their crosses. All the applied isozymes displayed polymorphism for the parents and their crosses. The banding pattern and intensity differences provided accurate results on the reliable variability among the tested genotypes.

Growth Regulators Improve Outcrossing Rate of Diverse Rice Cytoplasmic Male Sterile Lines through Affecting Floral Traits.

Cytoplasmic male sterility (CMS) provides an irreplaceable strategy for commercial exploitation of heterosis and producing high-yielding hybrid rice. The exogenous application of plant growth regulators could improve outcrossing rates of the CMS lines by affecting floral traits and accordingly increase hybrid rice seed production. The present study aimed at exploring the impact of growth regulators such as gibberellic acid (GA3), indole-3-acetic acid (IAA), and naphthalene acetic acid (NAA) on promoting floral traits and outcrossing rates in diverse rice CMS lines and improving hybrid rice seed production. The impact of foliar applications of growth regulators comprising GA3 at 300 g/ha or GA3 at 150 g/ha + IAA at 50 g/ha + NAA at 200 g/ha versus untreated control was investigated on floral, growth, and yield traits of five diverse CMS lines. The exogenously sprayed growth regulators, in particular, the combination of GA3, IAA, and NAA (T3) boosted all studied floral, growth, and yield traits in all tested CMS lines. Moreover, the evaluated CMS lines exhibited significant differences in all measured floral traits. L2, L3, and L1 displayed the uppermost spikelet opening angle, duration of spikelet opening, total stigma length, style length, stigma brush, and stigma width. In addition, these CMS lines exhibited the highest plant growth and yield traits, particularly under T3. Consequently, exogenous application of GA3, IAA, and NAA could be exploited to improve the floral, growth, and yield traits of promising CMS lines such as L2, L3, and L1, hence increasing outcrossing rates and hybrid rice seed production.

The effect of parental education on child health: Quasi-experimental evidence from a reduction in the length of primary schooling in Egypt.

This paper examines the impact of parental education on child health using a reduction in the length of primary schooling in Egypt. We use a fuzzy regression discontinuity design to compare the health outcomes of children whose parents were exposed to different schooling requirements because they were born either side of a threshold date. Using data from the Demographic and Health Survey (1992-2014), we find no effect of maternal education on child mortality or nutritional status. There is some evidence, although not entirely robust, that father's education reduces the likelihood of child stunting. We find, however, that father's education has no impact on child mortality or other measures of nutritional status. We provide suggestive evidence that, given the low levels of parental education in Egypt accompanied with the inferior quality of primary schooling, education has little effect on intermediate outcomes-literacy and utilization of antenatal care-that may improve the health of offspring.