Study of combining ability and heterosis were conducted on 12 F1 hybrids along with seven rice genotypes (three
cytoplasmic male sterile lines and four restorer varieties) to know the pattern of inheritance of some
morphological traits for selecting superior genotypes. The experiment was carried out according to line x tester
mating design, during 2007-08. Analysis of variance revealed significant differences among genotypes, crosses,
lines, testers and line x tester interactions for tiller number, plant height, days to 50% flowering, panicle length,
number of spikelets per panicle, spikelet fertility and grain yield traits. Variances of SCA were higher than the
GCA variances for traits except for plant height which indicated predominance of non-additive gene action in the
inheritance of the traits. The highest heterosis (106.60%) was observed in cross IR68899A x Poya followed by
other eight crosses for yield and most of its related traits. The proportional contribution of testers was observed
to be higher than that of the interactions of line x tester that revealed the higher estimates of GCA variance that is
additive gene action among the testers used. Within CMS parents, IR62829A and among male parents, IR50 and
Poya were observed to be good general combiners for most of the characters studied. The cross combinations
IR62829A x Mosa-tarom, IR68899A x Poya, IR58025A x IR50 and IR58025A x Poya were observed to be good
specific cross combinations for grain yield and most of its related traits due to highly significant SCA and
heterotic effects

The chamazulene and α-(−)-bisabolol contents and quality of the chamomile oil are affected by genetic background and environmental conditions. Salicylic acid (SA), as a signaling molecule, plays a significant role in the plant physiological processes. The aim of this study was to evaluate the chemical profile, quantity, and improve the essential oil quality as a consequence of the increase of chamazulene and α-(−)-bisabol using salicylic acid under normal and heat stress conditions by the gas chromatography-mass spectrometry (GC-MS) technique. The factorial experiments were carried out during the 2011–2012 hot season using a randomized complete block design with three replications. The factors include four salicylic acid concentrations (0 (control), 10, 25 and 100 mg·L−1), and three chamomile cultivars (Bushehr, Bona, Bodegold) were sown on two different planting dates under field conditions. Fourteen compounds were identified from the extracted oil of the samples treated with salicylic acid under normal and heat stress conditions. The major identified oil compositions from chamomile cultivars treated with salicylic acid were chamazulene, α-(−)-bisabolol, bisabolone oxide, β-farnesene, en-yn-dicycloether, and bisabolol oxide A and B. Analysis of variance showed that the simple effects (environmental conditions, cultivar and salicylic acid) and their interaction were significant on all identified compounds, but the environmental conditions had no significant effect on bisabolol oxide A. The greatest amount of chamazulene obtained was 6.66% at the concentration of 10 mg·L−1 SA for the Bona cultivar under heat stress conditions, whereas the highest α-(−)-bisabolol amount attained was 3.41% at the concentration of 100 mg·L−1 SA for the Bona cultivar under normal conditions. The results demonstrated that the application of exogenous salicylic acid increases the quantity and essential oil quality as a consequence of the increase of chamazulene and α-(−)-bisabolol under normal and heat stress conditions.

Abstract:The objective of this study was to investigate the effect of exogenous application of salicylic acid concentrations on the physiological and biochemical traits and essential oil content of chamomile under normal and heat stress conditions as induced by delayed sowing. The experiments were conducted during 2011-2012 as a factorial using a randomized complete block design with three replications, in a very hot region. The factors included five salicylic acid concentrations (0 (control), 1, 10, 25 and 100 mg¨L´1) and three chamomile cultivars (Bushehr, Bona, Bodegold). The seeds of chamomile were sown on two different sowing dates including an optimum planting date and a late planting date. The physiological traits (plant height, capitol diameter, 1000 grain weight, fresh and dried flower weight), total chlorophyll, proline and essential oil content were investigated. Analysis of variance showed that the effect of the environmental conditions (normal and heat stress) was significant on all physiological and biochemical traits with the exception of the essential oil content. The heat stress decreased physiological traits and total chlorophyll in comparison with the normal conditions but it had no significant effect on the essential oil content. Findings indicated that the application of exogenous salicylic acid improves essential oil content in chamomile cultivars under environmental heat stress conditions.

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