Yam Tuber Dormancy and Sprouting: The Role of Concentration Dynamics of Endogenous Gibberellic Acid

The role of endogenous gibberellic acid (GA ) in the regulation of yam (Dioscorea spp.) tuber 3 dormancy was investigated by determining the changes in the endogenous GA levels during 3 natural dormancy progression. Two Dioscorea rotundata cultivars ('Pona' and 'Labreko') and one Dioscorea alata cultivar ('CRI-Ahoɔdenfoɔ') used in these studies have varying dormancy duration. Endogenous GA levels determined for the yam tubers ranged from 1.53 – 3.05 mg/g dw 3 and 1.23 – 1.58 mg/g dw for 'Pona'; 1.53 – 3.40 mg/g dw and 1.25–1.57 mg/g dw for 'Labreko'; 1.48 – 3.62 mg/g dw and 1.28 – 1.60 mg/g dw for 'CRI-Ahoɔdenfoɔ', respectively, for the outer and inner portions. 'Pona' and 'Labreko' had dormancy break at 60 days after harvest (DAH), but at 90 DAH for 'CRI-Ahoɔdenfoɔ'. Generally, GA levels increased from harvest to the maximum 3 at 30 DAH, then declined to the minimum at 60 DAH before finally increasing again at 90 DAH for the outer portions of the yam tuber. For the inner portions of the tuber, GA levels rather 3 declined significantly to the minimum at 30 DAH, increased at 60 DAH and then decreased again at 90 DAH. GA levels in the outer portions of the tubers increased by 84-122%, 65-77% and 61- 3 65%, respectively, in 'CRI-Ahoɔdenfoɔ', 'Labreko' and 'Pona', but decreased in the inner portions by 19-23%, 24-26% and 26-28%. Essentially, higher amounts of endogenous gibberellins in yam tubers induced longer dormancy duration whereas lower amounts were indicative of dormancy termination and subsequent initiation of sprouting.&nbsp

Grain quality characteristics of imported rice in Ghana: Implications for breeding for consumer-preferred varieties

ABSTRACTRice is the fastest growing food source in Ghana. The country, however, imports about 70 per cent of its rice requirement due to low volumes of production and poor grain quality of domestic rice compared to imported ones.  In the study, 10 popular imported rice brands on the Ghanaian market were characterised for grain quality traits including grain dimensions, apparent amylose content, gelatinisation temperature, paste viscosity properties, and aroma using physiochemical properties and DNA markers. The rice brands came from Asia and the USA. The rice type from Asia was found to be Jasmine-styled aromatic long grained with low amylose content and gelatinisation temperature, whereas those of USA were conventional long grain with intermediate amylose content and gelatinisation temperature.  These findings were confirmed through DNA marker analyses, with the rice types from Asia and the USA revealing the presence of the TAC and GCC of the waxy gene SNP haplotypes, respectively. The implication for rice breeding in Ghana is discussed.Original scientific paper. Received 29 Oct. 14; revised 03 Aug 15

Improvement of Rice Production under Drought Conditions in West Africa: Application of QTLs in Breeding for Drought Resistance

Rice plays a paramount role in food and nutrition security in many West African countries. Despite the doubling of production during the last decade, rice consumption has grown faster, creating a deficit between the demand and supply. Although the West African sub-region remains the main rice-producing centre on the continent, production is severely hampered by biotic and abiotic stresses. Drought is one of the factors that most severely reduce grain yields of rice. Systems of production need to be established in order to mitigate yield loss as a result of drought. This review discusses the effects of drought on rice production in West Africa and its mitigation with an emphasis on the improvement of tolerance to drought stress. Yield stability can be achieved by developing drought-tolerant varieties through several processes encompassing profiling of known QTLs and identification of new ones, marker-assisted selection, genomic selection, and extensive multi-locational yield trials. We suggest a comprehensive strategy for breeding drought-tolerant rice varieties in West Africa