EFFECTS OF PRE-GERMINATION TREATMENTS AND STORAGE PERIODS ON GERMINATION, VIGOUR, CHEMICAL AND HEALTH COMPOSITION OF SEEDS OF THREE CASSAVA (Manihot esculenta Crantz) CULTIVARS

ABSTRACT
Seeds of three cultivars of cassava were collected from the CSIR-Crops Research Institute at Fumesua in the Ashanti Region to determine the effect of storage periods and seed pre germination treatments on the germination percentage, physicochemical and health properties of seeds from the three varieties of cassava. The experiment was conducted under laboratory conditions and a 3 x 3 x 7 factorial in Completely Randomized Design (CRD) with three replications was used. The first factor was cultivar at three levels (Ahwengyanka-1, Ahwengyanka-2 and Aworowa-3); the second factor was pre-germination treatments at seven levels (hot water, cold water, mechanical scarification, three concentrations of acid scarification and no treatment as the control); the third factor was storage period at three levels (no storage, three months storage and six months storage). The study revealed that seeds of cassava stored for up to three months produced about 40% germination after undergoing the various pre-germination treatments. Seeds of the Aworowa-3 cultivar stored for six months produced the highest germination percentage of 61.0%. Seeds mechanically scarified with sand paper produced the highest germination percentage of 48.9% whereas seeds with no treatment recorded the least percentage of 34.8%. Seven fungi pathogens were identified on the three cultivars of cassava seeds irrespective of the cultivar and period of storage. The study concluded that Aworowa-3 seeds without storage produced a higher germination percentage than Ahwengyanka-1 and Ahwengyanka-2 seeds without storage but all the seeds of the three varieties had the highest germination percentage when stored for six months.


CHAPTER ONE
1.0 INTRODUCTION
Cassava (Manihot esculenta Crantz) is the most important tropical root crop in many parts of Africa because of its edible roots (FAO, 2009). It is also cultivated for its leaves and tender shoots which are rich sources of proteins, vitamins A, B, C, and other minerals are consumed as vegetable (Fregene et al., 2000; IITA, 2001). In Africa, Ghana ranks third after Nigeria and the Democratic Republic of Congo as the largest cassava producing country (FAO, 2009). Cassava in Ghana is grown across all the agro-ecological zones and contributes 22% to Ghana’s Agricultural Gross Domestic Product (AGDP) (Parkes, 2009).

Cassava is vegetatively propagated by mature stem cuttings. This mode of propagation is the most widely used since cassava does not produce large amounts of sexual seeds; however, the wild species are naturally propagated through seeds (Teixeira, 1987). The seedlings that are obtained from cassava seeds are initially smaller than plants that are developed from vegetative cuttings and they require special care to become established. The seeds of cassava are oval in shape and have a cross section that is elliptic or circular. The seeds are approximately 100 mm long and 4 to 6 mm thick (Alves, 2002).

Seeds of cassava can remain viable when stored under ambient conditions for up to 1 year, although germination percentages may decline substantially after 6 months (Rajendran et al., 2000) in some cases. Under cold storage conditions (4°C and 70–80% relative humidity) cassava seeds can remain dormant for up to 7 years with no loss of germination thus dormancy is a usual occurrence in cassava seeds. Dormancy in seeds, therefore is known to inhibit the germination of intact viable seeds under favorable conditions (Bagheri and Asadi, 2003; Robert, 2003; Finch Savage and Leubner-Metzger, 2006). Germination of seeds of cassava can be favored by dry heat and complete darkness (Ellis et al., 1982). Generally, treatments used to break seed dormancy may include mechanical scarification, chemical scarification (especially sulfuric acid), cold-wet, hot water, electrasonic waves and stratification (Isvand et al., 2004; Dehghani, 2005).

Genetically, cassava clones are highly heterozygous and sexual propagation (propagation through seeds) results in a wide diversity of phenotypes, which is of interest to breeders (Ceballos et al., 2004). This discovery has endeared to breeders who have started to use cassava seeds as the starting material in their breeding programmes. However, a major problem with freshly harvested cassava seeds is its characteristic dormancy which is a well documented occurrence in Euphorbiaceae genera (Keleny and VanHaaren, 1967; Eakle and Garcia, 1977; Lago et al., 1978; Nassar and Teixeira, 1983). The period of dormancy in cassava seeds could last for a minimum period of 6-9 months under ambient temperatures (Ellis et al., 1982) with adverse consequences on breeding programmes. To overcome this problem so that cassava seed breeding programmes can be undertaken anytime without the time-related dormancy limitation, development of suitable dormancy-breaking techniques are of paramount importance. The general aim of the study therefore was to determine the most suitable pre-germination treatment of seeds for high germination of cassava seeds for breeding programmes.


Specifically, the objective was to;
Determine the effects of storage periods and seed pre-germination treatments on the germination percentage, physicochemical and health properties of seeds from the three varieties of cassava.

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Item Type: Ghanaian Project Material  |  Attribute: 83 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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