Pre-sowing seed treatment to improve germination in true cassava ( Manihot esculenta ) seeds

: The propagation of cassava (Manihot esculenta) through sexual seeds rather than by clones is a noval approach due to its manifold advantages like enhancing the multiplication rate several times, keeping the dreaded cassava mosaic diseases (CMD) under check, ease of seed storage and transport. Experiments were conducted at Tapioca and Castor Research Station during the years 2001 and 2002 to find out the effect of pre-sowing seed treatment using different chemicals and botanical leaf extracts in different concentrations. True cassava seeds (H226) were subjected to soaking in water, KNO3, CaCl 2 in 0.5 and 1 per cent solutions and Arappu (Albezia amara) and Pungam (Derris indica) fresh leaf extracts in 1 and 2 per cent solutions for 24 hours and compared with unsoaked seeds. The results of the data revealed that germination percentage and vigour index were maximum in seeds soaked in KNO 3 1 per cent solution for 24 hours when compared to unsoaked seeds.


Introduction
Cassava has enormous potential in India for poverty alleviation and food security due to its ability to grow well in marginal and wastelands under poor management and its capacity to yield high under such unfavourable conditions. Under laboratory conditions, cassava seeds do not germinate satisfactorily (Rajendran et al., 2000). Hence the study was undertaken to improve the germination percentage of cassava seeds.

Materials and Methods
Cassava true seeds of H226 cultivar was collected from Karumanthurai and the cleaned seeds were soaked in the following chemical solutions for 24 hours during the year 2001 and 2002 as experiment I and experiment II.

Total seedling length (cm)
Total seedling length was also followed the same trend as that of root length and shoot length (Table 1).

Dry matter production (mg/seedling)
The DMP was maximum in seedlings from the seeds soaked in arappu leaf extract (2%) solution (262 g) which was on par with the seedlings from the seeds soaked in KNO 3 1% (T4) solution (260 mg) (Table 1).

Vigour index
Vigour index was maximum in T4 (929) which was on par with T8 (921). The next best treatments were T7, T10 and T6 (Table 1).

Root length (cm)
Root length was high in seedlings obtained from seeds soaked in arappu leaf extract (2%) solution (2.6 cm) and it was low (1.6 cm) in unsoaked seed (Table 1).

Shoot length (cm)
Shoot length was more in the treatment of seeds soaked in arappu leaf extract (T8) 2% solution (10.8 cm) which was on par with KNO 3 1% and 0.5% solutions. (Table 1).

Total seedling length (cm)
Total seedling length followed the same trend as that of root and shoot lengths (Table 1).

Vigour index
The vigour index was maximum (792) in the seeds soaked in arappu leaf extract 2% solution, which was on par with treatment of KNO 3 1% solution and was minimum in unsoaked seeds (426) ( Table 1).
The germination percentage and vigour index were maximum in cassava seeds treated in one per cent KNO 3 solution when compared to the untreated seeds. The seeds soaked in arappu 2 per cent fresh leaf extract also showed on par results with that of one per cent KNO 3 solution.