Potato and sweetpotato in Africa: transforming the value chains for food and nutrition security.

Chapter 16 (Page no: 207)

Potato yield variation as affected by virus seed degeneration and growth conditions in Tunisia.

Virus diseases mainly affect crop growth by reducing the size of the canopy, thus inhibiting the interaction of the incoming solar radiation. Additional yield reduction may be caused by effects on the radiation use efficiency or on the dry matter allocation to the tubers. Research plots were established in 2012 at the Ariana Research Station Institut National de la Recherche Agronomique de Tunisie (INRAT) to determine the effect of seed-borne potato virus Y (PVY) and poor growing conditions on the yield of cultivar Spunta (fairly good resistance to virus PVYⁿ) during the spring crop season (February-June). Five potato seed origins were evaluated. They have five levels of PVY infection: 0%, 2%, 4%, 8% and 50%. They were grown under poor conditions: 50% of the normal fertilization doses, 0% added organic matter and high water salinity (around 4 g/l). The results showed significant general effects of the poor growing conditions on yield reduction whatever the infection level. The differences between yield origins were statistically significant and yields were negatively affected at 8% and 50% infection levels. Thus, the PVY infection levels have a negative effect on yield losses under poor crop management. These findings confirm the previous results recorded in the 2007 season crop. Useful applications in the Tunisian national seed programme were proposed and applied.

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