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Potato (Solanum tuberosum L.) is a staple food widely consumed in Tunisia and a source of nutrients beneficial for human health. The tubers are, indeed, important source of vitamins, minerals, and bioactive compounds, including carotenoids, polyphenols, and flavonoids. However, data regarding the functional quality of potato varieties grown and consumed in Tunisia are very scarce. For this reason, two field trials were conducted to focus on the effect of the growing season on the functional quality of four potato genotypes (Selena, El Beidha, Naima, and CL07F172.5): a first autumnal trial in Teboulba, Monastir (September 2015–February 2016), which is the late cropping season (LCS) and a second summer cropping season (SCS) in El ksour, El Kef region at an altitude > 1000 m (July 2015–October 2015). Total carotenoids, total phenolics, and flavonoids contents, as well as the hydrophilic radical scavenging activity and lipophilic radical scavenging activity (LRSA) were determined. The obtained results confirmed the importance of potato tubers as a source of bioactive compounds. All quality traits varied significantly among varieties and cropping seasons. Tubers grown under colder weather conditions (LCS: minimum and maximum averages temperatures and relative humidity (RH) ranging between 14.25 and 22.55°C and 25.46% and 83.07%, respectively) accumulated the highest total vitamin C content and exhibited the highest LRSA values. However, temperature and warmer growing conditions (SCS: minimum and maximum averages temperatures and RH ranging between 19.74 and 34.22°C and 35.46% and 87.51%, respectively) probably enhanced the synthesis and accumulation of total carotenoids, total phenolics, and total flavonoids, associated with higher LRSA values.

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Potato leafroll virus (PLRV) is a major constraint to potato production in North Africa. Serological (sandwich and cocktail ELISA) and molecular (RT‐PCR) tests were used to detect PLRV in 131 potato samples collected in different areas of Tunisia. RT‐PCR proved to be usable as a routine diagnostic test for epidemiological purposes, being more sensitive and reliable, and less time‐consuming, than serological tests. One RT‐PCR‐amplified portion of ORF3 (336 nt) was cloned and sequenced, and used for molecular characterization of Tunisian PLRV isolates. These showed high sequence identity with PLRV retrieved from GenBank.

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.