Monneveux, P.

Quiróz, R.

Ramírez, D.

Rolando, J.L.

Yactayo, W.

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59   IS THE DISCRIMINATION AGAINST 13C IN LEAFLETS AND TUBERS AN APPROPRIATE TRAIT TO DETERMINE GENOTYPIC DIFFERENCES RELATED TO DROUGHT TOLERANCE IN POTATO?  D.A. Ramírez, J.L. Rolando, W. Yactayo, P. Monneveux, R. Quiroz  International Potato Center, Lima, PERU   Drought tolerance selection through phenotyping entails prioritizing plant traits that synthesize and integrate critical physiological processes occurring during the crop’s growth. Potato studies where discrimination against 13C (∆) in leaflets (∆leaflet) and tubers (∆tuber) were monitored, concluded that ∆leaflet is not an appropriate trait for screening tolerance to mild water stress [1], and that ∆tuber differences do not reflect final yield [2]. The present study was designed to revisit these findings, comparing the ∆leaflet and ∆tuber throughout the phenology of two advanced varieties with acceptable yield under water limiting conditions (UNICA, CIP N°392797.22 and Sarnav, CIP N°397077.16) and contrasted with a cultivar commonly tested in carbon isotope studies (Désirée). The drought treatment consisted of a deficit irrigation with 50% of field capacity, which was established after tuber initiation onset (TIO). The control plants were watered until the soil reached field capacity. Six sequential harvests were carried out to assess ∆ in dry biomass of leaflets and tubers. Prior to each harvest, gas exchange was measured in leaflets. The variety Sarnav showed the higher final tuber dry biomass (75.96±1.96 g plant-1) under drought as well as the maximum tuber bulking (1.65±0.05 g day-1) under control conditions. The average difference control-drought, for both ∆leaflet and ∆tuber, was positively correlated with the drought tolerance index (DTI) [3]. DTI ranking among genotypes was Sarnav > Unica > Désirée. Despite Sarnav’s higher average stomatal conductance (242.4±15.4 mmol H2O m-2 s-1) and lower intrinsic water use efficiency (A/gs; 79.3±5.4 µmol/mol), low ∆leaflet (20.3±0.17‰) was evidenced under control treatment, attributed to a larger photosynthetic capacity [4]. Sarnav showed the lowest ∆tuber (15.8±0.17‰) of the three varieties under drought conditions, suggesting a more extensive use of carbon products synthesized in leaves for drought tolerant mechanism, thus confirming previous findings for this variety [5]. Due to the strong negative correlation found between ∆ and A/gs (rPearson between -0.77 and -0.89), the use of ∆ as a method for screening drought tolerance in advanced potato genotypes seems warranted. We recommend sampling for ∆ analyses before senescence i.e. between 30 and 60 days after TIO, or 350 and 700 ºC days of accumulated thermal time after TIO.   References [1] Deblonde, P.M.K.,Haverkort, A.J., Ledent, J.F. (1999). Responses of early and late potato cultivars to moderate drought conditions: agronomic parameters and carbon isotope discrimination. Eur. J. Agron. 11:91-105. [2] Jefferies, R.A., McKerron, D.K.L. (1997).Carbon isotope discrimination in irrigated and droughted potato. Plant Cell Environ. 20:124-130 [3] Fernandez, G. C. J. (1992) Effective selection criteria for assesing plant stress tolerance. Proceedings of the International Symposium on Adaptation of Vegetables and Other Food Crops in Temperature and Water Stress, ed. C.G. Kuo, Taiwan, pp. 257-270.  [4] Monneveux et al. (2004).Relationship between grain yield and carbon isotope discrimination in bread wheat under four water regimes. Europ. J. Agronomy 22:231-242. [5] Legay et al. (2011). Carbohydrate metabolism and cell protection mechanisms differentiate drought tolerance and sensitivity in advanced potato clones (Solanum tuberosum L.). Funct. Integr.Genomics 11:275-291.  

Is the discrimination against 13C in leaflets and tubers an appropiate trait to determine genotypic differences related to drought tolerance in potato?

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Is the discrimination against 13C in leaflets and tubers an appropiate trait to determine genotypic differences related to drought tolerance in potato?

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