Photosynthesis, transpiration and plant growth characters of different potato cultivars at various densities of Globodera pallida

Abstract

Plants of four potato (Solanum tuberosum L.) cultivars were grown in pots in a greenhouse at five densities of Globoderapallida between 0 and 300 eggs per gram of soil. Photosynthesis and transpiration of selected leaves were measured at 30, 37, 49 and 60 days after planting. Stem length was recorded at weekly intervals. Plants were harvested 70 days after planting and various plant variables were determined.At 30 days after planting, when second and third stage juveniles were present in roots, both photosynthesis and transpiration rates were severely reduced by G. pallida. In the course of time these effects became less pronounced. Water use efficiency was reduced by G. pallida between 30 and 49 days, but not at 60 days after planting. The results suggest independent effects of G.pallida on stomatal opening and on photosynthesis reactions. There were no consistent differences among cultivars in the response of leaf gas exchange rates and water use efficiency to nematode infection. Reduction of photosynthesis by G. pallida appeared additive to photosynthesis reduction due to leaf senescence.Total dry weight was reduced by 60 ~ at the highest G. pallida density. Weights of all plant organs were about proportionally affected. Shoot/root ratio was not affected and dry matter content was reduced. Stem length and leaf area were most strongly reduced during early stages of plant-nematode interaction. The number of leaves formed was only slightly reduced by G.pallida, but flowering was delayed or inhibited. Reduction of total dry weight correlated with reduction of both leaf area and photosynthesis rate. Leaf area reduction seems the main cause of reduction of dry matter production. Tolerance differences among cultivars were evident at 100 eggs per gram of soil only, where total dry weight of the intolerant partially resistant cv. Darwina was lower than that of the tolerant partially resistant cv. Elles and of the tolerant susceptible cv. Multa. The tolerance differences were not correlated with leaf photosynthesis and transpiration. Apparently these processes are not part of tolerance of plants.Additionallceywords: potato cyst nematodes, Solanum tuberosum L., host-parasite interaction, damage mechanism, tolerance, gas exchange, stomata, water use efficiency, total dry weight, leaf area, stem length.

Analyses of the effects of potato cyst nematodes (Globodera pallida) on growth, physiology and yield of potato cultivars in field plots at three levels of soil compaction

“…Thirty days after planting four potato cultivars in pots of soil with 100 eggs g-1 of G. pal/ida Stone, photosynthetic rates per unit leaf area were 70% lower than in uninfested controls (Schans & Arntzen, 1991). The photosynthetic rates increased again in the following weeks.…”

“…Trudgill (1980), Trudgill, Evans & Parrott (1975) and Trudgill & Cotes (1983a, b) proposed that nematodes reduce size and efficiency of the root system, leading to chronic nutrient deficiency and early crop senescence. Schans (1991) and Schans & Arntzen (1991), on the other hand, asserted that cyst nematodes primarily affect the hormonal balance of the plant, leading to stomatalclosure and impaired crop photosynthesis. According to the latter hypothesis, disturbance of carbon metabolism, and not nutrient metabolism, impairs crop growth.…”

Relationship between potato cyst nematodes and their principal host. II. Evaluation of mathematical descriptors relating potato yield and nematode density

“…The damaging effect of PCN is not only determined by PCN density, but also by such factors as cultivar, crop husbandry and environmental conditions such as soil type and season. This view was expressed by Wallace (1973) and is repeatedly found in discussions of other authors (Trudgill, 1986: Evans & Haydock, 1990: Elston et al, 1991 and was experimentally and theoretically further investigated by , Haverkort et al (1990Haverkort et al ( , 1991Haverkort et al ( , 1992, Schans (1991) and Schans & Arntzen (1991).…”

The Cyst Nematodes

“…Globodera pallida suppresses photosynthetic rates of potato at high inoculurn densities (Schans and Amtzen, 1991). Such plants typically yield less than a healthy plant.…”