Radiation Interception, Conversion and Partitioning Efficiency in Potato Landraces: How Far Are We from the Optimum?

Crop efficiencies associated with intercepted radiation, conversion into biomass and allocation to edible organs are essential for yield improvement strategies that would enhance genetic properties to maximize carbon gain without increasing crop inputs. The production of 20 potato landraces—never studied before—was analyzed for radiation interception ( ε i ), conversion ( ε c ) and partitioning ( ε p ) efficiencies. Additionally, other physiological traits related to senescence delay (normalized difference vegetation index (NDVI) s l p ), tuberization precocity ( t u ), photosynthetic performance and dry tuber yield per plant (TY) were also assessed. Vegetation reflectance was remotely acquired and the efficiencies estimated through a process-based model parameterized by a time-series of airborne imageries. The combination of ε i and ε c , closely associated with an early tuber maturity and a NDVI s l p explained 39% of the variability grouping the most productive genotypes. TY was closely correlated to senescence delay (r P e a r s o n = 0.74), indicating the usefulness of remote sensing methods for potato yield diversity characterization. About 89% of TY was explained by the first three principal components, associated mainly to t u , ε c and ε i , respectively. When comparing potato with other major crops, its ε p is very close to the theoretical maximum. These findings suggest that there is room for improving ε i and ε c to enhance potato production.

Potato Vine Killing or Desiccation

Revised! HS-925, a 3-page fact sheet by Chad M. Hutchinson and William M. Stall, describes mechanical, chemical, and combination methods of killing potato vines to ensure tuber maturity at harvest. Includes a table listing potato vine desiccants and references. Published by the UF Department of Horticultural Sciences, November 2007. HS925/HS181: Potato Vine Killing or Desiccation (ufl.edu)

The Effect ofCyperus esculentusTuber Maturity on14C Accumulation

Yellow nutsedge(Cyperus esculentusL.) tuber maturity was studied to determine its influence on accumulation of14C from urea and NAA (naphthaleneacetic acid). Radioactive carbon from the above sources accumulated in tubers in decreasing amounts as tubers became more mature when the plants to which they were attached were treated. Tubers that were young at treatment accumulated the highest concentration of radioactivity and parent tubers (most mature) accumulated the least14C. Tubers that were classified as mature, but not parents, accumulated insignificant amounts of radioactive carbon.

Epidemiology of Potato Gangrene in Tasmania

In Tasmania, Phoma exigua Desm. var. exigua accounts for 90% of potential inoculum on tuber surfaces and 90% of gangrene lesions in stored potato tubers. P. exigua Desm, var, foveata (Foister) Boerema accounts for the remaining 10%. Tubers lifted from pre-senescent crops contain negligible levels of surface-borne inoculum and develop few lesions in storage. Washing removes only a small percentage of potential inoculum on tuber surfaces, which initiates infections if tubers are wounded and held in an environment unfavourable for wound healing. Tuber resistance to gangrene disease is determined by the interaction between tuber cultivar, tuber maturity and the nature of the fungal isolate within both varieties of P. exigua. The resistance response is greatest at high temperatures and is characterized by three phases: lesion retardation, lesion arrest and lesion rejection. Lesion rejection represents the end product of tuber resistance response and is associated with the development of post-infectional periderm.

Studies on White Yam (Dioscorea rotundata) I. Growth Analysis

SUMMARYThe growth of two varieties of white yam was analysed from planting in December to harvest in September. Four stages were recognized, viz.: dormancy, rapid growth of vine and root, rapid tuber development accompanied by leaf senescence and tuber maturity followed by reduction in tuber weight. The period of rapid growth coincident with maximum demand for nutrients was early June, suggesting that fertilizer should be applied in mid-May so that it is available in June.