The heritability of resistance to early blight in diploid potatoes (Solanum tuberosum, subsp.Phureja andStenotomum)
The heritability of resistance to early blight caused byAlternaria solani (Ell. & Martin) Son was estimated for field grown, diploid potatoes at Fletcher, North Carolina in 1981. Fourteen breeding lines, selected from a random mated hybrid population ofSolanum tuberosum, subsp.phureja andstenotomum, were used. Resistance was measured as the slope obtained by regressing the logit of the disease proportion Y, measured as % defoliation, on time. A wide range of resistance was found. Narrow-sense heritability, as determined by offspring-midparent regression, on an individual plant basis, was calculated to be 0.825.
Population breeding as a tool for germplasm enhancement
The genetic basisof Solanum tuberosum ssp.tuberosum has been discussed focusing on the importance of increasing its genetic variability. A review of the work on germplasm enhancement, using both cultivated, primitive and wildSolanum species, carried out by several institutions, has been made. Through these research efforts, mainly based on a population breeding strategy, new sources of genetic variability for yield, tuber quality factors, and pest, disease, and stress resistance or tolerance have been identified. The utilization of these new breeding resources has already started to produce results. In the last few years at least 30 new varieties, carrying resistance to one or more pests, diseases, or stresses, have been released in several countries.CompendioSe ha discutido la base genética deSolanum tuberosum ssp.tuberosum enfocando la importancia de incrementar su variabilidad genética. Asimismo, se ha hecho una revisión del trabajo de mejoramiento de germoplasma llevado a cabo por varias instituciones, utilizando especies cultivadas primitivas y silvestres del géneroSolanum. Estos trabajos de investigación, principalmente basados en una estrategia de mejoramiento poblacional, han permitido identificar neuvas fuentes de variabilidad genética para rendimiento, factures de calidad del tubérculo, y resistencia o tolerancia a enfermedades, plagas, y factores climáticos adversos. La utilización de estos nuevos recursos genéticos para el mejoramiento-ha comenzado a producir resultados. En los últimos años se han liberado por lo menos 30 nuevas variedades en varios paises. Estas nuevas variedades se caracterizan por su resistencia a una o mas enfermedades, plagas, o factores climáticos adversos.
Control of the Green Peach Aphid and Its Effect on the Incidence of Potato Leaf Roll Virus
Although several insecticides provided excellent control of Myzus persicae (Sulzer), none prevented the occurrence of potato leaf roll virus (PLRV) infection duro ing 4 yr of experimentation. There appeared to be no correlation between populations of apterous aphids in treated plots during a given year and the occurrence of PLRV infection in tubers from the plots. The overall incidence of PLRV infection was highest in years of the greatest aphid populations but appeared to be correlated with the numbers of winged aphids as indicated by catches in Moericke traps.