Does radiation interception or radiation use efficiency limit the growth of wheat inoculated with tan spot or leaf rust?

SCHIERENBECK, M; FLEITAS; MIRALLES D.J; SIMON

FIELD CROPS RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 p. 65 - 76

0378-4290

tTan spot [Pyrenophora tritici-repentis (Died.) Drechs., anamorph Drechslera tritici-repentis) (Died.) Shoem.]and leaf rust (Puccinia triticina Eriks) are major diseases worldwide and some of the main biotic causesof yield and quality reduction in wheat (Triticum aestivum L.). Although wheat crop losses due to foliardiseases have already been studied based on an ecophysiological approach, none of these studies ana-lyzed the independent effects of foliar pathogens with different nutritional habits. The aim of the presentstudy was to determine the independent effects of (i) Py. tritici-repentis (necrothroph) and (ii) Pucciniatriticina (biotroph) on the physiological components of biomass production: accumulated intercepted bygreen tissue photosynthetic active radiation (IGPAR), radiation use efficiency calculated by interceptedradiation (RUEint) as well as by intercepted by green tissue (RUEgt) in a wide range of Argentine com-mercial bread wheat cultivars growing in two field environments. Field experiments were carried outduring two consecutive years combining a large range of wheat bread commercial cultivars and twolevels of inoculation to promote infection of Tan spot and Leaf rust diseases, including a control withoutinoculation. Treatments were arranged in an experimental split-split plot design with three replications,where the main plots were both diseases, subplots corresponded to inoculation treatments 1- withoutinoculation (WI), 2- low concentration of inoculum of each disease (LC), 3- high concentration of inocu-lum of each disease (HC) and ten Argentine bread wheat commercial cultivars were the sub-subplots.Area under disease progress (AUDPC), area under percentage of non-green leaf area (AU %NGLA), cropgrowth rate (CGR) and healthy area duration (HAD) were calculated. Green leaf area index (GLAI), above-ground biomass (AGB), IGPAR and RUE were measured at three different crop stages (GS39, GS61 andGS82). Increases of inoculum concentration decreased AGB between 8 and 20% mainly explained byreductions in HAD and decreases on IGPAR by 14?18% with higher reductions when the crop was inoc-ulated with Py. tritici-repentis than with P. triticina. Although both diseases reduced the physiologicalcomponents of accumulated biomass related to radiation interception (IGPAR), RUEint (−23%), RUEgt(−11%) and CGR (−29%) were more reduced, respect to WI, when plants were inoculated with P. triticinacompared to Pyrenophora tritici-repentis. The differential responses in RUE could be associated with thenutritional habit of P. triticina that reduces leaf nitrogen concentration, enhance assimilates consume byleaf respiration, reducing radiation use efficiency.