The Role of Viral Infection in Inducing Variability in Virus-Free Progeny in Tomato

The effect of virus-host interactions on subsequent generations is poorly understood. The evaluation of the effects of viral infection on inheritance of quantitative traits in the progeny of infected plants and elucidation of a possible relationship between chiasma frequency in the infected plants and variability of traits in the progeny were investigated. The current study involved genotypes of four intraspecific hybrids of tomato （Solanum lycopersicum L.）, their parental forms and two additional cultivars. Used as infection were the tobacco mosaic virus （TMV） and potato virus X （PVX）. The consequences of the effect of viral infection were evaluated based on chromosome pairing in diakinesis and/or by examining quantitative and qualitative traits in the progeny of the infected tomato plants. Tomato plants infected with TMV ＋ PVX were found to differ in chiasma frequency per pollen mother cell or per bivalent. Deviations have been observed for genotypes of both F1 hybrids and cultivars. At the same time, differences in mean values of the traits under study have only been found for progeny populations （F2-F4） derived from virus-infected F1 hybrids, but not in the case of progeny of the infected cultivars. The rate of recombinants combining traits of both parents increased significantly （2.22-8.24 times） in progeny populations of hybrids infected with TMV＋PVX. The above suggests that the observed effects could be the result of modification of recombination frequencies that can be manifested in heterozygous hybrids and make small contributions to variability in cases of ＇homozygous＇ tomato genotypes （i.e. cultivars）.

Explaining variation in productivity requires intraspecific variability in plant height among communities

While recent studies have shown the importance of intraspecific trait variation in the processes of community assembly,we still know little about the contributions of intraspecific trait variability to ecosystem functions.Here,we conducted a functional group removal experiment in an alpine meadow in Qinghai-Tibetan Plateau over 4 years to investigate the relative importance of inter-and intraspecific variability in plant height for productivity.We split total variability in plant height within each of 75 manipulated communities into interspecific variability(TV_(inter))and intraspecific variability within a community(ITV_(within)).Community-weighted mean height among communities was decomposed into fixed community-weighted mean(CWM_(fixed))and intraspecific variability among communities(ITV_(among)).We constructed a series of generalized additive mixed models and piecewise structural equation modeling to determine how trait variability(i.e.TV_(inter),ITV_(within),CWM_(fixed) and ITV_(among))indirectly mediated the changes in productivity in response to functional group removal.Community productivity was not only affected directly by treatment manipulations,but also increased with both inter-and intraspecific variability(i.e.CWM_(fixed) and ITV_(among))in plant height indirectly.This suggests that both the‘selection effect’and a‘shade-avoidance syndrome’can incur higher CWM_(fixed) and ITV_(among),and may simultaneously operate to regulate productivity.Our findings provide new evidence that,besides interspecific variability,intraspecific trait variability in plant height also plays a role in maintaining net primary productivity.