Enrico Santangelo

Constitutive co-suppression of the GA 20-oxidase1 gene in tomato leads to severe defects in vegetative and reproductive development.

To dissect the role of gibberellins in tomato development, we have constitutively down-regulated the gene GA 20-oxidase1 (GA20ox1). Plants co-suppressed for GA20ox1 (referred to as CO-6 plants) showed vegetative defects typical of GA deficiency such as darker and mis-shaped leaves and dwarfism. CO-6 plants flowered as the controls, although their flowers had subtle defects in the pedicel and in organ insertion. Analysis of male development revealed defects before, during and after meiosis, and a final pollen viability of 22%. The development of female organs and gametes appeared normal. Pollination experiments indicated that the pollen produced by CO-6 plants was able to fertilize control ovaries, but the analysis of the progeny showed that the construct was not transmitted. Ovaries of CO-6 plants showed high fruit set and normal fruit development when pollinated with control pollen. However these fruits were completely seedless due to a stenospermocarpic behaviour that was evidenced by callose layering in the endothelium between 7 and 15 days after pollination. We conclude that GA20ox1 in tomato exerts specific developmental roles that are not redundantly shared with other members of this gene family. For reproductive male development, silencing of this gene is detrimental for pollen production and either gametophytically lethal or severely hampering seed germination. In the pistil, the co-suppression construct does not affect the progamic phase, nor fruit set and growth, but it interferes with seed development after fertilization leading to seed abortion.

A H2O2-forming peroxidase rather than a NAD(P)H-dependent O2.- synthase may be the major player in cell death responses controlled by the Pto-Fen complex following fenthion treatment

Four tomato (Lycopersicon esculentum Mill.) near-isogenic lines were treated by foliar spraying with the insecticide fenthion. Two, Riogrande and Rimone, differed from each other only for the presence in the latter of the Fen gene, conferring propensity to develop foliar symptoms upon exposure to fenthion. The other two, namely RC332 and RC131, were the transgenic versions of Riogrande and Rimone, respectively, harbouring the Gox gene encoding for glucose oxidase of Aspergillus niger. The production of H2O2 as well as the activities of H+-ATPase, NAD(P)H-dependent superoxide synthase, catalase, peroxidase, and Cu,Zn-superoxide dismutase were evaluated in the foliar tissues up to 24 h after exposure to fenthion. The Fen gene conferred sensitivity to fenthion, regardless of the expression of a Gox transgene. A prolonged accumulation of H2O2 was observed in the leaves of Rimone and of RC131, which was instead transient in Riogrande and in RC332. In all the tomato lines, exposure to fenthion induced rapid but transient changes in the activities of most enzymes. The only exception was peroxidase activity in the leaves of Rimone and of RC131, which steadily increased until the end of the sampling period. It is suggested that the sensitivity of Rimone to fenthion might be due to the sustained activity of a H2O2-forming peroxidase.

The Cf-2 / Rcr3esc gene interaction in tomato (Lycopersicon esculentum) induces autonecrosis and triggers biochemical markers of oxidative burst at cellular level

A tomato plant (Lycopersicon esculentum Mill.) with necrotic leaf spots mimicking disease lesions was singled out in progeny under selection in Moscow (breeding material of Ignatova Svetlana). The progeny from spontaneous selfing of such a plant (V20368), in the presence of increasing temperature and high light intensity, exhibited spontaneous necrotic lesions on the leaves, with acropetal progression (autonecrosis). A similar phenotype, described in 1948 by Langford, appeared to be associated with the Cf-2 resistance gene, introgressed from L. pimpinellifolium. Recently, Kruger et al. (2002) demonstrated that the Cf-2 effect depends on a second gene (Rcr3pim) encoding a cysteine protease, and that autonecrosis is activated by the contemporary presence of Cf-2 and the L. esculentum allele Rcr3esc. In this work we characterised the V20368 mutant and verified that autonecrosis is caused by the presence of an interaction between Cf-2 and Rcr3esc. When the environmental conditions are favourable, this interaction triggers an oxidative burst, as evidenced by a strong increase in H2O2 production and activities of catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7) and ATPase (EC 3.6.1.3). In addition, by grafting the necrotic mutant on the cv. Riogrande and vice versa, we proved that the necrotic phenotype is not associated with the movement of a signal molecule, since the autonecrosis was not transmitted across the grafting point. Finally, the interaction between Cf-2 and Rcr3esc appeared to lower the threshold of stress perception, as evidenced by an increased sensitivity to the insecticide Fenthion.

Evaluation of sensors for poplar cutting detection to be used in intra-row weed control machine

In Short Rotation Coppice (SRC) of poplar, the weeds within the row have a detrimental effect.A photoelectric and capacitive sensors was used for detecting the poplar cuttings along the row.The detection system has proved able to recognize the poplar cuttings.The system appears suitable for a future evaluation on the intra-row weeding machines. For Short Rotation Coppice (SRC) cultivation, it is common practice to use herbicides during the first year, even if mechanical weeding is becoming an alternative practice for environmental and agronomic reasons. Much attention was paid to non-chemical weeding within the rows, but the low level of efficiency of available machinery has led to the development of automatic systems that are capable of weeding the spaces in the row and avoiding the plants.In the framework of this study, a photoelectric and a capacitive sensor (the latter specifically developed for identifying poplar cuttings), was tested. A small platform pulling the sensors was moved along a monorail in order to assess the capability of the sensors for localizing cuttings along the row. The study was conducted on one-year old poplar cuttings. At this stage the plants have little mechanical strength and are unable to withstand the impact of traditional mechanical probes situated on the retractable elements of weed control machinery (hoes, cultivators). Each sensor identified the plant according to its own functional parameters. The divergence between the response of the sensors and the actual position of the cuttings allowed for the accuracy assessment of detection.The capacitive sensor showed a higher amplitude of response in presence of a poplar cutting than the photoelectric sensor. No significant differences were observed for the various distances (0.15, 0.20 and 0.25m) of the detection system from the row and for the different speeds (1.0 and 1.5kmh-1) of the rail.The first results showed that the testing apparatus accurately detected poplar cuttings at the same speed used by common mechanical weed control machines. The sensors tested proved to be suitable to be included in intra-row weeding machines. This will be the main goal of future activities, an interesting prospect for firms producing agricultural machinery for biomass crops.

A Mower-Conditioner to Improve Fiber Sorghum Plant Drying

Abstract. Fiber sorghum [( L. (Moench.)] is recognized as having potential as an energy crop to allocate towards biogas or bioethanol production. However, due to the considerable amount of biomass produced, the harvesting presents some drawbacks. In Italy the cultivation of fiber sorghum is concentrated in the North where the harvesting occurs at the end of summer, on plants having, on average, 70% of moisture. For allowing the storage in bales, a product with at least 30% of moisture is required. Drying time of non-conditioned plants in open field may be too long, exposing the mowed biomass to adverse climatic conditions that may negatively affect the drying time and the success of the subsequent baling. The work presents the first results of a new mower-conditioner designed by CREA-ING (Rome-ITALY) able to guarantee high efficiency in stem conditioning. The experimental tests were conducted in northern Italy where the performance of the machine was analyzed. Importantly, the mechanical action of conditioning apparatus determined a deeper cracking along the stem. As a result, the time required to reach the minimum moisture threshold (30%) for baling was reduced to 72 h hafter mowing. After just 5 days from conditioning, the moisture content was around 20%. To our knowledge, compared with the data of the available literature, this is the best result on drying time. Moreover, the regression analysis showed that for this specific study, none of the tested climatic parameters resulted in a decrease of moisture content in the sorghum biomass, thus confirming that the drying is mainly due to the conditioning action.