Assessment of Rice Associated Bacterial Ability to Enhance Rice Seed Germination and Rice Growth Promotion

ABSTRACT The application of beneficial bacteria has recently been used for sustainable agriculture. In current research, 71 bacterial isolates were obtained from rice plant and the rhizosphere soil of different paddy fields in Guilan province, Iran. After primitive investigation, 40 bacteria with typical predominant characteristics were selected. By PCR-RFLP of their 16S r-DNA gene, 8 Operational Taxonomic Units (OTUs) totally consisted of 33 isolates were obtained. From all of them, 8 isolates were selected for rice seed germination experiment, then, effective isolates were used for pot experiment to evaluate their ability for promoting rice growth. All of them were able to increase rice growth and yield, but in different potential. These tested isolates were identified as Alcaligenes faecalis (DEp8, O1R4), Pantoea ananatis (AEn1), Bacillus vietnamensis (MR5), Bacillus idriensis (MR2) and Stenotrophomonas maltophilia by partial sequencing of their 16S r-DNA gene. Among them, AEn1 and MR5 produced indole-3- acetic acid (IAA) in larger amounts than the other isolates and the isolates AEn1 and O1R4 were able to solubilize phosphate in higher amounts. According to the results obtained, it can be concluded that AEn1, O1R4 and MR5 can be considered as bacterial inoculants to use as alternatives for chemical fertilizers.

Occurrence and distribution of ten viruses infecting cucurbit plants in Guilan province, Iran.

During the 2006 and 2007 growing seasons, a systematic survey was conducted in open-field of melon (Cucumis melo L.), cucumber (C. sativus L.), squash (Cucurbita sp.), and watermelon (Citrulus lanatus L.) crops in 16 major cucurbit-growing areas of Guilan province in Iran. Symptomatic leaf samples were collected and screened by double-antibody sandwich ELISA (DAS-ELISA) or RT-PCR to detect Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Cucurbit aphid-borne yellows virus (CABYV), Cucumber mosaic virus (CMV), Squash mosaic virus (SqMV), Papaya ringspot virus type W (PRSV-W), Watermelon chlorotic stunt virus (WmCSV), Melon necrotic spot virus (MNSV), Zucchini yellow fleck virus (ZYFV), and Ourmia melon virus (OuMV). The majority of tested samples (73.7%) were infected by at least one of the viruses considered. OuMV, ZYMV, WMV, and WmCSV were the most prevalent viruses and were detected in tested cucurbit plants. The incidence of multiple infections with 2 or more viruses was also relatively high, 63.3, 48.6, 42.7, and 26.7% of the infected samples of melon, cucumber, squash, and watermelon, respectively. The high incidence of OuMV and WmCSV suggested that these viruses might turn out to be an important threat for the melon and cucumber crops in the province.

Occurrence of Ourmia melon virus in the Guilan Province of Northern Iran.

A survey was conducted in 2005 and 2006 in the major cucurbit-growing areas in Guilan Province (northern Iran). Leaf samples were collected from plants of melon (Cucumis melo L.) (n = 119) and squash (Cucurbita sp.) (n = 150) showing various virus-like symptoms (mosaic, yellowing, chlorotic spot, and irregular ring spot) on leaves. All samples collected from 16 different regions were screened for the presence of 10 cucurbit viruses by double-antibody sandwich (DAS)-ELISA using polyclonal antibodies provided by H. Lecoq (INRA, Avignon, France) and V. Lisa (CNR, Torino, Italy). Virus-free cucurbits (melon, squash, and cucumber) grown in insect-proof cages were used as negative controls. Positive and negative controls were included in all tests. Ourmia melon virus (OuMV, genus Ourmiavirus) was the most prevalent virus in melon and was detected in 59% of the samples. OuMV was also detected in 20 of 150 (13%) squash samples. OuMV was detected in 4 of the 16 areas surveyed (Rasht, Somehsara, Masal, and Rood-Bar). The identification of OuMV was confirmed through differential host range reaction. Crude sap from symptomatic leaves was used to inoculate Chenopodium quinoa and Gomphrena globosa as local lesion hosts. Squash, melon, and cucumber were subsequently inoculated by using a single local lesion. Typical yellowing and chlorotic spot symptoms were observed after 40 to 45 days on melon and squash and leaf curling was observed on Nicotiana rustica. The OuMV presence in these symptomatic test plants was confirmed by DAS-ELISA and the tests were negative with Cucurbit aphid-borne yellows virus (CABYV) and Zucchini yellow mosaic virus (ZYMV) antisera. No symptoms were observed on Datura stramonium, Capsicum annum, Phaseolus vulgaris, Pisum sativum, Raphanus sativus, and Beta vulgaris, and OuMV was not detected by DAS-ELISA in these plants. Although showing no symptoms, OuMV-inoculated Vicia faba plants reacted positively in DAS-ELISA. The number of multiple infections of OuMV with other common cucurbit viruses was relatively high (46%), most frequently with ZYMV and CABYV. Since the first report of OuMV from melon in Azerbaijan-E-Gharbi Province, western Iran (1), there has been no report of OuMV occurrence in any other region of Iran or any other country in the world, and the sequence of OuMV remains to be determined. Our results show that OuMV is naturally spreading into other regions of Iran. Reference: (1) V. Lisa et al. Ann. Appl. Biol. 112:291, 1988.