Farah Naz

Powdery mildew resistance in some new wheat amphiploids (2n 5 6x 5 42) derived from A- and S-genome diploid progenitors

Triticum urartu possesses the A u genome common to bread wheat. Similarly, Triticum monococcum contains the A m genome, which is closely related to the A-genome donor of bread wheat. Aegilops speltoides of the Sitopsis section has the S genome, which is most similar to the B genome of bread and durum wheat when compared with all other wild grasses. Amphiploids developed through bridge crossing between A m /A u and S-genome diploid resources and elite durum cultivars demonstrate enormous diversity to improve both bread and durum wheat cultivars. We evaluated such A-genome amphiploids (Triticum turgidum £ T. urartu and T. turgidum £ T. monococcum ,2 n ¼ 6x ¼ 42; BBAAA m A m /A u A u ) and S-genome amphiploids (T. turgidum £ Ae. speltoides ,2 n ¼ 6x ¼ 42; AABBSS) along with their durum parents (AABB) for their resistance to powdery mildew (PM) at the seedling stage. The results indicated that 104 accessions (53.6%) of A-genome amphiploids (AABBA m A m /A u A u ) were resistant to PM at the seedling stage. Of their 24 durum parents, five (20.83%) were resistant to PM and 16 (66.6%) were moderately tolerant. Similarly, ten (50%) accessions of S-genome amphiploids (BBAASS) possessed seedling PM resistance, suggesting a valuable source of major resistance genes. PM screening of the amphiploids and parental durum lines showed that resistance was contributed either by the diploid progenitors or durum parents, or both. We also observed the suppression of resistance in several cases; for example, resistance in durum wheat was suppressed in respective amphiploids. The results from this germplasm screening will facilitate their utilization to genetically control PM and widen the genetic base of wheat.

First Report of pre-harvest fruit rot of strawberry caused by Botrytis cinerea in Khyber Pakhtunkhwa (KPK) province & Islamabad (Pakistan)

Strawberry (Fragaria × ananassa Duch.) is an emerging fruit crop in Pakistan, cultivated on approximately 1500 hectares. A survey was conducted during each crop season viz. 2014-2015 and 2015-2016 in geographically important strawberry growing regions of Khyber Pakhtunkhwa and Islamabad . Fruit rot was observed in all surveyed fields that indicates 100 % prevalence of the disease in the study area . Affected tissue was covered with a thin layer of grayish white to dark gray mycelium, which later became fuzzy due to profusion of conidiophores, and rot enveloped the entire fruit. Rotted fruit gradually dried, becoming hard and mummified. Fruit tissue segments at the margins of lesions on infected fruit were cut into 3- to 5 mm2 pieces, surface disinfected with 2% sodium hypochlorite for 1 min, rinsed by washing three times in sterile distilled water, and blotted dry. Disinfected segments were placed on Czapek-Dox (CZ) agar and incubated at 25 ± 2°C. Grayish colonies were observed 3 to 5 days later. Colonies...

First report of strawberry leaf spot caused by Alternaria alternata in Pakistan

Strawberry (Fragaria × ananassa Duch.) has recently become an economically important fruit crop in Pakistan and is cultivated on approximately 1500 ha. A survey across Punjab, Khyber Pakhtunkhwa (KPK) provinces and Islamabad (Islamabad Capital territory) was conducted during March and April of 2015-2016 growing season revealed black leaf spot symptoms on strawberry leaves. Leaf spots were irregular in shape, 3 to 6 mm in diameter, and blackish brown. Disease incidence was found 17 to 55 % in visited fields. Portions of symptomatic leaf tissue (3 × 5 mm) were excised from the margins of lesions; surface disinfected with 2% sodium hypochlorite for 2 min, rinsed three times in sterile distilled water (SDW) and blotted dry. Leaf tissue was then placed on Czapek Dox agar (CDA) and incubated at 25 ± 2°C with a 12-h photoperiod for 3 to 6 days. Morphology of the 78 isolates was examined; colonies were initially white, then turned light to dark brown and greyish black and produced abundant aerial hyphae. Conidiop...

First report of postharvest rot caused by Pestalotiopsis sp. on grapes in Punjab, Pakistan

Grapes (Vitis vinifera L.), a major crop in Pakistan, are cultivated mostly for the fresh market. In June 2016, severe fruit rot was observed in packing houses in Rawalpindi (33°38′19.2″N, 73°01′45.0″E) and Chakwal (32°56′01.5″N, 72°50′37.1″E) districts of Punjab province on cvs. King’s Ruby and Perlette after 3 to 5 days of postharvest storage. To determine incidence of symptoms, 10 boxes of each grape variety were selected randomly from each of five packing houses per district. Disease incidence was recorded at 4 to 6%. Initial symptoms occurred mainly on wounded berries; following infection, the fruit skin turned reddish brown, after which the area of discolored skin increased and whitish mycelium developed on the lesions. A total of 400 symptomatic berries were surface sterilized by immersing cheese cloth bags containing detached berries in 1% sodium hypochlorite for 1 min, then rinsing three times with sterile distilled water and allowing the berries to dry by placing them on filter paper for 45 s. Surface sterilized tissues at the margins of lesions were excised into 4-mm³ segments and then transferred to potato dextrose agar (PDA) and incubated at 25 ± 2°C. After 1 week, fungal colonies were white, floccose, and cottony, with black acervuli forming distinct concentric rings. A total of 29 isolates were examined morphologically; conidia were fusiform, straight or slightly curved, 4 to 5 celled, and 19.7 to 30.2 × 4.8 to 6.2 μm. The color of conidia was dark umber to olivaceous with a darker band at the septum between cells. Two to three appendages (22.6 ± 0.6 μm long) appeared at the apex of each conidium; apical appendages were not knobbed, whereas the basal end had a single appendage with a knobbed tip that was 5.7 ± 0.4 μm long. According to colony and conidia morphology, the isolates were identified as Pestalotiopsis clavispora (G.F. Atk.) Steyaert (Gonzalez et al. 2012; Guba 1961). The internal transcribed spacer (ITS1, 5.8s, and ITS2) region of isolates PSTL01, PSTL06, and PSTL12 was amplified using ITS1 and ITS4 primers. Sequence comparison revealed 99% genetic homology (accession nos. MF448223, MF571908, and MF571909) with previously reported isolates of P. clavispora (KY319134 and KM402033). To confirm pathogenicity, 10-µl aliquots of conidial suspension (10⁶ spores/ml) of PSTL01, PSTL06, or PSTL12 were pipetted onto three nonwounded and four wounded asymptomatic grape berries of cv. King’s Ruby per isolate; sterile distilled water was used as a negative control. The berries were incubated at 25 ± 2°C in sterile moist chambers, and the experiment was conducted twice. After 3 days, whitish mycelium and sunken lesions, similar in appearance to the original lesions, developed on both wounded and nonwounded inoculated berries, whereas no symptoms appeared on the negative controls. The morphology of the fungus that was reisolated on PDA was identical to that of the original cultures. Pestalotiopsis sp. has been reported to cause postharvest fruit rot on grapes in Korea (Deng et al. 2013). To our knowledge, this is the first report of Pestalotiopsis sp. causing fruit rot of grapes in Pakistan, where the disease poses a significant threat to sustainability of grape producers.

FIRST REPORT OF CURVULARIA LUNATA CAUSING LEAF SPOTS ON LOQUAT FROM PAKISTAN

The loquat (Eriobotrya japonica Lindl.) is achieving significant value in Pakistan. During the year 2014-2015, reddish brown circular spots were observed on leaves; these spots increased in size and coalesced to form oblong lesions. Samples were cut into small pieces (3 mm2), surface sterilized with sodium hypochlorite and transferred on Malt Extract Agar (MEA). These samples were incubated at 24±2°C and dark brown colonies with large stroma were observed. Septate condiophores were unbranched or simple and geniculate with dark brown scar. Brown conidia were straight to pyriform with 3-4 cells (large and curved center cell), ranging in size from 6.9 to 20.99 μm and produced apically in a sympodial manner. Morphological characterization was similar to Curvularia lunata (Ellis, 1971). PCR was used for amplification of rDNA region (White et al., 1990) and sequences of PAK34 and PAK35 was submitted to GenBank under accession Nos. KT280007 and KT280008. Both isolates were exhibiting 99% genetic homology with previously reported C. lunata isolates (KM246260, KM246262). Spore suspension (1 × 106 spore/ml) was sprayed on healthy loquat seedlings, kept in glasshouse at 30°C and plants developed lesions similar to those observed on naturally infected plants. Isolation was performed from inoculated loquat plants and morphological characterizations were similar to naturally isolated pathogens. Curvularia leaf spot diseases caused by C. lunata have been previously found on small evergreen tree. To our knowledge, this is the first report worldwide of C. lunata causing leaf spots on loquat.

Expression of a rice GLP in Medicago truncatula exerting pleiotropic effects on resistance against Fusarium oxysporum through enhancing FeSOD-like activity

To evaluate the effectiveness of a germin-like protein (GLP) in legumes against the serious soil-borne pathogen Fusarium oxysporum f. sp. lentis, an Oryza sativa root-expressed GLP (OsRGLP1) was expressed in the model legume Medicago truncatula using the recombinant vector pCOsRGLP1. The transgene was highly expressed in M. truncatula transformed lines as assessed by RT-qPCR. Consistent with the active status of the transgene there was an elevated accumulation of H2O2 in transformed progeny. Enzymatic characterization of T1 transgenic progeny showed increased superoxide dismutase (SOD) activity. The additional SOD activity in transgenic lines was insensitive to potassium cyanide and sensitive to H2O2 indicating its resemblance to FeSOD. The effectiveness of the OsRGLP1 gene was tested by monitoring the root disease after infection of wild-type and transgenic lines. Wild-type plants were greatly affected by the pathogen infection showing a percent disease index value of 50 compared to 10–18 for the transgenic lines. The tolerance of the transgenic lines leads to recovery in fresh weight and pod production to an almost normal level. Analysis of defense-related genes downstream of hydrogen peroxide (H2O2) in transgenic plants showed induction of salicylic acid and jasmonate signaling pathways and increased expression of some pathogenesis-related-1 (PR-1) genes and a plant defensin gene. Overall, the findings suggest that OsRGLP1 provides protection against the fungal pathogen F. oxysporum that may involve the direct influence of H2O2 on signaling pathways leading to the activation of defense-related genes.