Evaluation of Xa7 Introgressed Lines Against Bacterial Leaf Blight (BLB) Disease and Their Agronomic Performances

Bacterial leaf blight (BLB) is one of the major rice diseases in Malaysia. The disease can potentially cause a 30 to 50% yield loss to the rice crop. Hence, the utilization of resistant rice varieties to BLB is a crucial approach to prevent potential yield loss and to ensure the sustainability of the rice industry in Malaysia. This study aims to incorporate BLB resistant trait into a susceptible, high yielding, popular commercial variety MR219. The identified donor parent is IRBB7, harboring Xa7, a broad-spectrum BLB resistant gene which closely linked to two STS markers, the ID7 and ID15. Backcrossing was initiated, using IRBB7 as the donor and MR219 as the recurrent parents. Marker-assisted selection (MAS) was applied to monitor and confirm the introgression of Xa7 in the progenies of the cross based on alleles produced by the markers. We managed to generate 19 BC3F4 lines harboring homozygous Xa7 gene that were phenotypically resistant when challenged with Xanthomonas oryzae pv. oryzae through an artificial inoculation. The improved lines exhibited similar morphological and yield performance of the recurrent parent. Two lines, PB-2-107 and PB-2-34 were identified for their outstanding performances which are comparable to MR219. This study demonstrates the advantage of MAS application in the improvement of disease resistance traits in the elite rice cultivars.

Inheritance of Resistance to Pepper huasteco yellow vein virus in Capsicum annuum L.

Pepper huasteco yellow vein virus (PHYVV) is a major disease in pepper (Capsicum annuum) that causes quantitative and qualitative losses to the crop in Central America and part of North America. To date, no resistant cultivars are available, and breeding is hampered by the lack of knowledge of the inheritance of this trait. Sources of resistance to PHYVV have been identified in the wild peppers of Mexico. The objectives of this study were to determine the grade of dominance, to analyze the maternal influence, and to estimate the number of genes involved in this resistant trait to PHYVV in the resistant wild pepper accession UAS12. Three susceptible parent lines—‘Anaheim’ (Ana), ‘Ancho Gigante’ (AG), and ‘Yolo Wonder’ (YW)—were crossed with resistant UAS12 accession to develop F1 (reciprocal), F2, and BC1 progenies in three families. Plants from this study were inoculated with PHYVV through Bemisia tabaci, evaluated phenotypically, and the segregation of disease scores was studied. A single recessive gene was found to control resistance to PHYVV in the resistant UAS12 accession, although segregation patterns suggested that other minor genes could participate in the expression of this resistant trait. No proof was found for maternal inheritance of PHYVV resistance. The gene symbol phv is proposed for PHYVV resistance in UAS12 accession in pepper. These results provide useful information for the design of pepper breeding programs in the introgression of this trait into commercial pepper backgrounds.

Resistance to Pepper huasteco yellow vein virus and its heritability in wild genotypes of Capsicum annuum

<p><strong>Background: </strong><em>Pepper huastecto yellow vein virus</em> (PHYVV) is one of the main viruses affecting pepper (<em>Capsicum</em> spp.) plants in Mexico.</p><p><strong>Question: </strong>Why there are no pepper resistant cultivars to PHYVV currently? Could it be due for the lack of new pepper resistant sources and knowledge about the heritability of the resistant trait?</p><p><strong>Study species: </strong><em>Capsicum annuum, Pepper huasteco yellow vein virus </em>and<em> Bemisia tabaci</em>.</p><p><strong>Study site: </strong>Culiacan<strong> </strong>Sinaloa, Mexico; January 2013 to August 2014.</p><p><strong>Methods: </strong>Two assays were performed in 2013 and 2014 with three resistant wild lines of <em>Capsicum annuum</em> in the S2 and S3 generation under greenhouse conditions to analyze the resistance to the <em>Pepper huasteco yellow vein virus</em> (PHYVV) and its heritability. Plants were inoculated with PHYVV through <em>Bemisia tabaci</em> G. and by grafting.</p><p><strong>Results: </strong>Line UAS12 showed a significantly higher proportion of resistant plants, longer incubation time, and less amount of viral DNA, followed by lines UAS13, UAS10 and the Maverick cultivar under both inoculation methods in both assays. Distribution of symptoms revealed a bimodal tendency in both assays. The novel gene "<em>CchGLP</em>" which confer resistance to PHYVV in pepper plants, was identified in the three lines evaluated on this study. Heritability of line UAS12 was of 0.35 and 0.26 in the insects and grafting inoculations, and of 0.58 and 0.10 in the first and second assays, respectively. Lines UAS13 and UAS10 showed close to zero heritability in the first and second assays with both inoculation methods.</p><strong>Conclusions: </strong>Line UAS12 is the most promising genetic resource for its high resistance and for showing heritability for the resistance trait. The intermediate resistance of lines UAS13 and UAS10 could be also useful for breeding programs. At least two genes are involved in the resistance trait to PHYVV. Part of the resistance shown in these lines may be due to the presence of the "<em>CchGLP</em>" gene. Line UAS12 count with variability for the resistant trait and can, therefore, be used to improve resistance and the other two lines possibly are stable as they did not show heritability.

ChiC Gene Enhances Fungal Resistance in Indigenous Potato Variety (Diamant) Via Agrobacterium-Mediated Transformation

Potato (Solanum tuberosum), one of the indispensable food crops, is susceptible to various fungal phyto-pathogenic infections that result in considerable production losses both in terms of quality and quantity. Developing fungal-resistant cultivars by introducing pathogen-resistant genes through transgenic approach has been a powerful tool to provide defense against the fungal pathogens. The current study was undertaken to develop a fungal resistant trait in a local potato variety. To achieve this goal, a local Pakistani Potato variety (Diamant), was transformed with chitinase ChiC gene utilizing plasmid pEKB/ChiC using Agrobacterium tumefaciens strain EHA101. The infected explants were grown on MS medium supplemented with 2 mg/l BAP and 0.2 mg/l NAA. Explants were then sub-cultured on MS medium supplemented with 2mg/l BAP and 2mg/l GA3 for shooting. PCR examination confirmed the integration of ChiC gene in the potato genomic DNA. The transformed potato variety could also be used as fungus-resistant breeding material and offers new opportunities to develop improved potato cultivars for different agronomic and other desirable traits.