Genomic regions associated with chocolate spot (Botrytis fabae Sard.) resistance in faba bean (Vicia faba L.)

Chocolate spot (CS), caused by Botrytis fabae Sard., is an important threat to global faba bean production. Growing resistant faba bean cultivars is, therefore, paramount to preventing yield loss. To date, there have been no reported quantitative trait loci (QTLs) associated with CS resistance in faba bean. The objective of this study was to identify genomic regions associated with CS resistance using a recombinant inbred line (RIL) population derived from resistant accession ILB 938. A total of 165 RILs from the cross between Melodie/2 and ILB 938/2 were genotyped and evaluated for CS reactions under replicated, controlled climate conditions. QTL analysis identified five loci contributing to CS resistance on faba bean chromosomes 1 and 6, accounting for 5.0-23.4% of the total phenotypic variance. The sequences of SNP markers linked to resistance QTLs on chromosome 1 that have the largest effects encode multiple classes of putative disease and/or defense-related genes. The results of this study not only provide insight into disease-resistance QTLs, but can also be used as potential targets for marker-assisted breeding in faba bean genetic improvement for CS resistance. Keywords: Botrytis fabae; chocolate spot; faba bean; disease resistance; QTL mapping; candidate gene

Photosystem II Repair Cycle in Faba Bean May Play a Role in Its Resistance to Botrytis fabae Infection

Chocolate spot, which is caused by the necrotrophic fungus Botrytis fabae, is a major foliar disease occurring worldwide and dramatically reducing crop yields in faba bean (Vicia faba). Although chemical control of this disease is an option, it has serious economic and environmental drawbacks that make resistant cultivars a more sensible choice. The molecular mechanisms behind the defense against B. fabae are poorly understood. In this work, we studied the leave proteome in two faba bean genotypes that respond differently to B. fabae in order to expand the available knowledge on such mechanisms. For this purpose, we used two-dimensional gel electrophoresis (2DE) in combination with Matrix-Assisted Laser Desorption/Ionization (MALDI-TOF/TOF). Univariate statistical analysis of the gels revealed 194 differential protein spots, 102 of which were identified by mass spectrometry. Most of the spots belonged to proteins in the energy and primary metabolism, degradation, redox or response to stress functional groups. The MS results were validated with assays of protease activity in gels. Overall, they suggest that the two genotypes may respond to B. fabae with a different PSII protein repair cycle mechanism in the chloroplast. The differences in resistance to B. fabae may be the result of a metabolic imbalance in the susceptible genotype and of a more efficient chloroplast detoxification system in the resistant genotype at the early stages of infection.

عزل وتعريف مسبب مرض التبقع البني الشكولاتي (Botrytis faba) على أوراق الفول البلدي في منطقتي المرج والوسيطة بالجبل الأخضر

استهدفت هذه الدراسة تعريف الفطر المسبب لمرض التبقع البني على أوراق الفول، حيث جمعت عشوائياً أوراق الفول من حقول المرج، وحقول الوسيطة خلال فبراير ومارس 2017 في مراحل: الإزهار، والإثمار المتأخرة، تظهر عليها أعراض المرض عدد 50 نباتا/ حقلا. وقدرت نسبة الإصابة في العينات وشدتها، عزل مسبب مرض التبقع البنى من الأوراق المصابة طبيعيا، وبعد اختبار قدرته الإمراضية، نمي الفطر النقي على الأوساط الغذائية صلبة شملت كل من زابكس (Cz)، وبطاطس دكستروز أجار PDA) (، وبيئة مالت أجار(MA)، وحضنت عند 22 درجة مئوية، بينت نتائج الدراسة إصابة أوراق الفول المزروعة بحقول كل من المرج والوسيطة بمرض التبقع البني، حيث ظهرت أعراضه على شكل بقع بنية محمرة صغيرة على الأوراق، ومتوسط قطرها 0.52سم، وسجلت كمية المرض بحساب نسبة الإصابة، ووصلت في حقول المرج إلى 87.6%، في حين كانت شدة الإصابة أعلى في حقول الوسيطة، حيث بلغت 49.7%. كما أكدت الدراسة على قدرة الفطر النقي المعزول من أوراق الفول على إحداث الإصابة وتسجيل البقعة على أوراق نبات الفول صنف المصري بعد 48 ساعة من الحقن. واتضح من خلال القياسات أن المسبب المسؤول عن المرض هو الفطر Botrytis fabae، المميز بميسليوم مقسم داكن، متوسط سمكه (11.75 ميكرومتير)، وينتج الجراثيم الكونيدية في عناقيد عند أطراف متسلسلة متفرعة، وهي أحادية الخلية، مستديرة لونها بني خفيف، متوسط الطول 14.5 ميكروميتر والعرض 10.8 ميكروميتر، كما أعطت بيئة زابكس أعلى نمو ميسليومي، وجراثيم وأجسام حجرية مقارنة بالأوساط الغذائية الأخرى.

Screening of Faba Bean (Vicia faba L.) Germplasm Accessions against Grey Mould Disease Caused by Botrytis fabae Sard

Background: Faba bean (Vicia faba L.) is thirst most important grain legume in the world and the first one in Algeria. The chocolate spot disease caused by Botrytis fabae Sard (BF), is the major constraint of this culture in Algeria when caused a destructive damages.Methods: The aim of this study is to find the sources of resistance for Seven varieties of faba beans (Giza 02, Giza 40, Giza 461, Sakha 02, Sakha 03, Precoce de Seville), by using the detached leaflet inoculation test for resistance to the two isolates from BF represent two different regions of northwest Algeria (Mascara and Relizane). Result: A significant difference (P less than 0.05) was observed in the reaction of the varieties which manifest themselves by a different reaction vis-à-vis the isolates of BF. Total sensitivity was observed in the four (4) varieties Giza02, Sakha01, Sakha02 and Sakha03, two (2) varieties (Giza40 and Ziban), are tolerant, while the variety named ‘Precoce de Seville’ showed significant resistance to both isolates from BF. These results showed a similar pathogenic behavior of two isolates of BF and variability in the level of reactions of the varieties of beans. The variety ‘Precoce de Seville’ showed promising results to be valued and cultivated in order to reduce the damage caused by this disease and reduce the use of chemicals.