Production of indigenous mushrooms spawn using crop residues as substrates

Indigenous oyster mushrooms occur naturally when conditions are favourable. Achieving good quality spawn is a major challenge to small-scale farmers in Kenya, who strive to domesticate indigenous mushrooms. The use of wheat grain in mushroom growing industries for spawn production poses a threat to food security. The objective of this study was to evaluate crop residues as alternative substrates for indigenous mushrooms spawn production in Kenya. Different crop residues, including straws of wheat, barley and beans, maize cobs and sawdust were sterilised and tested for spawn production. Colonisation, pinning and mushroom yields were evaluated on bean and wheat straw substrates. There was a significant difference (P<0.05) in mycelia colonisation period when different spawn types were inoculated on bean and wheat straw substrates. Bean straw spawn had the shortest colonisation period (23 days) and was the best agricultural waste spawn. There was no significant difference (P<0.05) on pinning days and 2nd flush yields for the different types of spawn. There was a significant difference (P<0.05) between maize cob and wheat grain spawn in 1st flush yields. Bean straw spawn had a flush 1 yield of 125.2 g which, was not significant (P>0.05) compared to the wheat grain spawn (control) that gave a yield of 126.1 g. Results of this study indicate the suitability of various agricultural crop residues as alternative substrates for indigenous spawn production. &nbsp

Reaction of selected common bean genotypes to physiological races of Phaeoisariopsis griseola occurring in Kenya

The wide pathogenic variability occurring in Phaeoisariopsis griseola , the causal agent of angular leaf spot of common bean ( Phaseolus vulgaris L.), dictates that new sources of resistance be continuously identified. This study was undertaken to determine the reaction of selected bean genotypes to different races of P. griseola in order to identify potential sources of resistance to angular leaf spot. Selected bean genotypes from Eastern and Central Africa Bean Research Network (ECABREN) and National Dryland Farming Research Centre (NDFRC), Katumani in Kenya were separately inoculated with forty-four races of P. griseola and evaluated for disease development under greenhouse conditions. The genotypes included small- and large-seeded types. None of the genotypes was resistant to all the races, indicating a high complexity of the pathogen population. Thirteen genotypes were resistant (disease score 1 to 3) or moderately resistant (score 4 to 6) to at least 40 of the races. Small-seeded bean genotypes ECAB 0754 and ECAB 0617 were resistant or moderately resistant to all races except Mesoamerican race 33-39 and Afro-Andean race 58-18, respectively. Genotype ECAB 0754 exhibited the highest level of resistance, with an average disease severity of 1.1%. All the resistant or moderately resistant genotypes were of the small-seeded bean types which are commercially less popular. The commonly grown large-seeded genotypes were generally susceptible. Among the bean genotypes evaluated, the small-seeded pintos and browns/yellows possessed high levels of resistance. The results of this study indicate that different bean genotypes have varying levels of resistance to angular leaf spot that can be pyramided into appropriate background to provide durable resistance.Une large variabilit\ue9 pathog\ue9nique du Phaeoisariopsis griseola , l\u2019agent causal de la t\ue2che angulaire de feuilles du haricot commun ( Phaseolus vulgaris L.), sugg\ue8re qu\u2019il y\u2019ait une identification continue de nouvelles sources de r\ue9sistance. Cette \ue9tude \ue9tait entreprise pour d\ue9terminer la r\ue9action des g\ue9notypes de haricot s\ue9lectionn\ue9s aux diff\ue9rentes races de P. griseola afin d\u2019identifier de sources potentielles de r\ue9sistance \ue0 la maladie de t\ue2che angulaire de la feuille. Les g\ue9notypes de haricot fournis par l\u2019Eastern and Central Africa Bean Research Network (ECABREN) et le National Dryland Farming Research Centre (NDFRC), Katumani au Kenya \ue9taient s\ue9par\ue9ment inocul\ue9s avec quarante-quatre races de P. griseola pour l\u2019\ue9valuation en serre du d\ue9veloppement de maladies. Les g\ue9notypes comprenaient de petits et gros grains de semences. Aucune des g\ue9notypes n\u2019\ue9tait r\ue9sistant \ue0 toutes les races de maladies, indicant ainsi une complexit\ue9 \ue9lev\ue9e de la population des pathog\ue8nes. Treize g\ue9notypes \ue9taient r\ue9sistants (\ue9chelle de cotation: 1 \ue0 3) ou mod\ue9r\ue9ment r\ue9sistants (\ue9chelle de cotation: 4 \ue0 6) sur au moins quarante de toutes les races. Les g\ue9notypes de haricot \ue0 petits grains ECAB 0754 et ECAB 0617 \ue9taient r\ue9sistants ou mod\ue9r\ue9ment r\ue9sistants \ue0 toutes les races \ue0 l\u2019exception de Mesoamerican race 33-39 et Afro-Andean race 58-18, respectivement. Le G\ue9notype ECAB 0754 avait manifest\ue9 un niveau \ue9lev\ue9 de r\ue9sistance, avec un taux moyen de s\ue9verit\ue9 de 1.1%. Tous les g\ue9notypes r\ue9sistants ou mod\ue9r\ue9ment r\ue9sistants \ue9taient de ceux \ue0 petits grains commercialement moins populaires. Les g\ue9notypes \ue0 gros grains commun\ue9ment cultiv\ue9s \ue9taient g\ue9n\ue9ralement susceptibles. Parmi les g\ue9notypes \ue9valu\ue9s, ceux \ue0 petits grains "pintos" et bruns/jaunes \ue9taient dot\ue9s des niveaux \ue9lev\ue9s de r\ue9sistance. Les r\ue9sultats de cette \ue9tude montrent que diff\ue9rents g\ue9notypes de haricot poss\ue8dent de niveaux diff\ue9rents de r\ue9sistance \ue0 la maladie de t\ue2che angulaire de la feuille pouvant \ueatre combin\ue9s par pyramidage pour d\ue9velopper une vari\ue9t\ue9 de haricot \ue0 r\ue9sistance durable

A review of angular leaf spot resistance in common bean.

Angular leaf spot (ALS), caused by Pseudocer-cospora griseola, is one of the most devastating diseases of common bean (Phaseolus vulgarisL.) in tropical and subtropical production areas. Breeding for ALS resistance is difficult due to the extensive virulence diversity of P. griseolaand the recurrent appearance of new virulent races. Five major loci, Phg-1 to Phg-5, confer-ring ALS resistance have been named, and markers tightly linked to these loci have been reported. Quantitative trait loci (QTLs) have also been described, but the validation of some QTLs is still pending. The Phg-1, Phg-4, and Phg-5loci are from common bean cultivars of the Andean gene pool, whereas Phg-2 and Phg-3are from beans of the Mesoamerican gene pool. The reference genome of common bean and high-throughput sequencing technologies are enabling the development of molecular markers closely linked to the Phg loci, more accurate mapping of the resistance loci, and the compar-ison of their genomic positions. The objective of this report is to provide a comprehensive review of ALS resistance in common bean. Further-more, we are reporting three case studies of ALS resistance breeding in Latin America and Africa. This review will serve as a reference for future resistance mapping studies and as a guide for the selection of resistance loci in breeding programs aiming to develop common bean cultivars with durable ALS resistance

Colonisation of Resistant and Susceptible Bean Tissues by Phaeoisariopsis Griseola (Sacc) Ferr

Fungal development and the associated cellular reactions in three bean (Phaseolus vulgaris L.) cultivars/lines inoculated with Phaeoisariopsis griseola isolate PG18 were studied. Differences in the extent of fungal development and host cell integrity were used to compare the reactions of the three cultivars/lines (resistant, intermediate resistant and susceptible). Conidia of P. griseola germinated 4 hours after inoculation by producing germ tubes at either one, both tips or at the sides. However, germination in the resistant bean line M26 was slightly inhibited and most of the conidia had not germinated 4 hours after inoculation. Penetration occurred 24 hours after inoculation and was either direct or through the stomata. On M26, minute brown flecks were observed on the inoculated area 4 days after inoculation, whereas in cv Rosecoco-GLP-2 (susceptible) and line M29 (intermediate resistant), development of conspicously septed hyphae was observed. A prolonged biotrophic phase was noted in cv Rosecoco-GLP-2 and line M29 and lesions appeared on the 6th and 10th days, respectively, characterised by conspicously septed hyphae. Such septations were not observed in hyphae of the same isolate in slide culture. A transverse section of the infected tissue in cv Rosecoco-GLP-2 and line M29 taken 9 days after inoculation showed cell disintegration whereas the cells in line M26 were intact. The fungus only colonised the lower epidermal and spongy mesophyll layer. Sporuration in cv Rosecoco-GLP-2 and line M29 occurred 8 and 12 days after inoculation, respectively, but did not occur in line M26. The number of synnema per lesion and number of conidiophores per synnemata in cv Rosecoco-GLP-2 was significantly (P=0.05) higher than in line M29. Thus, resistance in bean line M26 to angular leafspot is probably due to inhibited germination, colonisation and sporulation whereas the intermediate response in line M29 could be due to delayed and limited sporulation of the fungus.Le d\ue9veloppement fongique et des r\ue9actions cellulaires associ\ue9es dans trois cultivars de haricot/lign\ue9e (Phaseolus vulgaris L.) inocul\ue9s avec l\u92isolat PG18 de Phaeoisariopsis griseola ont \ue9t\ue9 \ue9tudi\ue9es. Des differences dans l\u92extention du d\ue9veloppement fongique et l\u92int\ue9grit\ue9 de la cellule-hote ont \ue9t\ue9 utilis\ue9es pour comparer les r\ue9actions des trois cultivars/lign\ue9es (r\ue9sistant, intermediare r\ue9sistant et sensible). Les conidies de P. griseola ont germ\ue9 4 heures apr\ue8s inoculation en produisant des tubes de germes soit \ue0 un, deux bourgeons ou bien aux deux cot\ue9s. Cependant la germination dans la lign\ue9e M26 \ue9tait partiellement inhib\ue9e et presque toutes les conidies n\u92ont pas germ\ue9 4 heures apr\ue8s inoculation. La p\ue9n\ue9tration est apparue 24 heures apr\ue8s inoculation et \ue9tait soit directe ou \ue0 travers les stomates. Des t\ue2ches brunes miniscules \ue9taient observ\ue9es sur la zone inocul\ue9e 4 jours apr\ue8s inoculation sur la lign\ue9e M26, alors que dans le cv Rosecoco-GLP-2 (sensible) et la lign\ue9e M29 (intermediaire r\ue9sistante), des hyphes visiblement cloisonn\ue9es \ue9taient observ\ue9es. Une phase biotrophique prolong\ue9e a \ue9t\ue9 observ\ue9e chez le cv Rosecoco-GLP-2 et des l\ue9sions ont apparu entre le 6eme et le 10eme jour respectivement caract\ue9ris\ue9s par des hyphes visiblement cloisonn\ue9es. Tels cloisonnements n\u92ont pas \ue9t\ue9 observ\ue9s dans les hyphes du m\ueame isolat dans la boite de culture. Une section transversale des tissus infect\ue9s du cv Rosecoco-GLP-2 et de la lign\ue9e M29, pris 9 jours apr\ue8s inoculation ont montr\ue9 une d\ue9sint\ue9gration de la cellule alors que les cellules dans la lign\ue9e M26 \ue9taient intactes. Le champignon a colonis\ue9 seulement la partie \ue9pidermique inferieur et la couche de la m\ue9sophylle spongieuse. La sporulation dans le cv Rosecoco-GLP-2 et la lign\ue9e M29 ont apparu 8 et 12 jours apr\ue8s inoculation alors qu\u92elle n\u92a pas apparue chez la lign\ue9e M26. Le nombre de synnema par l\ue9sion et le nombre de conidiophores par synnemata chez le cv Rosecoco-GLP-2 \ue9taient significativement (P<0.05) plus \ue9lev\ue9s plus que chez la lign\ue9e M29. Ainsi, la r\ue9sistance chez la lign\ue9e M26 \ue0 la cercosporiose angulaire des feuilles est problablement due \ue0 la germination inhib\ue9e, \ue0 la colonisation et \ue0 la sporulation alors que la r\ue9ponse intermediaire dans la lign\ue9e M29 serait due \ue0 la sporulation limit\ue9e et retard\ue9e du champignon

Reaction of selected common bean genotypes to physiological races of Phaeoisariopsis griseola occurring in Kenya

The wide pathogenic variability occurring in Phaeoisariopsis griseola , the causal agent of angular leaf spot of common bean ( Phaseolus vulgaris L.), dictates that new sources of resistance be continuously identified. This study was undertaken to determine the reaction of selected bean genotypes to different races of P. griseola in order to identify potential sources of resistance to angular leaf spot. Selected bean genotypes from Eastern and Central Africa Bean Research Network (ECABREN) and National Dryland Farming Research Centre (NDFRC), Katumani in Kenya were separately inoculated with forty-four races of P. griseola and evaluated for disease development under greenhouse conditions. The genotypes included small- and large-seeded types. None of the genotypes was resistant to all the races, indicating a high complexity of the pathogen population. Thirteen genotypes were resistant (disease score 1 to 3) or moderately resistant (score 4 to 6) to at least 40 of the races. Small-seeded bean genotypes ECAB 0754 and ECAB 0617 were resistant or moderately resistant to all races except Mesoamerican race 33-39 and Afro-Andean race 58-18, respectively. Genotype ECAB 0754 exhibited the highest level of resistance, with an average disease severity of 1.1%. All the resistant or moderately resistant genotypes were of the small-seeded bean types which are commercially less popular. The commonly grown large-seeded genotypes were generally susceptible. Among the bean genotypes evaluated, the small-seeded pintos and browns/yellows possessed high levels of resistance. The results of this study indicate that different bean genotypes have varying levels of resistance to angular leaf spot that can be pyramided into appropriate background to provide durable resistance.Une large variabilité pathogénique du Phaeoisariopsis griseola , l’agent causal de la tâche angulaire de feuilles du haricot commun ( Phaseolus vulgaris L.), suggère qu’il y’ait une identification continue de nouvelles sources de résistance. Cette étude était entreprise pour déterminer la réaction des génotypes de haricot sélectionnés aux différentes races de P. griseola afin d’identifier de sources potentielles de résistance à la maladie de tâche angulaire de la feuille. Les génotypes de haricot fournis par l’Eastern and Central Africa Bean Research Network (ECABREN) et le National Dryland Farming Research Centre (NDFRC), Katumani au Kenya étaient séparément inoculés avec quarante-quatre races de P. griseola pour l’évaluation en serre du développement de maladies. Les génotypes comprenaient de petits et gros grains de semences. Aucune des génotypes n’était résistant à toutes les races de maladies, indicant ainsi une complexité élevée de la population des pathogènes. Treize génotypes étaient résistants (échelle de cotation: 1 à 3) ou modérément résistants (échelle de cotation: 4 à 6) sur au moins quarante de toutes les races. Les génotypes de haricot à petits grains ECAB 0754 et ECAB 0617 étaient résistants ou modérément résistants à toutes les races à l’exception de Mesoamerican race 33-39 et Afro-Andean race 58-18, respectivement. Le Génotype ECAB 0754 avait manifesté un niveau élevé de résistance, avec un taux moyen de séverité de 1.1%. Tous les génotypes résistants ou modérément résistants étaient de ceux à petits grains commercialement moins populaires. Les génotypes à gros grains communément cultivés étaient généralement susceptibles. Parmi les génotypes évalués, ceux à petits grains "pintos" et bruns/jaunes étaient dotés des niveaux élevés de résistance. Les résultats de cette étude montrent que différents génotypes de haricot possèdent de niveaux différents de résistance à la maladie de tâche angulaire de la feuille pouvant être combinés par pyramidage pour développer une variété de haricot à résistance durable