Common bean (Phaseolus vulgaris L.) is an important legume crop in Kenya and is a cheap source of proteins. The small scale farmers in Kenya produce common bean under low agricultural input systems and this predisposes the crop to pests and diseases. Among the diseases, angular leaf spot (ALS) is a major constraint to common bean production and contributes to yield losses as high as 80%. The causative pathogen Pseudocercospora griseola (Sacc.) Crous & Braun is highly variable and several races have been reported. There are few common bean genotypes with resistance to this disease. Therefore breeding for resistance to ALS is important for the country. This study was carried out to; i) evaluate the common bean production systems, constraints and farmer varietal preferences in Kenya, ii) evaluate local landraces and selected introductions of common bean for yield performance and reaction to ALS, iii) study the genetics of resistance to ALS in common bean and iv) develop a breeding method for durable resistance to ALS in common bean. To determine the common bean production systems, farmers’ preferred traits and their knowledge on common bean constraints including ALS, a survey was conducted in Kiambu county using a semi-structured questionnaire, interviews, and focus group discussions. The study revealed that farmers cultivate common beans during the short and long rain seasons. However, they experience better yields in the short rains due to reduced disease incidence. The majority of the farmers (71%) intercrop common bean and this ensures maximum utilisation of space. A high percentage (70%) of the farmers utilise their retained seed for production. The farmers identified ALS as one of the most important constraints to production. The only preventative measure they undertake to control the disease is weeding. The farmers reported that they would prefer improved varieties that were resistant to ALS. Farmers have a preference for particular common bean traits that include high yield (80%), resistance to insect-pests and diseases (72%), type I growth habit (52%), early maturity (68%), seed size and colour (21%) and cooking time (20%). These should be incorporated in breeding programmes. Two hundred common bean landraces and market class varieties were evaluated for ALS resistance in a nethouse at University of Nairobi, Kabete Field Station and for ALS resistance and yield in the field in KARI-Tigoni. The results showed that disease severity scores for the genotypes were similar in the two locations, with the top three resistant genotypes being Minoire, GBK 028123 and Murangazi with disease severity scores of 2.9, 2.9 and 3.2 in Kabete and 2.6, 2.8, and 2.9 in Thika respectively. These resistant genotypes can be used as sources of resistance in a breeding programme or they can be used as resistant varieties. All the market class varieties were susceptible to ALS (disease severity score 6.7-8.0). There was a non-significant correlation between disease and yield most likely because most of the resistant genotypes were exotic and hence not adapted to the local conditions. There was also a non-significant correlation between disease and seed size. The two hundred common bean genotypes were evaluated for yield at University of Nairobi, Kabete Field Station and KARI-Thika. The results indicated that the 2011 and 2012 seasons had similar mean yields and that yields at Kabete were higher than at KARI-Thika. The highest yielding genotypes across the two locations were; GLP 2 (766 kg ha-1), Nyirakanyobure (660 kg ha-1), GBK 028110 (654 kg ha-1), GLP 585 (630 kg ha-1) and Mukwararaye (630 kg ha-1). There was a significant genotype x environment interaction and hence it is important for breeders to carry out stability analysis, so as to recommend varieties for a wide range of environments. To study the genetics of ALS resistance in common bean, three inter-gene pool crosses: Super-rosecoco x Mexico 54, Wairimu x G10909 and Wairimu x Mexico 54 were made. The resistant genotypes were Mexico 54 and G10909, while Super-rosecoco and Wairimu were susceptible. The generations F1, F2, BC1P1 and BC1P2 for each of the crosses were developed. The parents P1, P2 and the five generations of each cross were evaluated for resistance to ALS in Kabete Field Station. Results showed that both dominance and additive gene action were important in the expression of resistance to ALS. However, additive gene action was predominant over dominance gene action. There was a moderately high narrow sense heritability estimate (52.9-71.7%). The minimum number of genes controlling resistance to ALS was between 2 and 3. The predominance of additive gene effects and the moderately high narrow sense heritability estimates recorded imply that progress in resistance to ALS could be made through selection in the early segregating generations. A double cross followed by selection against resistant genotypes was used to develop a method to breed for durable resistance to ALS in common bean. The method was used to accumulate minor genes of ALS resistance into single genotypes. Four intermediate resistant landraces were used to develop a double cross population that was screened using a mixture of ALS races. Selection in F1 and F2 population was done on the basis of intermediate resistance (disease severity score 4.0-6.0), while selection from F3 population was based on resistance (disease severity score 1.0-3.0). Ten advanced F4 lines along with their parents were evaluated for ALS resistance. The F4 advanced lines had a significantly improved resistance to ALS compared to their parents. Hence the method was successful in accumulating minor genes for resistance thus showing significant breeding progress in breeding for durable resistance. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

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Call number: LD2668 .T4 1979 F716 / Master of Science

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Osmotic adjustment is one of the adaptive responses of plant species to salinity, In tepary bean seedlings, salinity led to osmotic adjustment in different parts of the seedlings. The osmotic potential of the leaves increased to 340rnM(-1MPa)in seedlings treated with - 0.75 MPa NaCl. Water and osmotic potential of leaves and proximal parr of the roots were more negative than the controls whereas the turgor potential remained about the same. The osmotic adjustment of the tepary bean may result from the synthesis and accumulation of free sugars and amino acids or the accumulation of inorganic ions within the tissue. A quantitative analysis of the sugars and amino acids from salt stress treated tepary bean seedlings showed that they would contribute only -0.15 MPa to the osmotic adjustment whereas inorganic ions would contribute -0.45 MPa. The sum of these osmotic potentials is -0.6 MPa which is -0.4 MPa short of the observed osmotic values. These results suggest that additional substances also contribute to the osmotic adjustment of tepary beans.

Three rates of the plant growth regulator Foliar Triggrr were applied to green beans grown for processing at 5% bloom. The 6 oz rate increased yields of size 1 and 2 beans compared to all other treatments and the untreated check and had the fewest size 3 beans (which would be culls). The 11 oz rate was similar to the untreated check while the 16 oz rate decreased yields. Total bean numbers per plant were similar. Although treatment differences in this experiment were not statistically significant, a yield increase of 10.2% for the 6 oz rate compared with the untreated check may well result in increased economic returns.

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Orientador: Rogério Lopes Vieites / Banca: Angela Vacaro de Souza / Banca: Elisangela Marques Jeronimo Torres / Resumo: Higienizantes são recomendados para retardar ou reduzir o crescimento microbiológico, sendo utilizado pelas indústrias nos produtos minimamente processados para assegurar a qualidade do produto, diminuindo o número de microrganismos contaminantes, aumentando o período da vida de prateleira do vegetal. Este trabalho teve como objetivo avaliar o efeito de diferentes dosagens do ácido peracético e hipoclorito de sódio sobre as características microbiológicas, nutricionais e sensoriais do feijão-vagem minimamente processado. As vagens (Phaseolus vulgaris L.) foram selecionadas, retiradas as pontas, lavadas e processadas em fatias. Imediatamente foram submetidas aos tratamentos com ácido peracético: T1 - Controle, T2 - 0,01%,T3 - 0,02%, T4 - 0,03%, T5 - 0,04% e aos tratamentos com hipoclorito de sódio nas dosagens: T1 -Controle, T2 - 0,01%, T3 - 0,015% e T4 - 0,02%, que em seguida foram lavadas em água corrente. Subsequentemente foram drenadas, centrifugadas, separadas em porções de 180 g, acondicionadas em bandeja de poliestireno expandido com PVC e armazenadas sob refrigeração em câmara fria (5±1ºC e 85±5% de umidade relativa), por 10 dias. As análises realizadas foram: perda de massa fresca, taxa respiratória, cor instrumental, sólidos solúveis, pH, acidez titulável, Ratio, açúcar redutor, açúcar total, sacarose, compostos fenólicos totais, atividade antioxidante total, pigmentos, polifenoloxidase, peroxidase, aceitabilidade e intenção de compra. O delineamento utilizado foi o... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Hygienizers are recommended to slow or reduce microbiological growth being used by industries in minimally processed products to ensure product quality by reducing the number of contaminating microorganisms presents, increasing the shelf life of the vegetable. The objective of this study was to evaluate the effect of different dosages of peracetic acid and sodium hypochlorite on microbiological characteristics; nutritional and sensory characteristics of the minimally processed snap bean. The snaps (Phaseolus vulgaris L.) were selected, tipped, washed and sliced. They were immediately submitted to treatments with peracetic acid: T1 - Control, T2 - 0.01%, T3 - 0.02%, T4 - 0.03%, T5 - 0.04% and to treatments with sodium hypochlorite in dosages: T1 - Control, T2 - 0.01%, T3 - 0.015%, T4 - 0.02% which were then washed in running water. Subsequently they were drained, centrifuged, separated into 180 g portions, packed in a polystyrene tray expanded with PVC and stored under refrigeration in a cold room (5 ± 1 ° C and 85 ± 5% relative humidity) for 10 days. Soluble solids, pH, titratable acidity, ratio, reducing sugar, total sugar, sucrose, total phenolic compounds, total antioxidant activity, pigments, polyphenoloxidase, peroxidase, acceptability and intention were all analyzed: weight loss, respiratory rate, instrumental color, soluble solids, pH, and purchase. The design was completely randomized in factorial scheme. Data were submitted to analysis of variance and regression was ... (Complete abstract click electronic access below) / Mestre