Yield and Response of Bean Breeding Lines for Drought Tolerance to Field Diseases

Climate change has resulted in an increase in the intensity of droughts and rains, and higher temperatures which are adversely affecting crop production in Africa. It has also influenced the distribution and increased the occurrence of disease and pest epidemics. Common bean (Phaseolus vulgaris L.) is especially sensitive to these changes. Most released varieties are not well adapted to environmental extremes and extended periods of drought in particular has become a major constraint. In this study, 462 advanced breeding lines developed for drought tolerance were evaluated for yield, agronomic traits and disease response in two contrasting agro-ecologies, Kawanda in the Lake Victoria crescent and Kachwekano in the southwestern highlands. Analysis of variance indicated significant differences (P 1500 kg ha-1, the minimum anticipated commercial yield of new varieties, in all the trials, both seasons and in each year; 5.0 % also maintained above average yields. The most outstanding (1629-3944 kg ha-1) were; DAB299, DAB291, DAB234, DAD34, DAB478, DAB487, DAB543, DAB231, SCN20, SCR66, SCR60, and SER335. These are recommended for development of new varieties

Gain and performance in yield and micronutrient concentration in common bean improvement

Common bean (Phaseolus vulgaris L.) is a staple and nutritious leguminous food crop for all income categories in Africa. Efforts to improve its yield performance and nutritional components, especially Iron and zinc have resulted in the release of several varieties in the sub-Saharan African region. The objective of this study was to assess genetic progress in varieties released in 12 African countries through the Pan African Bean Research Alliance (PABRA) from 1973 to 2017, to inform current breeding decisions. A total of 214 released varieties, land races and breeding lines, of bush and climbing beans were evaluated for yield, micronutrient (Fe and Zn) concentration, and phenology in three locations (Kawanda and Kachwekano in Uganda, and Kitengule in Tanzania) in 2017–2018. There were significant differences (P 0.01) among genotypes for all traits except days to maturity (DPM). Genotype x environment interaction was also significant (P<0.05) for all assessed traits, except for iron in climbing beans. Across environments, repeatability (H2) was greater than 0.50 for all traits, except for DPM in climbing beans. Annual rates of genetic yield gains were 4.41 and 4.57 kg ha-1 for large and small seed bush beans, and -2.74 and 21.6 kg ha-1 for large and small seeded climbers. Similarly, gains in seed iron (FESEED) were 0.40 and 0.17 ppm for bush and climbing beans, respectively. These represented an annual relative gain over the oldest varieties of 0.6 and 0.7% kg ha-1 for yield of large and small seeded bush beans, -0.3 and 1.6% kg ha-1 for yield of large and small seeded climbers, 0.6 and 0.2% ppm for FESEED of bush and climbers. Overall, genetic progress was slow for both yield and FESEED

Characterization of Phaseolus coccineus interspecific germplasm accessions for disease resistance, grain market class and yield attributes

Sister species of the common bean (Phaseolus vulgaris L.) are an attractive genetic resource to broaden the genetic base of this crop, especially for adaptation to extreme environments. The runner bean (Phaseolus coccineus) in particular, has been shown to contribute to disease resistance and tolerance to low soil fertility, and has been used to introduce these traits into the common bean. The objective of this study was to identify germplasm with agronomic traits suitable for cultivation from an interspecific population (Phaseolus coccineus G35346 x P. vulgaris; SER 16) of 186 bush lines. The lines, coded ALB and one yield check, CAL96, were field evaluated for three rain seasons; 2011a (March-June), 2011b (September-November) and 2012 (March-June) at the National Agricultural Research Laboratories (NARL)-Kawanda, Uganda. Artificial inoculum of bean common mosaic virus (BCMV) was applied to the field experiment in 2011a. The morphological (seed type and growth habit) and agronomic attributes (plant vigour, days to physiological maturity; DPM and days to 50% flowering; DF), reaction to occurring diseases and yield performance were monitored. The lines including root rot resistant and susceptible checks; MLB-49-89A, RWR 719 and CAL 96, were also subjected to inoculum of two major root rot pathogens; Fusarium solani f.sp. phaseoli (isolate FSP3) and Pythium ultimum (isolate MS61) under screen house conditions to select for root rot resistance. Results indicated significant differences (P<0.05) among the interspecific lines for the parameters measured. Days to flowering and to DPM ranged from 31-39 and 81-86, respectively. Field disease pressure was generally low, but in general, 50% of the lines had yield above the mean; while 8% maintained above average yield in all seasons. The superior lines included; ALB169 (mean yield 2,564 kg ha-1), ALB214 (mean yield 2,125 kg ha-1), ALB196 (mean yield 2,084 kg ha-1), ALB5 (2,062 kg ha-1), ALB152 (2,016 kg ha-1), and ALB179 (2011 kg ha-1), compared to the check CAL96 (1,607 kg ha-1). These lines, except ALB169 and ALB179, were resistant root rot. More lines expressed resistance to Fusarium than to Pythium root rot, with 21.5% showing resistance to both root rot isolates. Over 91% of the lines were small or medium seeded (< 35.0 g per 100 seeds), with red monochrome seed pattern; characteristics that are important for farmer acceptance

Replication data for characterization of Phaseolus coccineus interspecific germplasm accessions for disease resistance, grain market class and yield attributes

P. coccineus interspecific lines (Agronomic quality, resistance levels in Fusarium and Pythium root rot, seed attributes) (2012-07-10

Replication data for agronomic quality and resistance of Andean beans and advanced breeding lines to root rots in Uganda

Root rots cause severe yield losses of up to >70% in common bean (Phaseolus vulgaris L.) in most parts of the world, with devastating effects on the major commercial bean cultivars in East and Central Africa. Increased intensity of droughts and rains, and higher temperatures influence the occurrence and distribution of root rots, resulting in increased epidemics. The causal pathogens tend to occur in a complex, and since most cultivars do not have broad resistance, adverse effects continue to occur. The objective of this study was to evaluate the levels of dual resistance of new breeding lines (BL) developed for root rot resistance, as well as Andean (ADP) genotypes, for resistance to Fusarium (FRR) and Pythium root rots (PRR). Altogether, 316 new BL developed for root rot resistance and 295 ADP bean genotypes were evaluated at Kawanda in Uganda. There were significant differences (P2000 kg ha-1 expressed high yield potential, considering that majority of the genotypes yielded below 1000 kg ha-1

Genetic variation, Heritability estimates and GXE effects on yield traits of Mesoamerican common bean (Phaseolus vulgaris L) germplasm in Uganda

Germplasm of common beans from the Mesoamerican gene pool races: Durango, Jalisco, Mesoamerica and Guatemala have highest genetic variation for the crop's improvement. The objective was to assign 50 common bean germplasm in Uganda into its gene pool races based on analyses of population structure. Secondly, to estimate heritability and effects of genotype × environment (GXE) interaction on common bean agronomic and yield traits in space and time. Sample genomic DNA was amplified in 2011 with 22 Simple sequence repeat markers (SSRs) and alleles separated using capillary electrophoresis. Field evaluations were conducted in 2010 and 2011 at NaCRRI and 2015 at CIAT – Kawanda. Multivariate analyses of SSRs data identified four subgroups within the germplasm: K4.1–K4.4, with corresponding Wrights fixation indices (F ST ) as 0.1829 for K4.1, 0.1585 for K4.4, 0.1579 for K4.2 and least for K4.3 at 0.0678. Gene pool race admixtures in the population (14%) were notable and attributed to gene flow. Four superior parents currently used in improving resistance to major diseases grouped as; Jalisco for MLB49-89A; Mesoamerica for MCM5001 and G2333; Durango for MEXICO 54. Heritability values for yield traits estimated using phenotypic data from above fixed parents, was above 0.81. Season and location had significant effect (P < 0.05) on numbers of: flower buds per inflorescence, pod formation and weight of 100 seeds. The findings will improve understanding of co-evolutionary relationships between bean hosts and pathogens for better disease management and will broaden the germplasm base for improving other tropical production constraints

Agronomic qualities of genetic pyramids of common bean developed for multiple-disease-resistance

Multiple co-infections by different pathogens on common bean (Phaseolus vulgaris L.) affect its productivity and cause complete crop loss in susceptible varieties. Therefore, gene pyramiding using marker assisted selection (MAS) and backcrossing, provide alternative cost-effective control measures to bean diseases. However, in the process of developing pyramids, linkage drags were likely to affect the qualities of progeny lines, hence, special attention was paid to this situation. The objective of this study was thus to assess the agronomic qualities of advanced genetic pyramids developed from a four-way cross for multiple disease resistance. The disease resistance genes (R) pyramided from four parents were: Co42 and Co-5 from G2333; Phg-2 from MEX54; Pythium ultimum Dennis from MLB49-89A and I & bc3 from MCM5001. The progeny lines were planted in an incomplete block design, and replicated thrice for two seasons (2015A and 2015B) in fields at CIAT, Kawanda in Uganda. Agronomic traits were highly heritable (0.6), except number of pods per plant (< 0.3). Backcrossing generated high-yielding bean lines, with 270 - 290 seed per plant and early maturity (95-100 days). Nine superior lines with desirable qualities, such as earliness (95 days), high seed rate (290 seeds per plant), and climbing ability, were obtained. Pyramiding R genes did not affect yield traits, except time to flowering and number of flower buds per plant due to transgressive segregation