Ruanda yaygın fasulyelerinde (Phaseolus vulgaris L.) antraknoz ve yaygın fasülye mozaik virüsüne karşı dirençlilik için moleküler ıslah

Bean anthracnose and Bean common mosaic virus (BCMV) are the diseases devastating the yield of common beans and constrain common bean production especially in East and Central Africa. Pyramiding resistance genes for bean anthracnose and BCMV diseases in Rwandan common bean varieties would ensure stability of the crop yield. However, there might be side effects of pyramided genes on plant agronomic traits. Cleaved Amplified Polymorphic Sequences (CAPS) and Sequence characterized amplified regions (SCAR) markers were used to facilitate the process of pyramiding two anthracnose and two BCMV resistance genes into four popular susceptible market-class bean varieties G54, RWR 1668, RWR 2355 and RWV 2361. Gene pyramiding was fulfilled through concurrent backcrossing and then selfing to fix the target genes. Resistance genes in backcross populations and advanced lines were evaluated with the aid of markers. The 92 F2, 52 BC1, 51 BC2, 44 BC3 and 76 BC3F2 families with resistance genes in different combinations were obtained. Marker-assisted gene pyramiding of anthracnose and BCMV resistance genes was successfully achieved for Rwandan common beans with bc-3+Co-1+I and bc-3+Co-2+I resistance genes combination and the lines developed are expected to confer resistance to all bean anthracnose races and BCMV strains and protect bean crop against bean anthracnose and BCMV diseases. Analysis of comparisons of means between recurrent parents and their respective advanced lines in regards to; days to emergence, days to flowering , plant height, number of pods per plant, pod length, number of seeds per pod, days to physiological maturity, seed weight per plant and 100-seed weight was done with paired students t-test. The highest student's t-test values significant at the two-tailed level were 10.45 and 9.47 obtained in regard to number of pyramided genes in two seasons, followed by 5.04 and 4.89 obtained in regard to seed weight per plant. The student's t-test values 3.14 and 4.64 recorded in regard to days to flowering between two groups were significant for first and second seasons respectively. The change in number of pods per plant between two groups was significant with t-values 3.91 and 3.02 in first and second season respectively. Another objective of this study was to determine the effect of pyramided genes on other plant agronomic traits with the help of correlation and path coefficient analyses. Correlation and path analyses were used to assess the relationship between number of pyramided genes and different plant agronomic characters. The number of pyramided genes was significantly negatively correlated with pod length (-0.33), number of seeds per pod (-0.342) and plant height (-0.243). The non-significant negative correlation was found between number of pyramided genes and days to emergence (-0.059), number of pods per plant (-0.125), number of days to physiological maturity (-0.057) and 100-seed weight (-0.042). Non-significant positive correlations were exhibited between number of pyramided genes and seed weight per plant (0.128) and days to flowering (0.011). The 100-seed weight and plant height had correlation coefficients (0.950 and 0.051) almost equal to the direct path coefficients (0.957 and 0.072), respectively. Number of pyramided genes had negative indirect effect on seed weight per plant through days to emergence (-0.017), days to flowering (-0.007), plant height (-0.056), pod length (-0.008), number of pods per plant (-0.002), days to physiological maturity (-0.013) and 100-seed weight (-0.057). The correlation coefficient between number of pyramided genes and direct effect was low and non-significant. Pyramiding number of resistance genes would affect yield through independent variables. Therefore, it is important for breeders to take into consideration the number of pyramided genes with yield related traits.