MORPHO-GENETIC DIVERSITY OF GAMMA IRRADIATED DOLICHOS BEAN (Lablab purpureus (L.) Sweet) GENOTYPES FOR CLIMATE CHANGE ADAPTATION.

Abstract

Dolichos bean (Lablab purpureus (L.) Sweet 2n=22 or 24 is a multipurpose legume mainly grown and used as a pulse, forage feed and in soil amendment for nitrogen fixation and green manure. Practically, it still yields below estimated potential of over 5000 kgha-1. Induced crop mutagenesis is a safer conventional breeding method and has played a major role in increasing global food security. The main objective of the study was to contribute to climate change adaptability through gamma ray irradiation of dolichos bean genotypes and selection of climate smart allelic accessions. Specific objectives were to: evaluate the effect of gamma irradiation doses on morpho-agronomic traits of mutant dolichos bean accessions, assess genetic variability estimates, determine the genetic diversity, and evaluate nutritional and mineral composition and to evaluate the adaptability potential of mutant accessions in north rift Kenya. Four dolichos bean varieties (maridadi, cream, black I and black II) were irradiated with 300 gy and 400 gy gamma rays in 2018 in Austria. The M1 to M4 generations of the accessions of four dolichos bean genotypes were advanced by forward genetics protocol at University of Eldoret in 2019 through 2021.M2 accessions were evaluated for effect of mutation and genetic estimates, 95 M3s for genetic diversity based on 20 SSR markers, 24 M4s were screened for nutritional and mineral composition and yield and adaptability potential. The results showed that dose 300gy and 400gy significantly (p=0.05) increased leaf length, raceme length, dry seed yield per plant and plant height across the accessions. Qualitative phenotypic variations were present in all mutant accessions except black I. There was a higher genetic estimate variability for the yield associated traits measured for eldo maridadi than for eldo black I indicating difference in genotype and impact of mutation. Genetic diversity of 95 accessions based on microsatellite markers produced 20 polymorphic primers mapping an average of 5.25 alleles per locus, polymorphic information content of 0.58 with analysis of molecular variance (AMOVA) among population of 45% and among and within individuals 54% and 1%.The nutritional test showed that accession BF032 (28.86±0.18%), MT076 (74.88±0.59%), BF137 (9.69±0.34%), MT049 (12.55±0.57%) and BT188 (449.69±0.02 kcal) had significantly higher percent crude protein, carbohydrate, crude fat, crude fibre and energy. WT018, BT114 and BT039 had significantly higher phosphorous, potassium, calcium and zinc (0.58±0.21mg/l, 2.81±0.00 mg/l, 175.65±2.27 mg/l and 3.64±2.29 mg/l respectively). Accessions BT188 (3919 kgha-1), MT049 (3315 kgha-1), GT032 (3512 kgha-1) and WT026 (4462 kgha-1) were identified as adaptable and best yielding while Baringo as the best location for dolichos production. The use of gamma irradiation in generating genetic variability in Kenyan dolichos bean genotypes for climate change adaptation was effective. The best accessions on nutrition and yield adaptability are an important genetic resource for building resilience to climate change in Kenya.