Race Durango Research Articles

Genetic Diversity among Latin American Andean and Mesoamerican Common Bean Cultivars

Knowledge of the relationship among existing crop cultivars helps broaden the genetic base of new cultivars, facilitates deployment of useful genes, reduces genetic vulnerability, and maximizes the use of available germplasm resources. In this study, our objective was to analyze the genetic base of common bean (Phaseolus vulgaris L.) cultivars released in Latin America from the onset of breeding activities until 1993. Each of the 203 cultivars of hybrid origin and their 194 ancestors were classified into one of six racial groups: Mesoamerica, Durango, Jalisco, Nueva Granada, Peru, or Chile. Genetic diversity was assessed, based on the pedigree, through the coefficient of parentage (r). The groups of 130 cultivars of Race Mesoamerica and 46 cultivars of Race Nueva Granada both received 79 and 76% of their genes, respectively, from ancestors of their same race. Furthermore, a 55% genetic contribution in the case of Race Nueva Granada cultivars and 41% for Race Mesoamerica was attributed to 12 and 10 ancestors of the same race, respectively. The 18 cultivars of Race Durango received 18% of their genes from Race Nueva Granada; the genetic contribution from their same race was as much as 43%. The three cultivars of Race Chile received half of their genes from Race Chile; the other half came from Races Nueva Granada, Mesoamerica, and Durango. Races Jalisco and Peru received little or no improvement and were used little in the improvement of cultivars of other races. When cultivars were grouped by different time periods, the increasing trend of using interracial hybridizations to broaden the genetic base of cultivars of Races Mesoamerica and Nueva Granada became evident.

Use of interracial hybridization in breeding the race Durango common bean

Recently, interracial hybridization was used successfully in breeding common bean (Phaseolus vulgaris L.), but its use has not been adequately documented. Approximately 125 lines with medium-sized seed were selected in the first cycle, mostly from race Durango × race Mesoamerica (both from the Middle American domestication center) single- and multiple-cross populations, for disease resistance and race Durango characteristics. Fifteen of these improved lines, three race Durango control cultivars, and one control cultivar each from races Jalisco and Mesoamerica were evaluated for 3 yr (1989–1991) at three locations in Colombia. A randomized complete block design with three replications was used. Lines were developed using visual mass selection for seed yield and/or resistance to diseases in F2 and F3, followed by single plant harvests in F4 or F5 and seed increases in F6 or F7. Lines resistant to bean common mosaic virus and possessing other desirable traits were yield-tested in F7 or F8. All but two lines outyielded Alteño and Flor de Mayo, the highest yielding control cultivars from races Durango and Jalisco, respectively. Two lines also outyielded Carioca, the race Mesoamerica control cultivar. Improved lines tended to possess higher yield per day. All lines were resistant to bean common mosaic virus and most lines also carried a high level of resistance to anthracnose. Plant, seed, and maturity characteristics of most improved lines were similar to those of race Durango control cultivars. These results support the use of interracial hybridization in improving race Durango common bean. Key words: Common bean, Phaseolus vulgaris, race Durango, interracial populations, seed yield, disease resistance

Combining Ability for Seed Yield and Its Components in Common Bean of Andean Origin

Knowledge of parental combining ability is essential for creating useful genetic variation through hybridization. Our objectives were to examine combining ability for yield and its components for large‐seeded common bean (Phaseolus vulgaris L.) of Andean origin and to test an earlier observation that germplasms from Middle American races Durango and Jalisco possess positive general combining ability (GCA) for seed yield. Sixty‐four parents from different races and gene pools were randomly assigned to groups of 16. Within a group, eight parents were randomly chosen as females, the rest as males, and crossed in a Design II mating scheme. The resulting 256 F2 populations were evaluated in a reps‐in‐sets design with two replications at Palmira and Popayán, Colombia, in 1989. The experimental unit was a four‐row plot, 5 m long. The GCA effects using line × tester analysis were measured for seed yield (kg ha−1), pods per square meter, seeds per square meter, 100‐seed weight (g), and days to maturity. Mean squares due to males and females (vs. those for males × females) were larger in magnitude and significant (P < 0.05) for all traits; the smaller mean squares for males × females were significant only for seed weight and days to maturity. Mean yields of populations between races Durango and Jalisco were the highest, while populations between races Chile and Nueva Granada were the lowest. Populations between races Chile and Durango had the next‐lowest yields. Positive GCA effects were found for yield (19 parents), seed weight (6 of the 19), seeds per square meter (20), pods per square meter (19), and days to maturity (29). Negative GCA was found for days to maturity (25 parents).

Races of common bean (Phaseolus vulgaris, Fabaceae)

Evidence for genetic diversity in cultivated common bean (Phaseolus vulgaris) is reviewed. Multivariate statistical analyses of morphological, agronomic, and molecular data, as well as other available information on Latin American landraces representing various geographical and ecological regions of their primary centers of domestications in the Americas, reveal the existence of two major groups of germplasm: Middle American and Andean South American, which could be further divided into six races. Three races originated in Middle America (races Durango, Jalisco, and Mesoamerica) and three in Andean South America (races Chile, Nueva Granada, and Peru). Their distinctive characteristics and their relationships with previously reported gene pools are discussed.