Two generations of PIC population selections and advanced lines under consideration for release were evaluated at the ARC Station in Cedara for disease resistance, under high temperature at the ARC Station in Vaalharts, and at Potchefstroom from 3/27-4/2/19.

 In the trials at Cedara, the principal disease was scab with both pod and leaf symptoms identified (photo below), but halo blight, rust, and angular leaf spot (ALS) were also found. An advanced first-generation of PIC population selections, with 80 entries in 3 replications from populations 1 to 153, were evaluated for potential release. A second set of PIC selections, from a second generation of PIC populations 154 to 275 and composed of 677 lines, were also evaluated in 3 replications. All plots were evaluated for pod load (1-9 scale), maturity (1-3 scale), and disease response (1-9 scale) and preliminary selections were completed.

Cedara photos from left to right: scab on leaves, on pods, Cedara field trials

At the Jan Kempdorp ARC Station in Vaalharts response to high temperature stress was evaluated. The bean trial at the Vaalharts field site was located at 27⁰56.759 S, 24⁰50.548 E and at 1162 masl and has average temperatures of 35-38⁰C (day) and 16-18⁰C night during the season. Visual ratings based on pod load were completed on the same set of 80 PIC lines as indicated above in three replications and on 285 lines (previously selected in Vaalharts) from the second generation mentioned above. In addition to pod load, disease response, maturity, and virus-like symptom data was also collected.

Vaalharts photos from left to right: Drs. Miklas, Fourie, and Porch at Vaalharts trials, virus symptoms, heat-adapted versus sensitive lines.

At the Potchefstroom trials of Deidre Fourie selections from the PIC breeding lines with a sugar or calima seed type were evaluated for potential release in South Africa. A number of these lines had promising yield potential in Potchefstroom. RILs from the Rojo x CAL 143 population combining multiple disease resistance were also evaluated for yield potential, seed type, and for potential release.

A subset of these PIC lines with commercial seed type will be evaluated in yield trials in South Africa, and sent to U.S. collaborators for phenotypic and genotypic evaluation and for potential release or use in breeding programs in the U.S.

ARS scientists Phil Miklas, Karen Cichy, and Tim Porch participated in this trip focused on the evaluation of breeding lines in collaboration with Sokoine University researchers Dr. Susan Nchimbi. Significant progress was made in advancing breeding populations directed towards release of improved varieties in Tanzania. Thirty promising F_4:7, 1^st generation 2014 PIC (Phaseolus Improvement Cooperative) and ~100 F_4:6, 2^nd generation 2015 PIC breeding lines were selected. In addition, ~300 F_4:5, 3^rd generation 2016 PIC single plant selections were completed in Arusha and Mbeya (photos from Arusha below). These breeding lines, derived from 109 PIC populations specifically developed to combine abiotic and biotic stress tolerance, showed superior agronomic potential compared with checks and local landraces. The diversity, scale, and potential of the material in the PIC breeding pipeline is invaluable and requires continued support to ensure the release of varieties that promise to increase the productivity of common bean in the E. African region.

Single plant selections (left) and selection of plant rows (right) from the PIC populations in Arusha, Tanzania.

Twelve superior lines from ADP evaluations during previous years were evaluated in on-station trials in Arusha, Mbeya, and Morogoro, and in on-farm trials in the Arusha and Mbeya areas (photos below). The first village near Arusha was Kikatiti (District of Arumeru) where bush beans were preferred (left photo below). The second village was Sakila (in Arumeru as well). This village was at a higher elevation with higher rainfall and fertile soils. A high incidence of white mold was found at this site. About 17 male and 2 female farmers participated in an evaluation of the material in the 12 entry ADP field trial with the local extension agent, indicating their most preferred and least preferred lines (middle photo below).

The first village near Mbeya was Ivuanga, in the District of Mbezi. The 4 male and 3 female farmers had selected individual plants to present the characteristics that they preferred. Several of the ADP were mentioned in this discussion as having good potential including ADP 395, ADP 468, and ADP 111 (right photo below). The two local checks in this area are Wanja and Kigoma. In the field, ADP 479, a red mottled, Calima type also looked promising. A second location in the village was also visited. This site had noticably lower soil fertility and reduced vigor. At this site, ADPs 395, 462, 468, and 479 again looked promising.  A second village was then visited in the vicinity, Nambala. An enthusiastic group of farmers composed of 13 men, 6 women, and 5 children showed us their plots, that had been irrigated by hand, that were at mid pod fill stage. It was too early to evaluate the material for yield performance, but they did indicate that palatability of the leaves was an important characteristic.

Family showing seed types in Kikatiti (left photo) and farmers evaluating APD lines in Sakila (middle photo) both near Arusha in the District of Arumeru. In the village of Ivuanga near Mbeya in the District of Mbezi, farmers evaluate ADP lines at maturity (right photo).

Dr. James Bokosi with promising breeding line at the Bwumbe Station near Blantyre, Malawi.

At Bunda College, with Dr. James Bokosi, promising breeding lines were selected from 35 PIC (Phaseolus Improvement Cooperative) populations at a field site located at 14⁰11.249 S, 33⁰46.478 E and at an elevation of 1195 masl. Single plant selections from the F4 generation had been completed one year ago in Malawi, resulting in over 400 selections; followed by a generation advance in South Africa with Deidre Fourie (ARC). Dr. Bokosi then selected a subset of approximately 280 lines based on seed type and these were planted at the Bunda and Bwumbe Stations. At Bunda, a high frequency of mosaic and black root symptoms were identified, signaling the presence of bean common mosaic virus. Lines were selected based on yield, plant stand, and disease resistance. Approximately 10-20% of the lines were selected that will then be included in regional trials during the next season.

At Bwumbe Station near Blantyre, the same set of PIC lines were planted in three replications at the Bwumbe Station located at 15⁰55.555 S, 35⁰04.389 E and at 1138 masl. At Bwumbe, charcoal rot (caused by Macrophomina phaseolina) was the major constraint, resulting in reduced plant stands and reduced yield. In addition, wilt likely caused by Fusarium oxysporum, and Angular leaf spot were also found. We noted that distinct selections were completed in Bwumbe in comparison with Bunda, indicating the effectiveness of this approach of selection from a diverse set of populations in each target production environment. Separate trials of selections from the Durango diversity panel (DDP), and an advanced line trial and a national trial both from Malawi, were evaluated. In the process one line was identified from the national trial with impressive yield, architecture, disease resistance, and seed quality traits.

Selection of PIC lines at Bunda College

In Vaalharts, South Africa we evaluated high temperature trials with Deidre Fourie at the Jankempdorp ARC Station. The bean trial at the Vaalharts field site is located at 27⁰56.759 S, 24⁰50.548 E and at 1162 masl and covered over 2 hectares with 3 replications of the DDP and ADP and 72 PIC populations. The average temperatures indicate high temperature stress during the daytime, but an ideal night-time temperature regime, that resulted in typical high temperature stress effects, including reproductive organ abscission and pin bean formation. Visual ratings based on pod load (1-9) were completed on the ADP and DDP trials and selections were completed in 72 PIC populations.

Identifying typical effects of high temperature stress, including poor seed set and pin pods at ARC Station in Vaalharts, South Africa.

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