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Ojwang J. David, Nyankanga O. Richard, Imungi Japheth and Olanya O. Modesto

Pigeon pea (Cajanus cajan) is an important crop in dry land and semiarid regions and is a supplementary source of dietary protein for the economic resource-constrained farmers. The aim of this research was to evaluate growth parameters of 12 vegetable pigeon pea cultivars at two locations in eastern Kenya. The number of days from planting to flowering, plant height, primary and secondary branches, and pod length and width were quantified in experimental plots in a randomized complete block design with three replications. Significant differences (P < 0.01) in days to 50% and 70% flowering (DTF) and plant maturity (DTM), respectively, were recorded among cultivars at both locations. The average plant height was significantly (P < 0.05) greater at Kiboko than at Kambi ya Mawe. The number of DTF and DTM were also greater at Kiboko than at Kambi ya Mawe site, because of supplemental irrigation. Similarly, mean pod length and width at Kiboko location exceeded that at Kambi ya Mawe by 6% and 8%, respectively. Positive and significant (P < 0.05) correlation coefficients between grain yield and pods per plant were observed, indicating that pod number is a useful indicator of yield potential of vegetable pigeon pea. The cultivars ICEAP 00068, ICEAP 00540, ICEAP 00554, ICEAP 00902, KAT 60/8, and MZ 2/9 were identified for high-yield potential under rain-fed conditions, whereas ICEAP 00902, ICEAP 00068, ICEAP 00557, ICEAP 00554, KAT 60.8, and MTHAWAJUNI showed the greatest potential when supplemental water applications were made. The cultivars KAT 60/8, ICEAP 00068, ICEAP 00554, and ICEAP 00902 were suitable for production under both rain-fed conditions and additional water applications. Yield potential of pigeon pea in the dry regions can be greatly enhanced by using cultivars with good plant growth characteristics and shoot density.

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Richard O. Nyankanga, Ocen Modesto Olanya, Hans C. Wien, Ramzy El-Bedewy, John Karinga and Peter S. Ojiambo

Tuber blight may result from infection of wounded or unwounded potato tubers exposed to sporangia from foliar blight, soil, or blighted tubers. However, there are limited data on the prediction of tuber blight in field or storage environment based on in vitro assays. To assess this relationship, potato cultivars with foliar blight resistance (R-genes) and general resistance were evaluated for tuber blight incited by Phytophthora infestans (US-1) based on wound-induced and unwounded tuber inoculations. Surface lesion diameter, lesion depth, and frequency distribution of blighted tubers were assessed in in vitro assays and tuber blight incidence determined in field experiments. Significant differences (P < 0.05) in lesion diameter and depth were recorded among cultivars. Surface lesion diameter, depth, and index ranged from 5 to 40, 2 to 16.3, and 15 to 656 mm, respectively, in wound-inoculated tubers. In nonwounded tuber assays, the incidence of blighted tubers ranged from 0% to 8.7% in both years. Tuber blight infection of potato cultivars varied between years in field studies. Although tuber infection differed among cultivars, the frequency of blighted tubers had a normal statistical distribution irrespective of R-genes, implying that foliar resistance may have limited effect on tuber blight occurrence based on in vitro experiments. Prediction of tuber blight based on inoculation assays can be effectively used to estimate and manage blight development in storage environments.