Origin

‘Isabella’ was derived from the simple cross 13KPP-264-05 × ‘Lázaro’ and developed by pedigree and bulk breeding methods. 13KPP-264-05 is a pigeonpea breeding line developed by the University of California, Riverside (Huynh and Roberts, personal communication). This genotype is insensitive to the photoperiod, has determinate upright growth habit, possesses flowers with petals of yellow color, and has early maturity (< 135 d after planting) in field evaluations in Puerto Rico (Viteri, personal communication). ‘Lázaro’ has determinate bushy-type growth habit, possesses flowers with petals of red colors on the outside and yellow on the inside, and reaches harvesting maturity between 130 to 149 d after planting (Sarmiento et al. 2021; Viteri et al. 2020). Twenty F₁ plants with red colored petal flowers (a dominant trait derived from ‘Lázaro’ to identify hybrids) were selected and harvested in Sep 2019 at the Isabela Research Substation, University of Puerto Rico. Forty seeds from the F₂ to F₅ progenies were sown in single rows in four continuous cycles of planting from Oct 2019 to Feb 2020, Mar to Jun 2020, Jul to Oct 2020, and Nov 2020 to Feb 2021. Ultimately, five plants with determinate bushy-type growth habits, red flowers (these traits are preferred for pigeonpea growers and were derived from ‘Lázaro’), early maturity, and higher yield per plant (>80 g) were selected. The seeds of the F₆ derived from the five F₅ plants were used to develop the breeding lines UPE-1, UPE-2, UPE-3, UPE-4, and UPE-5. The F₇ seeds of the UPE-4 breeding line, which had a high seed yield at Isabela (Table 1), were harvested in bulk to develop the cultivar Isabella. Then, F₈ seed of ‘Isabella’ was used for yield trials conducted at Isabela and Lajas Research Substations in 2022.

Table 1.

Flowering and harvest time, and mean dry seed yield of pigeonpea [Cajanus cajan (L.) Mill.] breeding lines and cultivars evaluated at Isabela, Puerto Rico, 2021.

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Yield Performance

Promising breeding lines UPE-1, UPE-2, UPE-3, UPE-4 (‘Isabella’), and UPE-5; their parents (13KPP-264-05 and ‘Lázaro’); and ‘ICPL 86012’ [i.e., an early maturity check from India (Chauhan et al. 1999)] were planted in a randomized completed block design with three replications at Isabela in Apr 2021. The experimental plot consisted of 40 plants of each genotype planted in four rows by 6 m long, with a spacing of 0.9 m between rows and 0.6 m between plants. In addition, seeds of ‘Lázaro’ and UPE lines were increased in nonreplicated plots in Jul 2021. Ten rows of 15.5 m long were planted with 250 plants (i.e., 25 plants per row separated by 0.6 m) with a spacing of 0.9 m between rows. The two central rows from each plot were harvested to estimate seed yield in kg·ha⁻¹. Likewise, ‘Isabella’, 13KPP-264-05, ‘Lázaro’, and ICPL 86012 were planted in Isabela and Lajas Research Substations in Nov 2021 and Apr 2022. Similar experimental plots were used; however, a new plant density was included in the trials where the 40 plants were planted in four rows of 3 m length, and each seed was separated 0.3 m instead of 0.6 m. The Isabela Substation is located at 126 m above sea level and has Oxisol soils, temperatures from 20 to 31 °C, mean annual precipitation of 1592 mm, and an average relative humidity of 70% (Muñoz et al. 2018). The Lajas Substation is located at 9 m above sea level and has temperatures between 19 to 33 °C, soils belonging to the Mollisol and Vertisol orders, an annual precipitation of 1143 mm, and an average relative humidity of 80% (Muñoz et al. 2018). Fisher’s least significant difference at P ≤ 0.05 was calculated to discriminate harvesting time (i.e., between 110 and 149 d after planting) and seed yield among genotypes. Data were analyzed using SAS 9.4 PROC GLM (SAS Institute 2012).

Plant Characteristics

‘Isabella’ is also insensitive to the photoperiod and has a determinate bushy-type growth habit with a plant height <1.0 m and between 1.2 to 1.7 m in short- and long-daylength plantings, respectively. These plant heights are optimal for the mechanical harvesting used in commercial plantings. ‘Isabella’ initiated flowering between 65 to 73 d and reached 50% of mature pods between 110 to 126 d after planting. The early maturity characteristic of Isabella allowed to harvest the seed between 16 to 25 d before ‘Lázaro’ (Tables 1 and 2). Thus, growers may be able to plant ‘Isabella’ even at the end of July or August and harvest green-fresh seed at November–December, which is the peak period for consumption of pigeonpea in Puerto Rico. Currently, ‘Lazaro’ is planted in June-July to harvest the seed for the peak of consumption (Viteri et al. 2020).

Table 2.

Harvest time and mean dry seed yield of pigeonpea [Cajanus cajan (L.) Mill.] cultivar ‘Isabella’ evaluated at Isabela and Lajas Substations, Puerto Rico, 2021 and 2022.

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‘Isabella’ has flowers with petals of red color on the outside and yellow color inside. Pods are green with brown marks with an average size of 6.7 × 0.9 cm. In each pod, between 4 to 6 circular seeds are mostly observed. Seeds are green at immature stage and beige with dark brown spots near and around the hilum at harvest. The average 100 mature seed weight is 14.6 g compared with ICPL 86012, which had a lower weight of 13 g, and 13KPP-264-05 and ‘Lázaro’, which had higher seed weights of 17.3 g. ‘Isabella’ had higher seed yield than ‘Lázaro’ in the long-daylength plantings in both locations (Tables 1 and 2). ‘Isabella’ also had a seed yield of 4342.5 kg·ha⁻¹ compared with ‘Lázaro’ that reached values of 3720.4 kg·ha⁻¹ in Isabela in Nov 2021. Furthermore, although there were not significant statistical differences, ‘Isabella’ had higher seed yield values than 13KPP-264-05 and ICPL 86012 pigeonpea genotypes in all evaluations (Tables 1 and 2).

Availability

A small quantity of seed of ‘Isabella’ for research purposes may be obtained from the corresponding author.