Yangaza Iman S, M S Nyomora Agnes, Joseph Charles O, Sangu Emmanuel M, Hormaza José I
Department of Botany, University of Dar es Salaam, P.O Box 35060, Dar es Salaam, Tanzania.
St. Augustine University of Tanzania, P.O Box 307, Mwanza, Tanzania.
Heliyon. 2024 Apr 2;10(7):e29059. doi: 10.1016/j.heliyon.2024.e29059. eCollection 2024 Apr 15.
Tanzania has a diverse agroecological area suitable for growing tropical fruits, including avocados. In Northern Tanzania, avocados have been growing under variable soil and altitudinal characteristics for over 100 years, allowing the naturalisation of this crop in this region. However, the region's avocado germplasm is uncharacterised, thus impeding the selection of elite genotypes for increased value and breeding programmes. This study examined the growth and fruit morphometric characteristics of avocado populations grown under variable soil pH and altitude in six districts in the Tanga, Kilimanjaro and Arusha regions. Variations in growth and fruit morphometric characteristics were compared using a one-way analysis of variance (ANOVA). Pearson product-moment correlations (r) were used to evaluate the relationship between studied growth and fruit morphometric traits. A linear mixed-effects model (LMM) was used to assess the influence of the soil pH, altitude, tree height, canopy diameter, and trunk diameter on fruit length, fruit diameter, pulp thickness, and seed diameter. Principal Component Analysis (PCA) was used to depict the extent of the racial admixtures in the avocado germplasm in the Northern regions of Tanzania. The results revealed a significant variation in growth and fruit morphometric characteristics ( < 0.05). The Korogwe population had the highest tree height, while the Karatu had the lowest. Tree height was positively correlated with the trunk diameter (r = 0.63, < 0.001. There was a positive correlation between fruit length and pulp thickness (r = 0.51, < 0.001), fruit diameter and pulp thickness (r = 0.47, < 0.001), and fruit length and fruit diameter (r = 0.36, < 0.001). The fruit diameter was positively correlated with the seed diameter (r = 0.61, < 0.001). There was a significant but weak association between fruit length and trunk diameter (-0.01), fruit length and canopy diameter (0.15), and between seed diameter and tree height (2.95e-2). These findings highlight the influence of individual tree genetic makeup on the variation in growth and fruit morphometric characteristics. The morphometric trait correlations may prove valuable in field measurements, especially when resources are limited. The study further indicates the presence of all avocado races within the local germplasm, highlighting its high diversity. Remarkably, the observed admixture of variant races implies gene flow among studied avocado populations, possibly facilitated by sharing seedlings among farmers or seed disposal through avocado fruit trading. Further study is needed, particularly in quantifying the above-ground biomass of local avocados in northern Tanzania, potentially contributing to carbon credit initiatives for fruit crops..
坦桑尼亚拥有多样化的农业生态区域，适合种植包括牛油果在内的热带水果。在坦桑尼亚北部，牛油果在不同的土壤和海拔特征条件下已生长了100多年，使得这种作物在该地区得以归化。然而，该地区的牛油果种质尚未得到鉴定，从而阻碍了为提高价值而选择优良基因型以及育种计划的开展。本研究调查了在坦噶、乞力马扎罗和阿鲁沙地区六个区不同土壤pH值和海拔条件下种植的牛油果种群的生长和果实形态特征。使用单因素方差分析（ANOVA）比较生长和果实形态特征的差异。皮尔逊积矩相关性（r）用于评估所研究的生长和果实形态特征之间的关系。使用线性混合效应模型（LMM）评估土壤pH值、海拔、树高、树冠直径和树干直径对果实长度、果实直径、果肉厚度和种子直径的影响。主成分分析（PCA）用于描述坦桑尼亚北部地区牛油果种质中种族混合的程度。结果显示生长和果实形态特征存在显著差异（P<0.05）。科罗圭种群的树高最高，而卡拉图的树高最低。树高与树干直径呈正相关（r = 0.63，P<0.001）。果实长度与果肉厚度呈正相关（r = 0.51，P<0.001），果实直径与果肉厚度呈正相关（r = 0.47，P<0.001），果实长度与果实直径呈正相关（r = 0.36，P<0.001）。果实直径与种子直径呈正相关（r = 0.61，P<0.001）。果实长度与树干直径（-0.01）、果实长度与树冠直径（0.15）以及种子直径与树高（2.95e-2）之间存在显著但较弱的关联。这些发现突出了个体树的遗传构成对生长和果实形态特征变异的影响。形态特征相关性在田间测量中可能很有价值，特别是在资源有限时。该研究进一步表明当地种质中存在所有牛油果种族，突出了其高度多样性。值得注意的是，观察到的不同种族的混合意味着所研究的牛油果种群之间存在基因流动，这可能是由于农民之间分享幼苗或通过牛油果果实交易进行种子处置所促成的。需要进一步研究，特别是在量化坦桑尼亚北部当地牛油果的地上生物量方面，这可能有助于水果作物的碳信用倡议。
